Organic chemistry of coal

Organic Chemistry of Coal John W. Larsen,

EDITOR

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.fw001

University of Tennessee

A symposium sponsored by the Division of Fuel Chemistry at the 174th Meeting of the American Chemical Society, Chicago, Illinois, August 29— September 1, 1977.

ACS

SYMPOSIUM

SERIES

AMERICAN CHEMICAL SOCIETY WASHINGTON, D. C. 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

71

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.fw001

Library of Congress CIP Data Main entry under title: Organic chemistry of coal. (ACS symposium series; 71 ISSN 0097-6156) Includes bibliographies and index. 1. Coal—Analysis—Congresses. I. Larsen, John W . , 1940. II. American Chemical Society. Division of Fuel Chemistry. III. Series: American Chemical Society. ACS symposium series; 71. TP325.0685 ISBN 0-8412-0427-6

662'.622 ASCMC8

78-8114 71 1-327 1978

Copyright © 1978 American Chemical Society A l l Rights Reserved. The appearance of the code at the bottom of the first page of each article in this volume indicates the copyright owner's consent that reprographic copies of the article may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc. for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating new collective works, for resale, or for information storage and retrieval systems. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. PRINTED IN THE UNITED STATES OF AMERICA

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ACS Symposium Series

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.fw001

Robert F. Gould, Editor

Advisory Board Kenneth B. Bischoff

Nina I. McClelland

Donald G. Crosby

John B. Pfeiffer

Jeremiah P. Freeman

Joseph V. Rodricks

E. Desmond Goddard

F. Sherwood Rowland

Jack Halpern

Alan C. Sartorelli

Robert A. Hofstader

Raymond B. Seymour

James P. Lodge

Roy L. Whistler

John L. Margrave

Aaron Wold

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.fw001

FOREWORD The ACS SYMPOSIUM SERIES was founded in 1974

to provide

a medium for publishing symposia quickly in book form. The format of the SERIES parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book. Papers published in the ACS SYMPOSIUM SERIES are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.pr001

PREFACE X T 7 i t h the Arab oil embargo the American political structure became * * aware that oil and gas resources are finite and that ours would not suffice to fuel our economy. This has led to the current, awkward attempts to develop a rational, long-term energy policy for the United States. Since coal constitutes more than 90 percent of American fossil fuels which can be used with current technology, a natural result of governmental attention has been the flow of money into chemical research on coal. This area had been badly neglected since the last time the government was worried about oil supplies. Previous government commitments to coal research have not been sufficiently long lived to allow the development of satisfactory coal conversion technologies. There is hope that the current commitment to coal research will last long enough to allow both an increase in our knowledge of coal chemistry and the application of this knowledge to improve old processes and to develop new ones. The new money for coal research has attracted some new people; various corporations have increased their activities in the area; and some individuals have discovered that the organic chemistry of coal is a fascinating research area. Thus, there has been a great increase in activity and much of it is now resulting in significant increases in our understanding. In each of the past several years there has been a meeting dedicated to the organic chemistry of coal. The papers in this volume were given at the 1977 meeting. Unfortunately, time limitations prevented the presentation of several excellent papers. Coals are extraordinarily complex, insoluble organic mixtures. Complete elucidation of their structures has remained beyond the capabilities of the organic chemist and his instruments. However, the increased attention has begun to give results. Comparison of the proceedings of our annual coal chemistry meetings ( University of Tennessee, 1975; Stanford Research Institute, 1976; this book, 1977) and conversations with workers active in the field will show that we are now just entering the rapid growth region of an exponential curve. We remain a long way from good structural models for coals and from a reasonable understanding of their chemistry, but the quality and quantity of work now being done is such that we will probably find answers to some of the fundamental questions in time to be of some aid to the development of conversion and cleaning processes. vii In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

But even without this practical goal, the problem of the structure and reactivity of this extraordinary complex material is worth solving simply because it is so complex and challenging. JOHN W. LARSEN

University of Tennessee

Knoxville, Tennessee

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.pr001

February, 1978

viii In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1 A Primer on the Chemistry and Constitution of Coal D.D.WHITEHURST

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

Mobil Research and Development Corp., P.O. Box 125, Princeton, NJ 08540

The purpose of this paper i s to review what i s known about the structure of coal and show how this information relates to the ultimate conversion of coal to conventional liquid fuels. Let us f i r s t consider some common beliefs about coal, as shown below: • • • • • •

Coal is highly aromatic. Its structure contains predominantly condensed polycyclic aromatic rings. The high degree of condensation makes coal d i f f i c u l t to liquify. Extreme pressures and temperatures are required for coal conversion. Organic sulfur is much more d i f f i c u l t to remove than organic oxygen. Liquefaction requires high hydrogen consumption.

By the end of this paper I hope to have shown that all of these statements are wrong. To initiate this discussion, I propose to present three aspects of coal and coal product structure. These include, aromaticity, functionality, and molecular weight. I w i l l then discuss reactivity of coal in non-catalytic hydrogenative processes and f i n a l l y , how structure and reactivity interrelate. Concerning the structure of coal, I would f i r s t like to say a few words about the origin of coal. It is generally agreed that coal originates primarily from plants. Through a series of evolutionary changes the primary products of the original decomposed plant matter becomes transformed through a series of steps in which the f i r s t product is humic acid. The humic acid 0-8412-0427-6/78/47-071-001$10.00/0 ©

1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

2

i s then transformed s e q u e n t i a l l y i n t o peat, l i g n i t e , subbituminous c o a l , b i t u m i n o u s c o a l , and f i n a l l y t o a n t h r a c i t e as shown i n F i g u r e 1. With t h e s e t r a n s f o r m a t i o n s , the c a r b o n c o n t e n t i n c r e a s e s and the oxygen content decreases. The r e s u l t i s t h a t the c a l o r i f i c v a l u e o f the c o a l i n c r e a s e s w i t h rank. A l s o shown i n F i g u r e 1, i s the f a c t t h a t c o a l as we know i t today, can be i d e n t i f i e d as composed o f a s e r i e s o f macérais, o r f o s s i l i z e d p l a n t fragments. These f o s s i l i z e d p l a n t fragments are r e l a t e d t o the o r i g i n a l p l a n t m a t t e r from which t h e y are d e r i v e d . The c o n s t i t u e n t s o f p l a n t s which c o u l d p o s s i b l y g i v e r i s e t o c o a l and commonly a s s o c i a t e d s t r u c t u r e s are shown i n F i g u r e 2. The s t r u c t u r e s t h a t we f i n d i n c o a l , o r c o a l l i q u i d s , must be t h o s e r e l a t e d t o the most s t a b l e o f the s t r u c t u r e s from the o r i g i n a l p l a n t fragments. There are two s c h o o l s o f thought on the major c o n s t i t u e n t o f c o a l . United States c o a l s c o n s i s t of p r i m a r i l y v i t r i n i t e , u s u a l l y 80% o r more. The c o m p o s i t i o n o f t h i s v i t r i n i t e i s b e l i e v e d t o be the r e s u l t o f the c o a l i f i c a t i o n o f e i t h e r c e l l u l o s e or l i g n i n s t r u c t u r e s , which c o n s t i t u t e the m a j o r i t y o f the p l a n t components (jL) . I t has been shown by G i v e n and o t h e r s , however, t h a t c e l l u l o s e undergoes v e r y r a p i d biodégradation i n p l a n t s which are decomposing t o d a y (2). The same i s t r u e f o r p r o t e i n . P l a n t c o n s t i t u e n t s which are most r e s i s t a n t t o b a c t e r i a l a t t a c k are t h o s e o f waxes, r e s i n s , t a n n i n s , l i g n i n s , f l a v o n o i d s , and p o s s i b l y a l k a l o i d s (_3) . A l t h o u g h the p r e v i o u s l y d i s c u s s e d s t r u c t u r e s are p r e s e n t i n p l a n t s today, and c o u l d be s i m i l a r t o t h o s e o f p l a n t s o f p r e h i s t o r i c t i m e s , i t i s not a n t i c i p a t e d t h a t the s t r u c t u r e s would s u r v i v e i n t a c t o v e r the l o n g p e r i o d s o f time r e q u i r e d f o r t h e i r t r a n s f o r m a t i o n t o coal. Some o f the s t r u c t u r a l f e a t u r e s however may p o s s i b l y be r e c o g n i z a b l e even i n t o d a y ' s c o a l . I t has r e c e n t l y been shown by G i v e n t h a t c e r t a i n components o f c o a l can be r e l a t e d t o s t r u c t u r e s e v o l v e d from l i g n i n s (4). I t s h o u l d a l s o be remembered t h a t the U.S. coals were l a y e d down i n two d i f f e r e n t g e o l o g i c a l ages; about 160 m i l l i o n y e a r s a p a r t , and the s t r u c t u r e s a s s o c i a t e d w i t h two g e o l o g i c a l ages may be s u b s t a n t i a l l y d i f f e r e n t . Aromaticity

of

Coal

T h e r e i s c o n t r o v e r s y on the p r o p o s e d p r i m a r y b a c k bone s t r u c t u r e o f c o a l . Some workers c o n t e n d t h a t c o a l i s p r i m a r i l y g r a p h i t e - l i k e , o t h e r s argue t h a t c o a l i s of a diamond-like s t r u c t u r e .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

wmTEHURST

Chemistry and Constitution of Coal

ORIGINAL PLANT

MATERIAL

3

COAL M A C E R A L (VISUAL

RESINOUS

MATERIAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

CUTICLES, SPORES CELLWALLS,RES1NS

PLANT

MICROSCOPY)

EXINiTc RESIN1TE

N

FRAGMENTS

WOOD, CORK SPORES,?OLLEN

V i T R I N l T E j 6 SUBSTANCES CARBONIZATION

FUSINITE M1CRONITE

RANK % C % 0

Ρ E A T — ^ L ! G Ν I T E — * 5 U S B I T U MI N O U S — * B I T U M I N O U S — * A N T H R A C I T E HIGH M E D . L O W CBA 60 70 80 93 35

CALORIFIC 12000 VALUE Bru/^-fnaf)

25 13000

Figure 1.

15 14000

3 16000

15500

Mode of formation of coal

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4

ORGANIC CHEMISTRY OF COAL

C-OH

Cellulose

\

*

OH

C-OH /h

Protein

c-s-s-c-ç-cC^.^o

3

NH

f*o

COJ

2

OH

c,

Waxes

(C, -C ) 7

26

XOOR

Resins Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

(C -C32>

3I

,COOR C-C

Terpenes

COOH

•C-C-C-C-OH HO"

Sterols HO'

Flavonoids

CO"® 0

OH OH

Tannins

^

OH Ο

COO-Sugar

^ O H

OH

OH

OH

OCH

3

Lignins

CHj-OH OH OH COOH

c-c

Alkaloids CH3O.

Figure 2.

Structures of coal precursors

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

1.

WHITEHURST

5

Chemistry and Constitution of Coal

Graphite

Diamond

B o t h o f t h e s e s t r u c t u r e s a r e low i n H/C r a t i o which i s consistant with the composition o f c o a l s . To g a i n i n s i g h t on t h e s t r u c t u r e o f c o a l , p a s t workers have attempted t o b r e a k c o a l down i n t o r e c o g n i z a b l e u n i t s and t h e n p i e c e them back t o g e t h e r as i s done i n n a t u r a l p r o d u c t c h e m i s t r y today. The most common t e c h n i q u e p r e s e n t l y p u r s u e d i s t h a t o f o x i d a t i v e degradation. W i t h o x i d a n t s such as HNO3, K2Cr207/HN03, KMNO4/OH"-, BuOOH/AIBN, o r p e r a c e t i c a c i d , workers have come t o t h e c o n c l u s i o n t h a t c o a l i s p r e d o m i n a t e l y a r o m a t i c and c o n t a i n s many condensed r i n g s (J5,6) . Other a u t h o r s u s i n g NaOCl/OH" have come t o a d i f f e r e n t conc l u s i o n , i n that they b e l i e v e c o a l contains large amounts o f q u a r t e r n a r y a l i p h a t i c carbon, o r i s diamonl i k e i n s t r u c t u r e and c o n t a i n s 50% a r o m a t i c c a r b o n o r l e s s (_7) . The p r e c e e d i n g methods o f o x i d a t i o n s e l e c t i v e l y oxidize only the a l i p h a t i c p o r t i o n of c o a l . A new method p i o n e e r e d b y Dieno u s e s t r i f l u o r o a c e t i c a c i d s i n c o m b i n a t i o n w i t h hydrogen p e r o x i d e . T h i s method s e l e c t i v e l y o x i d i z e s the aromatic r i n g s . Combination o f t h e s e two t e c h n i q u e s c o u l d be a v e r y p o w e r f u l i n s t r u c t u r a l c h a r a c t e r i z a t i o n o f c o a l (8) . Because o f t h e d i f f i c u l t y o f p i e c i n g back t o g e t h e r t h e fragmented p r o d u c t s o f c o a l , a number o f workers have attempted t o do d i r e c t c h a r a c t e r i z a t i o n o f coal. D i r e c t t e c h n i q u e s s u f f e r from t h e problem t h a t c o a l i s an opaque s o l i d which i s i n s o l u b l e i n i t s n a t u r a l form and r e l a t i v e l y few t o o l s have been a v a i l a b l e up u n t i l t h e p r e s e n t time f o r such d i r e c t measurements. I n t h e p a s t , t e c h n i q u e s such as X - r a y s c a t t e r i n g have

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

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ORGANIC CHEMISTRY OF COAL

been u s e d and c o n f l i c t i n g i n t e r p r e t a t i o n s as t o t h e predominant s t r u c t u r e o f c o a l have been r e p o r t e d . H i r s c h f i r s t r e p o r t e d t h a t c o a l was from 50-80% aromat i c , w i t h p r i m a r i l y 89% o r d e r e d s t r u c t u r e (9). Ergun l a t e r , using X-ray s c a t t e r i n g , concluded that c o a l i s l e s s a r o m a t i c and c o n t a i n s l a r g e q u a n t i t i e s o f amorphous r e g i o n s (10). F r i e d e l using u l t r a v i o l e t techn i q u e s c o n c l u d e d t h a t c o a l c o u l d not be p o l y a r o m a t i c and c o n t a i n e d l a r g e amounts o f a l i p h a t i c s t r u c t u r e (11). Given^ i n c h a r a c t e r i z i n g c o a l e x t r a c t s by polarographic r e d u c t i o n c o n c l u d e d t h a t low rank c o a l s were g r e a t e r than 20% a r o m a t i c and h i g h rank c o a l s were g r e a t e r than 50% a r o m a t i c (12)· P o l y c y c l i c a r o m a t i c r i n g s were bel i e v e d t o be p r e v a l e n t . R e c e n t l y , new t o o l s have e v o l v e d and f o r the f i r s t time c o a l can be c h a r a c t e r i z e d d i r e c t l y i n i t s n a t u r a l form. The most p r o m i s i n g o f t h e s e t o o l s i s a s o l i d s t a t e CP-C^ n m r d e v e l o p ed by P i n e s (JL3) . Working i n c o n j u n c t i o n w i t h P r o f e s s o r P i n e s , we have found t h a t t h e r e i s r e l a t i v e l y l i t t l e c o r r e l a t i o n between the hydrogen c a r b o n mole r a t i o and the p e r c e n t a r o m a t i c c a r b o n found i n c o a l or c o a l l i q u i d s , as shown i n F i g u r e 3. These d a t a g i v e some i n d i c a t i o n as t o why t h e r e has been so much d i f f i c u l t y i n the p a s t c o r r e l a t i n g a r o m a t i c c a r b o n c o n t e n t w i t h the e l e m e n t a l compos i t i o n o f the c o a l . T h e r e is,however, some c o r r e l a t i o n between the rank o f t h e c o a l and i t s a r o m a t i c i t y . This i s shown i n F i g u r e 4. I t can be seen t h a t the a r o m a t i c c a r b o n c o n t e n t i n c r e a s e s from about 40-50% f o r subb i t u m i n o u s c o a l t o over 90% f o r a n t h r a c i t e . I t w i l l be shown l a t e r t h a t t h i s a r o m a t i c i t y changes w i t h c o n v e r s i o n o f the c o a l under l i q u e f a c t i o n c o n d i t i o n s . The CP-C13 t e c h n i q u e i s somewhat new and s t i l l e v o l v i n g . I t does show p r o m i s e , however, i n c h a r a c t e r i z a t i o n o f c o a l i n t o a l i p h a t i c and a r o m a t i c components, but i n a d d i t i o n , h o l d s p r o m i s e f o r f u r t h e r s u b - d i v i s i o n o f the s t r u c t u r a l types. As shown i n F i g u r e 5, i t i s p o s s i b l e t o d i s t i n g u i s h i n model compounds, a r o m a t i c , a l i p h a t i c , a l i p h a t i c e t h e r , and condensed a r o m a t i c c a r b o n . We hope e v e n t u a l l y t o use t h e s e same s u b - d i v i s i o n s i n the c h a r a c t e r i z a t i o n of c o a l . As r e p r e s e n t a t i v e examples o f the s p e c t r a t h a t one can a c h i e v e , F i g u r e 5 shows t y p i c a l model compounds, the p a r e n t c o a l , SRC derived from a c o a l , u n c o n v e r t e d r e s i d u e and the s p h e r i c a l coke formed on extended t h e r m a l r e a c t i o n (14). 3

F u n c t i o n a l i t y of

Coal

F i g u r e 6 shows the major f u n c t i o n a l group t y p e s identified in coal. Oxygen o c c u r s p r e d o m i n a t e l y as

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Chemistry and Constitution of Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

WHiTEHURST

1.1

Figure 3.

Aromatic carbon vs. H/C

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

ORGANIC CHEMISTRY OF COAL

Figure 4.

Aromaticity increase with rank

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

wmTEHURST

Chemistry and Constitution of Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

p-Pt«thoxvb«n««n« (391)*

2.3-Dla«thrln«ohth«l«n« (480)

Mcnf rmγ Coal (7300)

Monf rmv SBC (S000) AC-70

M ^ t f f y R««^u« (8800) AC-70

Soh«ric»l Cok« (9200)

*The numbers i n p a r e n t h e s e s i n d i c a t e t h e number o f s p e c t r a accumulated t o g e n e r a t e t h e spectrum p r e s e n t e d . Note t h a t t h e s c a l e s a r e n o t a l l the same. Figure 5.

CP- C 13

NMR spectra of representative samples

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

10

ORGANIC CHEMISTRY OF COAL

p h e n o l i c or e t h e r i c groups w i t h l e s s amounts o f c a r b o x y l i c a c i d s or e s t e r s ; some c a r b o n y l s have a l s o been i d e n t i f i e d . S u l f u r has s i m i l a r c h e m i s t r y t o oxygen and a l t h o u g h s u l f o x i d e s have been i d e n t i f i e d i n t a r sands t h e i r p r e s e n c e i n c o a l i s l e s s w e l l d e f i n e d . N i t r o g e n o c c u r s p r e d o m i n a t e l y as p y r i d i n e o r p y r r o l i c t y p e r i n g s . M e t a l s are found as s a l t s or a s s o c i a t e d with porphyrins. Some r e c e n t work c o n d u c t e d by Ruberto i s summarized i n F i g u r e 7 (15). Shown t h e r e are q u a n t i t a t i v e a n a l y s i s o f the major t y p e s o f f u n c t i o n a l i t y , oxygenated s p e c i e found i n c o a l s and one s o l v e n t r e fined coal. I t can be seen t h a t subbituminous c o a l c o n t a i n s c o n s i d e r a b l y more c a r b o x y l i c a c i d t h a n b i t u minous c o a l s and somewhat more c a r b o n y l . After react i o n under l i q u e f a c t i o n c o n d i t i o n s , the c a r b o x y l i c a c i d s and c a r b o n y l s are almost c o m p l e t e l y absent, and the prédominent p r o d u c t s are p h e n o l i c t y p e oxygen. Our r e s u l t s i n d i c a t e t h a t i n a d d i t i o n t o p h e n o l i c type oxygen, e t h e r i c t y p e oxygen i s a major oxygenated s p e c i e (14). As c o a l i s c o n v e r t e d i n p r e s e n t day p r o c e s s e s , the above d e s c r i b e d f u n c t i o n a l i t y , o f c o u r s e , changes w i t h s e v e r i t y , b u t i n a d d i t i o n the s t r u c t u r e o f the c o a l and i t s e l e m e n t a l c a r b o n t o hydrogen r a t i o must a l s o change. F i g u r e 8 shows a comparison o f the hydrogen t o c a r b o n mole r a t i o f o r c o a l and a number o f o t h e r n a t u r a l p r o d u c t s , i n comparison w i t h t h a t o f p e t r o l e u m and the premium p r o d u c t s t h a t are d e s i r e d from the c o a l . It can be seen t h a t t h e r e i s a v e r y l o n g p a t h n e c e s s a r y i n the c o n v e r s i o n o f c o a l t o premium p r o d u c t s such as g a s o l i n e , s i n c e c o a l s c o n t a i n about .8 hydrogen/carbon. The d e s i r e d p r o d u c t s c o n t a i n about 2. This indicates t h a t i n any c o n v e r s i o n p r o c e s s o f c o a l , one o f the p r i mary g o a l s w i l l be e x t r e m e l y e f f i c i e n t use o f hydrogen. Most p r o c e s s e s p r e s e n t l y u s e d today are i n i t i a l l y t h e r m a l i n n a t u r e s i n c e c a t a l y s t s cannot c o n t a c t the b u l k o f the c o a l m a t r i x . But j u s t where does the t h e r m a l c h e m i s t r y o f c o a l become s i g n i f i c a n t ? F i g u r e 9 shows a s u p e r i m p o s i t i o n o f t h r e e t h e r m a l a n a l y s e s o f coal. These c o n s i s t o f t h e r m a l g r a v i m e t r i c , t h e r m a l m e c h a n i c a l , and d i f f e r e n t i a l t h e r m a l a n a l y s i s o f c o a l . T h i s f i g u r e i n d i c a t e s t h a t c o a l undergoes p r i m a r y dec o m p o s i t i o n i n the range o f 400-450°, a s s o c i a t e d w i t h t h i s temperature range i s the b u l k o f the s w e l l i n g o f the c o a l and s i g n i f i c a n t changes i n the t h e r m a l behavior of c o a l . I t i s not s u r p r i s i n g , t h e r e f o r e , t h a t most o f the p r e s e n t p r o c e s s e s b e i n g d e v e l o p e d today, o p e r a t e i n the range o f 400-450°C. But, a t t h i s temperature j u s t how f a s t does c o a l r e a c t ? We have shown t h a t i n the p r e s e n c e o f hydrogen donors

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Chemistry and Constitution of Coal

wmTEHURST

11

OXYGEN OH

R-COCS

R-O-R

R-C-R

SULFUR

(§φ Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

R-S-R

(g)

<Ô}-s-<ô> (-s-?)

R-S-S-R

NITROGEN

METALS S A L T S , PORPHYRINS Figure 6.

Functional groups found in coal

COALS OXYGEN CONTENT AS:

SRC

BURNING STAR (BITUMINOUS)

B E L L E AYR (SUD-DITUMINOUS)

B E L L E AYR (400°C,2000pslg )

HYDROXYLIC

(-OH)

2.4

5.6

6.56

CARBOXYLIC

(-COOH)

0.7

4.4

.10

CARBON YLIC

(

0.4

1.0

.09

ETHERIC

( - 0 - )

2.0

0.9

C=0)

.04

Δ HpO

7.4

CO C0

17 3.71

2

TOTAL

OXYGEN

6.3

11.9

18.1

ANALYSIS

ASH BASIS MINERAL

MATTER

5.9 BASIS

16.2 16.0

Gulf Research and Development Company Figure

7.

Distribution

of organic oxygen in coals and SRC (g O /100 g MAF coal) 2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

COKE and ANTHRACITE COAL

Hydrogen Production

Coking

m

—ι Γ"

-Γ

H n-x m

2

+ .9n H 0 + .55n 0 2

- η C0 2

(assume no H l o s t t o coke)

+ C

+ (.9n + .5ra)H

1.2 1.3= 1.4 1.5 HYDROGEN /CARBON MOLE RATIO

2

Figure 8.

T G A , TUA, and DSC of West Kentucky coal

(approximate b a l a n c e based on energy requirements)

n

C H

C Η η m

1.1

Τ

SHALE OIL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

,

„

distitlafe

^

\

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PREMIUM PRODUCTS

ο

i

2

>

Ο Ο

to

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

1.

WHiTEHURST

Chemistry and Constitution of Coal

13

CO

Ο eo

S

-s sο •s ο

ο

eo Ο

1 ο σ>

ε

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

14

ORGANIC CHEMISTRY OF COAL

b i t u m i n o u s c o a l s r e a c t v e r y r a p i d l y , 80% c o n v e r s i o n can be a c h i e v e d i n one minute a t 800°F (16,17). With subb i t u m i n o u s c o a l s , however, a t 800°F the r e a c t i v i t y i s c o n s i d e r a b l y slower, r e q u i r i n g i n the o r d e r o f 31 m i n u t e s t o a c h i e v e about 70% c o n v e r s i o n . In o r d e r t o a c h i e v e h i g h e r c o n v e r s i o n s w i t h subbituminous c o a l s i n s h o r t e r time, t e m p e r a t u r e s o f i n the o r d e r o f 840° can be used, where about 80% c o n v e r s i o n can be a c h i e v e d i n two t o t h r e e m i n u t e s (14). I t s h o u l d be noted, however, t h a t c o n v e r s i o n i n t h i s c a s e i s d e f i n e d as c o n v e r s i o n of c o a l to m a t e r i a l soluble i n p y r i d i n e . Whether c o a l w i l l a c t u a l l y d i s s o l v e or not, under the c o n d i t i o n s o f a l i q u e f a c t i o n , w i l l depend on the n a t u r e o f the s o l v e n t . F o r example, s o l v e n t s h i g h i n p h e n o l s and p o l y a r o m a t i c s p e c i e w i l l t r u l y d i s s o l v e the c o a l at t h e s e short times. S o l v e n t s which c o n s i s t p r i m a r i l y o f h y d r o c a r b o n s w i l l not d i s s o l v e the c o a l u n t i l i t i s c o n v e r t e d i n t o a much more h y d r o c a r b o n - l i k e s p e c i e . To put t h e s e r a p i d c o n v e r s i o n d a t a i n t o p e r s p e c t i v e , one must remember t h a t i n c o n v e r s i o n p r o c e s s e s such as the s o l v e n t r e f i n i n g o f c o a l , a c o n t a c t time o f about 3 m i n u t e s o c c u r s i n the p r e - h e a t e r o f t h a t p r o c e s s . This means t h a t the c o a l w i l l d i s s o l v e , at l e a s t b i t u m i n o u s c o a l s , i n the p r e - h e a t e r , and what i s c a l l e d the d i s s o l v e r i s p r i m a r i l y a r e a c t o r i n which the d i s s o l v e d c o a l i s upgraded. Composition of Coal

Products

The d i s c u s s i o n t h u s f a r was c o n c e r n e d p r i m a r i l y w i t h c o n v e r s i o n o f c o a l t o s o l u b l e form, b u t j u s t what does t h i s s o l u b l e form c o n s i s t o f ? G e n e r a l l y , i t has b e e n customary t o c l a s s i f y the q u a l i t y o f the c o a l p r o d u c t s i n terms o f s o l u b i l i t y c l a s s e s . These c o n s i s t o f hexane s o l u b l e m a t e r i a l s ( o i l s ) , benzene s o l u b l e m a t e r i a l s , which are termed a s p h a l t e n e s , and benzene i n s o l u b l e m a t e r i a l s , which have v a r i e t y o f names b u t we p r e f e r the term a s p h a l t o l s . We have r e c e n t l y d e s c r i b e d the s y s t e m a t i c changes which o c c u r on c o n v e r t i n g c o a l under t y p i c a l s o l v e n t r e f i n i n g c o n d i t i o n s t o the v a r i o u s s o l u b i l i t y c l a s s e s as a f u n c t i o n o f time (18). A g e n e r a l d e s c r i p t i o n i s shown i n F i g u r e 10 f o r subbituminous c o a l . Here i t can be seen t h a t the p r i m a r y p r o d u c t o f c o a l i s p y r i d i n e s o l u b l e , benzene i n s o l u b l e material. These are s u b s e q u e n t l y c o n v e r t e d t o b o t h benzene s o l u b l e and hexane s o l u b l e s p e c i e . The c l a s s i f i c a t i o n o f the p r o d u c t s o f c o a l i n terms o f s o l u b i l i t y , i s not v e r y g r a t i f y i n g , however, from the s t a n d p o i n t o f chemical understanding. Some o f our c h a r a c t e r i z a t i o n work has i n d i c a t e d t h a t s o l u b i l i t y i s somewhat r e l a t e d

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

WHITEHURST

Chemistry and Constitution of Coal

15

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

t o f u n c t i o n a l i t y b u t n o t p a r t i c u l a r l y r e l a t e d t o molecu l a r weight o r a r o m a t i c c o n t e n t . The p r o d u c t s a r e s t i l l h i g h l y complex and many s p e c i e o f s i m i l a r c h e m i c a l f u n c t i o n a l i t y c a n be f o u n d o v e r l a p p i n g i n t h e v a r i o u s solubility classes. We have c o n d u c t e d a c o n s i d e r a b l e amount o f work on the c h a r a c t e r i z a t i o n o f t h e components o f t h e v a r i o u s s o l u b i l i t y c l a s s e s (17-19). These a r e summarized as follows: •

Hexane s o l u b l e f r a c t i o n s ( o i l s ) have l i t t l e o r no f u n c t i o n a l i t y . They c o n s i s t o f hydrocarbons, ethers, t h i o e t h e r s , and n o n - b a s i c n i t r o g e n compounds (in decreasing order). Saturates are predominantly naphthenic. The m o l e c u l a r weight averages ~200-300.

•

Benzene s o l u b l e f r a c t i o n s (asphaltenes) are p r e d o m i n a n t l y m o n o - f u n c t i o n a l compounds. They c o n s i s t o f p h e n o l s o r b a s i c n i t r o g e n compounds and may a l s o contain ethers. The m o l e c u l a r w e i g h t s range from 300-700.

•

Benzene i n s o l u b l e f r a c t i o n s ( a s p h a l t o l s ) have m u l t i p l e f u n c t i o n a l i t y . They c o n s i s t o f p o l y p h e n o l s (up t o 5 OH/molecule) and m u l t i p l e b a s i c n i t r o g e n s o r mixed functionality. M o l e c u l a r w e i g h t s range from 400->2000.

I n a d d i t i o n t o t h e s e h i g h m o l e c u l a r weight p r o d u c t s o f c o a l , one p r o d u c e s h y d r o c a r b o n gases as w e l l as d i s t i l l a t e m a t e r i a l as t h e s e v e r i t y o f t h e r e a c t i o n i s increased. The c o m p o s i t i o n o f t h e d i s t i l l a t e m a t e r i a l which i s g e n e r a l l y u s e d as a r e c y c l e s o l v e n t , h a s been found t o be r e l a t i v e l y simple as shown i n F i g u r e 11. Here i t c a n be seen t h a t t h e s o l v e n t i s composed o f p r i m a r i l y 6 compounds. These a r e n a p h t h a l e n e , m e t h y l n a p h t h a l e n e , phenanthrene, p a r a c r e s o l and e i t h e r biphenyl or diphenyl ether. L o o k i n g once a g a i n a t t h e n o n - d i s t i l l a b l e p o r t i o n o f c o a l p r o d u c t s , we have found t h a t t h e i n i t i a l p y r i d i n e s o l u b l e benzene i n s o l u b l e m a t e r i a l s a r e h i g h e r m o l e c u l a r weight o r h i g h l y a s s o c i a t e d s p e c i e . These are r e l a t i v e l y r a p i d l y c o n v e r t e d t o lower m o l e c u l a r weight m a t e r i a l s i n t h e o r d e r o f 300-600 m o l e c u l a r w e i g h t . We have f u r t h e r c h a r a c t e r i z e d t h e s e n o n - d i s t i l l a b l e p r o d u c t s o f c o a l b y l i q u i d chromatography and s e p a r a t e d them i n t o d i s c r e t e c h e m i c a l c l a s s e s ; t h i s i s

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

ORGANIC CHEMISTRY OF COAL

Figure 11.

Gas chromatogram of solvent-range material of Illinois #6 coal

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

1.

WHTTEHURST

Chemistry and Constitution of Coal

17

d e s c r i b e d elsewhere (14,17-19). A r a t h e r s u r p r i s i n g r e s u l t o f the se s e p a r a t i o n s i s t h a t t h e m o l e c u l a r w e i g h t s o f common f u n c t i o n a l i t y c l a s s e s o f a g i v e n c o a l , were found t o be t h e same independent o f t h e degree o f c o n v e r s i o n , as shown i n F i g u r e 12. The predominant change which o c c u r s t o g i v e lower molecular weights i s the i n t e r c o n v e r s i o n o f the various f u n c t i o n a l i t y t y p e c l a s s e s . The s i g n i f i c a n c e o f t h i s r e s u l t i s that i t indicates that c o a l structures are composed o f r a t h e r s t a b l e n u c l e i which undergo f u n c t i o n a l i t y l o s s w i t h o u t major d i s r u p t i o n . We do n o t w i s h t o imply, however, t h a t t h e s e n u c l e i a r e monodispersed, b u t r a t h e r a r e i n d i c a t i v e o f some common b u i l d i n g b l o c k s from which c o a l i s composed. The m o l e c u l a r weight d i s tribution o f one o f t h e s e f u n c t i o n a l i t y c l a s s e s ( i n t h i s c a s e t h e h e t e r o c y c l i c compounds) from two d i f f e r e n t c o a l s a r e shown i n F i g u r e 13. I would l i k e now t o d i s c u s s t h e a r o m a t i c i t y o f s o l u b i l i z e d c o a l and how i t changes w i t h c o n v e r s i o n under t y p i c a l s o l v e n t r e f i n i n g c o n d i t i o n s . As shown i n F i g u r e 14, t h e a r o m a t i c i t y o f s o l v e n t r e f i n e d c o a l c a n be c o n s i d e r a b l y d i f f e r e n t from t h a t o f t h e p a r e n t c o a l , as i s t h e c a s e f o r subbituminous c o a l . F o r b i t u m i n o u s coal, the aromaticity i s s l i g h t l y higher b u t s t i l l quite s i m i l a r t o that o f the parent c o a l . As t h e c o a l i s c o n v e r t e d , f i r s t t o s o l u b l e form and t h e n t o l e s s f u n c t i o n a l m a t e r i a l , t h e a r o m a t i c i t y s y s t e m a t i c a l l y i n c r e a s e s b o t h f o r t h e c a r b o n and f o r hydrogen, as shown i n F i g u r e s 15 and 16, where t h e a r o m a t i c i t y o f the c o a l i s p l o t t e d versus the percent conv e r s i o n t o s o l u b l e form. The s i g n i f i c a n c e o f t h e s e two f i g u r e s i s t h a t t h e c o n v e r s i o n t o 80% s o l u b l e m a t e r i a l o c c u r s i n as l i t t l e as two t o t h r e e m i n u t e s . Extrapol a t i o n o f t h e a r o m a t i c hydrogen c o n t e n t t o 0% c o n v e r s i o n i n d i c a t e s that f o r t h i s bituminous c o a l the aromatic hydrogen c o n t e n t was o n l y 30%, w h i c h , i n c o n j u n c t i o n w i t h the e l e m e n t a l a n a l y s i s , i n d i c a t e s t h a t t h e a r o m a t i c s a r e highly substituted. A r o m a t i c c o n t e n t , a l t h o u g h somewhat r e l a t e d t o dea l k y l a t i o n o f a r o m a t i c r i n g s , i s p r i m a r i l y due t o t h e conversion o f a l i p h a t i c carbon i n t o aromatic carbon. The c o n c e n t r a t i o n o f m u l t i p l e a r o m a t i c r i n g s were f o u n d by p o l a r o g r a p h i c a n a l y s e s t o i n c r e a s e d r a m a t i c a l l y on extended r e a c t i o n o f t h e c o a l p r o d u c t s (14,17). This i n c r e a s e i n a r o m a t i c c a r b o n c o n t e n t c a n o c c u r b y one o f two p r o c e s s e s , e i t h e r hydrogen e l i m i n a t i o n from h y d r o a r o m a t i c r i n g s o r t h r o u g h rearrangement o f p o l y c y c l i c r i n g s t o more s t a b l e a r o m a t i c r i n g s .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

47 0

A

A

610

960

4

5

7

8

476

309

T

C

T

715

A

and 4 8 1 °

and 3 1 3

HIGH SEVERITY KENTUCKY SRC WILSONVILLE, ALA. T

1290*

T

A

545

470

Τ

440

LOW SEVERITY MONTEREY SRC (AC-58)

Figure 12.

T

A

1

x

Average molecular weight determinations of SESC-SRC

fractions

determina­

determinations

1142

τ 492

487

Τ

432

HIGH SEVERITY MONTEREY SRC (AC-59)

Τ - T e t r a h y d r o f u r a n was used as the s o l v e n t f o r m o l e c u l a r weight t i o n s by vapor p r e s s u r e osmometry.

C - C h l o r o f o r m was used as the s o l v e n t f o r m o l e c u l a r weight by vapor p r e s s u r e osmometry.

300°

T

315

C

LOW SEVERITY KENTUCKY SRC (RUN 10)

3

SESC FRACTION

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

C

C

740

A

580°

630

660

HIGH SEVERITY WYODAK SRC HRI Γ77-114-2Β

ο ο ο

Ο ο >

oo

Chemistry and Constitution of Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

wmTEHURST

SESC

100

20C

300

*0C

MO

600

FIMSA*

F r a c t i o n

70C

3

800

o f Wyodak

9Q0

tOUO

S R C

Figure 13. Molecular weight distribution in a coal liquid fraction. * Field ionization mass spectroscopic analysis. **By vapor phase osmometry.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY

\

} ALIPH

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

#· \

AROM y

- ^

AROM

ALIPH

Λ

• I »'

·

KENTUCKY COAL

WYODAK COAL

"ο—ilr

ALIPH

scale (ppm) AROM*

/I : :

KENTUCKY SRC <WHsonvlllt-SN!352)

WYODAK SRC (HRI-I77-II4-2B)

Figure 14.

CP-

, 3

C N M R specfra of coals and SRCs

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

OF COAL

Chemistry and Constitution of Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

WHTTEHURST

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

22

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

WHTTEHURST

Chemistry and Constitution of Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

-H, 2

23

H2 Elimination

->

,NCH

3

->

Rearrangement

HO i"

HO

I n c o n j u n c t i o n w i t h t h e l o s s o f m o l e c u l a r weight and i n c r e a s e i n a r o m a t i c i t y , the f u n c t i o n a l i t y o f t h e i n i t i a l l y d i s s o l v e d c o a l undergoes major change. Oxygen i s t h e p r i m a r y element o f c o n c e r n as f a r as f u n c t i o n a l i t y and s o l u b i l i t y c l a s s determination. I f one examines t h e e l e m e n t a l c o m p o s i t i o n o f c o a l and p r o d u c t s o f c o a l a t s h o r t and l o n g t i m e s , a r a t h e r i n t e r e s t i n g r e s u l t c a n be found. As shown below f o r e v e r y 100 c a r b o n atoms i n a c o a l , c o n v e r s i o n a t e i t h e r s h o r t o r l o n g time causes e s s e n t i a l l y no change i n t h e c o n t e n t o f n i t r o g e n . The hydrogen c o n t e n t i s s i m i l a r t o t h e p a r e n t c o a l a t s h o r t time, b u t becomes l e s s a t l o n g e r t i m e s . The oxygen c o n t e n t and s u l f u r c o n t e n t s b o t h a r e reduced s l i g h t l y a t s h o r t time b u t a r e s i g n i f i c a n t l y r e d u c e d a t l o n g e r times.

General Monterey C o a l

(mml)

Formula

C ^ ^ g N ^ g O ^ S j ^

Number Heteroatoms/ 100 C 14.9 12.0 7.5

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

24

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

Oxygen i s l o s t p r i m a r i l y as c a r b o n d i o x i d e and water, w i t h s m a l l e r amounts o f c a r b o n monoxide. The r a t e o f oxygen l o s s p a r a l l e l s the r a p i d i n i t i a l d i s s o l u t i o n o f c o a l and r a p i d l o s s o f h i g h m o l e c u l a r weight m a t e r i a l . About 40-50% o f the oxygen i s r e l a t i v e l y easy t o r e move (17). The l o s s o f s u l f u r i s k i n e t i c a l l y p a r a l l e l t o the l o s s o f oxygen as shown i n F i g u r e 17. This might be a n t i c i p a t e d i n view o f the o r i g i n o f the o r g a n i c s u l f u r o f c o a l , which i s b e l i e v e d t o be the r e s u l t o f exchange o f OH o r c a r b o n y l oxygen b y s u l f u r , due t o b i o l o g i c a l a c t i v i t y i n the sediment (20,21). The s i g n i f i c a n c e o f t h i s i s t h a t 40-50% o f the o r g a n i c s u l f u r i s a l s o e a s i l y removed. The r e m a i n i n g s u l f u r i s much more r e s i s t a n t t o a t t a c k and i s p r o b a b l y p r e sent i n h e t e r o c y c l i c r i n g s t r u c t u r e s . Hydrogen Consumption and

Reactive

Moieties

In c o n j u n c t i o n w i t h the l o s s o f oxygen and s u l f u r , as w e l l as m o l e c u l a r weight r e d u c t i o n o f the s o l u b l e c o a l s p e c i e , t h e r e i s hydrogen consumption r e q u i r e d f o r the p r o c e s s . T h i s hydrogen i n t h e c a s e o f s o l v e n t r e f i n i n g i s donated from the s o l v e n t t o the c o a l o r c o a l fragments. I n i t i a l l y , the l o s s o f oxygen r e q u i r e s r e l a t i v e l y l i t t l e hydrogen consumption and i s v e r y c l o s e t o s t o i c h i o m e t r i c r e q u i r e m e n t s (16,17). T h i s i s shown i n F i g u r e 18, where i t can be seen t h a t o n l y a f t e r about 30% o f the oxygen i s l o s t does the hydrogen consumption become g r e a t e r t h a n s t o i c h i o m e t r y . This h y d r o g e n consumption i n e x c e s s o f s t o i c h i o m e t r y i s due p r i m a r i l y t o the f o r m a t i o n o f gaseous p r o d u c t s o r lowe r m o l e c u l a r weight d i s t i l l a t e s such as s o l v e n t and not due t o the i n p u t o f hydrogen i n t o the h i g h e r molecu l a r weight p r o d u c t s o f c o a l . A n o t h e r way t o l o o k a t the c o n v e r s i o n o f oxygen i s t o compare the p r o d u c t c o m p o s i t i o n * o v e r a l l , w i t h the p e r c e n t oxygen removed from the t o t a l p r o d u c t . F i g u r e 19 shows t h a t i n o r d e r t o a c h i e v e maximum s o l u b i l i t y o f the c o a l about 60% o f the oxygen must be lost. A t the same time the SRC y i e l d maximizes. The f o r m a t i o n o f s o l v e n t range m a t e r i a l and l i g h t gases such as methane, t h e n become major p r o d u c t c o n s t i t u e n t s as the oxygen c o n t e n t i s r e d u c e d f u r t h e r . What t h e s e r e s u l t s i n d i c a t e i s t h a t h i g h hydrogen consumpt i o n i s n o t n e c e s s a r y i n o r d e r t o j u s t d i s s o l v e the c o a l o r t o remove a major p o r t i o n o f the oxygen. I n o r d e r t o g a i n an u n d e r s t a n d i n g o f what k i n d s o f r e a c t i o n s can be e n v i s i o n e d t o e x p l a i n the above r e s u l t s , we c o n d u c t e d a s e r i e s o f e x p e r i m e n t s u s i n g model compounds and r e a c t i o n s w i t h t y p i c a l s o l v e n t s

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

WHTTEHURST

Chemistry and Constitution of Coal

2.5

2.0 \

WEST KENTUCKY 1.3

a*

Κ

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

0.5

O.Ol

WYODAK

L

J 6

Figure 17.

!

L

8

wr. %o

I 10

1

I ,

12

Fer cent S in SRC vs. percent Ο in SRC

3.0 h-

/ WYODAK

0.0

0.2

0.4

0.6

0.8

MOLES 0 REMOVED

Figure 18.

Hydrogen consumption vs. moles oxygen removed

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

26

ORGANIC CHEMISTRY OF COAL

f o r c o a l under c o n d i t i o n s o f c o a l l i q u e f a c t i o n . I n t h e s e s t u d i e s we i d e n t i f i e d a number o f c h e m i c a l c l a s s e s w h i c h c o u l d be c o n v e r t e d a t r a t e s t h a t were comparable t o t h o s e o f r a p i d d i s s o l u t i o n o f c o a l (14). These a r e summarized i n F i g u r e 20, where f a s t r e a c t i o n s a r e t h o s e i n which 80% o r h i g h e r c o n v e r s i o n c a n be a c h i e v e d i n t e n m i n u t e s a t 800°F. I t c a n be seen t h a t b e n z y l i c e t h e r s o r b e n z y l i c t h i o e t h e r s c e r t a i n e s t e r s and q u i n o n e s r e a c t r a p i d l y enough t o account f o r t h e v e r y s h o r t c o n t a c t time c o a l d i s s o l u t i o n . I n a d d i t i o n , r i n g s t r u c t u r e s such as d i h y d r o p h e n a n t h r e n e s w i l l r a p i d l y dehydrogenate under t h e same c o n d i t i o n s . By c o n t r a s t w i t h t h e s e r e l a t i v e l y f a s t r e a c t i o n s we have a l s o i d e n t i f i e d a number o f low r e a c t i v i t y s p e c i e which can be r u l e d o u t as b e i n g r e s p o n s i b l e f o r c o a l d i s s o l u t i o n , t h e s e a r e summarized i n F i g u r e 21. Here i t c a n be seen t h a t s t r u c t u r e s such as a r o m a t i c e t h e r s , o r r i n g s t r u c t u r e d e t h e r s , h e t e r o c y c l i c hydrogen compounds, p o l y c o n d e n s e d r i n g s b o t h a r o m a t i c and a l i p h a t i c , have r e l a t i v e l y low r e a c t i v i t y . I f a r o m a t i c r i n g s a r e subs t i t u t e d o n t o a number o f t h e s e s t r u c t u r e s , t h e r e a c t i v i t y increases dramatically. This increase i n react i v i t y with higher aromatic s u b s t i t u t i o n c o u l d p o s s i b l y account a t l e a s t i n p a r t f o r t h e h i g h e r r e a c t i v i t y o f b i t u m i n o u s c o a l s r e l a t i v e t o subbituminous c o a l s . Speculations

on C o a l

Structure

Up t o t h i s p o i n t , I have d i s c u s s e d p r i m a r i l y t h e c h e m i s t r y o f d i s s o l v e d c o a l and how t h e c h e m i c a l n a t u r e o f t h e c o a l p r o d u c t s change w i t h t h e s e v e r i t y o f c o n version. I t s h o u l d be n o t e d t h a t a t v e r y s h o r t c o n t a c t times the i n i t i a l products o f c o a l d i s s o l u t i o n are very s i m i l a r i n b o t h a r o m a t i c i t y and f u n c t i o n a l i t y t o t h a t of the parent c o a l . I w i l l now d i s c u s s how t h i s i n f o r m a t i o n c a n be used t o h e l p g a i n a b e t t e r u n d e r s t a n d i n g o f t h e o r i g i n a l s t r u c t u r e o f p a r e n t c o a l . A number o f workers have attempted t o d e r i v e a r e p r e s e n t a t i v e s t r u c t u r e o f c o a l which i s c o n s i s t e n t i n i t s o b s e r v e d chemistry. One o f t h e f i r s t was t h a t o f P r o f e s s o r G i v e n , shown i n F i g u r e 22. T h i s s t r u c t u r e was n o t i n t e n d e d t o be t h e s t r u c t u r e f o r c o a l b u t m e r e l y t o r e p r e s e n t what k i n d s o f s t r u c t u r e s one s h o u l d e n v i s i o n as c o n s t i t u t i n g c o a l ( 2 2 ) . The s t r u c t u r e i s c o n s i s t e n t w i t h h i g h l y s u b s t i t u t e d a r o m a t i c s , which a r e n o t h i g h l y condensed, w i t h f u n c t i o n a l i t i e s which a r e known t o be p r e s e n t i n c o a l and w i t h i t s e l e m e n t a l c o m p o s i t i o n . A more r e c e n t , more s o p h i s t i c a t e d model, was p r e s e n t e d b y P r o f e s s o r W i s e r (23) and i s g i v e n i n F i g u r e 23. The s i g n i f i c a n c e o f t h i s f i g u r e i s t h e l o c a t i o n o f a number o f

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

27

Chemistry and Constitution of Coal

wmTEHURST

%

SOLUBLE

ο UJ

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

SOLVENT^^

0

2 0

4 0 %

Figure 19.

0

6 0

Θ 0

100

CONVERSION

Product yields vs. percent oxygen conversion for West Kentucky coal

OH

CH

SH

CH,

3

[ri]

<0>-CH -S-<0>

Co]

2

+ CH,

<^^CH ^-C-CH -^-^CO+C0 2

2

[H]

2

+( θ )

H 0 +? 2

[Η]

FRAGMENTS

[Η] ΓοΤοΊ

Figwre 2 0 .

FAS* reactions at

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

800°F

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

28

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

1.

WHiTEHURST

Chemistry and Constitution of Coal

Figure 22.

Figure 23.

Proposed structural elements of coal by Given

Representation of functional groups in coal

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

29

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

30

ORGANIC CHEMISTRY OF COAL

r e l a t i v e l y weak bonds i n d i c a t e d b y arrows which c a n account f o r t h e r a p i d b r e a k u p o f c o a l i n t o s m a l l e r more s o l u b l e fragments. I n view o f t h e p r e v i o u s d i s c u s s i o n o f t h e chemist r y o f t h e s o l v e n t r e f i n i n g o f c o a l and t h e c o m p o s i t i o n and c h e m i c a l n a t u r e o f t h e s o l u b l e p r o d u c t s , i t i s p o s s i b l e to e n v i s i o n the o r i g i n a l structure of c o a l i n a more g r o s s sense as a h i g h l y c r o s s l i n k e d amorphous polymer, which c o n s i s t s o f a number o f s t a b l e aggrag a t e s c o n n e c t e d b y r e l a t i v e l y weak c r o s s l i n k s . As shown i n F i g u r e 24, t h i s h i g h l y c r o s s l i n k e d s t r u c t u r e on r e a c t i o n a t h i g h t e m p e r a t u r e s t h e r m a l l y fragments i n t o r a d i c a l s which i n t h e p r e s e n c e o f hydrogen donor s o l v e n t s a r e capped and appear as s t a b l e s p e c i e . These s p e c i e c o n s i s t o f a g g r a g a t e s o r groups o f a g g r a g a t e s and c o r r e s p o n d t o m o l e c u l a r w e i g h t s i n t h e 300 t o 1000 m o l e c u l a r weight range. I n t h e absence o f hydrogen donor s o l v e n t s , t h e o r i g i n a l r a d i c a l s o r t h e s m a l l e r s o l u b l e s p e c i e may recondense t o form c h a r o r coke. We have attempted i n some o f our c h a r a c t e r i z a t i o n work t o d e r i v e r e p r e s e n t a t i v e s t r u c t u r e s o f such a g g r a g a t e s (14,17-19). Our work c o n s i s t e d o f d e r i v i n g t h e s t r u c tures o f the very i n i t i a l products o f c o a l d i s s o l u t i o n vfaich a r e p y r i d i n e s o l u b l e , benzene i n s o l u b l e m a t e r i a l s which we term a s p h a l t o l s , and r e p r e s e n t m o l e c u l e s which are h i g h i n m o l e c u l a r weight, low i n b o t h a r o m a t i c hydrogen and c a r b o n , and h i g h i n f u n c t i o n a l i t y , i n p a r t i c u l a r phenols. A r e p r e s e n t a t i v e example o f such s t r u c t u r e i s g i v e n i n F i g u r e 25, f o r t h e a s p h a l t o l der i v e d from a b i t u m i n o u s West Kentucky c o a l (18). A s t r u c t u r e such as t h i s s h o u l d n o t be c o n s i d e r e d as t h e s t r u c t u r e f o r a s p h a l t o l s , but merely represent a k i n d o f s t r u c t u r e , i n c l u d i n g r i n g s t r u c t u r e s as w e l l as f u n c t i o n a l i t y , t h a t one would e x p e c t t o f i n d i n t h e s e i n i t i a l p r o d u c t s o f c o a l and t h e r e f o r e r e f l e c t t h e structure of the c o a l i t s e l f . As t h e s e i n i t i a l p r o ducts o f c o a l are f u r t h e r converted, they increase i n a r o m a t i c c o n t e n t and l o s e f u n c t i o n a l i t y , becoming more hydrocarbon l i k e . The r i n g s t r u c t u r e s as we d i s c u s s e d p r e v i o u s l y , remain r e l a t i v e l y i n t a c t and t h e r e f o r e t h e l e s s p o l a r l e s s f u n c t i o n a l m a t e r i a l s i s o l a t e d from c o a l l i q u i d s can s t i l l r e f l e c t the s t r u c t u r e o f the o r i g i n a l coal. We have attempted t o show t h i s i n F i g u r e 26, where t h e h e t e r o c y c l i c r i n g s t r u c t u r e f r a c t i o n s o f two b i t u m i n o u s c o a l s and a subbituminous c o a l a r e shown f o r comparison. Here i t c a n be seen t h a t t h e b i t u m i n o u s c o a l c o n s i s t s o f more p l a n a r r i n g s t r u c t u r e s , whereas the subbituminous c o a l c o n t a i n s as an i n t e g r a l p a r t a h i g h l y condensed a l i p h a t i c s t r u c t u r e ( 1 4 ) . We do n o t know i f t h i s p a r t i c u l a r s t r u c t u r e i s predominant among

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

1.

WHTTEHURST

Chemistry and Constitution of Coal

Char or Coke Figure 25.

Formal average structure for West Kentucky asphaltol (SESC 8)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

31

32

ORGANIC CHEMISTRY OF COAL

C O A L Kentucky

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

Compos ition

C

|00 82 |.7°9.4 H

N

No. polycondensed saturated rings/100 c

av. 4

in Fr. 3 SRC short contact time

2

H consumption for 100% conversion short contact time g/100 g coal long contact time

Wyodak

Monterey C

1 0 0 8 8 1 . 6 ° 13.2 1.74 H

N

S

C

IOO 86 H

av. 6

a v . 10

0.43

0.63

0. 89

0. 96

2.03

2.80

S t r u c t u r e Fraction #3 short contact time rwi

Figure 26.

Skeletal structures in various coals

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Joy

N O

I8

1.

WHiTEHURST

Chemistry and

Constitution of Coal

33

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

subbituminous c o a l s o r i s s p e c i f i c t o the subbituminous c o a l t h a t we have examined. However, i t does show major r i n g s t r u c t u r a l d i f f e r e n c e s between the v a r i o u s c o a l s t h a t we have i n v e s t i g a t e d . In c o n c l u s i o n I would l i k e now t o m o d i f y s l i g h t l y my i n i t i a l s t a t e m e n t s as t o what i s b e l i e v e d about the c h e m i s t r y and c o n s t i t u t i o n o f c o a l . These c o n c l u s i o n s are summarized below. •

The a r o m a t i c i t y o f c o a l v a r i e s w i t h rank and can be as low as ~40% f o r subbituminous c o a l s .

•

There i s l i t t l e e v i d e n c e f o r h i g h l y condensed a r o m a t i c r i n g s i n c o a l o r the i n i t i a l l i q u e f a c t i o n p r o d u c t s . Mono-diaromatic r i n g s predominate.

•

Subbituminous c o a l c o n t a i n s s i g n i f i c a n t amounts o f p o l y c y c l i c a l i p h a t i c r i n g s .

•

High a r o m a t i c i t y i n c o a l products i s the r e s u l t o f the p r o c e s s e s b e i n g used t o c o n v e r t c o a l and not an i n t r i n s i c p r o p e r t y o f the s t a r t i n g m a t e r i a l .

•

C o a l i s e x t r e m e l y r e a c t i v e i n the p r e s e n c e o f hydrogen donors and "liquifies" easily.

•

A l t h o u g h hydrogen p r e s s u r e g i v e s s l i g h t i n c r e a s e s i n y i e l d at short times, i t i s not a n e c e s s i t y f o r c o a l c o n v e r s i o n t o s o l u b l e form. Temperatures above 750°F are n e c e s s a r y f o r r a p i d c o n v e r s i o n .

•

O r g a n i c s u l f u r and oxygen f u n c t i o n a l i t i e s have s i m i l a r c h e m i c a l b e h a v i o r . About 40-50% o f each element can be e a s i l y removed. H i g h e r c o n v e r s i o n s o c c u r much more s l o w l y .

•

Coal l i q u e f a c t i o n (conversion to soluble form) r e q u i r e s v e r y l i t t l e hydrogen consumption (~.3-.5% H).

Acknowledgment s Much o f the work p r e s e n t e d h e r e was c o n d u c t e d under a program j o i n t l y sponsored b y EPRI and M o b i l R e s e a r c h and Development C o r p o r a t i o n . Co-workers i n t h i s p r o j e c t are J . J . D i c k e r t , M. F a r c a s i u , and T.O. Mitchell. T e c h n i c a l a s s i s t a n c e was p r o v i d e d by B.O. Heady and G. O d o e r f e r .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

34

Literature Cited 1. 2. 3.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

4. 5. 6.

7. 8. 9. 10. 11. 12. 13. 14.

15.

16.

17.

Francis, W., "Coal, It's Formation and Composi­ tion", Edward Arnold (Publishers) L t d . , London, 1961. Given, P. Η., Personal Communication. Chen, A. S., "Flavanoid Pigments in the Red Man­ grove, Rhizophora mangle L . of the Florida Ever­ glades and in the Peat Derived From it", PhD Thesis, The Pennsylvania State University, Septem­ ber, 1971. Given, P. Η., Bimer, J., Raj, S., Oxidative Study of the Structure of V i t r i n i t e s , presented at the Fuel Division Chicago ACS Meeting, August 1977. Reference 1, pp. 717-755. Winans, R. E., Hayatsu, R., Scott, R. G . , Moore, L. P. and Studier, Μ. Η., "Examination and Com­ parison of Structure, Lignite, Bituminous, and Anthracite Coal", presented at the SRI Coal Chemistry Workshop, Menlo Park, California, August 1976. Chakrabartty, S. K. and Berkowitz, Ν . , Fuel (1974) 53, 240. Deno, N. C . , Fuel, in press. Hirsch, P. Β . , Proc. Inst. Fuel Conf., "Science in the Use of Coal", Sheffield Eng. 1958, p. A-29. Ergun, S. and Tiensuu, V . , Nature (1959), 183, 1668. Acta Cryst. (1959), 12, 1050. Friedel, R. A. and Queiser, J. Α . , Fuel (1959), 38, 369. Given, P. H. and Peover, Μ. Ε . , Fuel (1960), 39, 463. Pines, Α . , Gibby, M. G. and Waugh, J . S., J . Chem. Phys. (1973), 59, 569. Whitehurst, D. D., Farcasiu, Μ., Mitchell, T. O. and Dickert, J. J., "The Nature and Origin of Asphaltenes in Processed Coals", EPRI AF-480, Project 410-1, Annual Report July 1977. Ruberto, R. G . , "Oxygen and Oxygen Functional Groups in Coal and Coal Liquids" presented at the EPRI Contractor's Conference, Palo Alto, C a l i ­ fornia, May 1977. Whitehurst, D. D. and Mitchell, Τ. Ο., "Short Contact Time Coal Liquefaction"; "Liquid Fuels From Coal", R. T. Ellington, E d . , Academic Press, New York, 1977, p. 153. Whitehurst, D. D . , Farcasiu, M. and Mitchell, T . O . , "The Nature and Origin of Asphaltenes in Processed Coals", EPRI AF-252, Project 410-1, Annual Report, February 1976.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

WHITEHURST

18. 19. 20. 21. 22. 23.

Chemistry and Constitution of Coal

35

Farcasiu, Μ., Mitchell, T. O. and Whitehurst, D.D., Chem Tech (1977), 7 680. Farcasiu, Μ., Fuel (1977), 56, 9. Orr, W., "Sulfur", Handbook of Geochemistry, Vol. II/4, Springer-Verlag Berlin-Heidelburg. New York. Neavel, R., "Sulfur in Coal; It's Distribution in the Seam and in Mine Products", PhD Thesis, The Pennsylvania State University, 1966. Given, P. Η., Fuel (1960), 31, 147. Wiser, W., preprints Fuel Division ACS Meeting, 20(2), 122 (1975). March 6, 1978

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch001

RECEIVED

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2 Polymer Structure of Bituminous Coals

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

JOHNW.LARSEN and JEFFREY KOVAC Department of Chemistry, University of Tennessee, Knoxville, TN 37916

1-3

Many structures have been proposed for bituminous coals. The only point of agreement is that these coals contain varying amounts of small molecules M ( W < 1000) which are extractable and that they also contain a mixture of larger molecules. While agreement is not universal, most coal chemists would accept van Krevelen's statement that "coal has a polymeric character", that it consists of macromolecules. There is no agreement about the size distribution of the macromolecules and their degree of cross linking. Consideration of the bulk, plastic properties of coals leads not only to the conclusion that coal is a cross linked macromolecular network, but also provides estimates of the number average molecular weight per cross link (Mc ) . It is convenient to consider coal structure on several levels. Following the protein chemists (at quite a distance) we will define three structural levels. This division has been done on the basis of experimental convenience but also provides a very useful conceptual framework allowing the complete structure to be treated as the sum of three nearly independent levels of description (substructures). This approach is much more useful than trying to solve the whole structure all at once. Different techniques and approaches are usually used to gain information about each of the structural levels. We find this division aids greatly in sharpening our thinking about coal structure. 4

F i r s t order s t r u c t u r e i s the s i z e d i s t r i b u t i o n of the macromolecules and molecules i n c o a l and the degree of cross l i n k i n g . The topology of the macromolecular network a l s o f a l l s i n t h i s category as does the amount and i d e n t i t y of the smaller v o l a t i l e or e x t r a c t a b l e molecules present i n the c o a l . While we know a good b i t about the smaller, e x t r a c t a b l e molecules i n c o a l i t has not been recognized that a s i g n i f i c a n t body of i n f o r m a t i o n l e a d i n g to a coherent p i c t u r e of the f i r s t order s t r u c t u r e of bituminous c o a l s e x i s t s . I n t h i s paper we attempt

0-8412-0427-6/78/47-071-036$05.00/0 ©

1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

2.

LARSEN AND KOVAC

37

Structure of Bituminous Coals

to sketch t h i s f i r s t order s t r u c t u r e . Second order s t r u c t u r e i s the chemical i d e n t i t y of the cross l i n k s and the s t r u c t u r e s of the carbon s k e l e t o n of c o a l . For example, consider the view that the macromolecules comprising bituminous c o a l s are composed of p o l y c y c l i c aromatic and hydroaromatic u n i t s l i n k e d together by methylene b r i d g e s and ether l i n k a g e s . The secondary s t r u c t u r e would then be the i d e n t i t y and q u a n t i t y of the v a r i o u s l i n k s between the aromatic and hydroaromatic u n i t s as w e l l as the average and extreme s t r u c t u r e s (carbon s k e l e t o n only) of those hydroaromatic u n i t s . Perhaps i t i s worth taking a l i t t l e time to deplore the current emphasis on "average" s t r u c t u r e s . T h i s emphasis i s understandable; average s t r u c t u r e s are so easy to d e r i v e that even a computer can do i t and they provide a convenient c r u t c h when one wants to draw a c o a l s t r u c t u r e . However, f o r most purposes, a knowledge of the extremes of the range of s t r u c t u r e s present w i l l be much more u s e f u l i n p r e d i c t i n g the chemical behavior of coals. F i n a l l y , the t h i r d order s t r u c t u r e of c o a l i s the nature and d i s t r i b u t i o n of the f u n c t i o n a l groups. This needs l i t t l e comment or explanation. Our knowledge of t h i s area i s more complete than the other two, but l a r g e holes remain. Superimposed on a l l of t h i s i s the p h y s i c a l s t r u c t u r e of c o a l , the Neavel f r u i t c a k e . — Each maceral w i l l have f i r s t , second, and t h i r d order s t r u c t u r e . Each c o a l w i l l be a d i f f e r e n t mixture of macérais. F a c t o r s such as pore s t r u c t u r e w i l l have a strong e f f e c t on observed r e a c t i v i t y . The Nature of the Macromolecular Network. In t h i s paper we are concerned only w i t h f i r s t order s t r u c t u r e . We begin by c o n s i d e r i n g the time dependent response of bituminous coals to a constant s t r e s s and show that t h i s behavior i s cons i s t e n t only w i t h bituminous c o a l being a cross l i n k e d , three dimensional macromolecule. I f a cross l i n k e d polymer network i s subjected to a s t r e s s , i t w i l l deform u n t i l i t reaches the l i m i t set by the cross links. Chains w i l l be s t r e t c h e d and s t r a i g h t e n e d as the m a t e r i a l deforms, but the presence of covalent cross l i n k s places a l i m i t on t h i s deformation. Thus, a p l o t of s t r a i n (eg. length of a piece of c o a l under tension) vs_ time w i l l i n c r e a s e then l e v e l out. Furthermore, when the s t r e s s i s removed, the polymer w i l l r e t u r n to i t s o r i g i n a l dimensions. I f the macromolecules are entangled or h e l d together by weak f o r c e s , there w i l l be no i n t e r n a l l i m i t on the flow and the deformation w i l l continue to i n c r e a s e w i t h time. Thus w i t h a polymer which i s not cross l i n k e d a constant f i n i t e value w i l l not be reached and the s t r a i n w i l l not be r e c o v e r a b l e . Very high entangled m a t e r i a l s may be e x c e p t i o n a l , but given the h i g h l y planar s t r u c t u r a l u n i t s i n c o a l t h i s seems most u n l i k e l y . There i s some data i n the l i t e r a t u r e d e s c r i b i n g the time ç 1 7

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

38

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

2.

LARSEN AND KOVAC

Structure of Bituminous Coals

39

dependence of s t r e s s on s t r a i n f o r c o a l s . Much of i t i s o l d work done to study the behavior of c o a l i n v a r i o u s processing operations, such as g r i n d i n g . — The r e s u l t s o f t e n have not been completely described and the work o f t e n was done on l a r g e samples and so some of the behavior might be due t o p h y s i c a l flaws such as cracks and not be r e p r e s e n t a t i v e of the i n t r i n s i c molecular s t r u c t u r e of the c o a l . The best study i s that of Morgans and Terry and the s t r a i n - t i m e curve f o r Barnsley Hards bituminous c o a l i s shown i n F i g . 1.— Only 0.5% of the t o t a l s t r a i n was i r r e c o v e r a b l e . A C l a r a i n showed 1% unrecoverable s t r a i n . — These data a r e q u i t e c o n s i s t e n t w i t h bituminous c o a l being c o v a l e n t l y c r o s s - l i n k e d macromolecules i n which hydrogen bonding and van der Waals f o r c e s c o n t r i b u t e i n only a small way to macromolecular a s s o c i a t i o n . This s t r u c t u r e i s a l s o i n c o n s i s t e n t with pure entanglement model. However, i f there i s a mixture of c r o s s - l i n k s and entanglements, measurements such as these cannot d i s t i n g u i s h t h i s from a cross l i n k e d s t r u c t u r e . I f there a r e enough chemically bonded cross l i n k s t o complete the polymer network, the modulus w i l l be increased by entanglements and both s t r u c t u r e s i n F i g . 2 w i l l behave the same i n a l i n e a r compression or extension experiments.

Figure 2.

Entanglement and cross-linked networks

The p r i n c i p l e p o i n t here i s that bituminous c o a l s a r e c o v a l e n t l y cross l i n k e d macromolecules. Weak a s s o c i a t i v e f o r c e s such as hydrogen bonds and van der Waals i n t e r a c t i o n s cannot e x p l a i n the r e s u l t s of these experiments. Average Molecular Weight Per Cross L i n k . Having e s t a b l i s h e d that c o a l i s a cross l i n k e d macromolecule, the next step i s to determine the frequency of the cross l i n k s . There a r e two independent approaches which can be used. The f i r s t i s to u t i l i z e data from s o l v e n t s w e l l i n g of c o a l and the

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

40

ORGANIC CHEMISTRY OF COAL

second i s to use the moduli derived from the behavior of the polymer under s t r e s s to c a l c u l a t e the number average molecular weight per cross l i n k (M ) . I f the macromolecules i n c o a l are cross l i n k e d to form a network, i t i s p o s s i b l e to use a q u a n t i t a t i v e model of the e l a s t i c p r o p e r t i e s of a polymer network to o b t a i n an estimate of the average frequency of the cross l i n k s . For an i s o t r o p i c network only one parameter, the e l a s t i c modulus, c o n t r o l s the p h y s i c a l p r o p e r t i e s of the network. This parameter can be measured by any one of a v a r i e t y of experiments. Data are a v a i l a b l e f o r solvent s w e l l i n g and mechanical measurements of Young's modulus of bituminous c o a l s so these experiments w i l l be used as inde­ pendent methods of determining the e l a s t i c modulus. I t should be emphasized that the two experiments are measuring e s s e n t i a l l y the same q u a n t i t y . In t h i s paper the simplest s t a t i s t i c a l theory of polymer network e l a s t i c i t y * w i l l be used to c a l c u l a t e the number average molecular weight per cross l i n k (M ) from the two d i f f e r e n t kinds of measurements. Before p r e ­ senting the experimental data we w i l l d e s c r i b e the s t a t i s t i c a l theory of polymer network emphasizing the p h y s i c a l model on which i t i s based and presenting the equations necessary to c a l c u l a t e M . The i n t e r e s t e d reader w i l l f i n d a l u c i d e x p o s i t i o n of the subject of polymer network e l a s t i c i t y i n The Physics of Rubber E l a s t i c i t y by L.R.G. T r e l o a r . — The s t a t i s t i c a l theory of polymer network e l a s t i c i t y assumes that the e l a s t i c r e s t o r i n g f o r c e i n a polymer network r e s u l t s from s t r e t c h i n g each chain i n the network from i t s most probable (equilibrium) conformation to a l e s s probable (stretched) conformation. Only the entropie f a c t o r s are considered, the i n t e r m o l e c u l a r f o r c e s are ignored. For the r e l a t i v e l y long chains found i n many polymers (eg. n a t u r a l rubber) i t i s safe to assume that the p r o b a b i l i t y of any chain conformation i s given by a Gaussian d i s t r i b u t i o n . — The entropy i s then given by Boltzmann's formula

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

1 1

1 2

S = -k In Ρ

(1)

where Ρ i s the p r o b a b i l i t y , and the f o r c e (f) i s obtained by d i f f e r e n t i a t i o n with respect to length (1), f = - | f

(2)

I t i s a l s o assumed that each chain i n the network c o n t r i b u t e s independently to the f o r c e . P h y s i c a l l y t h i s means that entangle­ ments between chains are not important and that i n the model chains are allowed to pass through each other as the network i s extended. T h i s i s sometimes c a l l e d the phantom chain assumption. With these assumptions one can d e r i v e s t r e s s - s t r a i n r e l a t i o n s h i p s f o r v a r i o u s experiments. For example, f o r a sample extended i n one dimension by a f a c t o r

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2.

LARSEN AND KOVAC

41

Structure of Bituminous Coals

χ -

s t r a i n e d length unstrained

length 2

f = G (λ - λ " ) where G i s the e l a s t i c

(3)

(shear) modulus

f

G =

W

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

C

In eq. (4) ρ i s the d e n s i t y , R the gas constant, Τ the absolute temperature and M the average molecular weight per cross l i n k . G appears as the s i n g l e e l a s t i c constant i n a l l s t r e s s - s t r a i n measurements. Since p, R, and Τ are a l l experimental q u a n t i t i e s any measurement of G allows a c a l c u l a t i o n of M . A convenient method of determining M i s 6y e q u i l i b r i u m solvent s w e l l i n g . I f a polymer network i s brought i n t o contact with a good s o l v e n t , the solvent w i l l be absorbed by the network u n t i l the s w e l l i n g pressure i s e x a c t l y balanced by the e l a s t i c f o r c e of the network. Using the s t a t i s t i c a l theory of polymer network e l a s t i c i t y and the Flory-Huggins theory of polymer s o l u t i o n s , the f o l l o w i n g equation can be d e r i v e d . — M

c

=

P

I 2

V

V

2

1

t-

l n

1

V

( - 2

)

V

~2

"

x

V

2

]

( 5 )

where p i s the o r i g i n a l d e n s i t y of the polymer, V the molar volume of the s o l v e n t , V the volume f r a c t i o n of the polymer at e q u i l i b r i u m , and χ the F l o r y i n t e r a c t i o n parameter r e l a t e d to the heat of t r a n s f e r of solvent from pure solvent to the pure polymer i n u n i t s of k T . — χ must be determined experimentally but given χ, then M i s easy to o b t a i n from e q u i l i b r i u m swel­ ling. One measurement of solvent s w e l l i n g was made by Sanada and H o n d a — who studied the s w e l l i n g of a number of Japanese c o a l s i n p y r i d i n e a f t e r e x t r a c t i n g them with p y r i d i n e . The choice of solvent i s not a good one s i n c e some of i t i s incorporated i n t o the c o a l . — Unfortunately a numerical e r r o r was made i n calculating M so the values shown i n the paper are i n c o r r e c t . The c o r r e c t values f o r the molecular weights are given i n Table 1. The r e s u l t s are numerically reasonable and behave as expected. The sudden drop with high rank coals (Yatake) i s expected, due to the approach of a more graphite l i k e , more h i g h l y cross l i n k e d s t r u c t u r e . The general increase i n M from low to high rank (excluding a n t h r a c i t e s ) can be a s c r i b e d £o the presence of l a r g e r molecules assembled together to form the macromolecules or to fewer cross l i n k s i n the higher rank c o a l s . The f i r s t explanation i s more i n tune with c u r r e n t thought. A rather d i f f e r e n t a p p l i c a t i o n of the same p r i n c i p l e i s contained i n a paper by K i r o v et a l . — They studied the e q u i l i b r i u m s w e l l i n g or three c o a l s by 17 s o l v e n t s . In t h i s way 2

2

C

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

42

ORGANIC CHEMISTRY OF COAL

Table I .

Average Molecular Weight per Cross Link i n Some Japanese Coals

Coal

% C

% H

M c

65.1

5.0

1190

Nakago

74.3

5.3

684

Takamatsu

79.0

5.0

832

Bibai

80.9

5.9

825

Ashcbetsu

81.1

5.5

1120

Yubari - I

84.9

6.2

1640

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

Odaira

Yubari - I I I

85.2

6.3

1500

Hoshima

86.6

5.6

1840

Yatake

88.7

4.4

Hongei

93.0

3.3

a)

assuming χ = 0.8

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

49.^

2. LARSEN AND KOVAC

Structure of Bituminous Coals

43

they were able to c a l c u l a t e the best values of χ and V to f i t t h e i r data (V i s the molecular volume per cross l i n k ) ? T h e i r values of V were converted to M by m u l t i p l y i n g by an estimated d e n s i t y f o r t h e s e c o a l s of 1.3. 0

Table I I .

C

Average Molecular Weight per Cross L i n k f o r Some A u s t r a l i a n Coals

Coal

M

% H

% C

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

c Hebe

75.9

4.5

1530

Greta

82.4

6.2

1200

Bulli

88.2

5.1

522

The agreement between the two s e t s of r e s u l t s i s s u r p r i s i n g l y good. The drop o f f a t very high rank i s reproduced and the order of magnitude of the M values i s the same. T h i s s t r o n g l y supports the n o t i o n that these values a r e reasonable. Values of M can a l s o be c a l c u l a t e d from measurements of the mechanical p r o p e r t i e s of c o a l . From s t u d i e s c a r r i e d out by van K r e v e l e n * i t i s c l e a r that the shear modulus G i s constant a t about 1.6 χ 1 0 dyne/cm f o r c o a l s having between 82 and 92% carbon. A f t e r t h i s i t r i s e s s h a r p l y , as expected due to the r a p i d l y i n c r e a s i n g cross l i n k i n g i n the a n t h r a c i t e s and n e a r - a n t h r a c i t e s . Using t h i s value f o r G, and assuming ρ = 1.3g. cm" , M = 2 . The G values used here were d e r i v e d from sound v e l o c i t y measurements. Bangham and M a g g s — have reported values f o r Young's Modulus f o r three c o a l s measured by compression. For a cross l i n k e d polymer which undergoes no volume change on compression, the shear modulus i s 1/3 Young's modulus. - - Table I I I contains t h e i r data and the c a l c u l a t e d values f o r M . The r e s u l t s are a l s o very s m a l l . Other values f o r Young's modulus f o r bituminous c o a l s can be found i n the literature. A l l a r e s i m i l a r and g i v e very low values f o r M^. 1 7

1 8

1 0

2

3

5

LZ

Table I I I .

Values f o r M C a l c u l a t e d from the Young's Modulus of Bangham and Saggs—

Coal

Young's Modulus 2 (dyne/cm )

Welsh A n t h r a c i t e Welsh Steam Coal Northumberland House Coal The

40 χ 1 0

9

7 χ 10

9

q

20 χ 10

Shear Modulus 2 (dyne/cm ) 13 χ 1 0

9

2.3 χ 1 0

9

M

c

(g/mole)

ç 6.7 χ 10

2.5 14

4.8

2 3 10 - 10 discrepancy i n M^ between the solvent s w e l l i n g

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

44

ORGANIC CHEMISTRY OF COAL

and the s t r e s s - s t r a i n measurements must be i n v e s t i g a t e d . Both solvent s w e l l i n g and the s t r e s s - s t r a i n measurements give i n f o r ­ mation about the same property of the network, the e l a s t i c modulus. This modulus i s then used to c a l c u l a t e Μ , using the same model i n both cases. This descrepancy must be due to experimental d i f f e r e n c e s and not to some f a i l u r e of the model. There must be d i f f e r e n t f a c t o r s operating i n the two types of experiments. In some polymer systems, s t r e s s induced c r y s t a l ­ l i z a t i o n w i l l produce a l a r g e modulus and t h e r e f o r e a small value of M · Perhaps an increase i n i n t e r m o l e c u l a r i n t e r a c t i o n s due to the increased order i n u n i d i r e c t i o n a l s t r e s s i s worth i n v e s t i g a t i n g . One sure source of some of the descrepancy' i s that extracted coals were used f o r the solvent s w e l l i n g and unextracted c o a l s were used i n the s t r e s s - s t r a i n measurements. The presence of small molecules w i t h i n the polymer network w i l l have s e v e r a l e f f e c t s ; the density of the system w i l l change, and small molecules w i l l occupy volume i n the network thus h i n d e r i n g the i n t e r n a l motions of the chains. The h i n d e r i n g of the motion w i l l tend to increase the modulus of the network and hence lower the apparent molecular weight. We propose two q u a l i t a t i v e arguments to e x p l a i n part of the discrepancy. 1) Swollen network theory Consider the unextracted c o a l to be a swollen polymer network. For concreteness assume a t y p i c a l value of 30% e x t r a c t a b l e m a t e r i a l and 70% network m a t e r i a l . According to the simple theory of rubber e l a s t i c i t y the modulus of a swollen rubber i s given by

G' =

ψ

V f (6) c where V i s the volume f r a c t i o n of the network and ρ i s the density of the unswollen r u b b e r . — I f one d i d not consider the e f f e c t of s w e l l i n g than the modulus would be given by f

2

G = ψ (7) M c G (or G') i s an experimental quantity and we are i n t e r e s t e d i n the values of M obtained from d i f f e r e n t i n t e r p r e t a t i o n s of G. Hence, we equate the r i g h t hand sides of (1) and (2) pRT p'RT 1/3 M M 2 c c (8) =

f

Μ·

C _

P'VJ

/

3

£

Μ

" ρ c The r a t i o MVM represents the r a t i o of the true to the apparent M ? fy . i s always l e s s than u n i t but f o r V = 0.7, V| = 0.9 so V| can be assumed to be near one. The question 1

c

3

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2. LARSEN AND KOVAC

Structure of Bituminous Coals

then i s the change i n d e n s i t y with s w e l l i n g . I f upon e x t r a c t i n g the c o a l there i s n e g l i g i b l e volume change, then the swollen density p' w i l l be greater than the unswollen d e n s i t y p. To get an estimate, assume u n i t d e n s i t y of the swollen network, equal d e n s i t i e s of network and e x t r a c t a b l e m a t e r i a l and no change of volume upon e x t r a c t i n g . Then f o r 70% network we obtain M

1 / 3

c K0.7) M 0.7 c Hence the true molecular weight w i l l be l a r g e r than the apparent M . (2) Intermolecular O b s t r u c t i o n s . The theory here was developed by J . L. Jackson and co-workers. I t i s based on the n o t i o n that the polymer network i s excluded from p a r t of the volume a v a i l a b l e to i t . The " i n t e r m o l e c u l a r o b s t r u c t i o n s " are taken i n t o account by means of a s i t e f r a c t i o n occupied by the polymer on a l a t t i c e . A smaller s i t e f r a c t i o n represents a l a r g e r number of obstruc­ tions. In the improved theory Jackson obtains the f o l l o w i n g s t r e s s - s t r a i n r e l a t i o n s h i p f o r l i n e a r extension. 1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

±

2

β

Ζ

7

/

2 1 9 2 2

C

This i s eq. (18) i n Jackson's p a p e r . — f i s the s i t e f r a c t i o n and M the number of segments between cross l i n k s . I t i s harder to compare the moduli here because of the form of the equation. We w i l l d e f i n e the modulus at a p a r t i c u l a r s t r a i n as

c c To o b t a i n an estimate of the e f f e c t s of the s i t e f r a c t i o n we w i l l solve eq. (5) f o r v a r i o u s values of f f o r the s p e c i a l case

pRT M

=

100

λ

=

1.1

Jackson c a l c u l a t e s f - 0.95 - 0.98 f o r t y p i c a l rubbers so we w i l l assume that i n the obstructed network f = 0.95 and w i l l c a l c u l a t e the change i n f o r v a r i o u s degrees of e x t r a c t i o n .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

45

46

Table

ORGANIC CHEMISTRY OF COAL

4.

Values of M

c

f o r Various S i t e F r a c t i o n s

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

Site Fraction (f)

M

c

0.95

5.61

0.85

4.03

0.75

3.15

0.65

2.51

The t a b l e shows c l e a r l y that f o r a f i x e d modulus the apparent chain l e n g t h must increase as the number of o b s t r u c t i o n s i n c r e a s e s . I f we consider the e x t r a c t e d c o a l to have a s i t e f r a c t i o n of 0.7 and the unextracted c o a l to have a s i t e f r a c t i o n of 0.95 then there w i l l be a f a c t o r of two d i f f e r e n c e i n the apparent M . Both She arguments developed here are q u a l i t a t i v e but they both show that the molecular weight d e r i v e d from the simple theory f o r the unextracted c o a l i s probably smaller than the r e a l M · Using the Jackson theory one obtains at l e a s t a f a c t o r of two d i f f e r e n c e . The explanations given here are based on simple models and are meant only to be suggestive. The very l a r g e modulus observed i n l i n e a r extension experiments could a l s o be due to i n t e r m o l e c u l a r f o r c e s not accounted f o r i n the s t a t i s t i c a l theory. For example, Su and Mark and co-workers have r e c e n t l y determined that the l a r g e i n c r e a s e i n modulus at high extension of rubbers i s due to s t r e s s - i n d u c e d c r y s t a l ­ l i z a t i o n . — A s i m i l a r phenomenon could occur i n the unextracted c o a l s . A proper r e s o l u t i o n of the discrepancy must come from a systematic study of the molecular weight of e x t r a c t e d c o a l s by both methods. Use of the S t a t i s t i c a l Model. In t h i s paper the s t a t i s t i c a l theory of polymer network e l a s ­ t i c i t y has been used to c a l c u l a t e the average molecular weight per cross l i n k i n v a r i o u s c o a l s from experimental data on s o l ­ vent s w e l l i n g and mechanical behavior. Although the numerical values f o r M obtained from the solvent s w e l l i n g data are q u i t e reasonable, Ehey should only be regarded as order of magnitude estimates because the assumptions u n d e r l y i n g the s t a t i s t i c a l theory are probably not f u l f i l l e d i n the c o a l s t r u c t u r e . Some of the assumptions w i l l be discussed i n the f o l l o w i n g paragraphs along with the p o s s i b i l i t y of c o r r e c t i n g them. The primary assumption of the s t a t i s t i c a l theory i s that the chains obey Gaussian s t a t i s t i c s , that i s , that the proba­ b i l i t y d i s t r i b u t i o n of the end-to-end d i s t a n c e (R) has the form P(R) = constant χ e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

2.

LARSEN AND KOVAC

Structure of Bituminous Coals

47

I t i s easy to show that any chain w i l l obey Gaussian s t a t i s t i c s i f i t i s both long and f l e x i b l e . — The chains i n the c o a l network are u n l i k e l y to be e i t h e r long or f l e x i b l e . The molecu l a r weights obtained are of the order of 1000 which correspond to 10-15 aromatic r i n g s per c h a i n . A chain composed l a r g e l y of fused aromatic r i n g s i s b e t t e r c h a r a c t e r i z e d as short and stiff. A simple modified Gaussian theory i s c u r r e n t l y being developed to t r y to more a c c u r a t e l y represent the c o a l n e t w o r k . — P r e l i m i n a r y c a l c u l a t i o n s i n d i c a t e that M w i l l be l a r g e r by approximately a f a c t o r of two using the modified Gaussian model. A f u r t h e r and more d i f f i c u l t problem i s the assumption that the chains a c t independently. Entanglements and i n t e r molecular f o r c e s which tend to i n c r e a s e the modulus could w e l l be important as w e l l as "loose-end" c o r r e c t i o n s which tend to decrease the modulus. The phenomenon of s t r e s s induced c r y s t a l l i z a t i o n might a l s o be found. Developing a model to account f o r cooperative network e f f e c t s w i l l be d i f f i c u l t . In s p i t e of these drawbacks, the r e s u l t s of a p p l y i n g t h i s model to c o a l are reasonable, and at l e a s t a good beginning i n our attempts to determine the f i r s t order s t r u c t u r e of c o a l . I f one accepts the M values f o r bituminous c o a l s are of the order of 1500-1800, estimates of the number of subunits per cross l i n k can be made. Here we assume that bituminous c o a l s are composed of aromatic and hydroaromatic u n i t s l i n k e d t o gether. The Heredy-Neuworth depolymerization i s thought to cleave the a l k y l chains l i n k i n g the aromatic u n i t s . — Most of the bituminous c o a l s which have been depolymerized g i v e products having number average molecular weights between 300 and 500,-^ although a few are l a r g e r . Accepting these r e s u l t s at face value (molecular weight d i s t r i b u t i o n s have not been done), one concludes that the average cross l i n k chain contains 3-6 aromatic u n i t s . In a very i n s i g h t f u l paper, van Krevelen t r e a t e d c o a l as a cross l i n k e d polymer g e l and the e x t r a c t a b l e m a t e r i a l as the unreacted "monomer".— T h i s treatment leads to an average molecular weight value of 400 f o r the s t r u c t u r a l u n i t . T h i s i s i n e x c e l l e n t agreement with the depolymerization r e s u l t s . This h i g h l y cross l i n k e d s t r u c t u r e f o r c o a l suggests that donor s o l v e n t l i q u e f a c t i o n i n v o l v e s major degradation of the coal. I t a l s o has i m p l i c a t i o n s f o r the use of s o l u b i l i t y d i f f e r e n c e s to f o l l o w the progress of c o a l conversion ( i . e . asphaltenes, preasphaltenes, etc.) I t must be emphasized that t h i s i s the f i r s t systematic use of bulk s o l i d p r o p e r t i e s of c o a l to a determination of i t s s t r u c t u r e . The c o n c l u s i o n that c o a l i s a three dimensionally cross l i n k e d macromolecular network r e s t s on a q u a l i t a t i v e treatment of s t r a i n - t i m e curves and seems sound. The use of two d i f f e r e n t techniques, s t r e s s - s t r a i n measurements and s o l v e n t s w e l l i n g , to measure the e l a s t i c modulus of the network gives c o n f l i c t i n g r e s u l t s which are probably due to d i f f e r e n c e s i n

American Chemical Society Library 16th St. N. W. Washington, D. C. 20036 1155

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

48

the sample pretreatment and d i f f e r e n c e s which are a r t i f a c t s of the experimental procedure. One technique was a p p l i e d to a swollen or obstructed network (whole c o a l - the e x t r a c t a b l e m a t e r i a l i s d i s s o l v e d i n and swells or o b s t r u c t s the network) and the other to an e x t r a c t e d , unswollen network. To examine t h i s s t r u c t u r a l hypothesis f u r t h e r we a r e attempting to r e s o l v e the discrepancy between the s t r e s s s t r a i n and solvent s w e l l i n g measurements and to d e r i v e a s t a t i s t i c a l mechanical theory of polymer network e l a s t i c i t y which f i t s bituminous c o a l s . This work i s i n progress.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

Acknowledgement : We are g r a t e f u l to the Department of Energy (JWL), NSF (JWL), and the F a c u l t y Research Fellowship Fund of the U n i v e r s i t y of Tennessee (JK) f o r support of t h i s work. Abstract The p h y s i c a l p r o p e r t i e s of bituminous coals can be used to determine the nature of t h e i r macromolecular s t r u c t u r e . Bitu­ minous coals are c r o s s - l i n k e d macromolecular networks and a pre­ l i m i n a r y estimate of the number average molecular weight per cross l i n k is 1500-1800.

Literature Cited 1. Vahrman, Μ., Chem. in Britain, 8, 16 (1972); Fuel, 49, 5 (1970). 2. Sternberg, Η., Storch Award Address, Fuel Div. Preprints, ACS National Meeting, Sept. 1976. 3. van Krevelen, D. W., Elements of Coal Chemistry Rotterdam, 1948, p. 170 Dryden, I.G.C., Chem. and Ind., 502 (1952); Fuel, 30, 39 (1952). 4. van Krevelen, D. W., Coal Elsevier Publishing Co., New York, N.Y., 1961, p. 440. 5. Neavel, R., (Exxon-Baytown) numerous lectures and seminars. 6. Ferry, John D., Viscoelastic Properties of Polymers, John Wiley and Sons, Inc., New York, 1961. 7. van Krevelen, D. W., and Hoftyzer, P. J., Properties of Polymers, Elsevier Publishing Co., New York, 1972. 8. The most recent summary is Brown, R. L. and Hiorno, F. J., in Chemistry of Coal Utilization, Suppl. Vol., H. H. Lowry Ed., John Wiley and Sons, Inc., New York, 1963. 9. Morgons, W. Τ. Α., and Terry, Ν. B., Fuel, 37, 201 (1958). 10. Macrae, J . C. and Mitchell, A. R., Fuel, 36, 423 (1957). 11. Treloar, L. R. G., The Physics of Rubber Elasticity, Clarendon Press, Oxford, 1975. 12. Flory, P. J., Principles of Polymer Chemistry, Cornell University Press, Ithaca, N.Y., 1953.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch002

2.

LARSEN AND KOVAC

Structure

of Bituminous

Coals

49

13. Flory, P. J., Statistical Mechanics of Chem. Molecules, John Wiley and Sons, New York, 1969. 14. Sanada, Y., and Honda, H., Fuel, 45, 295 (1966). 15. Collins, C. J., Hagaman, E. W., and Raan, V. F., Coal Technology Quarterly Report, Oak Ridge National Laboratory, ORNL 5252, Dec. 31, 1976, p. 143. 16. Kirov, N.Y., O'Shea, J . Μ., and Sergeant, G. D., Fuel, 47, 415 (1968). 17. Schuyer, J., Dijkstra, H., and van Krevelen, D. W., Fuel, 33, 409 (1954). 18. van Krevelen, D. W., Chermin, H. A. G., and Schuyer, J., Fuel, 38, 438 (1959). 19. Bangham, D. H., and Maggs, F. A. P., Proceedings of a Conference on the Ultra-fine Structure of Coals and Cokes, BCURA, 1944, Lewis, H. K. and co., Ltd., London, p. 118. 20. Jackson, J. L., Shen, M. C., and McQuarrie, J. Chem. Phys., 44, 2388 (1966). 21. Jackson, J. L., J. Chem. Phys., 57, 5124 (1972). 22. Kovac, J., "Modified Gaussian Model of Rubber Elasticity," Macromolecules, in press. 23. Heredy, L. Α., and Neuworth, M. B., Fuel, 41, 221 (1962). 24. Larsen, J. W. and Kuemmerle, E. W., Fuel, 55, 162 (1976). 25. van Krevelen, D. W., Fuel, 47, 229 (1966). 26. Su, T. Κ. and Mark, J. E., Macromolecules, 10, 120 (1977). RECEIVED April 5, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3 Oxygen and Oxygen Functionalities in Coal and Coal Liquids

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

RAFFAELEG.RUBERTO and DONALDC.CRONAUER Gulf Research and Development Co., Pittsburgh,PA15219

The work d e s c r i b e d in this paper is p a r t o f an on-going p r o ject sponsored jointly by Gulf and the Electric Power Research Institute o f P a l o Alto, California. The purpose o f this p r o j e c t is to develop an understanding of the r e a c t i o n s i n v o l v i n g oxygen f u n c t i o n a l groups i n coal d u r i n g h y d r o g e n a t i v e liquefaction. To a c h i e v e t h i s g o a l , it is necessary to first liquefy c o a l under s e l e c t e d and controlled c o n d i t i o n s . Subsequently, the c o n c e n t r a t i o n s o f oxygen and individual oxygen­ - c o n t a i n i n g groups are determined. The overall m a t e r i a l balance and c o n v e r s i o n are then calculated. T h i s paper is concerned with the analytical aspects o f this work. It outlines the v a r i o u s analytical methods t h a t have been used and the results t h a t have been o b t a i n e d with s e l e c t e d experiments. Analytical Methods Analysis o f Oxygen. Coal c o n t a i n s both o r g a n i c and i n o r g a n i c oxygen, and v a r i o u s methods are used i n an attempt to q u a n t i f y it ( T a b l e I). The o r g a n i c oxygen is usually calculated by subtracting from 100 the v a l u e s f o r C , H , N , S, and a s h . T h i s method has two disadvantages: 1) all the errors i n c u r r e d in the o t h e r d e t e r m i n a t i o n s are combined in t h e oxygen v a l u e ; and 2) the ash does not r e p r e sent the m i n e r a l m a t t e r as it was originally p r e s e n t i n coal. This, however, is still the procedure recommended as ASTM D3176-4. (1) Chemical and n u c l e a r methods to directly determine oxygen are a l s o available. These methods are applicable to many types o f samples. Due to their e x t e n s i v e use, they need no description here. However, it is important to note t h a t the n u c l e a r methods measure t o t a l oxygen, and the chemical methods typically measure o r g a n i c oxygen and a t l e a s t p a r t o f the i n o r g a n i c oxygen. T h i s i s not a problem when i n o r g a n i c oxygen i s absent. 0-8412-0427-6/78/47-071-050$10.00/0 ©

1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

Oxygen and Oxygen Funtionalities

TABLE I DETERMINATION OF OXYGEN 1.

BY DIFFERENCE (ASTM D3176-74)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

0 =100 - ( C + H + N + S + ASH) 2.

CHEMICAL A.

OXIDATIVE METHODS:

VARIOUS METHODS USING SOLIDS,

LIQUIDS, OR OXYGEN AS OXIDANTS.

VERY CUMBERSOME

AND NOT MUCH USED. B.

REDUCTIVE METHODS - HYDROCRACK SAMPLE IN H TO CONVERT A L L THE 2

OXYGEN TO H 0 2

- DECOMPOSE SAMPLE IN N OVER C TO CONVERT A L L 2

OF THE OXYGEN TO CO - DETERMINE H 0 OR CO 2

3.

NEUTRON ACTIVATION Ο

1 6

+Ν

Ν

1

6

+ Ρ - 9.62 MEV

J

DECAYS WITH t]/2

β

+ γ

MEASURE A C T I V I T Y OF β OR

= 7.38 SEC.

γ RAYS.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

51

52

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

In t h i s work, o x y g e n i s d e t e r m i n e d by a m o d i f i e d U n t e r z a u c h e r method (_2) by M i c r o - A n a l y s i s , I n c . , W i l m i n g t o n , DE. An i n - h o u s e n e u t r o n a c t i v a t i o n method (3_) and t h e ASTM d i f f e r e n c e method a r e a l s o used f o r s e l e c t e d s a m p l e s . O p t i m i z a t i o n o f Coal P a r t i c l e S i z e . To o b t a i n a m e a n i n g f u l a n a l y s i s o f c o a l , i t i s n e c e s s a r y t o p u l v e r i z e a sample t o i n s u r e t h a t t h e oxygen f u n c t i o n a l g r o u p s a r e e x p o s e d and can be r e a c h e d by v a r i o u s r e a g e n t s . The f i n e r t h e c o a l sample i s , t h e more s i t e s w i l l be e x p o s e d and a n a l y z a b l e . On t h e o t h e r hand, t h e r e i s a p o s s i b i l i t y o f o b t a i n i n g e x c e s s i v e l y f i n e p a r t i c l e s which r e t a i n a s m a l l s t a t i c c h a r g e and a r e d i f f i c u l t t o wet. To d e t e r m i n e an optimum p a r t i c l e s i z e f o r a n a l y s i s , samples o f t h r e e p a r t i c l e s i z e s o f e a c h c o a l , namely,- t o t a l p u l v e r i z e d c o a l , on-100 mesh, and t h r o u g h - 3 2 5 mesh, were e x a m i n e d . F o r e a c h c o a l s a m p l e , t h e t o t a l h y d r o x y l g r o u p s were d e t e r m i n e d by t h e a c e t y l a t i o n method, and t h e c a r b o x y l g r o u p s were d e t e r m i n e d by t h e i o n e x c h a n g e method. The d a t a a r e r e p o r t e d i n T a b l e I I . Examination o f the data i n d i c a t e s t h a t the determined value o f t h e OQH was a l w a y s lower f o r t h e on-100 mesh samples than f o r t h e t h r o u g h - 3 2 5 mesh s a m p l e s . The d i f f e r e n c e between t h e l o w e s t and t h e h i g h e s t v a l u e s was s m a l l , but a p p a r e n t l y s i g n i f i c a n t , due to the c o n s i s t e n c y o f the r e s u l t s . The d i f f e r e n c e o f t h e COOH c o n c e n t r a t i o n s between samples o f d i f f e r e n t s i z e s was even s m a l l e r , and f o r t h e s u b b i t u m i n o u s and b i t u m i n o u s c o a l s t h e r e s u l t s a c t u a l l y r e v e r s e d . In p e r f o r m i n g t h e s e e x p e r i m e n t s , i t was n o t e d t h a t t h e c o a l d u s t w e t t e d p o o r l y and t e n d e d t o move t o t h e w a l l s o f t h e r e a c t i o n f l a s k . I t i s p o s s i b l e t h a t w i t h t h e s m a l l e r p a r t i c l e s i z e samples t h i s e f f e c t was p r o n o u n c e d , and t h e low v a l u e s were due t o p o o r m i x i n g . (Mixing was n o t a p r o b l e m w i t h t h e a c e t y l a t i o n method f o r t h e d e t e r m i n a t i o n o f t h e OH g r o u p s , s i n c e e x t e n s i v e r e f l u x i n g was n e c e s s a r y . ) On t h e b a s i s o f t h e above o b s e r v a t i o n s , i t was d e c i d e d t o use c o a l o f p a r t i c l e s i z e o f 100% t h r o u g h 200 mesh. An a d d i t i o n a l q u e s t i o n r e m a i n e d , namely, were t h e d i f f e r e n c e s i n t h e s e a n a l y t i c a l r e s u l t s due t o s i t e a v a i l a b i l i t y o r t o s e g r e g a t i o n o f c o a l sub-components by c r u s h i n g and s i e v i n g ? I t has been d e m o n s t r a t e d t h a t some c o n c e n t r a t i o n o f m a c é r a i s can be a c h i e v e d by c r u s h i n g and s i z i n g . (4) S i n c e m a c é r a i s do c o n t a i n d i f f e r e n t amounts o f o x y g e n , ( 5 j i t i s p r o b a b l e t h a t t h e 0 - f u n c t i o n a l i t i e s v a r y . To a v o i d any p o s s i b i l i t y o f s e g r e g a t i n g t h e s e f u n c t i o n a l i t i e s a c c o r d i n g t o p a r t i c l e s i z e , i t was d e c i d e d t o g r i n d t h e c o a l s u n t i l t h e t o t a l sample p a s s e d t h r o u g h a 200-mesh sieve. The g r i n d i n g , s i e v i n g , t r a n s f e r r i n g , and a l l t h e o t h e r o p e r a t i o n s were c a r r i e d o u t i n a n i t r o g e n a t m o s p h e r e . The r e s u l t s , t h e r e f o r e , a r e n o t due t o p o s s i b l e a l t e r a t i o n s o f t h e oxygen f u n c t i o n a l groups during the handling steps.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

Oxygen and Oxygen Funtionalities

TABLE I I EFFECT OF PARTICLE S I Z E ON DETERMINATION OF 0-FUNCTIONALITIES (HC1-TREATED)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

"OH WT % COAL

"COOH WT % COAL

LIGNITE TOTAL

3.6

3.5

PLUS 100 MESH

2.0

3.1

MINUS 325 MESH

4.1

3.6

TOTAL

1.2

2.4

PLUS 100 MESH

1.1

2.3

MINUS 325 MESH

1.6

1.8

1.7

.7

SUBBITUMINOUS COAL

BITUMINOUS COAL TOTAL PLUS 1 0 0 MESH MINUS 325 MESH

1.5 2.1

.7 .6

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

53

ORGANIC CHEMISTRY OF COAL

54

E f f e c t o f HC1 P r e t r e a t m e n t o f C o a l . HC1 p r e t r e a t m e n t o f c o a l i s o f t e n recommended t o i n s u r e t h a t no s a l t s a r e p r e s e n t a n d t h a t a l l t h e o x y g e n f u n c t i o n a l g r o u p s a r e i n a f r e e s t a t e . As a t e s t o f t h e n e c e s s i t y o f s u c h p r e t r e a t m e n t , a sample o f on-100 mesh l i g n i t e was r e p e a t e d l y a n a l y z e d f o r COOH g r o u p s b e f o r e and a f t e r t r e a t m e n t w i t h HC1. The r e s u l t s a r e shown i n T a b l e I I I . S i n c e t h e c o n t e n t o f t h e COOH g r o u p s was c o n s i d e r a b l y h i g h e r f o r t h e H C 1 - t r e a t e d s a m p l e s , HC1 t r e a t m e n t i s deemed t o be n e c e s s a r y . T h e p r o c e d u r e f o r t h e a n a l y s i s o f COOH g r o u p s i s t h a t o f Blom et a l . (6) Table I I I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

EFFECT OF HC1 PRETREATMENT ON DETERMINATION OF -COOH IN LIGNITE (PLUS -100 MESH SAMPLE) Run No. 1 2 3 4 5 6 A f t e r HC1 Treatment

Wt % O m n H 1.0 0.8 0.7 0.8 0.9 1.1 3.1

D e t e r m i n a t i o n o f T o t a l OH G r o u p s . The c o n c e n t r a t i o n o f -OH i n c o a l i s d e t e r m i n e d by t h e a c e t y l a t i o n method o f Blom e t a l . ((5) T h i s method c o n s i s t s o f f i r s t a c e t y l a t i n g t h e -OH g r o u p s w i t h a c e t i c a n h y d r i d e i n t h e p r e s e n c e o f p y r i d i n e . The a c e t y l a t e d products a r e then hydrolyzed; the l i b e r a t e d a c e t i c a c i d i s d i s t i l l e d a n d q u a n t i f i e d by t i t r a t i o n w i t h s t a n d a r d NaOH s o l u t i o n . The o v e r a l l r e a c t i o n s a r e a s f o l l o w s :

C

H

C

3 — C

Pv

.0 CH~—CC ^0 R - 0 0 C C H + 1/2 B a ( 0 H ) R - OH +

> CHo - C00H + R - 00CCH-,

0

(1)

3

3

2

1 Q Q

1/2 B a ( 0 0 C C H ) + 1/3 H P 0 3

2

3

4

o > C

R - OH + 1/2 Ba ( 0 0 C C H )

2

> C H COOH + 1/6 B a ( P 0 )

2

3

3

3

4

(2) (3)

The -OH c o n t e n t o f c o a l c a n n o t be q u a n t i f i e d f r o m t h e amount of a c e t i c a c i d l i b e r a t e d i n r e a c t i o n (1) because t h e r e s u l t s a r e n o t r e p r o d u c i b l e . (6_)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

Oxygen and Oxygen Funtionalities

55

T h i s a p p r o a c h , however, s h o u l d be a p p l i c a b l e t o c o a l l i q u i d s . To c h e c k t h i s p o i n t a n d a l s o t o d e t e r m i n e t h e a c c u r a c y o f t h e method, a s y n t h e t i c m i x t u r e was p r e p a r e d ( T a b l e I V ) . A more com­ p l e x o r c o n c e n t r a t e d m i x t u r e c o u l d n o t be p r e p a r e d due t o l i m i t e d s o l u b i l i t i e s o f many compounds i n t e t r a l i n . T e t r a l i n was used a s an i n e r t s o l v e n t t o i n s u r e h o m o g e n e i t y i n s a m p l i n g . The s y n t h e t i c m i x t u r e was a n a l y z e d r e p e t i t i v e l y , o b t a i n i n g the f o l l o w i n g r e s u l t s :

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

Wt % 0

Q H

= 1.02, 1.01, 1.06, 0.99, 0.75, 0.82, 1.05

W i t h t h e e x c e p t i o n o f two v a l u e s , t h e s e r e s u l t s were r e p r o ­ ducible but high, since the expected concentration o f hydroxylic oxygen was 0.82%. An e x p l a n a t i o n was n o t o b v i o u s , a n d i t was decided t o check the a c e t y l a t i o n o f i n d i v i d u a l oxygen-containing compounds. The l i s t o f compounds examined a n d t h e a n a l y t i c a l r e s u l t s a r e shown i n T a b l e V. T h e f o l l o w i n g i s a d i s c u s s i o n o f r e s u l t s o b ­ t a i n e d w i t h t h e s e compounds. NAPHTH0L, 2,3,5,-TRIMETHYLPHENOL a n d 2,6,-DIMETHYLPHENOL were a c e t y l a t e d q u a n t i t a t i v e l y , even though 2,6-dimethylphenol i s h i n ­ d e r e d . Phenol i t s e l f was n o t c h e c k e d , b u t i n v i e w o f t h e above r e s u l t s , i t should not present d i f f i c u l t i e s . DECAHYDR0-2-NAPHTH0L c o u l d n o t be c o m p l e t e l y a c e t y l a t e d i n t h e f i r s t s e t o f e x p e r i m e n t s , b u t i t was q u a n t i t a t i v e l y a c e t y l a t e d by d o u b l i n g t h e c o n c e n t r a t i o n o f t h e a c e t y l a t i n g a g e n t ( s e c o n d s e t of data, Table V). TRIPHENYLMETHANOL c o u l d n o t be c o m p l e t e l y a c e t y l a t e d w i t h a n y of the conditions attempted. Increasing the concentration o f the a c e t y l a t i n g agent and t r i p l i n g the r e a c t i o n times (with r e s p e c t t o t h e o t h e r d e t e r m i n a t i o n s ) d i d n o t p r o v e t o be h e l p f u l . PYR0GALL0L a p p e a r e d t o be s e n s i t i v e t o t h e c o n c e n t r a t i o n o f t h e a c e t y l a t i n g a g e n t , p r o b a b l y b e c a u s e i t c o n t a i n s t h r e e OH g r o u p s . T h e f i r s t two a c e t y l a t i o n s were i n c o m p l e t e a s i n d i c a t e d by t h e d a t a i n T a b l e V. T h e p r o d u c t s o f t h e s e r e a c t i o n s were s o l u b l e i n w a t e r b u t c o u l d n o t be t i t r a t e d w i t h an i n d i c a t o r . I n f a c t , p y r o g a l l o l i s very s o l u b l e i n water and gives i t a yellow­ i s h c o l o r t h a t masks t h e c o l o r o f t h e i n d i c a t o r . T h e a c e t a t e d e r i v a t i v e i s , i n s t e a d , a white, w a t e r - i n s o l u b l e m a t e r i a l , and t h i s makes t h e c o l o r i m e t r i c t i t r a t i o n v e r y e a s y . C o r r e c t v a l u e s were d e t e r m i n e d by i n c r e a s i n g r e a c t a n t c o n c e n t r a t i o n . BENZYL ETHER c o u l d n o t be a c e t y l a t e d , a s e x p e c t e d . However, t h e HEXADECYL ETHER was p a r t i a l l y a c e t y l a t e d , i n d i c a t i n g t h a t t h e a l i p h a t i c e t h e r bond i s c l e a v e d , t h e r e b y f o r m i n g a n a l c o h o l . T h i s a l c o h o l c a n then be a c e t y l a t e d . BENZOIC ACID c a n n o t be a c e t y l a t e d . I t s c o n c e n t r a t i o n was d e t e r m i n e d by d i r e c t t i t r a t i o n i n aqueous s o l u t i o n . C a r b o n y l compounds s u c h a s Β Ε Ν Ζ 0 Ρ Η Ε Ν 0 Ν Ε ( I ) c o u l d n o t be a c e t y l a t e d , w h i l e ANTHR0NE ( I I ) was q u a n t i t a t i v e l y a c e t y l a t e d . T h i s b e h a v i o r i s b e l i e v e d t o be due t o t h e f a c t t h a t I i s a

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

56

TABLE IV

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

TEST MIXTURE OF OXYGEN COMPOUNDS

WT % COMPOUND IN MIXTURE

WT % OXYGEN IN MIXTURE

COMPOUND

OXYGEN FUNCTION

ANTHRONE

CARBONYL

0.66

0.05

PHENOL

HYDROXYL

1.89

0.32

DECAHY DRO-2-NAPHTHOL

HYDROXYL

1.29

0.14

TRIPHENYLMETHANOL

HYDROXYL

0.87

0.05

NAPHTHOL

HYDROXYL

1.24

0.14

2,6-DIMETHYLPHENOL

HYDROXYL

1.23

0.17

BENZYL ETHER

ETHER

2.24

0.18

N-HEXADECYL ETHER

ETHER

0.76

0.03

BENZOIC ACID

CARBOXYLIC

0.54

0.14

TETRALIN

NONE

89.27

0.00

100.00

1.22

TOTAL CARBONYLIC OXYGEN, WT %

0.05

TOTAL CARBOXYLIC OXYGEN, WT %

0.14

TOTAL ETHER OXYGEN, WT %

0.21

TOTAL HYDROXYL OXYGEN, WT %

0.82 1.22

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

-OH -OH -OH -OH -OH -0-0-

NAPHTHOL

DECAHYDR0-2-NAPHTH0L

TRIPHENYLMETHANOL

2,3,5-TRIMETHYLPHENOL

PYROGALLOL

BENZYL ETHER

8.8 1.98

=C=0

-

BENZOPHENONE

COAL LIQUID F l l - 1 6

1 , 6 , 1.5, 1.6

1.7, 0.4, 0.6

8.3, 9.6, 9.2, 9.0

26.2, 24.2 (DIRECT TITRATION)

2.7, 1.3

0.9, 0.5, 0.4

3.9, 1 0 . 3 , 38.5*, 3 6 . 1 *

11.9, 11.5

2.1, 4.9, 3.7, 2.5, 3.9

7 . 8 , 5.7, 6.9, 10.4*, 10.4*, 9.8*

10.7, 10.5

14.2, 1 3 . 7 , 12.7, 12.9

WT % 0 DETERMINED AS -OH OXYGEN

*THE ANALYTICAL METHODS WERE MODIFIED FOR THESE DETERMINATIONS, S E E TEXT.

8.2

=C=0

26.2

-COOH

BENZOIC ACID

3.4

8.1

38.1

11.7

6.2

10.4

11.1

13.1

OXYGEN CONTENT

ANTHRONE

N-HEXADECYL ETHER

-OH

OXYGEN FUNCTION

2,6-DIMETHYLPHENOL

COMPOUND

TESTING OF MODEL COMPOUNDS BY ACETYLATION FOR -OH FUNCTIONALITY

TABLE V

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

58

ORGANIC CHEMISTRY OF COAL

s t a b l e ketone, w h i l e I I i s t a u t o m e r i z e d t o t h e a n t h r o l which can be a c e t y l a t e d . From t h e a b o v e r e s u l t s , i t i s e v i d e n t t h a t most -OH compounds b e l i e v e d t o be p r e s e n t i n c o a l l i q u i d s c a n be a c e t y l a t e d and t h i s t y p e o f o x y g e n - c o n t a i n i n g group d e t e r m i n e d . However, some o f t h e OH f u n c t i o n a l i t i e s c a n be " h i n d e r e d " w i t h a r e s u l t i n g low v a l u e d e t e c t e d . In c o n t r a s t , some compounds s u c h a s a n t h r o n e ( c o n t a i n i n g a c a r b o n y l o x y g e n ) have t h e p o t e n t i a l t o show up a s c o n t a i n i n g -OH f u n c t i o n a l i t y . I n summary, s e v e r a l p r o b l e m s e x i s t i n t h e e x a c t d e t e r m i n a t i o n o f -OH f u n c t i o n a l i t y . However, t h e r e s u l t s should f a l l i n a reasonable range c o n s i d e r i n g t h e complexity o f coal l i q u i d s . D e t e r m i n a t i o n o f C a r b o x y l i c Groups. The c a r b o x y l i c g r o u p s i n c o a l and c o a l l i q u i d s a r e d e t e r m i n e d by an i o n e x c h a n g e method u s i n g c a l c i u m a c e t a t e . (6j The method c o n s i s t s o f r e a c t i n g t h e sample w i t h e x c e s s c a l c i u m a c e t a t e a t room t e m p e r a t u r e f o r 18 t o 20 h o u r s , and t h e n d e t e r m i n i n g t h e a c e t i c a c i d l i b e r a t e d by t i t r a t i o n w i t h s t a n d a r d NaOH s o l u t i o n . RC00H + 1/2 C a ( C 0 0 C C H ) 3

^ R C 0 0 ( l / 2 Ca) + CH C00H

2

3

D e t e r m i n a t i o n o f C a r b o n y l i c Groups. T h i s method t a k e s a d v a n t a g e o f t h e r e a c t i o n o f c a r b o n y l groups w i t h h y d r o x y l a m i n e t o f o r m t h e c o r r e s p o n d i n g oxime. (6J R -C=0 + 0HH N-HC1 2

2

>• R -C=N0H + H 0 + HC1 2

2

The p r o d u c t s a r e r e c o v e r e d a n d a n a l i q u o t i s used t o d e t e r m i n e t h e n i t r o g e n c o n t e n t . A n o t h e r a l i q u o t i s r e a c t e d w i t h a c e t o n e and s u l f u r i c a c i d t o decompose t h e oxime, and t h e n i t r o g e n c o n t e n t o f t h e new p r o d u c t s i s d e t e r m i n e d . The c a r b o n y l c o n t e n t o f t h e c o a l can be c a l c u l a t e d f r o m t h e d i f f e r e n c e i n n i t r o g e n c o n t e n t between t h e oxime d e r i v a t i v e s and t h e decomposed oximes. Blom (6J f o u n d t h a t t h e d e t e r m i n a t i o n o f t h e c a r b o n y l c o n t e n t f r o m t h e HC1 r e l e a s e d i n t h e a b o v e r e a c t i o n was n o t r e p r o d u c i b l e w i t h ' c o a l . The c a r b o n y l c o n t e n t o f c o a l l i q u i d s , however, c a n be d e t e r mined f r o m t h e HC1 r e l e a s e d i n t h e above r e a c t i o n . To t e s t t h e method, a s o l u t i o n o f two c a r b o n y l compounds ( a n t h r o n e and benzophenone) was p r e p a r e d and a n a l y z e d . D u p l i c a t e oxygen d e t e r m i n a t i o n s were 0.63 a n d 0.65 wt %, w h i l e t h e a c t u a l c o n t e n t was 0.64 wt %. D e t e r m i n a t i o n o f E t h e r Groups. Ether groups i n c o a l a r e d e t e r m i n e d by r e a c t i o n o f c o a l w i t h HI t o c o n v e r t t h e e t h e r s i n t o t h e c o r r e s p o n d i n g h y d r o x y l s and h a l i d e s . {7) The h y d r o x y l s a r e d e t e r m i n e d by t h e a c e t y l a t i o n method, and t h e d i f f e r e n c e i n hyd r o x y l c o n t e n t between t h e H I - t r e a t e d and t h e u n t r e a t e d sample r e p r e s e n t s t h e amount o f e t h e r g r o u p s . T h i s method i s commonly r e f e r r e d t o a s t h e Z e i s e l method, and i t i s g e n e r a l i z e d by t h e following reactions:

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

A r - 0 - CH. AR - 0 - AR

H I

AR - 0

- AR

CH

2

HI

Oxygen and Oxygen Funtionalities

59

^ A r - OH + C H I 3

> AR - OH + AR - I HI

H I

>• AR - OH + A r

> AR - OH + AR - H CH

2

- I

A d i r e c t method f o r d e t e r m i n i n g e t h e r oxygen i n c o a l l i q u i d i s n o t a v a i l a b l e . A minimum amount o f e t h e r oxygen can be d e t e r ­ mined by s u b j e c t i n g t h e o i l s t o a SARA s e p a r a t i o n . (8) T h i s s e p ­ a r a t i o n concentrates a l l o f the n e u t r a l ethers i n the n e u t r a l o i l f r a c t i o n . T h e oxygen c o n t e n t o f t h e n e u t r a l o i l s i s a measure o f t h e e t h e r o x y g e n p r e s e n t . N e u t r a l compounds c o n t a i n i n g c a r b o n y l groups may a l s o a p p e a r i n t h i s f r a c t i o n , a n d a c o r r e c t i o n may be n e c e s s a r y . T h e e t h e r oxygen o b t a i n e d i n t h i s way i s a minimum b e c a u s e compounds w h i c h c o n t a i n b o t h an e t h e r l i n k a g e a n d a p o l a r g r o u p w i l l be i s o l a t e d w i t h t h e r e s i n s f r a c t i o n a n d n o t w i t h t h e n e u t r a l o i l s . We have made no e f f o r t t o d e t e r m i n e t h e e t h e r oxy­ gen i n c o a l l i q u i d s . P r o d u c t i o n o f the Coal L i q u i d s V a r i o u s e x p e r i m e n t s have been c a r r i e d o u t t o p r o d u c e c o a l liquids a t different reaction conditions. The d e t a i l s o f t h i s p a r t o f t h e e x p e r i m e n t a t i o n a r e beyond t h e s c o p e o f t h i s paper a n d can be f o u n d i n R e f e r e n c e _9. Only a g e n e r a l i z e d f l o w d i a g r a m i s g i v e n below t o i n d i c a t e what a r e the feeds and the products. Coal Solvent Hydrogen

R Ε A C Τ

Gas

0

Cold Traps

Dry Gas

Slurry

R A n a l y s i s o f Feed S t r e a m s C o a l . T h e u l t i m a t e a n d p r o x i m a t e a n a l y s e s o f B e l l e A y r subb i t u m i n o u s c o a l , o b t a i n e d by s t a n d a r d ASTM methods, (1_) a r e shown in Table VI. The a n a l y s i s o f t h e oxygen f u n c t i o n a l g r o u p s , o b t a i n e d by t h e methods o u t l i n e d a b o v e , i s shown i n T a b l e V I I . T h e s e two t a b l e s a l s o c o n t a i n t h e a n a l y s e s o f t h e B u r n i n g S t a r ( I l l i n o i s No. 6) b i t u m i n o u s c o a l w h i c h w i l l be used i n t h e n e x t phase o f t h e p r o j e c t .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

60

TABLE VI ULTIMATE AND PROXIMATE ANALYSES OF COALS COAL RANK

BELLE AYR SUBBITUMINOUS

BURNING STAR BITUMINOUS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

ULTIMATE ANALYSIS (WT % DRY BASIS) CARBON

69.28

71.55

HYDROGEN

4.34

4.46

NITROGEN

1.01

1.23

OXYGEN, DETERMINED DIFFERENCE SULFUR ASH, TOTAL

19.93

12.57

14.52

5.85

0.51

3.64

10.34

METALS

4.93

13.27 6.55

PROXIMATE ANALYSIS (AS I S ) % MOISTURE

30.25

% ASH

7.01

13.45 11.19

% VOLATILE

28.26

31.68

% FIXED CARBON

34.48

43.68

HEAT OF COMBUSTION AS IS DRY

(BTU/LB) 8,141 11,671

10,711 12,375

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

RUBEKTO AND CRONAUER

Oxygen and Oxygen Funtionalities

TABLE V I I ANALYSES OF OXYGEN FUNCTIONALITY IN COALS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

(WT % MAF COAL BASIS)

BURNING STAR (BITUMINOUS)

COAL

BELLE AYR (SUBBITUMINOUS)

OXYGEN CONTENT AS: HYDROXYLIC (-0H)

2.4

5.6

CARBOXYLIC (-C00H)

0.7

4.4

CARBONYLIC (=C=0)

0.4

1.0

ETHERIC (-0-)

2^8

0.9

6.3

11.9

ASH BASIS

5.9

16.2

MINERAL MATTER BASIS

—

16.0

TOTAL

OXYGEN BY DIFFERENCE:

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

62

S o l v e n t . To a v o i d t h e p r o b l e m o f d i s t i n g u i s h i n g the oxygen f u n c t i o n a l i t i e s o f the s o l v e n t from those of the c o a l - d e r i v e d l i q u i d s , t h e e x p e r i m e n t s were c a r r i e d o u t u s i n g h y d r o p h e n a n t h r e n e s as s o l v e n t . The s o l v e n t ' s a n a l y s i s i s shown i n T a b l e V I I I . This s o l v e n t i s e s s e n t i a l l y f r e e o f oxygen and i s an e f f e c t i v e c o a l l i q u e f a c t i o n a g e n t . (10)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

A n a l y s i s o f Product Streams A n a l y s i s o f C o l d T r a p M a t e r i a l s . The m a t e r i a l s c o l l e c t e d i n t h e wet i c e and d r y i c e t r a p s were q u a n t i t a t i v e l y c o m b i n e d , an o r g a n i c s o l v e n t was added t o t a k e up t h e w a t e r - i n s o l u b l e o r g a n i c m a t e r i a l s , and t h e two l a y e r s were s e p a r a t e d by f i l t r a t i o n t h r o u g h a phase s e p a r a t i n g f i l t e r p a p e r . The h y d r o c a r b o n s i n the o r g a n i c p h a s e were q u a n t i f i e d by G L C The p h e n o l s i n t h e aqueous phase were i n i t i a l l y q u a n t i f i e d by GLC t e c h n i q u e s ; (10J however, t h e q u a n t i t i e s were a l w a y s v e r y s m a l l , and t h e y a r e no l o n g e r b e i n g determined. A n a l y s i s o f G a s e s . The gas s t r e a m was a n a l y z e d by an o n - l i n e GLC u n i t t o q u a n t i f y t h e c o n t e n t o f t h e h y d r o c a r b o n g a s e s and carbon oxides. A n a l y s i s o f t h e S l u r r y . The s l u r r y s t r e a m c o n t a i n i n g t h e l i q u i d p r o d u c t s , t h e u n r e a c t e d c o a l , and t h e c o a l m i n e r a l m a t t e r was d i v i d e d i n t o " f i l t r a t e " and "wet c a k e " by f i l t r a t i o n . These two f r a c t i o n s were s u b j e c t e d t o t h e s o l v e n t e x t r a c t i o n s e p a r a t i o n scheme i l l u s t r a t e d i n F i g u r e 1. From t h i s , t h e v a r i o u s components were c a l c u l a t e d : oils asphaltenes preasphaltenes pyridine insolubles

= = = =

samples - pentane i n s o l u b l e s p e n t a n e i n s o l u b l e s - benzene i n s o l u b l e s benzene i n s o l u b l e s - p y r i d i n e i n s o l u b l e s as d e t e r m i n e d .

A s e q u e n t i a l e x t r a c t i o n t e c h n i q u e was n o t used b e c a u s e e x p e r i m e n t a t i o n has shown t h a t t h e d i s t r i b u t i o n o f t h e s e components v a r i e s d e p e n d i n g on w h e t h e r t h e p e n t a n e t o p y r i d i n e o r t h e r e v e r s e s e q u e n c e i s u s e d . I t i s our o p i n i o n t h a t t h e scheme i l l u s t r a t e d i n F i g u r e 1 m i n i m i z e s t h e s o l v e n t - s o l u t e i n t e r a c t i o n s and g i v e s t h e b e s t e s t i m a t e o f t h e s e components. The t o t a l " f i l t r a t e " and "wet c a k e " and s e l e c t e d s o l v e n t ext r a c t i o n f r a c t i o n s were a n a l y z e d f o r oxygen f u n c t i o n a l g r o u p s u s i n g t h e methods d e s c r i b e d a b o v e . The n o r m a l i z e d m a t e r i a l b a l a n c e s o f t h r e e s e l e c t e d r u n s a r e shown i n T a b l e IX, t o g e t h e r w i t h p e r t i n e n t run c o n d i t i o n s . The o x y g e n and oxygen f u n c t i o n a l g r o u p s d i s t r i b u t i o n s a r e shown i n T a b l e X. T h i s t a b l e r e p o r t s the t o t a l oxygen and the oxygen i n t h e h y d r o x y l i c , c a r b o x y l i c , c a r b o n y l i c , and e t h e r i c f u n c t i o n a l i t i e s , as w e i g h t p e r c e n t o f t h e t o t a l p r o d u c t s . It is

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

RUBERTO AND CRONAUER

Oxygen and Oxygen Funtionalities

TABLE V I I I ANALYSIS OF HYDROPHENANTHRENE SOLVENT

ELEMENTAL ANALYSIS Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

CARBON HYDROGEN NITROGEN

WT % 91.08 8.83 0.006

OXYGEN SULFUR

0.08

GAS CHROMATOGRAPHIC ANALYSIS HYDROPHENANTHRENES PER-

9.8

OCTA-

24.5

HEXA-

2.8

TETRADI-

18.3 6.2

PHENANTHRENE

14.9

UNKNOWNS

23.5

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

OILS

SOLUBLE

I

INSOLUBLE

INSOLUBLES

PYRIDINE-

OILS

SOLUBLE

Figure 1.

ASPHALTENES

PREASPHALTENES

ASPHALTENES

n-PENTANE SOLUBLE

OILS ASPHALTENES PREASPHALTENES

INSOLUBLE

S ο ο ο Ρ

INSOLUBLES

M

S

• 2

ο

l-H

INSOLUBLES

PYRIDINE-

PYRIDINE

2

PYRIDINE-

PREASPHALTENES

INSOI.IIRI F

Solvent extraction scheme

BENZENE

SAMPLE

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

3.

RUBERTO AND CRONAUER

65

Oxygen and Oxygen Funtionalities

TABLE IX NORMALIZED MATERIAL BALANCES RUN NO.

Fll-32

EP-2

EP-18

400.0

450.0

400.0

CONDITIONS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

TEMPERATURE, °C PRESSURE, MPa

13.79

13.79

13.79

SPACE T I M E , MIN.

12.49

12.64

23.85

26.43

26.37

26.34

2.83

2.79

2.82

10.82

10.79

10.79

SOLVENT (HPh)

60.10

59.97

59.93

HYDROGEN CONS.

-0.18

0.05

0.12

100.00

100.00

100.00

1.87

4.07

2.08

62.63

70.85

68.64

ASPHALTENES

3.23

4.24

3.48

PREASPHALTENES

5.71

2.93

2.85

PYRIDINE INSOL.

14.11

5.48

10.34

WATER

12.45

12.43

12.60

100.00

100.00

100.00

FEED COAL, MAF ( B E L L E AYR) ASH MOISTURE

TOTAL PRODUCTS GAS OILS

TOTAL

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

66

ORGANIC CHEMISTRY OF COAL

TABLE X FRACTION AND OXYGEN DISTRIBUTIONS (WT % OF PRODUCTS) Fll-32

EP-2

EP-18

28.15

54.46

55.06

HYDROXYLIC OXYGEN

0.25

0.48

0.34

CARBOXYLIC OXYGEN

0.02

0.01

0.0

CARBONYLIC OXYGEN

0.01

0.05

0.03

ETHERIC OXYGEN

0.03

0.14

0.32

TOTAL OXYGEN

0.31

0.69

0.69

3.23

1.85

1.54

FILTRATE

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

TOTAL

ASPHALTENES HYDROXYLIC OXYGEN

0.12

CARBOXYLIC OXYGEN

0.0

CARBONYLIC OXYGEN

< 0.01 0.12

TOTAL OXYGEN WET CAKE 61.61

31.88

33.58

HYDROXYLIC OXYGEN

2.65

1.05

2.89

CARBOXYLIC OXYGEN

0.01

0.0

0.0

CARBONYLIC OXYGEN

0.0

0.0

0.06

5.02

3.65

4.56

39.57

10.20

15.14

HYDROXYLIC OXYGEN

6.17

1.07

1.97

CARBOXYLIC OXYGEN

0.01

0.0

0.0

CARBONYLIC OXYGEN

0.13

0.0

0.05

TOTAL OXYGEN

5.56

1.14

2.06

TOTAL

TOTAL OXYGEN n - C INSOL. 5

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

67

Oxygen and Oxygen Funtionalities

TABLE X ( c o n t ' d ) 14.11

5.42

10.34

HYDROXYLIC OXYGEN

1.57

0.66

1.03

CARBOXYLIC OXYGEN

0.0

0.0

0.0

CARBONYLIC OXYGEN

0.01

0.0

0.04

ETHERIC OXYGEN

0.08

0.0

0.09

TOTAL OXYGEN

2.20

0.68

1.80

4.08

2.84

3.32

3.63

2.52

2.95

1.87

4.07

2.08

0.65

1.41

0.99

8.37

9.59

9.28

7.44

8.52

8.25

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

PY. INSOL.

WATER OXYGEN GAS OXYGEN WATER (TRAPS) OXYGEN

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

68

ORGANIC CHEMISTRY OF COAL

TABLE XI OXYGEN BALANCE (WT % ) Fll-32

DCEP-2

DCEP-1

2.10

1.53

3.23

0.03

0.01

0.0

0.01

0.05

0.9

0.24

0.11

0.14

0.41

WATER OXYGEN

9.59

11.07

11.04

11.20

ASH OXYGEN

1.48

-

-

-

GAS OXYGEN

-

Feed HYDROXYLIC OXYGEN COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

SOLVENT TOTAL

1.48

1.48

CARBOXYLIC OXYGEN COAL SOLVENT

1.16

TOTAL

1.16

-

CARBONYLIC OXYGEN COAL SOLVENT TOTAL

0.26

0.26

ETHERIC OXYGEN COAL SOLVENT TOTAL

UNKNOWN OXYGEN TOTAL OXYGEN % FEED

0.24

-

0.65

1.41

0.99

1.08

2.36

2.60

1.69

15.29

17.41

17.33

-

113.9

113.3

17.61 115.2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

RUBERTO AND CRONAUER

Oxygen and Oxygen Funtionalities

69

n o t e d t h a t t h e e t h e r i c o x y g e n i n t h e t o t a l f i l t r a t e was o b t a i n e d by s u b t r a c t i n g t h e h y d r o x y l i c + c a r b o x y l i c + c a r b o n y l i c oxygen f r o m t h e t o t a l o x y g e n , w h i l e t h a t i n t h e " p y r i d i n e i n s o l u b l e s " was d e t e r m i n e d b y t h e same method used f o r c o a l . T a b l e X I summarizes t h e v a r i o u s f o r m s o f oxygen a c c o r d i n g t o t h e f r a c t i o n s where t h e y a p p e a r a n d compares t h e r e s u l t s w i t h t h e feed. These r e s u l t s i n d i c a t e that c a r b o x y l i c , c a r b o n y l i c , and e t h e r i c oxygen f u n c t i o n a l i t i e s o f c o a l a r e reduced during t h e l i q u e f a c t i o n r e a c t i o n r e s u l t i n g i n a n i n c r e a s e i n h y d r o x y l i c oxy­ gen f u n c t i o n a l i t y and i n t h e p r o d u c t i o n o f c a r b o n o x i d e s a n d water.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

Conclusions A n a l y t i c a l techniques f o r determining the content o f various oxygen f u n c t i o n a l g r o u p s i n c o a l s have been c o n f i r m e d a n d have been m o d i f i e d t o q u a n t i f y t h e same g r o u p s i n c o a l l i q u i d s p r o d u c e d f r o m B e l l e A y r s u b b i t u m i n o u s c o a l . I t has been shown t h a t c a r ­ b o x y l i c , c a r b o n y l i c , a n d e t h e r i c oxygen f u n c t i o n a l g r o u p s o f c o a l are reduced during l i q u e f a c t i o n , r e s u l t i n g i n carbon oxides, water, and an increase o f h y d r o x y l i c groups.

Abstract This on-going work was undertaken to develop an understand­ ing o f the reactions involving oxygen and oxygen functional groups during the production of synthetic fuels from coal by hydrogenative liquefaction. Analytical procedures have been adopted to determine the major oxygen-containing groups in coal and coal l i q u i d s , namely, hydroxylic, carboxylic, carbonylic, and etheric. The changes of concentration of these groups have been observed during the liquefaction of Belle Ayr subbituminous coal in hydrophenanthrene solvent. It has been found that carboxylic, carbonylic, and etheric oxygens are rapidly removed, resulting i n the production o f carbon oxides, water, and hydroxylic groups. Acknowledgment The a u t h o r s w i s h t o e x p r e s s t h e i r g r a t i t u d e t o t h e E l e c t r i c Power R e s e a r c h I n s t i t u t e f o r p a r t i a l s u p p o r t o f t h i s work; t o K. A. K u e s e r f o r p r e p a r i n g t h e s a m p l e s ; a n d t o W. C R o v e s t i , D. M. J e w e l l , R. G. G o l d t h w a i t , and A. B r u c e K i n g f o r h e l p f u l discussions.

Literature Cited 1. 2.

1975 Annual Book of ASTM Standards, Part 26. A l u i s e , V. Α., Hall, R. T., Staats, F. C., and Becker, W. W., Anal. Chem. (1947), 19, 347.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch003

70

3. Stallwood, R. Α . , Mott, W. E., and Fanale, D. T., Anal. Chem. (1963), 35, 6. 4. Given, P. H., Cronauer, D. C., Spackman, W., Lovell, H. L., Davis, Α . , and Biswas, B., Fuel, London (1975), 54, 40. 5. Van Krevelen, D. W., "Coal," Elsevier Publishing Company, New York, 1961. 6. Blom, L., Edelhausen, L., and Van Krevelen, D. W., Fuel, London, (1957), 36, 135. 7. Bhaumik, J. Ν., Mukherjee, A. K., Mukherjee, P. N., and Lahiri, Α., Fuel, London (1962), 41, 443. 8. Ruberto, R. G., and Jewell, D. Μ., Proceedings of the NSF Workshop, "Analytical Needs of the Future as Applied to Coal Liquefaction," Greenup, KY, 1974. 9. Cronauer, D. C ., and Ruberto, R. G . , Annual Report to EPRI on Research Project 713-1, January 1977. 10. Ruberto, R. G . , Cronauer, D. C . , Jewell, D. M., and Seshadri, K. S., Fuel, London (1977), 56, 25. 11. Brady, R. F., Jr., and Pettitt, B. C., J. of Chromat. (1974) 93, 375. RECEIVED

February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4 Asphaltenes and Preasphaltenes—Components of an Original hvb Bituminous Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

ANNA MARZEC, DANUTA BODZEK, and TERESA KRZYZANOWSKA Petroleum and Coal Chemistry Department, Polish Academy of Sciences, 44-100 Gliwice, 1-go Maja 62 St., Poland

Asphaltenes are considered to be the principle intermediates in the conversion of coal to oil products. Weller (1) stated that the catalytic conversion of coal involves two consecutive first order reactions: Coal

Asphaltenes

Oil

(1)

At 400°C, k was reported to be 27 times higher than k and at 400°C k was 10 times higher than k . Liebenberg and Potgleter (2) derived another mechanism which includes the following reactions: 1

2

1

2

Coal

Asphaltenes

Coal

Asphaltenes

(2)

Coal

Oil

(3)

Oil

They tentatively determined the sum k + k at 400°C and 440°C in the conversion of coal with tetralin and no added catalyst. More recently Yoshida et al. (3) established that the mechanism for catalytic conversion of Hokkaido coal includes Reaction 1 and Reaction 3. It is worth emphasizing that according to their experiments, k is considerably higher or lower than k and k , depending upon the type of coal. Sternberg et al. (4,5) have proposed that preasphaltenes are the intermediates between coal and asphaltenes. Contrary to this, Schwager and Yen (6) considered that "preasphaltenes may arise from reactive coal depolymerization moieties, which are... repolymerized into materials more difficult to degrade than the original coal substance". Collins et al. (7) claim that "carbon-carbon scission must be considered as an important factor in asphaltene formation" and in 1

2

4

1

0-8412-0427-6/78/47-071-071$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

72

ORGANIC CHEMISTRY OF COAL

preasphaltene formation as w e l l . The statement i s based on r e ­ s u l t s from the thermal treatment (over 300°C) of model compoundsa r y l a l k a n e s , diphenylalkanes and a r y l a l k y l ethers. I t leads to the c o n c l u s i o n that asphaltenes and preasphaltenes are not ex­ pected to be present i n any product i f i t had not p r e v i o u s l y been t r e a t e d a t high temperature. Schweighardt and Sharkey (8) presented i n 1977 the f o l l o w i n g scheme f o r l i q u e f a c t i o n : COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

PREASPHALTENES

The scheme i n c l u d e s almost a l l previous concepts (1,2,3,4,5), introduces a new r e a c t i o n (preasphaltenes -> o i l s ) , and emphasizes the r e v e r s i b l e character of k2,k^, and Ky r e a c t i o n s . We have found that asphaltenes and preasphaltenes are the components of low temperature c o a l e x t r a c t s . Coals were e x t r a c t ­ ed a t ambient temperature and precautions i n the a n a l y t i c a l pro­ cedures were observed. Therefore, the components of the e x t r a c t s are considered to be the components of an o r i g i n a l c o a l . EXPERIMENTAL High v o l a t i l e A bituminous c o a l J ( v i t r i n i t e 60%, i n e r t i n i t e 33%, e x i n i t e 6%) and hvcb c o a l W ( v i t r i n i t e 45%, i n e r t i n i t e 45%, e x i n i t e 10%) have been i n v e s t i g a t e d . Proximate and u l t i m a t e ana­ l y s e s are presented (Table 1). Coal samples having a p a r t i c l e s i z e below 1,4 mm were used. Table 1. Proximate and u l t i m a t e analyses of the c o a l s and u l t i m a t e analyses of the e x t r a c t s .

Coal J M , Ash, daf c

y

C H Ν

Yield

C /

4,34 4,02 39,05 82,34 5,40 1,64 0,57 10,05

-

BE extract from Coal J

DMF extract from Coal J

-

-

82,43 7,45 1,00 0,64 8,48

-

81,07 7,04 1,41 0,84 9,64 8,76

Coal W 4,09 9,00 37,40 80,67 5,11 1,40 0,87 11,95

-

, yields BE extract from Coal W

-

82,65 7,08 1,15 1,55 7,57 4,47

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4.

a) b)

MARZEC ET AL.

Ultimate a n a l y s i s i n wt % of daf c o a l , by d i f f e r e n c e , c) y i e l d s i n wt % of daf c o a l ,

Extraction The samples were s u c c e s s i v e l y extracted ethanol 7:3 w mixture and by dimethylformamide.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

73

Asphaltenes and Preasphaltenes

by benzene-

Benzene-ethanol e x t r a c t i o n was performed i n a Soxhlet apparatus f o r 150 hours. Y i e l d s and u l t i m a t e a n a l y s i s o f the ext r a c t s a r e given i n (Table 1). Although the y i e l d s a r e low, they are considerably higher than the separate benzene e x t r a c t and ethanol e x t r a c t y i e l d s (ca. 0.1 wt % ) . Temperature curriculum o f the extracted compounds: a f t e r ext r a c t i o n a t ambient temperature the e x t r a c t s o l u t i o n was exposed only to temperatures below 100°C (the bottom f l a s k of the water bath heated Soxhlet) f o r 18 hours. A f t e r each 18-hour p e r i o d , the s o l u t i o n was removed and f r e s h solvent used. The t o t a l ext r a c t s o l u t i o n was c a r e f u l l y f i l t e r e d and the s o l v e n t s were evaporated from i t i n a r o t a r y apparatus a t 50°C and reduced p r e s s u r e . Dimethylformide e x t r a c t i o n of the r e s i d u e ( i . e . the benzeneethanol i n s o l u b l e s ) was c a r r i e d out a t ambient temperature by mec h a n i c a l a g i t a t i o n , f i l t r a t i o n , and a d d i t i o n of f r e s h DMF. This was repeated as many as 25 times. Y i e l d s and u l t i m a t e a n a l y s i s of the DMF e x t r a c t a r e given (Table 1 ) . Temperature curriculum of the extracted compounds: the t o t a l e x t r a c t s o l u t i o n was f r e e d frcm the solvent (DMF) i n a r o t a r y apparatus a t 70 C and reduced pressure. e

F r a c t i o n a t i o n of the e x t r a c t s This was c a r r i e d out according to a scheme (Figure 1) based on the procedure described by Schweighardt et a l . (9,10) f o r a n a l y s i s of hydrogenated c o a l l i quids. The f o l l o w i n g group components have been i s o l a t e d : preasphaltenes i . e . , benzene i n s o l u b l e s / p y r i d i n e s o l . asphaltenes i . e . , hexane insolubles/benzene s o l u b l e s b a s i c f r a c t i o n of asphaltenes a c i d i c / n e u t r a l f r a c t i o n of asphaltenes benzene and hexane s o l u b l e s . Moreover, the preasphaltenes derived from BE e x t r a c t have been separated i n t o b a s i c and a c i d i c / n e u t r a l f r a c t i o n s by dry HC1 treatment (Figure 1). An attempt to separate the preasphaltenes derived from DMF e x t r a c t r e s u l t s i n the s e p a r a t i o n of a s i g n i f i cant amount of HC1 adducts i n s o l u b l e i n DMF. However, the next steps of the procedure f a i l e d s i n c e - f r e e bases cannot be obtained as they a r e i n s o l u b l e i n toluene; on the other hand, toluene cannot be replaced by DMF which e a s i l y mixes w i t h NaOH aqueous s o l u t i o n , - some HC1 adducts a r e s o l u b l e i n DMF and cannot be separated from the a c i d i c / n e u t r a l f r a c t i o n .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

S

PYRIDINE INSOLUBLES HEXANE SOLUBLES

1

HCL

I

TOLUENE

ASPHALTENES

BASIC CPDS

1

ACIDIC AND NEUTRAL CPDS

NaOH a q . -H TOLUENE

1

HEXANE

I

PARTIAL BENZENE EVAPORATION

BENZENE SOLUBLES

Figure 1. Fractionation scheme of the extracts, (x) Benzene-ethanol 7:3 vv mixture applied in the analysis of BE extract, dimethylformamide applied in the analysis of DMF extract, (xx) Some HCl adducts of basic compounds soluble in DMF are present in the acidic/neutral fraction of preasphaltenes derived from DMF extract, (xxx) Free preasphaltene bases derived from DMF extract cannot be obtained.

C

ACIDIC AND NEUTRAL pD xx/

NaOH a q . + TOLUENES

3

SOLVENT ^ I HCL

PRAASPHALTENES

!

BENZENE INSOLUBLES I PYRIDINE

BE EXTRACT OR DMF EXTRACT I BENZENE I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

4.

MARZEC ET AL.

Asphaltenes

and

Preasphaltenes

75

In a i l cases, the content of preasphaltenes was determined by the d i f f e r e n c e : benzene i n s o l u b l e s minus p y r i d i n e i n s o l u b l e s . Temperature curriculum of the f r a c t i o n a t e d compounds: a l l group components were f r e e d from the s o l v e n t s i n a r o t a r y apparatus a t 50°C or a t 70°C (preasphaltenes) and reduced pressure except p y r i d i n e i n s o l u b l e s - they were d r i e d at 110°C. Other anal y t i c a l work was done a t ambient temperature. Samples were stored i n n i t r o g e n .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

S o l u b i l i t y t e s t of i s o l a t e d group components Small samples of each group component i s o l a t e d from BE ext r a c t and DMF e x t r a c t were r e d i s s o l v e d i n the same solvent which had been a p p l i e d i n the c o a l e x t r a c t i o n . A l l of them were e a s i l y d i s s o l v e d a t ambient temperature. Therefore, no i n d i c a t i o n was found of any p o l y m e r i z a t i o n (6} or other chemical change accompanying the f r a c t i o n a t i o n procedure and causing any s o l u b i l i t y decrease. Contrary to t h i s , the p y r i d i n e i n s o l u b l e s was derived from both e x t r a c t s and f r e e d from p y r i d i n e at 110°C are almost i n s o l u b l e i n the BE mixture and DMF r e s p e c t i v e l y . The

group composition of the e x t r a c t s

The y i e l d s of the group components of the e x t r a c t s a r e given (Figure 2, F i g u r e 3, F i g u r e 4). The successive e x t r a c t i o n of the hvab c o a l J leads to the c o n c l u s i o n that a t l e a s t 1 wt % of the asphaltenes and 6 wt % of the preasphaltenes on a daf b a s i s are present i n the o r i g i n a l c o a l . However, the r e a l content of a s phaltenes i n the c o a l i s s t i l l not known s i n c e we do not know a solvent which i s capable of e x t r a c t i n g a l l of them. TLC

a n a l y s i s of the e x t r a c t s and t h e i r group components

The samples were developed on the TLC p l a t e s using the i n d i cated solvent mixtures (Table 2 ) . N e u t r a l g e l (type MN-Kieselgel HF) on 20x20 cm p l a t e s was used. F u l l development c y c l e was 16 cm high; 1/2 c y c l e was r e a l i z e d as f o l l o w s : the p l a t e was kept i n the chamber u n t i l the solvent reached 1/2 height. I t was then r e moved from the chamber, d r i e d i n n i t r o g e n , and r e i n s e r t e d i n the chamber. The spray reagents used f o r the f u n c t i o n a l group d e t e c t i o n are presented i n Table 3. The p r e p a r a t i o n of the reagents i s based on the E. Merck handbook - "Anfarbereagenzien f u r Dunnschicht- und Papier-Chromatographie" (Darmstadt, 1970). The same reagents were used by us i n a n a l y s i s of the hydrogenated c o a l l i q u i d s (11).

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

ASPHALTENES*/ 27 %

HEXANE SOLUBLES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

24 %

PYRIDINE INSOLUBLES 1 % Figure 2. Benzene-ethanol extract from hvcb coal W 4.5% on daf coal, (x) The ratio of acidic/ neutral cpds and bases is 3.1.

PYRIDINE INSOLUBLES 1 % Figure 3. Benzene-ethanol extract from hvab coal J 4.5% on daf coal, (x) The ratio of acidic/ neutral cpds and bases is 3.9. (xx) The ratio of acidic/neutral cpds and bases is 12.4.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

MARZEC ET AL.

Asphaltenes

and

Preasphaltenes

Figure 4. Dimethylformamide extract from hvab coal J 8.8% on daf coal, (x) The ratio of acidic/neutral cpds and bases is 3.4.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

78

ORGANIC CHEMISTRY OF COAL

Table 2.

Thin-Layer Chromatography C o n d i t i o n s

Solvent

BE,DMF e x t r a c t s

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

BE preasphaltenes

system

methanol:benzene : chloroform methanol:benzene

Solvent ratio

Development cycle

1 1: 1

1/2, f u l l

3 7

full

DMF preasphaltenes

methanol:benzene : chloroform

1 1 1

full

BE preasphaltene bases

methanol:benzene : chloroform

1 1: 1

1/2, 3/4, full

BE preasphaltene acidic/neutral f r .

methanol: benzene : chloroform

1 1 1

1/2, 3/4, full

BE,DMF asphaltenes

methanol:benzene

3 7

full

BE,DMF asphaltene

methanol: c h l o r o form

1 1

full

BE,DMF asphaltene acidic/neutral f r .

methanol: c h l o r o form

1: 1

1/2, f u l l

R e s u l t s of TLC a n a l y s i s of the c o a l e x t r a c t as w e l l as i t s separ a t i o n products are summarized i n Table 4, The r e s u l t s i n d i c a t e that asphaltenes and BE preasphaltenes d e r i v e d from c o a l e x t r a c t s c o n t a i n heterocompounds which may be separated i n t o b a s i c and acidic/neutral fractions. Phenol and p y r r o l d e r i v a t i v e s are p r e sent i n the a c i d i c f r a c t i o n , p y r i d i n e d e r i v a t i v e s i n the b a s i c portion. Therefore, analogous r e s u l t s have been obtained i n TLC a n a l y s i s of asphaltenes e x t r a c t e d from c o a l at ambient temperature ( t h i s paper) and asphaltenes d e r i v e d from the high temperature c o a l conversion products (5, 9_ 10, 11), 9

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4.

MARZEC ET AL.

Table 3.

Asphaltenes

and Preasphaltenes

79

Thin-Layer Spray Reagents Detec­ tion limit (ug)

F u n c t i o n a l group i n d i c a t i o n Ar-OH Phenol type

N-H r i n g Pyrrol type

Fast Blue Salt Β

redviolet

brownviolet

FeCl 3% i n 0, 5n HCl

violet

dark green

yellowviolet

purplebrown

1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

Wachmeister s Reagent

=N-ring Ar-NH Pyridine Amines type 2

-

-

yelloworange

0,01

blue

0,01

brown-

0,1

light a

violet )

Erlich's Reagent 1

Dragendorff s Reagent Iodoplatinate

light yellow

0,05

yellow

-

-

orange

pinkred

0,1

-

-

brown

beige

0,5

a f t e r few hours Table 4.

R e s u l t s of Spray Reagent Test

Ar-OH Phenol type BE,DMF e x t r a c t s BE,DMF p r e a s p h a l ­ tenes BE preasphaltene bases BE preasphaltene acidic/neutral f r . BE,DMF asphaltenes BE,DMF asphaltene bases BE,DMF asphaltene acidic/neutral f r .

+ +

+

F u n c t i o n a l group =N-ring N-H r i n g Pyridine Pyrrol type type

+ +

+

+ +

xx)

Ar-NH

X ) 2

Amine

+ +

+

+

+ +

+ +

TLC-Spray Reagent i n d i c a t i o n of amine presence i s not an i r ­ r e f u t a b l e proof. Meaningless t e s t - preasphaltenes are contaminated during s e p a r a t i o n procedure.

by p y r i d i n e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

80

ORGANIC CHEMISTRY OF COAL

Mass spectrometry of some group components F i e l d I o n i z a t i o n MS. Molecular weight d i s t r i b u t i o n s of the samples l i s t e d (Table 5) were determined using FI MS technique. The technique o f f e r s a unique way to c h a r a c t e r i z e c o a l d e r i v e d products and to understand t h e i r nature i n molecular terms (12). The s p e c t r a were obtained on a V a r i a n MAT 711 and recorded at v a r i o u s probe temperatures (50°C, 100°C, 150°C, 200°C, 250°C, 300°C). The h e i g h t s of each molecular peak were summed and the t o t a l i n t e n s i t y of a l l ions was c a l c u l a t e d f o r each sample. The molecular weight d i s t r i b u t i o n (Table 5) was c a l c u l a t e d using FI s e n s i t i v i t i e s from Severin's paper (13).

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

Table 5.

Molecular Weight D i s t r i b u t i o n Molecular Range of Ions (% of t o t a l amount)

Sample

EB hexane s o l u b l e s

78

187

301

401

501

601

Maxi mum M obser701 ved

186

300

400

500

600

700

800

4

25

35

22

12

2

-

630

9

6

2

790

8

29

23

23

16

41

29

14

-

-

-

500

7

21

35

25

8

3

1

750

6

30

40

19

5

-

-

600

10

34

26

20

9

1

-

690

EB preasphaltenes

7

27

39

22

5

-

-

590

DMF

5

26

24

21

15

8

1

735

DMF hexane s o l u b l e s EB asphaltene bases DMF asphaltene bases EB asphaltene acidic/neutral f r . DMF asphaltene acidic/neutral f r .

preasphaltenes

The instrument's c a p a b i l i t y f o r r e c o r d i n g high molecular weight masses was checked by running the s p e c t r a of FPC c a l i b r a t i o n standards (800 and 1200 GPC p o l y p r o p y l e n e g l y c o l s ) . Peaks up to 800 amu and 1200 amu r e s p e c t i v e l y , have been detected. A l l i n v e s t i g a t e d samples were abundant i n compounds w i t h i n 187-500 amu range. They c o n s t i t u t e d over 70% of each sample. No molecular masses over 630 amu and over 790 amu were detected f o r BE and DMF d e r i v e d group components r e s p e c t i v e l y . Nearly a l l mol e c u l a r peaks w i t h i n the molecular ranges presented i n the Table 5 were observed i n the FI s p e c t r a of each sample. I t means that at l e a s t a few hundred compounds are present i n each sample. I t should be n o t i c e d that the t o t a l i n t e n s i t y of the preasphaltene and asphaltene base s p e c t r a (spectra of n i t r o g e n concent r a t e s ) are c o n s i d e r a b l y lower than the other group components. The reason i s unknown, however lower s e n s i t i v i t i e s of the n i t r o g e n

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

MARZEC ET AL.

4.

Asphaltenes

and

81

Preasphaltenes

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

compounds should be considered f i r s t . High R e s o l u t i o n MS i s the a n a l y t i c a l technique that can f u r n i s h s i g n i f i c a n t i n f o r m a t i o n on the hetero-compounds i n c o a l l i q u i d s (14,15). HR MS analyses of the asphaltenes d e r i v e d from BE and DMF e x t r a c t s were performed u s i n g V a r i a n MAT 711 and J e o l JMS D-100 spectrometers. The s p e c t r a were recorded at a r e s o l v i n g power of approximately 1/8000, 70 eV i o n i z i n g v o l t a g e and at v a r i o u s temp­ eratures from ambient temp, to 300°C. A d i r e c t i n s e r t a t i o n probe was used. C a l c u l a t i o n of the p r e c i s e masses and formulas were c a r r i e d out on a Texas Instruments 980 Β computer. The i d e n t i f i e d formulas are l i s t e d i n Tables 6 and 7. Only those formulas which had been detected by both spectrometers were considered. I t i s evident that the presented data do not c o n t a i n a l l compounds o c c u r i n g i n the samples s i n c e more molecular masses were recorded u s i n g FI MS than are r e p o r t e d data (Tables 6 and 7). However, some i n t e r e s t i n g c o n c l u s i o n s can be drawn from HR MS data. The most s t r i k i n g i s that there are s i g n i f i c a n t d i f f e r e n c e s between the composition of asphaltenes d e r i v e d from BE e x t r a c t and from DMF e x t r a c t . For i n s t a n c e C H2n-23 P 2n-33 N

n

C

H

N

U

t

0

C

H

N

a

n

d

C

H

U

U

t

o

C

H

N

a

n

d

r

p

t

0

C

H

f

o

r

m

u

l

a

s

n 2n-18 2 ? n 2n-26 2 n 2n-6° n 2n-12° found i n BE asphaltenes are e n t i r e l y absent i n DMF asphaltenes.

CONCLUSIONS Asphaltenes and preasphaltenes are components of the o r i g i ­ nal coal. Therefore some amount of these group components i n c o a l l i q u e f a c t i o n products i s not the product of thermal or c a t a l y t i c conversion. The r e a l content of asphaltenes and preasphaltenes i n an o r i g i n a l c o a l i s s t i l l an unsolved problem. We have to know more about electron-donor and -acceptor p r o p e r t i e s of s o l v e n t s as w e l l as about the s t r e n g t h of e l e c t r o n donor-acceptor bonds o c c u r i n g i n c o a l s i n order tc s e l e c t a s o l v e n t capable of e x t r a c t i n g the t o t a l amount of these components from any o r i g i n a l c o a l . The f u n c t i o n a l groups detected i n the preasphaltenes and asphaltenes (TLC and HR MS data) o c c u r i n g i n the o r i g i n a l c o a l , have proton-donor and e l e c t r o n - a c c e p t o r c h a r a c t e r i s t i c s (OH-phen o l , NH-pyrrol type) and electron-donor c h a r a c t e r i s t i c s (oxygen compounds, =N-pyridine type, p o s s i b l y amines). Therefore, hydro­ gen bonds as w e l l as e l e c t r o n donor-acceptor bonds should be con­ s i d e r e d to be r e s p o n s i b l e f o r b i n d i n g together the e x t r a c t a b l e heterocompounds and the c r o s s - l i n k e d macromolecules that form three-dimensional network of an o r i g i n a l c o a l (16). The molecular weights of the bulk of the e x t r a c t a b l e com­ pounds are i n the 187-500 amu range.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

82

ORGANIC CHEMISTRY OF COAL

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In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

-

19 20 22

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8 12 14 16 18 20 22 24 26

1

Table 6, continued

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Hydroxy-Nitrogen

Compounds

Aminocresoles Nitrosobenzes, A c e t h y l p y r i d i n e s Hydroxyindoles, Aminobenzofuranes Hydroxyquinolines Azahydroxyfluorenes Azafluorenones Pyridodibenzofuranes Benzophenoxazines

A z a i n d o l e s , Benzimidazoles Acenaphthydrines Carbolines Phenylazaindoles, Phenylbenzimidazoles Phenylquinazolines Diazapyrenes Diazachrysenes Diazabenzofluoranthenes Diazahenzopyrenes

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

ORGANIC CHEMISTRY OF COAL

84

Table 7. HR MS Data on the Hydroxy- and Dihydroxy Compounds of A c i d i c / N e u t r a l Parts of Asphaltenes derived from BE and DMF Extracts *) . 3

Carbon Number D i s t r i b u t i o n Acidic/Neutral Acidic/Neutral asphaltenes asphaltenes from from BE e x t r a c t DMF e x t r a c t

Possible Structural Types

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

C L 0 η 2n-z _

6 8 10 12 16

8,9 17 13,14 12-14 12-16

18,21

18

14-16

16,17

20

-

16,17

22 24

17-19 19,23

21

Phenoles Naphthenophenoles Benzofuranes, Indenoles Naphtoles, F u r y l b e n z o l e s Dibenzofuranes, Hydroxyfluorenes Hydroxyantracenes/hydroxyphenantrenes Diphenylfuranes, Naphthylphenoles Hydroxypyrenes Hydroxychrysenes

-

— C H 0 η 2n-z 2 0

6 18 22

-

9,10

15 16-20

-

—

o

Dihydroxybenzenes Dihydroxyantracenes Dihydroxypyrenes

Hydroxy- and dihydroxy compounds have not been detected i n the asphaltene bases derived from BE and DMF e x t r a c t s .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4.

MARZEC ET AL.

Asphaltenes

and

Preasphaltenes

85

ACKNOWLEDGEMENT This research was supported by P o l i s h Academy of Sciences's Program No. 03.10. The authors g r a t e f u l l y acknowledge P r o f . Dr. Wlodzimierz K i s i e l o w who f i r m l y encouraged us to begin r e s e a r c h on c o a l o r ­ ganic chemistry by a s o l v e n t e x t r a c t i o n and f o r h i s fruitful dis­ cussions. We wish to thank a l s o : Dr. J. Szafranek, Eng. M. S t o b i e c k i and Eng. A. P l a z i a k f o r p r o v i d i n g mass s p e c t r a ; Mrs. J. Piecha, Miss S. Urbaniec and Mr. K. Kowalski f o r t h e i r t e c h n i c a l a s s i s ­ tance and a n a l y t i c a l work; Dr. M. Boduszynski f o r p r o v i d i n g GPC standards.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch004

LITERATURE CITED 1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16.

Weller S., P e l i p e t z M.S., Friedman S., Ind. Eng. Chem., (1951) 43, 1572 and 1975. Liebenberg B.J., P o t g l e t e r H.C.J., F u e l (1973) 52, 130. Yoshida R., Maekawa R., Ishii T., Takeya G., F u e l (1976) 55, 337. Sternberg H.W., ACS Div. F u e l Chem., P r e p r i n t s (1976) 21 (No.7) 1. Sternberg H.W., Raymond R., Schweighardt F.K., ACS D i v . Petroleum Chem., P r e p r i n t s (1975) 20 (No. 4) 763. Schwager I . , Yen T.F., ACS Div. F u e l Chem., P r e p r i n t s (1976) 21 (No.5) 199. C o l l i n s C.J., Raaen V.F., Benjamin B.M., Kabalka G., F u e l (1977) 56, 107. Schweighardt F.K., Sharkey A.G., "Coal Chemistry Workshop P r e p r i n t s " , Paper No.6, Stanford Research I n s t i t u t e , Stanford, 1976. Sternberg H.W., Raymond R., Schweighardt F.K., Science (1975) 188, 49. Schweighardt F.K., Retcofsky H.L., Raymond R., ACS Div. F u e l Chem., P r e p r i n t s (1976) 21 (No. 7) 27. Bodzek D., Krzyzanowska T., Lotocka Z., Marzec Α., Nafta (1977) 33, 96. (In P o l i s h ) . John G.A. St., Butrill S.E., Anbar Μ., ACS Div. F u e l Chem., P r e p r i n t s (1977) 22 (No.5) 141. Severin D., O e l e r t H.H., Bergman G., E r d o l u. Kohle (1972) 25 (No.9) 514. Sharkey A.G., Shultz J.L., Schmidt C . E . , F r i e d e l R.A. PERC/ RI-77/7, P i t t s b u r g h Energy Research Center, April 1977. A c z e l T., Lumpkin H.E., ACS Div. Petroleum Chem., P r e p r i n t s (1977) 22 (No.3) 911. Kovac J . , Larsen J.W., ACS Div. F u e l Chem., P r e p r i n t s (1977) 22 (no.5) 181.

RECEIVED February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5 Phenols as Chemical Fossils in Coals

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

J. BIMER Instiute of Organic Chemistry, Polish Academy of Sciences, Warsaw, Poland P.H.GIVEN and SWADESH RAJ Fuel Science Section, Material Sciences Department, Pennsylvania State University, University Park,PA16802 It is generally considered that vitrinite, the principal maceral in most coals, represents coalified, partly decayed wood. Hence lignin should be one of the important precursors to the vitrinites in coals. Accordingly, it would be interesting to know whether any chemical fossils related to lignin could be found in coals. The purpose of this paper is to report what we believe to be a successful search for such fossils. The experimental approach exploited a degradation reaction developed in a study of soil humic acids by Burges et al. (1) This reaction involves a reductive degradation with sodium amalgam and hot water. Thin layer chromatography of the ether soluble part of the product (yield, about 20%) showed the presence of a number of phenols and phenolic acids, most of whose structures bore obvious relationships to known microbial and chemical degradation products of lignin (I) but some to the A ring of flavonoids (II).

where R = COOH, CHO, -CH=CH-C00H,-CH -C0-C00H, e t c . ; R = H or OCH3 or OH; R3 = H or OCH3 or OH. The group may represent a side chain of 1, 2 ( r a r e l y ) or 3 carbon atoms, i n various s t a t e s of o x i d a t i o n . Burges et a l. t h e r e f o r e concluded that the humic acids they studied were condensates of phenolic compounds from the degradation of plant products with amino acids (see a l s o F l a i g ) (2). ±

2

2

0-8412-0427-6/78/47-071-086$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5.

BIMER ET

AL.

Phenols

as

Chemical

87

Fossils

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

Humic a c i d s can be e x t r a c t e d from peats and l i g n i t e s but not from bituminous c o a l s . However, o x i d a t i o n of bituminous c o a l s with aqueous performic a c i d generates i n high y i e l d (80-110% by weight) m a t e r i a l s that c l o s e l y resemble humic a c i d s (3). In p r e l i m i n a r y s t u d i e s performed some years ago by one of us (J.B.) while on leave of absence from h i s I n s t i t u t e , the Burges r e d u c t i v e degradation was a p p l i e d to humic a c i d s e x t r a c t e d from some peats and l i g n i t e s , and produced by o x i d a t i o n of a number of bituminous c o a l s . A number of i d e n t i f i c a t i o n s of products were made by gas chromatography w i t h c o - i n j e c t i o n of standards, but at that time f a c i l i t i e s were only r a r e l y a v a i l a b l e to permit c o n f i r m a t i o n by mass spectrometry. Such c o n f i r m a t i o n has been more f u l l y obtained r e c e n t l y by another of the authors S.R.), who a l s o studied a wider range of c o a l s ( t o t a l l i n g 43 samples). I t i s proposed i n t h i s p r e l i m i n a r y p u b l i c a t i o n to d e s c r i b e the experimental procedures and to g i v e a s u f f i c i e n t s e l e c t i o n of the data to show what was found by c o - i n j e c t i o n and l a t e r confirmed by mass spectrometry. The major c o a l measures of the United States were l a i d down e i t h e r i n the Carboniferous era (ca. 300 m. years B.P.), or i n the Cretaceous and T e r t i a r y (130-60 m. years B.P.). Between these two eras a great d e a l of e v o l u t i o n occurred i n the p l a n t kingdom; a s s o c i a t e d with t h i s were some changes i n the nature of groups R and R3 i n s t r u c t u r e I above. However, having s t a t e d the f a c t , we need not pursue t h i s matter here. 2

Experimental Humic a c i d s were e x t r a c t e d from peats and l i g n i t e s with sodium hydroxide f o l l o w i n g standard procedures.

0.5N

The o x i d a t i o n of c o a l s with aqueous performic a c i d i s h i g h l y exothermic. F i v e gm of c o a l was d i s p e r s e d i n 50 ml of anhydrous formic a c i d , and 50 ml of 30% hydrogen peroxide was added i n 2 ml p o r t i o n s at such a r a t e that the temperature d i d not exceed 55°C (however, i n the e a r l i e r phase, the c o a l / f o r m i c a c i d suspension was cooled i n i c e during the a d d i t i o n of H 0 ) . The mixture was then allowed to stand at room temperature with s t i r r i n g f o r 24 hours. The washed and d r i e d s o l i d product was e x t r a c t e d w i t h IN NaOH under n i t r o g e n and c e n t r i f u g e d . The e x t r a c t was p r e c i p i t a t e d by a c i d i f i c a t i o n to pH 1. The washed and d r i e d humic a c i d s were r e d i s s o l v e d i n a l k a l i and, f o l l o w i n g the procedure of Burges et a l . (1), t r e a t e d with 3% sodium amalgam while the s o l u t i o n was heated i n an o i l bath at 110-115° f o r 4-5 hours. 2

2

A f t e r removal of mercury, the r e s u l t i n g s o l u t i o n was a c i d i f i e d to pH 1 and c e n t r i f u g e d ; the supernatant was c a r e f u l l y r e moved and the r e s i d u e extracted twice by c e n t r i f u g a t i o n with

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

88

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

ether and twice with methylene c h l o r i d e . Solvents were removed and the r e s i d u e s mixed. The residues were t r e a t e d with S y l o l HTP reagent (Supelco, Inc., B e l i e f o n t e , Pa.) under the c o n d i t i o n s r e c ommended f o r converting phenols to t r i m e t h y l s i l y l ethers and c a r b o x y l i c a c i d s to the corresponding e s t e r s . Experiment showed OV 101 column packing (3% on 80/100 mesh Supelcoport) to be the most e f f e c t i v e f o r gas chromatography o f the s i x packings t e s t e d . GC analyses, with and without c o - i n j e c t i o n of standards, were performed with a Hewlett-Packard No. 5750 instrument, equipped with flame i o n i z a t i o n d e t e c t o r s . GC/MS a n a l yses i n the l a t e r phase were made by Mr. David M. Hindenlang, using a Finnigan model 3000 instrument under the charge of Dr. L a r r y Hendry of the Chemistry Department of t h i s U n i v e r s i t y . OV 101 columns were again used. The GC/MS instrument was provided w i t h a data system, and t h i s was used to subtract the mass spectrum at the foot of each peak j u s t before i t began to e l u t e , or j u s t a f t e r i t had done so, from the spectrum recorded as the maximum o f the peak was e l u t e d . Such a procedure i s c e r t a i n l y a r b i t r a r y , but d i s c space could not be monopolized f o r continued storage o f our data w h i l e other procedures were t e s t e d and i n t e r p r e t a t i o n s worked out. Consequently, the raw MS data, massaged as d e s c r i b e d above, were reported f o r standards and unknowns as p r i n t o u t s t a b u l a t i n g m/e values and r e l a t i v e i n t e n s i t i e s , and comparisons were made by v i s u a l i n s p e c t i o n of the p r i n t e d data. Results On the dry b a s i s the weight of crude o x i d i z e d c o a l was u s u a l l y 85-105% of the weight of raw c o a l . The y i e l d s of daf humic a c i d s were i n the range 65-90% of dmmf c o a l . Within the range of rank s t u d i e d (78-87%C dmmf), the y i e l d tended to i n c r e a s e with i n c r e a s ing rank. Pétrographie s t u d i e s of the o x i d i z e d products of three c o a l s (by Dr. Alan Davis and Mr. Harvey Z e i s s , to whom we are i n debted) showed that the v i t r i n i t e s were g r e a t l y a l t e r e d compared with t h e i r appearance i n the raw c o a l s , while s p o r i n i t e and the i n e r t macérais had changed l i t t l e or not a t a l l . These apparently unaltered macérais could s t i l l be recognized i n the NaOH-insoluble m a t e r i a l s . Thus the humic a c i d s were derived very l a r g e l y from the v i t r i n i t i e macérais. The y i e l d s of ether s o l u b l e products from the r e d u c t i v e degradation were i n the range 10-40% o f the weight of humic a c i d s taken; y i e l d s when the r e a c t i o n i s a p p l i e d to s o i l humic a c i d s were about 20% (1). Y i e l d s from humic a c i d s from the younger Western c o a l s tended t o be somewhat higher than those from Carboniferous c o a l s of the eastern U. S. Chromatograms obtained i n the e a r l i e r phase of the work are shown i n F i g u r e s 1 and 2, where the names of compounds i d e n t i f i e d , mostly by c o - i n j e c t i o n , are entered against the corresponding peaks ( t r i v i a l names are used i n the f i g u r e s because they are u s u a l l y

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

BiMER ET AL.

Phenols

as Chemical

Fossils

89

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

5.

Figure 1.

Chromatogram of degradation products (as TMS derivatives) from C Seam Coal, Benham, Kentucky (HVA, PSOC13)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

90

ORGANIC CHEMISTRY OF COAL

I

Ο

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In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5.

BiMER ET AL.

Thenols

as

Chemical

Fossils

91

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

shorter; a l i s t of equivalent systematic names i s given i n the Appendix. Comparison of the s t r u c t u r e s with I and I I above w i l l show which may be b i o l o g i c a l l y r e l a t e d ) . I t w i l l be seen that r e s o l u t i o n i s moderately good but that even so a number of major peaks are u n i d e n t i f i e d . These curves are t y p i c a l of what was found f o r products from the s i x c o a l s studied. A l l 3 dihydroxy-benzenes were commonly found and 2 of the trihydroxy-benzenes. 2,6-Xylenol was f r e q u e n t l y found i n both the e a r l i e r and l a t e r work, and was the only one of s i x x y l e n o l s to be i d e n t i f i e d . S e v e r a l of the compounds f r e q u e n t l y encountered ( v a n i l l i n and v a n i l l i c a c i d , s y r i n g i c aldehyde and a c i d , p. hydroxy-benzoic a c i d ) are w e l l known as degradation products of l i g n i n . A peak i s seen i n F i g u r e 1 l a b e l l e d 2,5dihydroxy-benzoic a c i d (2,5-DHBA), and another l a b e l l e d 2,4-, 3,4-, 3,5-dihydroxy-benzoic a c i d . Experiments with known compounds showed that the l a t t e r three isomers could not be r e s o l v e d under the c o n d i t i o n s used. L a t e r work, u s i n g GC/MS, showed that of the three only the 3,4-isomer was i n f a c t present, and t h i s i s l i g n i n - r e l a t e d . However, the 2,5-isomer i s not, though i t could be derived from the A r i n g of f l a v o n o i d s . 2,3,4-Trihydroxy-benzoic a c i d has no obvious b i o l o g i c a l a s s o c i a t i o n s , though the 3,4,5-isomer ( g a l l i c a c i d ) occurs widely i n the p l a n t kingdom (both isomers were i d e n t i f i e d ) . When, l a t e r , a wider range of samples was studied (with somewhat more severe c o n d i t i o n s of o x i d a t i o n ) , some very p o o r l y r e solved chromatograms were obtained; the products e v i d e n t l y o f t e n represent very complex mixtures of substances. S u r p r i s i n g l y , the products from n e a r l y a l l of the younger western c o a l s were r e s o l v e d p o o r l y or very poorly, while the r e s o l u t i o n of those from the I n t e r i o r and Eastern provinces ranged from mediocre to good. Repr e s e n t a t i v e examples of each type are shown i n F i g u r e s 3 and 4. The r e s o l u t i o n i n F i g u r e 3 i s so bad that one might question whether any i d e n t i f i c a t i o n s are p o s s i b l e . In Table 1, we have assembled d e t a i l s of the mass spectra of four substances a l l e g e d to be ident i f i e d from the GC/MS run shown i n F i g u r e 3, with d e t a i l s of the spectra of the standards. The agreement i s s u r p r i s i n g l y good, and the i d e n t i f i c a t i o n s are, taken w i t h matching of r e t e n t i o n times, reasonably secure. When r e s o l u t i o n i s b e t t e r , as i n F i g u r e 4, one can s u r e l y be c o n f i d e n t i n the i d e n t i f i c a t i o n s ; examples of the correspondence of mass s p e c t r a l data are shown i n Table 2. I t should be added that even when the GC/MS system i s used, many prominent peaks remain u n i d e n t i f i e d . However, many of these showed fragments at m/e=73 i n the corresponding mass s p e c t r a , so that they e v i d e n t l y contained the t r i m e t h y l s i l y l group and were t h e r e f o r e phenols or a c i d s or both.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

ORGANIC CHEMISTRY OF COAL

Figure 3. Total ion current chromatogram of degradation products (as TMS derivatives) from Red Seam (HVC), Kayenta, Arizona (PSOC 312)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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5.

Figure 4.

Total ion current chromatogram of degradation products (as TMS derivatives) from Ohio No. 1 Seam (HVC), Jackson, Ohio (PSOC 202)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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ORGANIC CHEMISTRY OF COAL

Table I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

Data f o r MS I d e n t i f i c a t i o n of Substances i n Degradation Products of Coal from Black Mesa, A r i z o n a (HVC)(PSOC 312)

m/e p/p+i 205 57 45 145 55 89 67

m/e p/p+i 194 23 193 209 151 45 165

Cinnamic A c i d Unknown Standard 3.98 100 82 48 27 25 20 18

Vanillin Standard 6.95 100 83 53 37 29 27 9

4.13 100 86 39 23 20 16 14

Unknown 5.15 88 100 45 60 38 33 17

P- Hydroxybenzoic Standard m/e p/p+i 73 193 267 223 45 75 126

Acid Unknown

3.28 100 45 44 42 21 15 13

2.73 100 63 59 56 41 23 17

P- Hydr oxyc innamic A c i d Unknown Standard ml e p/p+i 13 219 235 293 191 45 75

6.00 100 76 61 32 21 16 15

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5.27 83 100 79 41 39 25 19

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Fossils

Table I I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

Data f o r MS I d e n t i f i c a t i o n of Substances i n Degradation Products of Coal from Ohio No. 1 Seam (HVC)(PSOC 202)

m/ e

Hydroxybenzoic Standard

Acid Unknown

m/e

p/p+i 73 193 267 223 45 75 126

3.28 100 45 44 42 21 15 13

3.18 100 52 48 41 34 19 14

p/p+1 73 45 141 327 312 89 297

P-

m/e p/p+1 73 75 117 225 181 129 297

Ferulic Acid Standard 2.71 100 48 38 24 22 22 20

Syringic Acid Unknown Standard 3.72 100 18 15 12 10 10 9

Unknown 2.93 100 49 35 32 30 25 31

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.15 100 29 23 19 13 15 10

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ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

In c o n s i d e r i n g the o r i g i n of the substances shown as i d e n t i f i e d i n Figures 1-4, one must assume with bituminous coals that c a r b o x y l i c a c i d groups r e s u l t l a r g e l y or e n t i r e l y from the performic a c i d o x i d a t i o n . There i s every reason to suppose that some of the hydroxyl groups were present as such i n the raw c o a l s , but one must n e c e s s a r i l y enquire to what extent i s new OH introduced by the o x i d a t i o n (performic a c i d i s a known reagent f o r c o n v e r t i n g alkenes to epoxides and c l e a v i n g them; t h i s process occurs by a concerted e l e c t r o p h i l i c mechanism. However, the mechanism of a t t a c k on c o a l s could be q u i t e d i f f e r e n t and might, f o r example, f o l l o w a f r e e r a d i c a l mechanism). The substances named i n Figures 1-4 can be a r b i t r a r i l y c l a s s i f i e d as f o l l o w s : (1) "non-committal" substances - those l i k e phenol, p. c r e s o l and benzoic a c i d , whose s t r u c t u r e s are r e l a t i v e l y simple and contain no obvious c l u e s to o r i g i n , (2) those whose s t r u c t u r e s could o b v i o u s l y be r e l a t e d to b i o l o g i c a l p r e c u r s o r s , such as v a n i l l i c , s y r i n g i c , f e r u l i c and other s u b s t i t u t e d cinnamic a c i d s , (3) those whose s t r u c t u r e s are r e l a t i v e l y complex but do not d i s p l a y any obvious a s s o c i a t i o n with b i o l o g i c a l p r e c u r s o r s , such as the dimethyldihydroxybenzene shown i n Figure 1 (isomers not identified). Of these c l a s s e s , (1) r e q u i r e s no f u r t h e r comment here, while (3) presumably may i n c l u d e - or c o n s i s t l a r g e l y of compounds whose OH groups are an a r t i f a c t of the o x i d a t i o n process. T h i s leaves open the question, to what extent are the compounds of c l a s s (2) chemical f o s s i l s or a r t i f a c t s ? Many of the substances i d e n t i f i e d have methoxyl groups i n the 3 - p o s i t i o n or the 3,5-positions, as i n l i g n i n s . These groups could h a r d l y have beeen introduced by the performic a c i d o x i d a t i o n , and t h e r e f o r e i n d i c a t e a chemical f o s s i l status f o r the substances. On the other hand, Blom et a l . (4) s t a t e that methoxyl groups are eliminated by metamorphism i n the subbituminous range. We must admit that the s t r u c t u r e s we i d e n t i f y as methyl phenyl ethers represent a small weight f r a c t i o n of the whole c o a l s : but can a l s o point out that Blom et a l . present no evidence that the Z e i s e l procedure, which they used i n t h e i r analyses, was completely e f f e c t i v e (the reagent HI may not have penetrated the pore s t r u c t u r e f u l l y ) , or even that i t produced with c o a l s the r e s u l t s found with simple compounds. Whatever the mechanism of the performic a c i d o x i d a t i o n with c o a l s , one would expect that i f i t introduces new OH groups, more than one isomer would u s u a l l y be produced. Theref o r e , where a peak i n the chromatograms was i d e n t i f i e d as due to a l i g n i n - r e l a t e d substance l i k e v a n i l l i n or c a f f e i c a c i d , the mass spectra corresponding to neighboring chromatographic peaks were c a r e f u l l y examined to determine whether they could represent spectra of p o s i t i o n isomers. Such isomers were r a r e l y detected. On the other hand, some of the r e l a t i v e l y complex substances not obviously r e l a t e d to b i o l o g i c a l precursors e v i d e n t l y d i d have i s o mers present.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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We conclude that some of the OH groups i n the products may w e l l have been introduced by the performic a c i d o x i d a t i o n , but that most of the substances of s t r u c t u r e r e l a t e d to l i g n i n s were probably not a r t i f a c t s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

The question, to what extent do the f i n d i n g s reported here r e l a t e to the composition of whole c o a l s , must be l e f t f o r d i s c u s s i o n i n a l a t e r paper when a more complete set of data can be presented. In concluding t h i s paper, we should draw a t t e n t i o n to some i m p l i c a t i o n s of the f i n d i n g s , i f the p r o v i s i o n a l assumption can be made that the f i n d i n g s do indeed have relevance to the s t r u c t u r e of v i t r i n i t e macérais i n c o a l s : 1. o-Dihydroxybenzenes, and s t i l l more trihydroxybenzenes, are n o t o r i o u s l y e a s i l y o x i d i z e d . T h i s , i f such s t r u c t u r e s are indeed present i n v i t r i n i t e s , could e x p l a i n why i t i s so d i f f i c u l t to n i t r a t e or s u l f o n a t e c o a l s , even with m i l d reagents, without accompanying o x i d a t i o n (_3), and a l s o why c o a l s so r e a d i l y o x i d i z e i n weathering. P a r t i a l l y methylated polyphenols are l e s s r e a c t i v e , but s t i l l q u i t e r e a d i l y s u s c e p t i b l e to o x i d a t i o n . 2. <9r£?z0-dihydroxybenzene d e r i v a t i v e s are capable of c h e l a t i n g boron and other elements. Less i n f o r m a t i o n i s a v a i l a b l e about o.hydroxy-methoxy d e r i v a t i v e s , but there seems no reason why they should not be capable of c h e l a t i o n . 3. During c a t a l y t i c hydrogénation of c o a l s of any rank to l i q u i d f u e l s , under c o n d i t i o n s that g i v e h i g h conversion, a subs t a n t i a l f r a c t i o n of the oxygen i s removed. However, i n i n t e r a c t i o n s of c o a l w i t h hydrogen donor solvent alone, or i n a p p l i c a t i o n s of the SRC process, oxygen removal i s l e s s complete and the products may r e t a i n o.dihydroxybenzene s t r u c t u r e s , a p o i n t perhaps worthy of note by those concerned with the composition of c o a l liquids. It i s worth n o t i n g here that i n a study of the products of l a s e r p y r o l y s i s of c o a l s i n the i o n i z a t i o n chamber of a time-off l i g h t mass spectrometer, homologous s e r i e s of what appeared to be dihydroxybenzenes were noted (5). The technique could not d i s t i n g u i s h p o s i t i o n a l isomers, but the f i n d i n g i s suggestive when taken with the data i n t h i s paper. Ac know1ed gement s The authors are indebted to Mr. David Hindenlang and Dr. L a r r y Hendry f o r a s s i s t a n c e with o b t a i n i n g GC/MS data. They are a l s o g r a t e f u l to Dr. W i l l i a m Spackman f o r f u l l y c h a r a c t e r i z e d c o a l samp l e s from the Penn State/DOE Coal Sample Base assembled under h i s direction.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

Appendix.

T r i v i a l and Systematic Names of Relevant Phenolic Substances

resorcinol

1,3-d ihydroxyb enz ene

pyrocatechol

1,2-dihydroxybenzene

phloroglucinol

1,3,5-trihydroxybenzene

pyrogallol

1,2,3-trihydroxybenzene

orcinol

3.5- dihydroxytoluene

2-methyl r e s o r c i n o l 2.6- dihydroxytoluene guaiacol

2- methoxyphenol

vanillin

3- methoxy-4-hydroxybenzaldehyde

vanillic

acid

3-methoxy-4-hydroxybenzoic a c i d

syringic

acid

3,5-dimethoxy-4-hydroxybenzoic

acid

cinnamic a c i d

phenyl-3-propenoic a c i d

ferulic

3-methoxy-4-hydroxyphenyl-3-propenoic acid

acid

caffeic acid

3,4-dihydroxyphenyl-3-propenoic a c i d

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Literature Cited Burges, M. Α., Hurst, H. M., and Walkden, S. B., Geochim. et Cosmochim. Acta (1964), 28, 1547. (2) F l a i g , W., in "Coal Science" (1966), Adv. i n Chem. S e r i e s No. 55, Amer. Chem. Soc., p. 58. (3) Given, P. H., Brown, J . Κ., Lupton, Vera, and Wyss, W. F., Proceedings of I n s t i t u t e of F u e l Conference, "Science in the Use of C o a l " (1958), S h e f f i e l d , p.A-38. (4) Blom, L., Edelhausen, L., and van Krevelen, D. W., F u e l (1957), 36, 135; (1959), 38, 537. (5) V a s t o l a , F. J . , P i r o n e , A. J . , Given, P. Η., and Dutcher, R. R., in "Spectrometry of F u e l s " , ed. F r i e d e l , R. Α., Plenum, New York (1970), p. 29.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch005

(1)

RECEIVED February 10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

6 Oxidation of Coal by Alkaline Sodium Hypochlorite SUJIT K. CHAKRABARTTY

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

Fuel Sciences Division, Alberta Research Council, Edmonton, Alberta, Canada

The use of halogens in alkaline solution to effect the oxidation of ketones (1) and of hypochlorite as a bleaching agent are well-known, but the application of alkaline sodium hypochlorite to oxidize coal has only been recently reported. The close proximity of the standard potentials of halogens in various oxidation states and the ease of disproportionation into species with varying degrees of oxidizing power are responsible for rendering aqueous halogen solutions versatile oxidants (2). For this reason, various mechanisms can be encountered in the course of any reaction between a substrate and a halogen in aqueous media. With sodium hypochlorite (at pH above 10, 99 per cent of the available active oxidant is OCl ), the reaction rates depend on several variables, e.g. concentration of the oxidant, pH, buffer-constituents, ionic strength, temperature, presence of catalyst, etc. Under defined reaction conditions, the hypochlorite anion can perform very selective oxidations; the haloform reactions, the oxidation of enolizable ketones to carboxylic acids, the oxidation of active methine, methylene and methyl groups to ketone or carboxyl functions, the replacement of active hydrogen by halogen, decarboxylation and decarbonyl at ion are some of the well-studied reactions used in preparative organic synthesis (lc,2). Since coal contains a fair amount of labile hydrogens, hypochlorite is expected to initiate at least one of these reactions. The cleavage of aromatic rings by hypochlorite anion is a pertinent question f o r coal-oxidation studies. In t h e p r e s e n c e o f a c a t a l y s t , p a r t i c u l a r l y ( 3 ) , R u 0 , 0 s 0 , RhCl and I r C l , sodium h y p o c h l o r i t e d e g r a d e s benzene r i n g s ; 3 - p h e n y l p r o p i o n i c a c i d i s o x i d i z e d t o s u c c i n i c a c i d (94 p e r c e n t y i e l d ) ; p h e n y l c y c l o h e x a n e c a n be o x i d i z e d t o c y c l o h e x a n e c a r b o x y l i c a c i d (25 p e r c e n t ) . W i t h o u t c a t a l y s t , p h e n o l s and n a p h t h o l s (4) a r e known t o r e a c t w i t h s o d i u m h y p o c h l o r i t e a t m o d e r a t e t e m p e r a ture. The r e a c t i o n o f p i c r i c a c i d w i t h h y p o h a l i t e t o g i v e h a l o p i c r i n (5) i s a n o t h e r r e m a r k a b l e r e a c t i o n t h a t r e s u l t s i n t h e c o m p l e t e f r a g m e n t a t i o n o f a benzene r i n g i n t o s i x s i n g l e c a r b o n -

4

4

0-8412-0427-6/78/47-071-100$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3

6.

CHAKRABARTTY

Oxidation

by Alkaline

Sodium

Hypochlorite

u n i t s under v e r y m i l d c o n d i t i o n s . In a l l t h e s e c l e a v a g e r e a c ­ t i o n s , i n i t i a l l y an e x t e n s i v e h a l o g e n a t i o n o f t h e benzene r i n g occurs u n t i l the a r o m a t i c resonance s t a b i l i z a t i o n i s s u f f i c ­ i e n t l y weakened. Low pH c o n d i t i o n s f a v o u r h a l o g e n a t i o n and addition of hypohalite acid. L a n d o l t and c o - w o r k e r s (6) u n d e r t o o k o x i d a t i o n o f a r o m a t i c compounds a t c o n s t a n t pH. I η h t o 6 h o u r s i n a n i t r o g e n atmo­ s p h e r e , n a p h t h a l e n e , w i t h an e x c e s s o f sodium h y p o c h l o r i t e a t 6 0 - 7 0 C was o x i d i z e d a t pH 8.5~9 t o p h t h a l i c a c i d (70 p e r c e n t ) . A t pH above 11, t h e y i e l d o f c l e a v a g e p r o d u c t s d e c r e a s e s c o n ­ s i d e r a b l y and u n o x i d i z e d n a p h t h a l e n e a l o n g w i t h some c h l o r i n a t e d p r o d u c t s were r e c o v e r e d . A l t h o u g h 2-methy1 n a p h t h a 1ene r e a c t e d s i m i l a r l y t o n a p h t h a l e n e a t pH 8.5-9, 1 - n i t r o - 2 - m e t h y 1 n a p h t h a ­ l e n e r e a c t e d t o g i v e o n l y 10 p e r c e n t y i e l d o f 3 ~ n i t r o - 4 m e t h y 1 p h t h a l i c a c i d and 80 p e r c e n t r e c o v e r y o f s t a r t i n g com­ pounds. P h e n a n t h r e n e was f o u n d t o be l e s s r e a c t i v e t h a n n a p h t h a l e n e , and a n t h r a c e n e was i n e r t . The o x i d a t i o n o f methy1-3-naphthy1 k e t o n e w i t h sodium hypo­ c h l o r i t e a t pH above 10 g i v e s 88 p e r c e n t y i e l d o f 2 - n a p h t h o i c a c i d ("7). But f u r t h e r t r e a t m e n t o f 2 - n a p h t h o i c o r 2 , 3 - n a p t h a l e n e d i c a r b o x y l i c a c i d w i t h e x c e s s sodium h y p o c h l o r i t e ( p r e ­ sumably a t pH l o w e r t h a n 10) r e s u l t e d i n c l e a v a g e o f an aroma­ t i c r i n g ; p h t h a l i c , t r i m e l l i t i c a n d / o r p y r o m e l l i t i c a c i d s were o b t a i n e d as c l e a v a g e p r o d u c t s (k). From t h i s d i s c u s s i o n i t i s q u i t e e v i d e n t t h a t sodium hypo­ c h l o r i t e i s a v e r s a t i l e o x i d a n t . The d e g r e e o f s e l e c t i v i t y f o r t h i s o x i d a n t w o u l d depend on how p r e c i s e l y t h e r e a c t i o n c o n d i ­ tions are controlled. F o l l o w i n g t h e p r o c e d u r e d e v e l o p e d by Newman and Holms (7) f o r s y n t h e s i s o f 2 - n a p h t h o i c a c i d f r o m m e t h y 1 - 2 - n a p h t h y l k e t o n e , s e v e r a l c o a l samples w e r e t r e a t e d w i t h h y p o c h l o r i t e a n i o n by C h a k r a b a r t t y and c o - w o r k e r s (8). Three moles o f O C l " were used f o r each gram-atom o f c a r b o n i n c o a l . I t was o b s e r v e d t h a t s u b b i t u m i n o u s c o a l s w o u l d r e a d i l y r e a c t under t h i s c o n d i t i o n b u t b i t u m i n o u s c o a l s w i t h d r y , a s h - f r e e c a r b o n g r e a t e r t h a n 82 p e r c e n t r e q u i r e d p r e v i o u s r e a c t i o n w i t h n i t r o n i u m t e t r a f 1 u o r o b o r a t e i n acetonîtrîle s o l v e n t . The s u b b i t u m i n o u s c o a l s and d e r i v a t i z e d b i t u m i n o u s c o a l s r e a c t e d e q u a l l y w e l l w i t h h y p o c h l o r i t e and gave w a t e r s o l u b l e p r o d u c t s ( s t r u c t u r a l l y f a r l e s s c o m p l e x t h a n s o - c a l l e d humic a c i d ) a t 40-60° i n 2-3 h o u r s and a t 20-28° i n 2-3 d a y s . The p r o d u c t s o f o x i d a t i o n were c a r b o n d i o x i d e and c a r b o x y l i c a c i d s . Table 1 l i s t s t h e y i e l d s from d i f f e r e n t c o a l s r e a c t e d a t 60° w i t h i n i t i a l pH = 12. The w a t e r - s o l u b l e p r o d u c t s were i s o l a t e d , w e r e m e t h y l a t e d w i t h d i a z o m e t h a n e , and were a n a l y z e d by g e l p e r m e a t i o n chromat o g r a p h y (GPC), g a s c h r o m a t o g r a p h y ( G L C ) , mass s p e c t r o m e t r y (MS), and 1 M and 13Q nmr a n a l y s i s . Acetic, propionic, succinic, g l u t a r i c , a d i p i c , benzene- and t o l u e n e - ( w i t h 2 t o 6 c a r b o x y l as w e l l a s w i t h some n i t r o g r o u p s ) c a r b o x y l i c a c i d s were i s o l a t e d and i d e n t i f i e d . The a v e r a g e m o l e c u l a r w e i g h t o f t h e e

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

101

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

102

ORGANIC CHEMISTRY OF COAL

more c o m p l e x p r o d u c t s h a v i n g p o l y c o n d e n s e d a r o m a t i c a n d / o r h e t e r o a r o m a t i c ( m o s t l y s u b s t i t u t e d by numbers o f c a r b o x y l g r o u p s ) , were between 600 and 800. More t h a n 90 p e r c e n t o f c a r b o n i n c o a l c o u l d be a c c o u n t e d f o r f r o m t h i s p r o d u c t a n a l ysis. TABLE I . Y i e l d

of oxidation

p r o d u c t s from d i f f e r e n t c o a l s

Carbon D i o x i d e

Carboxylic Acids a s COOH-Group

Rank

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

%Z,dmf.

76.1 80.5 83.1 85.0 86.4 90.2

mmole/gCarbon

43.2 43.4 40.3 38.3

38.1 34.5

%Zoa\-

Carbon

51.8 52.1

48.4 46.0 45.7 41.4

meq/gCarbon

13.6 14.6 16.4 14.1 21.3 14.0

% CoalCarbon

16.3 17.5 19.7 17.0 25.6

16.8

With the help o f nmr measurement, m o l e c u l a r w e i g h t d a t a , and e l e m e n t a l a n a l y s i s , i t was p o s s i b l e t o c a l c u l a t e t h e r e c o v e r y o f c a r b o n i n d i f f e r e n t c a r b o n f u n c t i o n a l g r o u p s (9). For a t y p i c a l b i t u m i n o u s c o a l ( d . a . f . C - 88%), 18 p e r c e n t o f t o t a l c a r b o n s u r v i v e s o x i d a t i o n as a s i n g l e b e n z e n e r i n g , 6 p e r c e n t a s 2, 3 o r 4 c o n d e n s e d a r o m a t i c ( a n d / o r h e t e r o a r o m a t i c ) r i n g s , 7 per c e n t a s m e t h y l o r m e t h y l e n e and 20 p e r c e n t a s c a r b o x y l groups (Table I I ) . From v a r i o u s r e a c t i o n s some k e t o n e s and e t h e r s a l s o were o b s e r v e d o c c a s i o n a l l y as p r o d u c t s . The most r e v e a l i n g d a t a of t h e s e s t u d i e s a r e t h a t , i r r e s p e c t i v e o f t h e rank o f t h e c o a l , a p p r o x i m a t e l y two t h i r d s o f t h e t o t a l c a r b o n i s o x i d i z e d t o c a r b o n d i o x i d e and c a r b o x y l f u n c t i o n s . I t i s p e r t i n e n t t o know the n a t u r e o f c a r b o n f u n c t i o n a l g r o u p s i n c o a l t h a t u n d e r g o t h i s o x i d a t i o n so r e a d i l y . Mayo and K i r s h e n (10) s t u d i e d t h e o x i d a t i o n o f t h e p y r i d i n e i n s o l u b l e r e s i d u e f r o m I l l i n o i s No. 6 c o a l w i t h t h e o b j e c t i v e o f a t t a i n i n g maximum y i e l d s o f s o l u b l e p r o d u c t w i t h minimum c o n s u m p t i o n o f o x i d a n t and minimum l o s s o f c a r b o n a s c a r b o n d i o x ide. B e c a u s e t h e u n r e a c t e d c o a l and t h e s o l u b l e a c i d s compete for the o x i d a n t , repeated o x i d a t i o n s w i t h small p r o p o r t i o n o f NaOCl were employed w i t h e x t r a c t i o n s and s e p a r a t i o n s o f s o l u b l e a c i d s between s t e p s . In one e x p e r i m e n t 80 p e r c e n t o f t h e o r i g i n a l c a r b o n was a c c o u n t e d f o r a s f o l l o w s : 13.6 p e r c e n t i n u n d i s s o l v e d r e s i d u e , 59.4 p e r c e n t i n c o l o u r e d a c i d s s o l u b l e i n aqueous b i c a r b o n a t e , 7.1 p e r c e n t i n l i g h t e r c o l o u r e d a c i d r e a d i l y s o l u b l e i n w a t e r and 19.9 p e r c e n t i n c a r b o n d i o x i d e . The c o l o u r e d a c i d s had a number a v e r a g e m o l e c u l a r w e i g h t o f a b o u t 900 and a n e u t r a l e q u i v a l e n c e o f 352. The w a t e r s o l u b l e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

6. CHAKRABARTTY

TABLE

II.

Oxidation

Percentage soluble

by Alkaline

Sodium

o f coal-carbons

products,

computed

recovered from

103

Hypochlorite

as

water-

nmr and combustion

data C

Product-Fraction

#1

mono-nuclear

#2

mono-nuclear

#3

polynuclear*

#4

polynuclear*

#5

polynuclear

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

Fr

Hoi Wt 623

0

Mol

Wt

23.7

s k e l e t a l

4 a r e as

s t r u c t u r a l

C

types

o f

total

a l k y l

4.2 2.1

8.4 4.9 0.8 2.4 3.9 20.4

12.0 5.8 0.8 3.1 2.9

Total Probable

ç ^carboxyl

arom

24.6 12.8 1.6 5.5 5.9 50.4

trace trace

0.6 6.9

t h e compounds

i n F r 3 and

f o l lows :

< ll.7 2.5°2.5 0.7 0.1 c

H

M

S

(

)

C 0 0 M e

)

7

( M e )

0

770

< l*W ™eV™ 4 C

(C

H)

Wl.8 O.I2 S

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

104

acids The

h a d M.W. a b o u t

structural

Chakrabartty

and Dorn

hypochlorite

oxidation

Until

a

intermediate is

with

oxidation ring

on

products and

products

isolated

i t

is

coal.

quite

parts

of

cation

carbanion-type

But

of

carboxylic carbon.

tinent

to

rings rings,

major

reaction, in

is

l a r l y , same may

the

further

fact

that

react

rings

presumed arises

that

the

functional

premise,

groups.

loss

sary

a c t i v a t i n g

a c i d i t y a

are

is

si tes

in

Though ing

agent

cated

that

was

the which

(3)

acid.

How-

from

the

oxidation

deactivate

and

aroma-

ring-cleavage

Thus

i t may be

a f t e r

n i t r a t i o n

ring-cleavage

and co-workers hypochlorite

a c i d i c

is

the decrease

more

with

protons.

probably

(?)

as

been

becomes

a c i d i c

the elemental

H/C

r a t i o ,

postulated

a

(8(d))

once

and the progres-

the

neces-

incorporated,

on a

composition

bridged

the

The

secondary of

coal,

oxygen

content

reactive.

than

the

increases,

However,

would

low-rank

from

in oxygen

occurs.

suggested

oxidation In

arises

t h e rank

e . g . -N02, has

proton or

prim-

coal,

tricycloa1kane

t o accommodate

the

BrOnsted

coal.

nitronium

tetraf1uoroborate

(11), r e c e n t this

carbon

a c i d i t y

the atomic

configuration

of

and the coal

carbon Keeping

p a r t i c u l a r l y

acid,

follow

acid

hypohalite

coals

the

Simi-

1).

arises

groups

is

s i g n i f i -

m e l l i t i c

(Figure

and aromatic

towards

weight

group,

restored

carbon.

aro-

become

to m e l l i t i c

bituminous

Chakrabartty

With

BrOnsted

t e r t i a r y

acid

of

coal

on

in molecular

sive

on

of

a c i d i t y

of

data

(2) s h o u l d

to

of

the coal,

and suppresses

structures

the a c c e s s i b i l i t y

BrBnsted

in

reaction.

this

on

peraro-

complex

Nitro

attack

is

a l i the

more

mechanism

inert

of of

the surviving

and co-workers(6)).

the a c t i v i t y

major

increase

are

n i t r a t e d .

non-aromatic

the r e a c t i v i t y

depend

coals

being

this

i t

i n d i -

structure.

part

To produce

system

of

further

the form

may be o x i d i z e d

with

in the

cleavage

oxidation

(4) a n d f i n a l l y

(see, Landolt

From that

a f t e r

from

not a

to

d i f f i c u l t

f o r electrophi1ic

reactions

is

degrade

that

by m i n e r a l s

t h e more

hypochlorite occur-

standpoint,

structure.

coal

to produce

bituminous

only

coal in

how

reaction

minor on

the

oxidation

Isolation

in

very

one assumes

polycondensed

path

the major

If

1

of

of

non-aromatic

function

hypochlorite

(l)

largest

oxidation

ever,

t i c

then

like

a

in

groups

provides

and the carbon

catalyzed

understanding

structure

on

constitute

formed.

analysis

formulate

polymer.

reactions

groups

stages

c h l o r o - a l k y l

acids

completed.

measurement.

structural

the structural

probably

c h l o r o - a l k y l C-nmr

to

chlorine.

y e t t o be

Haloform-type

how t h e c a r b o x y l

matic

cant

1

the coal

carbon

acids

From

know

matic

a

a

is

the early

of

and d i c a r b o x y l i c

the chloroalkyl

total

at

d i f f i c u l t

suggests

mono-

1 3

r e l i a b l e

The presence

products

certain

by

per cent

10-15

the products i d e n t i f i e d

(9)

a l i p h a t i c

phatic

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

of

d e t a i l e d

a v a i l a b l e ,

reacts

and contained

200

analysis

reagent

s i l y l - d e r i v a t i v e s

of

work

by

G. A.

can o x i d i z e

secondary

is

Olah

a well-known et

benzylic

alcohols

to

a l

n i t r a t -

(12) h a v e

alcohols

carbonyl

indi-

and compounds.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

CHAKRABARTTY

Oxidation

Figure 1.

by Alkaline

[·_•

COOH

Sodium

and/or

Hypochlorite

-CZ/-OH]

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

106

ORGANIC CHEMISTRY OF COAL

The nitrolysis of alkanes, as well as cleavage of ethers could be affected by this reagent very smoothly. Consequently, the reaction of coal with this reagent may introduce, in addition to nitro group, various other oxygen functional groups such as ketone, aldehyde and alcohol. (The total acetylable groups determined after nitration was found to increase considerably.) From this background, it can also be argued that the mechanism of hypochlorite oxidation of coal, after being treated with nitronium tetraf1uoroborate, may be similar to phenol oxidation, and a substantial amount of carbon dioxide is generated from cleavage of aromatic rings. The oxidation studies with hypohalite have been reported on whole coals and few hand-picked vitra in samples. The difference in reactivity between macérais have yet to be studied. Reaction in non-aqueous media can enlarge the scope of applicability of this reagent, e.g. selective oxidation of heterocyclic components by two-phase reactions. All coals are very susceptible to halogenation. With hypohalite, under both high and low pH conditions, halogenation of the substrate is a primary reaction. Consequently, halogenation of coal vis-a-vis hypohalite oxidation would be a useful topic for structural studies. Literature Cited: 1.

2. 3. 4.

5. 6. 7. 8.

a. Fuson, R. C. and Bull, Β. Α., Chem Rev 15, 275 (1934) b. Holst, G., Chem Rev 5 4 , 169 (1954) c. Fieser, L. F. and Fieser, Μ., Reagents for Organic Synthesis, John Wiley & Sons, New York, Vol 1 (1967), Vol 11 (1969) Chakrabartty, S. Κ., in Oxidation in Organic Chemistry, Part D., Chapter 5 , Ed. W. S. Trahanovsky, Academic Press, New York (1978) Wolf, S., Hasan, S. K. and Campbell, J . R., J. Chem. Soc. D ( 2 1 ) , 1420 (1970) a. Moye, C. J. and Sternell, S., Austral. J . Chem., 19, 2107 (1970) b. Landolt, R. C., Fuel 5 4 , 229 (1975) c. Mayo, F. R., i b i d . , 273 (1975) Birch, A. J., Moye, C. J., Richards, R. W. and Vanek, Z., J . Chem. Soc. 3586 (1962) Angert, J . L . , Gatton, S. L . , Reilly, M. T. and Landolt, R. G., Fuel 5 6 , 224 (1975) Newman, M. S. and Holms, H. L., in Org. Syn. C o l l . Vol. 2 , 428 (A. H. Blatt, Ed.) Wiley, New York (1943) Chakrabartty, S. K. and Kretschmer, H. O. a. J . Chem. Soc. Perkin 1, 222 (1974) b. Fuel 51, 160 (1972) c. ibid, 5 3 , 132 (1974)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

6.

8.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch006

9. 10.

11. 12.

CHAKRABARTTY

Oxidation

by Alkaline

Sodium

Hypochlorite

Chakrabartty, S. K. and Berkowitz, N. d. ibid., 5 3 , 240 (1974) e. ibid., 55, 362 (1976) f. Nature, 261 ( 5 5 5 5 ) , 76 (1976) Chakrabartty, S. K. and Dorn, H., to be published Mayo, F. R., Huntington, T. and Kirshen, N. Paper No. 1 4 , Preprints 1976 Coal Chemistry Workshop Standford Research Institue Mayo, F. R. and Kirshen, N., in Quatarly Reports on "Homogenous Catalytic Hydrocracking Process for Conversion of Coal to Liquid Fuels, Basic and Exploratory Research". US Energy Research and Development Administration Contract No. Ε ( 4 9 - 1 8 ) - 2 2 0 2 for periods ending on (a) Jan. 1976; (b) April 1976; (c) July 1976; (d) October 1976; (e) January 1977 and (f) April 1977 Fieser, L. F. and Fieser, M., Reagent for Organic Synthesis, Vol I, John Wiley & Sons, Inc., 1967 a. Olah, G. A. and Ho T-L, Synthesis 609 (1976) b. Olah, G. A. and Ho T-L, Synthesis (Press) c. Olah, G. A. and Lin, H. C., J . Amer. Chem. Soc. 93, 1259 (1971) d. Olah, G. A. and Ho T-L, J . Org. Chem. 42 (18), 3097 (1977)

RECEIVED

February

10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

107

7 Oxidative Degradation Studies of Coal and Solvent­ -Refined Coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

RYOICHI HAYATSU, RANDALL E. WINANS, ROBERT G. SCOTT, LEON P. MOORE, and MARTIN H. STUDIER Chemistry Division, Argonne National Laboratory, Argonne, IL 60439

The bulk of the organic matter in coals consists of a macromolecular material of complex and variable composition. Many workers have attempted to degrade coals to smaller molecules which could be identified and interpreted in terms of coal structure. Oxidation has been one of the more important degradation methods. To date a number of oxidizing agents have been used. Among these were HNO , HNO -K Cr O , ΚΜnO , O , H O O and NaOCl, all drastic oxidants. Because these reagents in general result in extensive ring degrada­ tions, with benzene carboxylic acids the only aromatic compounds identified, they have been of limited useful­ ness. Our approach has been to examine the products both from drastic oxidants and more selective ones designed to break up the macromolecules into identifiable units with a minimum of chemical change so that units indige­ nous to coals can be identified. We have found aqueous Na Cr O to be selective and have reported a number of polynuclear aromatic units which resulted from the dichromate oxidation of a bituminous coal and which we believe to be indigenous to the coal (1,2). We have explored a number of oxidizing agents using the samples listed in Table I. In addition to four coals, a sol­ vent refined coal (SRC) and two completely abiotic samples, the synthetic Fischer-Tropsch polymer, and the polymer from the Murchison meteorite, were used for comparison and to test the oxidation methods. Results and Discussion Identification of products: In general the pro­ ducts of oxidation were chiefly carboxylic acids which were esterified with diazomethane to increase their volatility for easier analysis by time-of-flight mass 3

3

2

2

7

4

2

3

2

2

7

0-8412-0427-6/78/47-071-108$05.00/0 This chapter not subject to U.S. copyright. Published 1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

2

7.

HAYATSU ET AL.

Oxidation

Degradation

Studies

109

Table I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

Elemental A n a l y s i s o f Samples

No. 1 2 3 4 5 6 7 8 9

Sample L i g n i t e (Sheridan Wyoming) Bituminous ( I l l i n o i s Seam #2) Bituminous ( P i t t s b u r g h Seam #8) A n t h r a c i t e (Pennsylvania PSOC #85) SRC (from P i t t s b u r g h Seam #8) SRC benzene-methanol ext.* Char S y n t h e t i c Polymer (from Fischer-Tropsch) (3) Polymeric M a t e r i a l from Murchison M e t e o r i t e (3)

C

(maf %)

H

N

S

67. 3

4. 8

1. 3

1.2

0 (by d i f f ) 25.4

77. 8

5.4

1.4

2.1

13.3

82. 7

5.5

1. 3

2.8

7.7

91. 3 87. 2 86. 2 84. 9

3.9 5.5 5.6 1.7

0. 6 1.8 1.8

1.1 1.2 0. 7

3.1 4.3 5.7

80. 0

5.1

1.3

0.0

13.6

76. 1

4.6

2.8

1. 3

15.2

—- —-

* The SRC was f r a c t i o n a t e d i n t o 3 f r a c t i o n s on the b a s i s o f s o l u b i l i t y : hexane (4.5%), benzene-methanol mixture (82.3%), p y r i d i n e (11.8%) and a small r e s i d u e (1.4%).

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

110

ORGANIC CHEMISTRY OF COAL

s p e c t r o m e t r y (TOFMS) w i t h a v a r i a b l e temperature s o l i d i n l e t , GC-TOFMS and h i g h r e s o l u t i o n mass s p e c t r o m e t r y (HRMS) (1-3). N i t r i c A c i d O x i d a t i o n . A l l samples o f T a b l e I e x c e p t #6 were r e f l u x e d w i t h 70% HN0 f o r 16-24 hours y i e l d i n g c l e a r orange c o l o r e d s o l u t i o n s . The a c i d s o l u t i o n s were e v a p o r a t e d t o d r y n e s s under reduced p r e s s u r e and the r e s i d u e weighed. The m e t h y l a t e d a c i d s were a n a l y z e d by GC-MS, HRMS and the s o l i d probe. F r a g m e n t a t i o n p a t t e r n s and p r e c i s e mass d e t e r m i n a t i o n o f b o t h m o l e c u l a r i o n s and fragments, i n p a r t i c u l a r (M-OCH ) / were used f o r i d e n t i f i c a t i o n . In F i g u r e 1 a r e summarized t h e d a t a f o r benzene c a r b o x y l i c a c i d s (as t h e i r methyl e s t e r ) . The s y n t h e t i c sample had been p r e p a r e d by h e a t i n g CO, H and NH w i t h an F e - N i c a t a l y s t a t 200°C f o r s i x months (_3) . I t was a macrom o l e c u l a r m a t e r i a l i n s o l u b l e i n o r g a n i c s o l v e n t s , HC1, HF and KOH. D e s p i t e the d r a s t i c n a t u r e o f t h e n i t r i c a c i d o x i d a t i o n i t appears t h a t u s e f u l i n f o r m a t i o n can be o b t a i n e d by the p r o c e d u r e . F o r example t h e y i e l d o f t o t a l a c i d s and t h e number o f c a r b o x y l i c a c i d groups per benzene r i n g seem c o r r e l a t e d w i t h t h e degree o f c o n d e n s a t i o n o f the o r i g i n a l m a t e r i a l . The s p e c t r a from the s y n t h e t i c sample from t h e F i s c h e r - T r o p s c h r e a c t i o n , and from c h a r a r e r e l a t i v e l y s i m p l e c o n s i s t i n g p r i m a r i l y o f t h e benzene c a r b o x y l i c a c i d e s t e r s w i t h from two t o s i x e s t e r groups. The c o a l samples and c o a l d e r i v e d p r o d u c t s (except f o r char) a r e more complex and cont a i n e d n i t r o s u b s t i t u t e d e s t e r s and p y r i d i n e d e r i v a tives. Note the s i m i l a r i t y between the s y n t h e t i c samp l e and the c h a r p r e p a r e d from I l l i n o i s b i t u m i n o u s c o a l by h e a t i n g under vacuum t o 800°C. The abundance o f the benzene h e x a c a r b o x y l i c a c i d s f o r t h e s e two s u g g e s t s a h i g h degree o f c o n d e n s a t i o n i n the o r i g i n a l samples. The s i m i l a r i t y i n d i s t r i b u t i o n o f t h e o x i d a t i o n products from the two b i t u m i n o u s c o a l s (the I l l i n o i s and P i t t s burgh) i s s t r i k i n g . The s o l v e n t r e f i n e d c o a l d e r i v e d from t h e P i t t s b u r g h #8 c o a l i s shown l a t e r ( F i g u r e 3, T a b l e I I ) t o have a h i g h e r degree o f a r o m a t i c r i n g c o n d e n s a t i o n than i t s f e e d c o a l . Thus i t i s s u r p r i s i n g t o see the s h i f t t o fewer a c i d groups f o r SRC. This may mean t h a t many a l i p h a t i c c r o s s l i n k s were d e s t r o y e d i n the SRC p r o c e s s and e v o l v e d as l i g h t h y d r o c a r b o n s . The r e s u l t s from the m e t e o r i t i c polymer (not shown i n F i g u r e 1, see R e f e r e n c e (_3) ) were v e r y s i m i l a r t o t h o s e o f the s y n t h e t i c polymer. 3

+

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

3

2

3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

Figure 1. Abundances (%) of benzene carboxylic acids, determined as their methyl esters, produced by nitric acid oxidation, η = number of (COOCH ) groups per benzene ring. 3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

112

ORGANIC CHEMISTRY OF COAL

15%-HN03. Ferguson and Wims have r e p o r t e d t h a t 15%-HN0 s e l e c t i v e l y o x i d i z e s d i a l k y l b e n z e n e t o a l k y l b e n z o i c a c i d s (£) . R e f l u x i n g o f l i g n i t e c o a l (sample #1) w i t h 15%-HN03 f o r 16 hours gave a r o m a t i c a c i d s (58.2 wt% o f the o r i g i n a l c o a l ) and humic a c i d - l i k e m a t e r i a l (63.5 wt%) r e s p e c t i v e l y . R e l a t i v e abundances o f b e n z e n e c a r b o x y l i c a c i d s were v e r y s i m i l a r t o t h o s e o f 70%-HNO o x i d a t i o n p r o d u c t o f l i g n i t e (see F i g . 1 ) . In a d d i t i o n t o the b e n z e n e c a r b o x y l i c a c i d s , however, a s e r i e s o f m e t h y l b e n z e n e c a r b o x y l i c a c i d s (17 wt% o f t o t a l a r o m a t i c a c i d ) and o f m e t h y l f u r a n c a r b o x y l i c a c i d s (3.7 wt%) were p o s i t i v e l y i d e n t i f i e d . Nitro derivat i v e s o f b e n z e n e c a r b o x y l i c a c i d s were a l s o found as minor p r o d u c t s . 3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

3

Sodium Dichromate O x i d a t i o n . In g e n e r a l 1-3 g o f sample was heated a t 250°C f o r 36-40 hours w i t h e x c e s s Na Cr 0 (60-120 ml o f 0.4 M-0.6 M) w i t h s t i r r i n g . T h i s p r o c e d u r e o x i d i z e s s i d e c h a i n s and a l i c y c l i c appendages t o p o l y n u c l e a r a r o m a t i c systems w i t h a minimum o f d e g r a d a t i o n o f a r o m a t i c r i n g s ( j l / 2 ^ 5 ^ ) . we have found t h a t model compounds a r e o x i d i z e d i n h i g h y i e l d s (7895%) t o t h e i r c o r r e s p o n d i n g c a r b o x y l i c a c i d s . Samples 1, 2, 3, 4, 6, and 9 were o x i d i z e d w i t h N a C r 0 7 w i t h a h i g h degree o f c o n v e r s i o n t o s o l u b l e o r v o l a t i l e compounds (70-100%). Mass a n a l y s i s o f t h e gaseous f r a c t i o n o b t a i n e d from the o x i d a t i o n showed the p r e s e n c e o f o n l y CO and C 0 . No H 2 , CH4 o r l i g h t hydrocarbons were d e t e c t e d . The y i e l d s o f s o l u b l e compounds were 50-70% o f the w e i g h t o f the o r i g i n a l samples. The a n t h r a c i t e a l s o y i e l d e d 17% o f a humic a c i d t y p e m a t e r i a l o f h i g h m o l e c u l a r weight s o l u b l e i n alkaline solution. In F i g u r e 2 a r e shown g r a p h i c a l l y the r e l a t i v e abundances o f a r o m a t i c and h e t e r o a r o m a t i c u n i t s produced by the d i c h r o m a t e o x i d a t i o n o f t h r e e c o a l s (samples 1, 2, and 4 ) . I t i s obvious t h a t the degree o f a r o m a t i c c o n d e n s a t i o n i n c r e a s e s w i t h rank o f c o a l from l i g n i t e t o b i t u m i n o u s t o a n t h r a c i t e . This o x i d a t i o n p r o c e d u r e has a l s o been s u c c e s s f u l l y a p p l i e d t o SRL and i t s f e e d c o a l ( l i g n i t e , N o r t h Dakota) (7). The N a C r 0 7 - a q o x i d a t i o n p r o c e d u r e has been q u e s t i o n e d because o f t h e p o s s i b i l i t y t h a t major s t r u c t u r a l r e arrangement w i t h p y r o l y t i c f o r m a t i o n o f p o l y n u c l e a r a r o m a t i c compounds might o c c u r d u r i n g t h e r e a c t i o n a t 250°C (8j . The f a c t t h a t no p o l y n u c l e a r a r o m a t i c compounds w i t h more than two f u s e d r i n g s were d e t e c t e d i n the o x i d a t i o n p r o d u c t s o f l i g n i t e (sample 1) and t h a t the degree o f c o n d e n s a t i o n i n c r e a s e s w i t h rank o f c o a l i s i n t e r n a l l y c o n s i s t e n t and s u g g e s t s t h a t c o n d e n s a t i o n during o x i d a t i o n with N a C r 0 7 i s minimal. In a b l a n k 2

2

7

2

2

2

2

2

2

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

HAYATSU ET AL.

Oxidation

Degradation

Studies

? 20-

(e) (e) (c) (c)

Figure 2. Relative abundances of aromatic and heteroaromatic units produced by sodium dichromate oxidation of lignite, bituminous, and anthracite coals. Identification based on TOF variable temperature solid inlet, GC-TOFMS and high resolution MS. Aromatic units in the upper graph (left to right): benzene, naphthalene, phenanthrene,fluoranthene/pyrene,chrysene, anthraquinone, naphthacenequinone/benzanthraquinone,fluorenoneIphenalenone, benzanthrone. Heteroaromatic units in the lower graph (left to right): phthalan, chroman, dibenzo-p-dioxin, xanthone, benzoxanthones, dibenzofuran, benzonaphthofurans, benzothiophene, dibenzothiophene, benzonaphthothiophenes, pyridine, quinoline/isoquinoline, carbazole, acridone, acridine/benzoquinoline. (a) Determined as methyl esters of carboxylic acids and as nonacidic compounds. The benzene unit is normalized to 100 for the lignite and bituminous coals. Phenanthrene is normalized to 100 for anthracite. Aromatic units with a carbonyl group may have resulted from oxidation of a methylene group, (b) In an earlier paper we reported on the basis of published data (1) "that the pyrene ring would have been extensively degraded." However, we have found it to be rather stable under the oxidation conditions we used, (c) These compounds were identified in the nonacidic fraction only, (d) Becausefluoreneand bifluorene were observed in other experiments such as pyrolysis we feel thatfluorenoneis more probable than phenalenone. (e) Identification tentative.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

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ORGANIC CHEMISTRY OF COAL

experiment b i t u m i n o u s c o a l (sample #2) which had been e x t r a c t e d w i t h an o r g a n i c s o l v e n t t o remove t r a p p e d compounds was h e a t e d a t 250°C f o r 40 hours w i t h water. An i n s o l u b l e r e s i d u e 96.2% and i n o r g a n i c s a l t s 2.9% were o b t a i n e d . Mass a n a l y s i s o f the r e s i d u e was i n d i s t i n g u i s h a b l e from t h a t o f the o r i g i n a l c o a l and the H/C r a t i o was unchanged. F u r t h e r m o r e , d e t a i l e d p y r o l y s i s s t u d i e s o f the c o a l showed no e v i d e n c e o f s i g n i f i c a n t t h e r m a l d e c o m p o s i t i o n u n t i l h e a t e d above 250°C. The gas chromatograms o f t h e o x i d a t i o n p r o d u c t s (as methyl e s t e r s ) from the P i t t s b u r g h c o a l (sample 3) and i t s SRC (benzene methanol e x t r a c t - s a m p l e 6) a r e shown i n F i g u r e 3. The numbered peaks a r e i d e n t i f i e d i n T a b l e I I . A g r e a t e r degree o f a r o m a t i c c o n d e n s a t i o n o f the SRC e x t r a c t o v e r t h a t o f i t s f e e d c o a l i s observed. F o r example, naphthalene and phenanthrene r i n g s a r e much more abundant i n t h e SRC. The d i b e n z o f u r a n r i n g i s the most abundant h e t e r o c y c l i c t o have s u r v i v e d the SRC p r o c e s s . F i f t e e n a r o m a t i c r i n g systems were i d e n t i f i e d i n the Na Cr207 o x i d a t i o n p r o d u c t o f the m e t e o r i t e p o l y mer: benzene, b i p h e n y l , n a p h t h a l e n e , phenanthrene, f l u o r a n t h e n e (or p y r e n e ) , c h r y s e n e , f l u o r e n o n e , benzophenone, a n t h r a q u i n o n e , d i b e n z o f u r a n , b e n z o t h i o p h e n e , dibenzothiophene, p y r i d i n e , q u i n o l i n e or i s o q u i n o l i n e and c a r b a z o l e (3). These d a t a s u p p o r t t h e g e n e r a l l y accepted idea t h a t the polymeric m a t e r i a l i n m e t e o r i t e s has a h i g h l y condensed a r o m a t i c s t r u c t u r e (3^9-/10.) ^ g i v e s us c o n f i d e n c e i n t h e d i c h r o m a t e o x i d a t i o n p r o cedure. We have r e c e n t l y d e v e l o p e d a n o t h e r s e l e c t i v e Na Cr 07 oxidation. R e a c t i o n m i x t u r e (3 g SRC, 80 ml o f benzene and 60 ml o f a c e t i c a c i d ) was s t i r r e d a t room temperature, and 18 g o f N a C r U 7 i n 70 ml o f a c e t i c a c i d was added i n 2-3 ml p o r t i o n s o v e r a p e r i o d o f 10-12 h o u r s . T h e r e a f t e r , s t i r r i n g was c o n t i n u e d a t 40°C f o r 60 hours w i t h 97% o f the sample b e i n g o x i dized. A f t e r f i l t r a t i o n o f the r e a c t i o n m i x t u r e , humic a c i d - l i k e m a t e r i a l (49.4 wt%) was i s o l a t e d from the i n s o l u b l e r e s i d u e by d i s s o l u t i o n i n methanol and alkaline solution. A r o m a t i c a c i d f r a c t i o n (26.5 wt%) and n e u t r a l f r a c t i o n (5.7 wt%) were r e c o v e r e d r e s p e c t i v e l y from the f i l t r a t e . The a r o m a t i c a c i d f r a c t i o n was e s t e r i f i e d and was then a n a l y z e d by GC-TOFMS, TOFMS-solid i n l e t and HRMS. The r e s u l t showed t h e p r e s e n c e o f t h e same p o l y n u c l e a r a r o m a t i c and h e t e r o c y c l i c r i n g systems which were found i n t h e a q - N a C r U 7 o x i d a t i o n p r o d u c t o f sample #6 (see F i g . 3a and T a b l e II). Major p r o d u c t s were b e n z e n e c a r b o x y l i c a c i d s ( d i and t r i ) and t h e i r methyl d e r i v a t i v e s , n a p h t h a l e n e 2

a n <

2

2

2

2

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

Oxidation Degradation Studies

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

HAYATSU ET AL.

Figure 3. Gas chromatograms of methylated Na Cr 0 oxidation products of (a) SRC benzene-methanol extract and (b) its feed coal, Pittsburgh #8. Separations were made on an OV-101 SCOT column. 2

2

7

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

116

ORGANIC CHEMISTRY OF COAL

Table I I Aromatic Acids Found i n the Oxidation o f SRC and I t s Feed C o a l s I d e n t i f i e d as Methyl E s t e r s a

C Peak Number

Number o f -COOCH 3

R e l a t i v e Abundance (+ 1 5 % ) b

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

SRC E x t r a c t 1 5 10 4 2 8 16

Benzene

Biphenyl Naphthalene

13 20

Phenanthrene

19

Pyrene/Fluoranthene

11

Fluorenone

14

Anthraquinone

7 17

Dibenzofuran

15

Xanthone

3 12

Benzothiophene Dibenzothiophene Pyridine Carbazole

18

6

Benzoquinoline/Acridine

2 3 4 1 1 2 3 4 1 2 3 4 1 2 1 2 3 1 2 1 2 3 1 2 3 1 1 2 3 1 2 1 2 3

100 58 9 3 47 82 24 7 82 8,15 5 ι (τ) 7 4 4 δ δ 26 δ 32 9 10 4 6 2 (Τ) 2

4 δ 3 5 2

C

9

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Coal 100 29 10 9 30 29 8 δ 28 8 7 δ 2 8 2 4 21 4 9 7 δ 4 8 5 5 (Τ) δ 4 1 4 2 11 22

7.

HAYATSU ET AL.

Oxidation

Degradation

117

Studies

Table I I (Footnotes) a

9 2 % o f the e x t r a c t was o x i d i z e d and the y i e l d o f t o t a l a c i d i c and n o n - a c i d i c l e s s v o l a t i l e compounds was 59%. For the feed c o a l , 84% o f the c o a l was o x i d i z e d ; Y i e l d o f t o t a l s was 58%.

^Benzene d i c a r b o x y l i c

a c i d methyl e s t e r i s normalized t o 100.

Q

Peak no. 6 i s t e n t a t i v e l y d

i d e n t i f i e d as

trimethoxyxanthone.

Peak no. 9 shows prominent mass ions a t 216 and 215. HRMS shows t h e i r elemental composition corresponding to Ci2Hio03N C 1 2 H 9 O 3 N o r C9H12O6, C 9 H 1 1 O 6 . I d e n t i f i c a t i o n has not been made at t h i s time.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

f

Τ = i d e n t i f i c a t i o n tentative; = not detected; χ = peak con­ s i s t s o f more than one component which are d i f f i c u l t t o i d e n t i f y by GC-MS. I t a l i c s i n d i c a t e t h a t i d e n t i f i c a t i o n and e s t i m a t i o n o f r e l a t i v e abundances were made by TOF v a r i a b l e temperature s o l i d i n l e t and HRMS, because o f d i f f i c u l t y o f i d e n t i f i c a t i o n by GC-MS.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

c a r b o x y l i c a c i d s (mono and d i ) , phenanthrene monoc a r b o x y l i c a c i d , f l u o r e n o n e m o n o - c a r b o x y l i c a c i d and dibenzofuran mono-carboxylic a c i d . Higher molecular w e i g h t a c i d m e t h y l e s t e r s were a l s o seen i n t h e s p e c t r a o f TOFMS-solid i n l e t and HRMS. I n a d d i t i o n t o t h e above o b s e r v a t i o n , d i p h e n y l e t h e r was i d e n t i f i e d as i t s mono and d i c a r b o x y l i c a c i d methyl e s t e r s . This looks l i k e an i m p o r t a n t f i n d i n g because t h e d i p h e n y l e t h e r system has been c o n s i d e r e d t o be p r e s e n t i n c o a l and c o a l product. However t h e r e has so f a r been l i t t l e d i r e c t evidence. F u r t h e r o x i d a t i o n o f t h e humic a c i d ­ l i k e m a t e r i a l a f f o r d e d t h e same a r o m a t i c a c i d s . P h o t o c h e m i c a l O x i d a t i o n s : O x i d a t i o n by a i r bub­ b l i n g t h r o u g h an aqueous HC1 s o l u t i o n w h i l e i r r a d i a t i n g w i t h u l t r a v i o l e t l i g h t from a h i g h p r e s s u r e mercury lamp was i n v e s t i g a t e d (1-3)· T a b l e I I I a r e shown the r e s u l t s o b t a i n e d w i t h model compounds. From t h e r e s u l t s w i t h t h e model compounds i t appears t h a t a r o m a t i c h y d r o c a r b o n s a r e r e a d i l y o x i d i z e d t o benzene carboxylic acids. On t h e o t h e r hand N - h e t e r o c y c l i c s resist oxidation. I n T a b l e IV a r e l i s t e d t h e a r o m a t i c c a r b o x y l i c a c i d s i s o l a t e d from a b i t u m i n o u s c o a l (sample #2) a f t e r p h o t o - c h e m i c a l o x i d a t i o n . The p r o ­ d u c t s from l i g n i t e (sample #1) were p r i m a r i l y benzene carboxylic acids with only traces of pyridine t r i c a r ­ b o x y l i c a c i d s and xanthone d i - and t r i c a r b o x y l i c a c i d s . S e v e r a l a l i p h a t i c c a r b o x y l i c a c i d s were i d e n t i f i e d (after methylation) i n the photo-oxidation product o f b i t u m i n o u s c o a l by TOF v a r i a b l e temperature s o l i d i n l e t and HRMS. They are m e t h y l e s t e r s o f m a l o n i c a c i d , s u c c i n i c a c i d , g l u t a m i c a c i d and s a t u r a t e d monocarb o x y l i c a c i d s ( C H - ( C H ) - C O O C H η = 1-7). The f r a g ­ ments f o r 3-methyl and 3,3-dimethyl a l i p h a t i c c a r b o x y ­ l i c a c i d m e t h y l e s t e r s were a l s o seen i n t h e mass spectra. A s i m i l a r o b s e r v a t i o n was made f o r t h e o x i d a t i o n product o f l i g n i t e . I

3

2

n

n

3

Hydrogen P e r o x i d e - A c e t i c A c i d : I t i s probable t h a t i n t h e o x i d a t i o n e x p e r i m e n t s d e s c r i b e d above a r o m a t i c u n i t s w i t h p h e n o l i c groups would have been destroyed. S c h n i t z e r e t a l . (11) have shown t h a t an a c e t i c acid-H202 m i x t u r e under m i l d c o n d i t i o n s o x i d i z e s humic a c i d s w h i l e p r e s e r v i n g p h e n o l s . Using t h i s pro­ c e d u r e we have o x i d i z e d l i g n i t e (sample #1) and b i t u ­ minous c o a l (sample #2) w i t h o v e r 80% c o n v e r s i o n t o methanol s o l u b l e a c i d s and have m e t h y l a t e d t h e a c i d s produced.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

HAYATSU ET AL.

Oxidation

Degradation

119

Studies

Table I I I Photochemical O x i d a t i o n o f Model

Compound

acenaphthene

0 0 8 5 7 3 8 10

phenanthrene

24

pyrene

12

dibenzofuran xanthone dibenzothiophene carbazole N-Et-carbazole

32 78 43 78 83 8

p-cresol anisole naphthalene

1, 4-diMe-nccphthalene 2,6-diMe-naphthalene

indane Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

Unreactei (%)

fluorene

poly ( 2-vinylpyridine) -•polystyrene polymer

a

Compounds

3

Major O x i d a t i o n P r o d u c t s

0

unident. small s p e c i e s , polymer unident. small s p e c i e s , polymer phthalic acid phthalic acid benzene-1,2,4-tricarboxylic a c i d phthalic acid fluorenone p h t h a l i c , naphthalene-1,8d i c a r b o x y l i c acids p h t h a l i c a c i d , phenanthrene-9,10diketone benzene t r i - and t e t r a c a r b o x y l i c acids styrene, s a l i c y l i c a c i d u n i d e n t i f i e d c h l o r o compounds s t y r e n e , thiophenol polymer polymer pyridine-2-carboxylic, pyridine2-aldehyde, benzoic, malonic, and s u c c i n i c a c i d s

T h e o x i d a t i o n was c a r r i e d out i n 10% aq. HC1 s o l u t i o n f o r 6-10 days. Values are accurate to +10%.

A f t e r p r e l i m i n a r y separation i n t o a c i d i c , n e u t r a l , and b a s i c f r a c t i o n s , products were i d e n t i f i e d by TOFMS with v a r i a b l e temperature s o l i d i n l e t . Except f o r the f i r s t two samples and the two carbazoles, a l l i d e n t i f i c a t i o n s were checked by h i g h r e s o l u t i o n MS. F o r the i t a l i c i z e d samples, GC-MS was used as w e l l , a f t e r e s t e r i f i c a t i o n o f the product. A l l major products were accompanied by l e s s e r amounts o f t h e i r monochloro d e r i v a t i v e s .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

120

Table IV Aromatic Acids Found i n the Photochemical O x i d a t i o n o f Bituminous C o a l : I d e n t i f i e d as Methyl E s t e r s ' 9 ' a

Nucleus

Number o f -COOCH

3

P r e c i s e Mass (M-OCH )

+

3

elemental observed Dev. χ comp. 10

Relative kbundance^ + 15-20%

3

2

C9H7O3

163.0388 -0.7

3

C11H9O5

221.0457

0.8

100

4 5

C13H11O7 C15H13O9

279.0510 0.6 337.0555 -0.3

97 29

6 2 3

C17H15O11 C9H6O3CI CiiH 0 Cl

395.0593 -2.0 196.9990 -1.5 255.0066 0.6

4 24 31

4

C13H10O7CI

313.0125

26

5

C15H12O9CI 371.0124 -4.4

2

Fluorenone

2

C16H9O4

265. 0494 -0. 6

9

Anthraquinone

2 3

C17H9O5

293. 0451 351. 0520

0. 2 1. 6

3 1

2 (T) 3 (T)

CnHgOit

205. 0478 -2. 2 263. 0572 1. 8

2 1

1. 2 0. 6

9 7

253. 0477 -2. 3 311. 0560 0. 6

3 2

Benzene

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

h

Cl-benzene

Phthalan

8

5

C19H11O7

C13H11O6

C16H9O5 C18H11O7

Xanthone

2 3

Dibenzofuran^ and/or naphthofuran

2 3

C15H9CH

Pyridine

2 3 4

C H 0 NCi Ci H O N

Quinoline and/or isoquinoline Carbazole^

Acridone

281. 0461 339. 0510

C17H11O6

1.1

42

C12H10O7N

197. 9974 222. 0408 280 0488

1. 6 0. 5 3 2

3 3 3.5

1 2

CioH ON C H 0 N

156 .0412 -3 7 214 0468 -3 5

0.5 2

1 2 3

Ci H ON C15H10O3N C17H12O5N

194 .0598 -0 7 252 .0660 -0 .0 310 .0708 -0 .6

4 2 2

1 2 3

Cii H 0 N CieHioOi+N Ci Hi 0 N

222 .0525 -2 .9 280 .0592 -1 .8 338 .0635 -2 .8

5 2 1

8

5

0

3

8

5

6

1 2

8

3

8

+

8

3

8

2

2

6

e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

HAYATSU ET AL.

Oxidation Degradation Studies

121

Table IV Footnotes a

Some p r e l i m i n a r y r e s u l t s were r e p o r t e d e a r l i e r (_1). I d e n t i f i c a t i o n based on TOF v a r i a b l e temperature s o l i d i n l e t , GC (Carbowax 20 M)-TOFMS and high r e s o l u t i o n MS. b Benzene t r i c a r b o x y l i c a c i d methyl e s t e r i s normalized t o 100. R e l a t i v e abundances were estimated from the GC and an i n t e g r a t i o n o f the base peak o f each compound d u r i n g the time t h a t the samp l e was completely v o l a t i l i z e d i n the MS. Q

Monochlorobenzene c a r b o x y l i c a c i d s were always obtained when c o a l o r model compounds were o x i d i z e d i n 10% HC1 aq. s o l u t i o n . C h l o r o c a r b o x y l i c a c i d s o f other aromatics were a l s o observed i n very low y i e l d .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

d R e l a t i v e l y l a r g e amounts o f dibenzofurans were found t o be p r o duced by Na2Cr207-oxidation (1), while p h o t o - o x i d a t i o n produced dibenzofuran c a r b o x y l i c a c i d s i n low y i e l d . Perhaps t h i s shows the photochemical procedure destroyed dibenzofuran. For p y r i d i n e d i c a r b o x y l i c a c i d , o n l y c h l o r o d e r i v a t i v e s were found. ^The previous estimates o f r e l a t i v e abundances (1) were somewhat high. g The products o f l i g n i t e p h o t o - o x i d a t i o n i n 5% KOH aq. s o l u t i o n were very s i m i l a r t o those shown i n t h i s Table. In a d d i t i o n some mono- and dimethylbenzene c a r b o x y l i c a c i d s were i d e n t i f i e d . ^ P o l y n u c l e a r aromatic c a r b o x y l i c a c i d s such as naphthalene and phenanthrene found i n the Na2Cr2Û7 o x i d a t i o n product (see F i g . 2) are not observed i n t h i s product. From our model experiments, we have found t h a t these aromatic compounds are o x i d i z e d by the present procedure. Τ = identification tentative.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

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ORGANIC CHEMISTRY OF COAL

The gas chromatogram o f t h e a r o m a t i c p o r t i o n o f t h e m e t h y l a t e d p r o d u c t from l i g n i t e i s shown i n F i g u r e 4. The i d e n t i f i c a t i o n o f i n d i v i d u a l compounds was made by c o i n c i d e n t MS and HRMS o f t h e m i x t u r e . The m e t h y l e s t e r s i d e n t i f i e d gave t h e f o l l o w i n g approximate d i s tribution: 36.1% benzene, 7.6% methylbenzene (not shown i n F i g . 4, because o f v e r y s m a l l p e a k s ) , 22.1% methoxybenzene, 15.9% f u r a n and 18.2% d i b a s i c a l i p h a t i c s . F o r t h e b i t u m i n o u s c o a l t h e methoxy d e r i v a t i v e s were h a l f as abundant. These r e s u l t s s u g g e s t t h a t t h e l i g n i t e has t w i c e t h e p h e n o l i c c o n t e n t o f t h e bituminous c o a l . I t i s i n t e r e s t i n g t o note t h a t m e t h y l f u r a n t e t r a c a r b o x y l a t e and o t h e r f u r a n d e r i v a t i v e s have been i d e n t i f i e d . I t appears t h a t t h e c o a l s a r e a c t i n g as c a t a l y s t s for this oxidation. I f 2,6-dimethylnaphthalene i s r e a c t e d w i t h H2O2 under t h e same c o n d i t i o n s as used f o r the c o a l s , o n l y 2,6-dimethylnaphthaquinone i s i s o l a t e d in essentially quantitative yield. With t h e a d d i t i o n o f a s m a l l amount o f l i g n i t e t o t h e r e a c t i o n , 5-methyl p h t h a l i c a c i d i s o b t a i n e d as t h e major p r o d u c t . Also no h y d r o x y l a t e d benzene c a r b o x y l i c a c i d s were i s o l a t e d which i n d i c a t e s t h a t t h i s p r o c e d u r e does n o t hydroxyl a t e aromatic r i n g s . T r a n s i t i o n m e t a l s a r e known t o c a t a l y z e r e a c t i o n s o f hydrogen p e r o x i d e . Part of the c a t a l y t i c e f f e c t may be due t o t h e m i n e r a l m a t t e r i n the c o a l . No p o l y h y d r o x y l benzene c a r b o x y l i c a c i d s have been o b s e r v e d i n t h e p r o d u c t s from e i t h e r c o a l . It is e x p e c t e d t h a t t h e s e s p e c i e s would undergo r i n g o x i d a t i o n and subsequent d e g r a d a t i o n . However, t h e concent r a t i o n i n c o a l o f these species i s probably small. These compounds a r e e x p e c t e d t o be v e r y r e a c t i v e and p r o b a b l y would n o t s u r v i v e t h e c o a l i f i c a t i o n p r o c e s s . We have examined aqueous NaOH e x t r a c t o f t h e Wyoming lignite. Numerous h y d r o x y l a t e d a r o m a t i c h y d r o c a r b o n s and a r o m a t i c a c i d s were i d e n t i f i e d , b u t no p o l y h y d r o x y l a t e d s p e c i e s were d e t e c t e d (L2). Sodium H y p o c h l o r i t e O x i d a t i o n : On t h e b a s i s o f r e s u l t s o f o x i d a t i o n o f c o a l w i t h NaOCl, C h a k r a b a r t t y e t a l . have s u g g e s t e d t h a t c o a l has a non-aromatic t r i c y c l o a l k a n e o r polyamantane" s t r u c t u r e (.13) . They p o i n t e d o u t t h a t no e v i d e n c e f o r a r o m a t i c compounds o t h e r t h a n benzene d e r i v a t i v e s was found i n t h e i r o x i d a t i o n product. The s p e c i f i c i t y o f NaOCl as an o x i dant has been q u e s t i o n e d (14-17) and i s s t i l l i n d i s pute. We a r e a t t e m p t i n g t o r e s o l v e t h e q u e s t i o n and have o x i d i z e d samples 6, 9 and 2 , 6 - d i m e t h y l n a p h t h a l e n e 11

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

220

Methyl esters from hydrogen peroxide-acetic

240

on an OV-101

180

acid oxidation of lignite separated

200

SCOT

160

column.

I50°C

g"

É3

ι—·

Numbered compounds: 1. methyl o-methoxybenzoate; 2. methyl m- or τρ-methoxybenzoate; 3. methyl methylfurandicarboxylate; 4. methyl benzenedicarboxylate; 5. methyl carbomethoxyphenylacetate; 6. methyl methoxybenzenedicarboxylate; 7. methyl l,2,3-benzenetricarboxyfote; 8. methyl 1,2,4-benzenetricarboxyhte; 9. methyl methoxybenzenetricarboxylate; 10. methyl furantetracarboxylate; 11. methyl methoxybenzenetricarboxyfote; 12. methyl 1,2,3,4-benzenetetracarboxylate; 13. methyl 1,2,4,5-benzenetetracarboxylate; 14. methyl 1,3,4,5-benzenetetracarboxyfote; 15. methyl methoxybenzenetetracarboxylate; 16. methyl benzenepentacarboxylate.

Figure 4.

250

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

124

ORGANIC CHEMISTRY OF COAL

under c o n d i t i o n s d e s c r i b e d by C h a k r a b a r t t y e t a l . f 1 3 . 18). Of p a r t i c u l a r i n t e r e s t i s the o x i d a t i o n o f t h e p o l y m e r i c m a t e r i a l from the M u r c h i s o n m e t e o r i t e (sample 9). Numerous s t u d i e s have shown t h i s m a t e r i a l t o be a h i g h l y condensed a r o m a t i c s t r u c t u r e . A l l samples were n i t r a t e d a c c o r d i n g t o the method o f C h a k r a b a r t t y e t a l . When n i t r a t i o n was f o l l o w e d by NaOCl o x i d a t i o n a t 60°C f o r 3-4 hours a l m o s t no o x i d a t i o n was o b s e r v e d f o r n i t r a t e d samples 6 (SRC) o r 9 ( m e t e o r i t e ) w h i l e 26% o f n i t r a t e d d i m e t h y l n a p h t h a l e n e was c o n v e r t e d t o benzene c a r b o x y l i c a c i d s and t h e i r n i t r o and/or m e t h y l d e r i v a tives. No n a p h t h a l e n e a c i d s were d e t e c t e d . When t h e r e a c t i o n was c o n t i n u e d f c r 15 h o u r s , a t 65-70°C 57% o f sample 9 and 42% o f sample 6 were o x i d i z e d t o w a t e r s o l u b l e a c i d s . P o l y n u c l e a r a r o m a t i c and h e t e r o c y c l i c a c i d s were n o t d e t e c t e d i n the o x i d a t i o n p r o d u c t s o f e i t h e r sample a l t h o u g h b o t h are h i g h l y a r o m a t i c . Benzene c a r b o x y l i c a c i d s were the major p r o d u c t s ( n i t r o and/or m e t h y l d e r i v a t i v e s and a m e t h y l c h l o r o d i c a r b o x y l i c a c i d ) . A p p a r e n t l y p o l y n u c l e a r a r o m a t i c systems were d e s t r o y e d and the p r o d u c t d i s t r i b u t i o n c l o s e l y r e sembled t h a t from a n i t r i c a c i d o x i d a t i o n . N o n - n i t r a t ed b i t u m i n o u s c o a l (sample #2) was a l s o o x i d i z e d w i t h NaOCl (60°C 14 h o u r s ) w i t h a h i g h degree o f c o n v e r s i o n to s o l u b l e m a t e r i a l ( 8 8 % ) . The y i e l d o f o r g a n i c a c i d s and humic a c i d - l i k e m a t e r i a l were 9.8 wt% and 49 wt% respectively. I d e n t i f i e d major o r g a n i c a c i d s (as Me e s t e r s ) were benzene c a r b o x y l i c a c i d s (from d i t o p e n t a ) and t h e i r m e t h y l and/or c h l o r o d e r i v a t i v e s . F u r a n mono and d i c a r b o x y l i c a c i d s and t h e i r m e t h y l d e r i v a t i v e s were a l s o found i n r e l a t i v e l y h i g h abundance. A l t h o u g h they a r e v e r y minor p r o d u c t s , napht h a l e n e mono- and f l u o r e n o n e m o n o - c a r b o x y l i c a c i d s were i d e n t i f i e d . F u r t h e r o x i d a t i o n o f the humic a c i d l i k e m a t e r i a l gave t h e same o r g a n i c a c i d s a g a i n i n a h i g h degree o f c o n v e r s i o n . O b v i o u s l y more work i s needed t o c l a r i f y the r o l e o f NaOCl i n the o x i d a t i o n of c o a l . V a r i o u s o x i d i z i n g agents a t t a c k c o a l and c o a l p r o d u c t s i n v a r i o u s ways. To g a i n i n s i g h t i n t o t h e t r u e n a t u r e o f c o a l s , the u s e o f a number o f degradat i o n reagents i s necessary. Acknowledgements : T h i s work was s u p p o r t e d by t h e Department o f E n e r g y - F o s s i l Energy, D i v i s i o n o f C o a l C o n v e r s i o n - L i q u e f a c t i o n . C h e m i c a l and i n s t r u m e n t a l t e c h n i q u e s used were d e v e l o p e d w i t h s u p p o r t from t h e O f f i c e o f B a s i c Energy S c i e n c e s .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

HAYATSU ET AL.

Literature [1]

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[3]

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch007

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125

Cited

Hayatsu, R., S c o t t , R. G., Moore, L. P., and S t u d i e r , Μ. H . , N a t u r e (1975) 257, 378; see a l s o Nature (1976) 261, 77. H a y a t s u , R., Winans, R. Ε . , S c o t t , R. G., Moore, L. P., and S t u d i e r , Μ. Η., t o appear in F u e l (1978). Hayatsu, R., Matsuoka, S., S c o t t , R. G., S t u d i e r , Μ. H., and A n d e r s , Ε . , Geochim. Cosmochim. A c t a (1977) 41, 1325. F e r g u s o n , L. Ν., and Wims, A. L., J. Org. Chem. (1960) 25, 668. Friedman, L., Fischel, L., and S c h e c h t e r , H., J . Org. Chem. (1965) 30, 1453. Wiberg, Κ. B. (Ed), " O x i d a t i o n i n O r g a n i c Chemis­ try", P a r t A, page 90, Academic P r e s s , New York, 1965. The results were p r e s e n t e d in p a r t . Duty, R. C., H a y a t s u , R., S c o t t , R., Moore, L., S t u d i e r , M. H., and Winans, R., 1978 P i t t s b u r g h C o n f e r e n c e , C l e v e l a n d , O h i o , F e b r u a r y 27-March 3, 1978. C h a k r a b a r t t y , S. Κ., and B e r k o w i t z , Ν., N a t u r e (1976) 261, 76. B a n d u r s k i , E. L., and Nagy, Β., Geochim. Cosmo­ chim. A c t a (1976) 40, 1397. Nagy, Β., "Carbonaceous M e t e o r i t e " , E l s e v i e r , Amsterdam, 1975. S c h n i t z e r , Μ., and S k i n n e r , I . Μ., Can. J . Chem. (1974) 52, 1072. Unpublished data. C h a k r a b a r t t y , S. Κ., and B e r k o w i t z , Ν., F u e l (1974) 53, 240; see a l s o F u e l (1976) 55, 362. A n g e r t , J . L., G a t t o n , S. L., Reilly, M. T., and L a n d o l t , R. G., F u e l (1977) 56, 224. Mayo, F. R., F u e l (1975) 54, 273. Ghosh, G., B a n e r j e e , Α., and Mazumder, Β. Κ., F u e l (1975) 54, 294. L a n d o l t , R. G., F u e l (1975) 54, 299. C h a k r a b a r t t y , S. Κ., and Kretschmer, Η. Ο., F u e l (1972) 51, 160.

RECEIVED February 10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

8 Chemistry of Coal Liquefaction F R A N K R. M A Y O , J O H N G . H U N T I N G T O N , and N O R M A N A . K I R S H E N

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch008

SRI International, Menlo Park, CA 94025

This paper is an extension of an e a r l i e r review (1) and a summary of four manuscripts submitted to F u e l ( 2 - 5 ) . Coal is considered to be mostly a c r o s s l i n k e d high polymer, with condensed aromatic aggregates that are difficult to cleave and connecting l i n k s that are relatively easy to cleave (breakable s i n g l e bonds). A range of s o l u b l e m a t e r i a l s is mixed with the predominantly i n s o l u b l e m a t e r i a l . A s s o c i a t e d with these primary bond r e l a t i o n s are s i g n i f i c a n t i n t e r a c t i o n s between phenolic groups and p y r i d i n e - t y p e bases ( 1 , 2 ) . Thus, r e l a t i v e l y small p o l y f u n c t i o n a l molecules, c o n t a i n i n g both phenolic and b a s i c groups, even if not bound to the network, r e q u i r e complexing s o l v e n t s , such as p y r i d i n e , to d i s s o l v e them. Table I shows some

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch008

8.

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Chemistry

of Coal

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127

r e s u l t s of f r a c t i o n a t i n g the p y r i d i n e e x t r a c t of Illinois No. 6 c o a l and a s o l v e n t - r e f i n e d c o a l (SRC) from the same c o a l (1,2). About two-thirds of the p y r i d i n e - s o l u b l e m a t e r i a l s will d i s s o l v e only i n p y r i d i n e ; they have higher oxygen and n i t r o g e n contents and higher molecular weights than the other s o l u b l e f r a c t i o n s . Recent experiments i n d i c a t e that ethylenediamine will e x t r a c t from c o a l much more m a t e r i a l , of higher molecular weight. The i n s o l u b l e extracted c o a l in the upper s e r i e s of f r a c t i o n s i n Table I , obtained i n about 85% y i e l d , i s a p r e f e r r e d m a t e r i a l f o r l i q u e f a c t i o n s t u d i e s , uncomplicated by admixed s o l u b l e materials. Progress i n breaking bonds can be followed by forma­ t i o n of p y r i d i n e - s o l u b l e products and probably a l s o by increased s w e l l i n g of the i n s o l u b l e m a t e r i a l i n a chosen s o l v e n t . The p y r i d i n e - s o l u b l e , t o l u e n e - i n s o l u b l e f r a c t i o n s of both c o a l e x t r a c t and SRC a r e p r e f e r r e d substrates f o r f o l l o w i n g the upgrading of syncrudes. They have f a i r l y high molecular weights and r a t h e r narrow molecular weight d i s t r i b u t i o n s , and a l l the f r a c t i o n s f i t a smooth curve f o r number-average molecular weight against r e t e n ­ t i o n time i n gel-permeation chromatography (_2) . Both the extracted c o a l and the p y r i d i n e - s o l u b e f r a c t i o n have elementary analyses (dry^ m i n e r a l f r e e ) and nuclear magnetic resonance (NMR) spectra (3) that a r e very s i m i l a r ; they apparently d i f f e r s i g n i f i c a n t l y only i n molecular s i z e . As f a r as we can determine, the only s i n g l e bonds i n c o a l that might be broken and a s s i s t i t s l i q u e f a c t i o n under m i l d condi­ t i o n s a r e the f o l l o w i n g (Ar = a r y l ; R = a l i p h a t i c o r b e n z y l ) : Ar-CH -Ar 2

Ar-(CH ) -Ar η 2

Ar-OAr

J

R-OAr

\ and t h e i r S analogs

R-O-R

1

The same types of bonds a r e probably involved i n s c i s s i o n s under s t r o n g l y a c i d i c c o n d i t i o n s , as with phenol plus boron t r i f l u o r i d e etherate. A r y l - a r y l bonds are too strong to be included, and complete cleavage of r i n g s r e q u i r e s breakage of two bonds i n the same r i n g . The breakdown of c o a l f r a c t i o n s by r e f l u x i n g a l c o h o l i c KOH i n d i c a t e s that an e s t e r group may have to be added to t h i s l i s t (but see below). We now consider the s o l v e n t - r e f i n i n g process i n terms of Table I and the bonds broken. The s o l v e n t - r e f i n i n g process con­ s i s t s mainly of conversion of i n s o l u b l e c o a l to the p y r i d i n e s o l u b l e , t o l u e n e - i n s o l u b l e f r a c t i o n of SRC (1,2). The net r e s u l t i s l o s s of about 20% of the o r i g i n a l carbon as gases and v o l a t i l e l i q u i d s , l o s s of three-quarters of the o r i g i n a l oxygen (mostly as water with process hydrogen), an increase i n a r o m a t i c i t y , and some

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

128

bond breakage. Because the r e l a t i o n s between s o l u b i l i t y and molecular weight a r e the same i n the c o a l e x t r a c t and SRC s e r i e s (1,2), the net phenol-base r e l a t i o n s have changed l i t t l e , and so the observed bond breakage appears to be a s s o c i a t e d with net l o s s of ethers, some bonds of the A r - ( C H ) - A r type, and perhaps the f r a c t u r e of some r i n g s a f t e r hydrogénation. The conversion of SRC to o i l or d i s t i l l a t e r e q u i r e s a l a r g e hydrogen input and a cons i d e r a b l e r e d u c t i o n i n molecular weight and heteroatom content. The hydrogen i s r e q u i r e d i n part to cap the fragments l e f t when heteroatoms a r e removed as H 0, H S, and NH , but much of the hydrogen may be r e q u i r e d to reduce condensed aromatic systems that cannot be cleaved to p a r t i a l l y hydroaromatic systems that can be cleaved, e s p e c i a l l y by reforming c a t a l y s t s . This working hypothesis leads us to suggest cheaper a l t e r n a t i v e routes to l i q u e f a c t i o n . F i r s t , there are i n d i c a t i o n s that ether cleavage alone, without removal of oxygen or a d d i t i o n of hydrogen, can render c o a l s o l u b l e (6). The a l k y l a t i o n requirement (6) now seems to be a s s o c i a t e d more with reducing phenol-base i n t e r a c t i o n s (1,2) by O - a l k y l a t i o n (7) than with C - a l k y l a t i o n ( 6 ) . As w e l l as the a l k a l i metal route, there should be lowertemperature, lower-pressure routes f o r ether cleavage, as by a c i d s and bases. Whether ether cleavage alone w i l l convert our c o a l to preasphaltenes, asphaltenes, or o i l s , or some of each, as i n Table I, i s not known. We have i n v e s t i g a t e d the p o s s i b i l i t y that s e l e c t i v e o x i d a t i o n w i l l cleave many of the breakable s i n g l e bonds l i s t e d above and that we can d i s t i n g u i s h among them chemically. Oxidation of d i arylmethanes should give ketones that can be converted to e s t e r s with a p e r a c i d and then hydrolyzed. Longer a l i p h a t i c chains between a r y l groups should be o x i d i z e d d i r e c t l y to p a i r s of a c i d s . The a l k y l ethers should be o x i d i z e d to e s t e r s . H y d r o l y s i s of e s t e r s should then r e s u l t i n cleavage. D i a r y l ethers are e a s i l y cleaved by a l k a l i metals. M i l d o x i d a t i o n s of extracted c o a l with subsequent base h y d r o l y s i s have indeed produced s o l u b l e m a t e r i a l s ( 5 ) , but considerable oxygen i s incorporated. Oxidation and NMR s t u d i e s i n d i c a t e that the SRC f r a c t i o n s with the most aromatic hydrogen are most r e a c t i v e , and that t h i s kind of hydrogen i s l o s t preferentially i n oxidation Ç 5 ) . S i m i l a r m i l d o x i d a t i o n s or treatments with a l c o h o l i c KOH of the p y r i d i n e - s o l u b l e , t o l u e n e - i n s o l u b l e f r a c t i o n of c o a l e x t r a c t have r e s u l t e d i n marked reductions i n molecular weight and cons i d e r a b l e s o l u b i l i t y i n a l c o h o l i c KOH, with only moderate i n creases i n oxygen content ( 5 ) . The s i m i l a r e f f e c t of the two treatments and the absence of a l a r g e a d d i t i v e e f f e c t i n succ e s s i v e treatments r a i s e doubts about the presence of e s t e r groups, which would be unaffected by o x i d a t i o n alone. I n v e s t i g a t i o n s of r e l a t i v e reactivitès of pure aromatic compounds i n competitive o x i d a t i o n s (4) have brought out some d i f f i c u l t i e s i n breaking down c o a l by mild o x i d a t i o n . By f a r the most r e a c t i v e compounds a r e anthracene and i t s a l k y l d e r i v a t i v e s , 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch008

2

2

n

3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch008

8.

MAYO ET AL.

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Coal

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9,10-dihydroanthracene, t e t r a l i n , xanthene, and f l u o r e n e , a l l of which o x i d i z e i n i t i a l l y to peroxides or ketones without carboncarbon cleavage. Benzene d e r i v a t i v e s i n the l i s t of breakable s i n g l e bonds are one or two orders of magnitude slower i n comp e t i t i v e oxidations. Benzyl-type hydrogen atoms next to naphthalene and phenanthrene r i n g s are intermediate i n r e a c t i v i t y . These c o n s i d e r a t i o n s suggest that s e l e c t i v e o x i d a t i o n of breakable s i n g l e bonds i n c o a l w i l l be d i f f i c u l t without l o s s of f u e l values i n o x i d i z i n g more r e a c t i v e groupings, but our moderate success with the p y r i d i n e - s o l u b l e f r a c t i o n of c o a l e x t r a c t , and the more l i m i t e d success with extracted c o a l (5), i n d i c a t e that the prop o r t i o n s of the very r e a c t i v e but unbreakable c y c l i c compounds must be low. The d i f f e r e n c e between the s o l u b l e and i n s o l u b l e f r a c t i o n s may correspond to the d i f f e r e n c e s between branching and c r o s s l i n k i n g , w i t h more o x i d a t i o n being r e q u i r e d to break down the network s t r u c t u r e . These s t u d i e s have l e d us to t r y to dehydrogenate hydroaromatic groups i n c o a l to aromatic groups. We have had some success when ethylene was used as an acceptor f o r hydrogen i n the pyridine-soluble fraction. We hope that t h i s dehydrogenated, s t i l l - s o l u b l e m a t e r i a l w i l l have more tendency to o x i d i z e at breakable s i n g l e bonds, and increase the p o s s i b i l i t y that m i l d o x i d a t i o n may be used to break down c o a l more e f f i c i e n t l y . The ethane obtained from dehydrogenation could serve as a source of hydrogen i n f u r t h e r processing. The r e p o r t of Chakrabartty and Berkowitz (8) that c o a l i s o x i d i z e d mostly to carbon d i o x i d e and benzene p o l y c a r b o x y l i c a c i d s with household bleach (0.8 M aqueous sodium h y p o c h l o r i t e ) and t h e i r c o n c l u s i o n that bituminous c o a l c o n s i s t s mostly of benzene r i n g s and polyamantane-like s t r u c t u r e s aroused c o n s i d e r a b l e i n t e r e s t and o p p o s i t i o n and stimulated a more c a r e f u l study (3). Our work was c a r r i e d out mostly with p y r i d i n e - e x t r a c t e d I l l i n o i s No. 6 c o a l at 30°. I t now appears that at pH 11, with an extremel y f i n e l y d i v i d e d c o a l , and repeated treatments with small proport i o n s of h y p o c h l o r i t e , the major product i s a mixture of b l a c k , b i c a r b o n a t e - s o l u b l e a c i d s of molecular weight above 1000. These a c i d s appear to have become s o l u b l e by d e s t r u c t i o n of some aromatic, p o s s i b l y p h e n o l i c , r i n g s , with l i t t l e l o s s of a l i p h a t i c carbon or cleavage of our "breakable s i n g l e bonds" (_3 ). However, o x i d a t i o n of a coarser s u b s t r a t e leads to more degradation, and o x i d a t i o n with excess h y p o c h l o r i t e leads to the products reported by Chakrabarrty and coworkers. The b l a c k a c i d s c o n t a i n a high p r o p o r t i o n of a l i p h a t i c carbon, but such a low p r o p o r t i o n of hydrogen to carbon that they must c o n t a i n a high p r o p o r t i o n of t e r t i a r y a l i p h a t i c carbon atoms, and probably of bridged and condensed a l i p h a t i c r i n g s . C o n s i d e r a t i o n of the coal-forming process, however, i n d i c a t e s that the p r o b a b i l i t y of formation of r e g u l a r , polyamantane, r i n g s t r u c t u r e s i s u n l i k e l y . The s o l u b l e b l a c k a c i d s represent a new and c h a l l e n g i n g s t a r t i n g p o i n t f o r i n v e s t i g a t i n g the a l i p h a t i c m a t e r i a l than connects the condensed

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

130

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aromatic s t r u c t u r e s i n c o a l . The s u s c e p t i b i l i t y of some, but not a l l , s u b s t r a t e s to o x i d a t i o n by sodium h y p o c h l o r i t e i s pH dependent ( 3 ) . Acknowledgement Various p o r t i o n s of t h i s research were supported by the U.S. Energy Research and Development A d m i n i s t r a t i o n under Contract EF-76-C-01-2202, and by the N a t i o n a l Science Foundation under Grants AER74-13359 A02 and AER75-06143.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch008

Abstract The s t r u c t u r e of bituminous c o a l i s d i s c u s s e d in terms of aromatic aggregates and breakable s i n g l e bonds. The s o l v e n t ­ - refining process i s i n t e r p r e t e d , and low-temperature, low-pressure a l t e r n a t i v e s are d i s c u s s e d . The l a t t e r i n c l u d e combinations of s e l e c t i v e o x i d a t i o n , dehydrogenation, alkali treatment, and v a r i o u s other means of ether cleavage. Aqueous sodium hypochlorite is a remarkable o x i d i z i n g agent, c o n v e r t i n g some of the aromatic aggregates to a c i d s and CO , and l e a v i n g a s o l u b l e remainder as a new m a t e r i a l f o r s t r u c t u r e d e t e r m i n a t i o n . Such i n v e s t i g a t i o n s of the s t r u c t u r e of c o a l should yield new i n f o r m a t i o n on what bonds i n c o a l are most easily broken f o r liquefaction and how t h i s process might be accomplished most economically. 2

Literature Cited 1. Mayo, Frank R., Huntington, John G., and K i r s h e n , Norman A., " P r e p r i n t s of the 1976 Coal Chemistry Workshop," p. 189, Stanford Research Institute, Menlo Park, (1976). 2. Mayo, Frank R., and K i r s h e n , Norman A., "Comparison of F r a c t i o n s of P y r i d i n e E x t r a c t and Solvent-Refined Coal from Illinois No. 6 C o a l , " manuscript submitted to F u e l . 3. Mayo, Frank R., and K i r s h e n , Norman A., "Oxidations of Coal by Aqueous Sodium H y p o c h l o r i t e , " manuscript submitted to Fuel. 4. Huntington, John G., Mayo, Frank R., and K i r s h e n , Norman A., " M i l d Oxidations of Coal Models," manuscript submitted to Fuel. 5. Huntington, John G., Mayo, Frank R., and K i r s h e n , Norman A., " M i l d Oxidations of Coal F r a c t i o n s , " manuscript submitted to Fuel. 6. Sternberg, H. W., D e l l e Donne, C. L., Pantages, P., Moroni, E. C., and Markby, R. E., F u e l (1971), 50, 432. 7. F l o r e s , Ruben A., G e i g e l , M a r i a A., and Mayo, Frank R., "Hydrogen F l u o r i d e - C a t a l y z e d A l k y l a t i o n s of P i t t s b u r g h Seam (hvb) C o a l , " manuscript submitted to Fuel 8. Chakrabartty, S. K., and Berkowitz, N., F u e l (1974), 53, 240, and previous papers. RECEIVED February 10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

9 Early Stages of Coal Carbonization: Evidence for Isomerization Reactions

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

S. K. CHAKRABARTTY and N. BERKOWITZ Fuel Sciences Division, Alberta Research Council, Edmonton, Alberta, Canada

At temperatures between

350° and 425°C, the molecular struc-

tures that characterize coal are rapidly, and very obviously, transformed into more stable carbon configurations through loss of ''volatile matter" (as tar and gas). But little is known about possible configurational changes at lower temperatures. Thermograms of coal (1) indicate specific heat effects as endo- and exotherms from

200°C

up, but because enthalpy changes recorded

in this manner include sensible heats as well as heats of reaction, it is difficult to assess the nature of the chemical processes which produce the thermograms. On the other hand, low-temperature chemical changes, if such did in fact occur, should be reflected in the "reactivity" of heat-treated coal - and, in particular in its response to oxidation; and if oxidation could be performed so as to yield identifiable products, it should be possible to detect the major configurational changes in the distribution of oxidation products. It was previously shown (2) that subbituminous coals and derivatized bituminous coals react readily with sodium hypochlorite, and that they are thereby completely converted into water-soluble materials. The principal products are carbon dioxide and carboxylic acids. For a typical bituminous coal, 18 per cent of total carbon survive oxidation as single benzene ring 6 per cent as 2, 3 or 4 condensed aromatic (and/or heteroaromatic) rings, 7 per cent as methyl or methylene and 20 per cent as carboxyl groups. Acetic, propionic, succinic, glutaric, adipic, benzene- and toluene-carboxy1ic acids constitute the simple products of oxidations. In all, over 90 per cent of carbon in coal could be accounted for from the product yields. Although there are some uncertainties about the mechanism of coal-oxidation by hypochlorite, it is reasonable to expect that, under constant reaction conditions, the same mechanism would hold for variously heat-treated coal samples. Accordingly we thought it pertinent to determine whether this technique could be used to monitor low-temperature changes in coal-carbonization. The present paper reports the results of such an

0-8412-0427-6/78/47-071-131$05.00/0 ©

1978 American Chemical Society

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exploratory

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

Experimental

study. and R e s u l t s

For t h e p u r p o s e s o f t h i s i n v e s t i g a t i o n , two c o a l s - a W e s t e r n A l b e r t a l v b c o a l w i t h C = 30%, a n d a K e n t u c k y hvb c o a l w i t h C = 85% - w e r e u s e d . Ten g s a m p l e s o f t h e s e c o a l s , e a c h s i z e d t o -60 +115 mesh, were preheated i n h e l i u m f o r 2 h r a t t h e d e s i r e d temperature, c o o l e d , and then s t o r e d u n d e r p u r e He u n t i l r e q u i r e d . No s i g n i ­ f i c a n t w e i g h t l o s s e s o r changes i n e l e m e n t a l c o m p o s i t i o n s w e r e o b s e r v e d w i t h e i t h e r c o a l up t o 375°C, b u t 5-10% w e i g h t l o s s e s , and s l i g h t (0.5-1.2%) i n c r e a s e s i n c a r b o n c o n t e n t s , w i t h c o r ­ responding r e d u c t i o n s i n oxygen were noted a f t e r p r e h e a t i n g a t 390°-400°C. For t h e o x i d a t i o n e x p e r i m e n t s , 2 g (preheated) samples were f i r s t " a c t i v a t e d " by r e a c t i o n w i t h n i t r o n i u m - t e t r a f l u o r o b o a t e i n a c e t o n i t r i l e , a n d t h e r e a f t e r t r e a t e d w i t h 125 ml o f an aq 1.6N s o d i u m h y p o c h l o r i t e s o l u t i o n a t 60°C. The pH o f t h e r e a c t i o n m i x t u r e was m a i n t a i n e d a t 12 by a d d i n g NaOH p e l l e t s a t r e g u l a r invervals. When r e a c t i o n was c o m p l e t e , t h e m i x t u r e was a c i d i ­ f i e d ; i n s o l u b l e m a t t e r was f i l t e r e d o f f ; and s o l u b l e c a r b o x y l i c a c i d s were e x t r a c t e d w i t h e t h e r . The r e s i d u a l s o l u t i o n was f r e e d o f w a t e r by l o w - p r e s s u r e d i s t i l l a t i o n a t 40°C, and s o l i d m a t e r i a l l e f t b e h i n d was e x t r a c t e d w i t h a n h y d r o u s m e t h a n o l . The e t h e r - a n d m e t h a n o l - e x t r a c t s w e r e t h e n c o m b i n e d , c o n ­ v e r t e d t o m e t h y l e s t e r s by r e a c t i o n w i t h d i a z o m e t h a n e , and s e p a r a t e d by g e l p e r m e a t i o n c h r o m a t o g r a p h y on a (Water A s s o c ­ i a t e s ' ) P o r a g e l column i n t o two f r a c t i o n s w i t h m o l e c u l a r w e i g h t s <600 a n d >600 r e s p e c t i v e l y ( f r a c t i o n s A and B ) . Fraction Β (mol w t <600) was f u r t h e r s u b d i v i d e d i n t o " s i m p l e " ( B , l ) a n d " c o m p l e x " (B,2) a c i d s by e l u t i o n c h r o m a t o g r a p h y on a F l o r i s i l column. (From t h i s c o l u m n , m e t h y l e s t e r s o f " c o m p l e x " a c i d s c o u l d o n l y b e e l u t e d w i t h 10:1 c h l o r o f o r m - m e t h a n o l , w h i l e e s t e r s o f " s i m p l e " a c i d s c o u l d be t a k e n o f f w i t h p e n t a n e , h e x a n e a n d 2:1 h e x a n e - c h l o r o f o r m . ) The " s i m p l e " a c i d s ( f r a c t i o n B , l ) were q u a n t i t a t i v e l y a n a ­ l y z e d by GC on 0V-17/Chromosorb WHP a n d r e f e r e n c e t o peak a r e a v s . c o n c e n t r a t i o n d i a g r a m s f o r a u t h e n t i c compounds. Where no a u t h e n t i c compounds were a v a i l a b l e f o r m e t h y l e s t e r s o f t o l u e n e c a r b o x y l i c a c i d s , c o n c e n t r a t i o n s w e r e computed f r o m r e s p o n s e f a c t o r s d e r i v e d from those a p p r o p r i a t e f o r t h e methyl e s t e r s o f benzene c a r b o x y l i c a c i d s . D e t a i l e d s t u d y o f t h e o x i d a t i o n p r o d u c t s showed t h a t t h e raw a n d v a r i o u s l y p r e h e a t e d c o a l s f u r n i s h e d s u b s t a n t i a l l y i d e n ­ t i c a l amounts o f c a r b o n d i o x i d e ( F i g u r e 1), b u t t h a t t h e r e were s i g n i f i c a n t , though c o m p l e x , v a r i a t i o n s i n t h e y i e l d s o f c a r ­ b o x y l i c a c i d s ( F i g u r e s 2-6) and t h a t t h e s e y i e l d s depended on t h e n a t u r e o f t h e c o a l a s w e l l as on t h e p r e h e a t t e m p e r a t u r e . T h u s , w h i l e t h e l v b c o a l had t o be p r e h e a t e d t o a t l e a s t 350°C

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Figure 1.

Yield of carbon dioxide from variously heat-treated samples

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

s*

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ORGANIC CHEMISTRY OF COAL

b e f o r e i t p r o d u c e d g r e a t e r t h a n t h e i n i t i a l amounts o f c a r b o x y l i c a c i d s , t h e hvb c o a l needed o n l y t o be p r e h e a t e d t o 200°C b e f o r e doing so (Figure 2 ) . T h e s e o b s e r v a t i o n s a c c o r d w e l l w i t h t h e e n t h a l p y changes r e c o r d e d by d i f f e r e n t i a l t h e r m a l a n a l y s i s (]_), a n d a r e , i n o u r view, c l e a r l y i n d i c a t i v e o f t h e r m a l l y induced a l t e r a t i o n o f t h e i n i t i a l c a r b o n c o n f i g u r a t i o n s i n t h e two c o a l s . F r a c t i o n A - composed o f a c i d s w i t h m o l . w t s . i n e x c e s s o f 600 - p r e s u m a b l y r e p r e s e n t s condensed a r o m a t i c f r a g m e n t s o f t h e o r i g i n a l and h e a t - t r e a t e d samples; and i f s o , t h e f a c t t h e y i e l d s of t h i s f r a c t i o n i n c r e a s e w i t h p r e h e a t temperatures s u g g e s t s t h a t a r o m a t i z a t i o n b e g i n s a t t e m p e r a t u r e s a s low as 150°C i n hvb c o a l and a t 200°C i n l v b c o a l ( F i g u r e 3 ) . F r a c t i o n B,2 - w h i c h r e p r e s e n t s o v e r 50 p e r c e n t o f t h e t o t a l a c i d p r o d u c t f r o m each s a m p l e a n d c o n s i s t s o f " c o m p l e x " a c i d s w i t h m o l . w t s . <600 - c a n b e t e n t a t i v e l y i d e n t i f i e d a s o r i g i n a t i n g i n coal fragments t h a t produce " p r e - a s p h a l t e n e s " i n c o a l l i q u e f a c t i o n and a r e a l s o i n t e r e s t i n g ( F i g u r e 4 ) . In the c a s e o f l v b c o a l , B,2 y i e l d s r e a c h a maximum a t 375°C and t h e n d e c l i n e p r e c i p i t o u s l y a t 390°C, b u t t h e d e c l i n e i s compens a t e d by an a l m o s t e q u i v a l e n t i n c r e a s e i n t h e y i e l d o f h i g h m o l e c u l a r w e i g h t (>600) m a t e r i a l . In c o n t r a s t , B,2 y i e l d s f r o m the hvb c o a l a t t a i n a maximum a t 200°C, f a l l t o minimum a t 300°C, and t h e n r i s e t o a n o t h e r maximum a t 400°C. The " s i m p l e " a c i d s w i t h m o l . w t s . <600 ( F r a c t i o n B , l ) , w h i c h w e r e c o m p l e t e l y c h a r a c t e r i z e d and i n v a r i a b l y a c c o u n t e d f o r 22-30 p e r c e n t o f t h e t o t a l a c i d p r o d u c t s , a r e e v i d e n t l y produced from e a s i l y o x i d i z a b l e o p e n - s t r u c t u r e d c o a l f r a g m e n t s ; and f r o m t h e l v b c o a l , t h e y i e l d o f t h i s f r a c t i o n d e c r e a s e d s t e a d i l y as p r e h e a t t e m p e r a t u r e s r o s e . However, i n t h e c a s e o f t h e hvb c o a l , t h e y i e l d was f o u n d t o remain c o n s t a n t up t o 300°C, and t o f l u c t u a t e t h e r e a f t e r ( F i g u r e 5 ) . F i n a l l y , some n o t e must be t a k e n o f t h e d i s t r i b u t i o n p a t t e r n o f p e n t a - and hexa-carboxy1 benzenes v i s - a - v i s t h a t o f t r i - a n d t e t r a - c a r b o x y 1 t o l u e n e s . Q u i t e g e n e r a l l y , maxima f o r b e n z e n e s a r e a l m o s t c o i n c i d e n t w i t h minima and maxima o f t o l u enes. B u t h e r e a g a i n , s i g n i f i c a n t d i f f e r e n c e s between l v b a n d hvb c o a l a r e o b s e r v e d . F o r t h e l v b c o a l , maxima o f b e n z e n e s l i e a t 175° a n d 375°C, w h i l e f o r t h e hvb c o a l , t h e y a p p e a r a t 350° and 400°C. Maximum y i e l d s o f t o l u e n e s w e r e o b t a i n e d f r o m lvb c o a l a f t e r p r e h e a t i n g a t 300°C, a n d f r o m hvb c o a l a f t e r p r e h e a t i n g a t 150°C ( F i g u r e s 6 and 7 ) . S i n c e a m e t h y l g r o u p a t t a c h e d t o an a r o m a t i c r i n g i s most r e a c t i v e towards h y p o h a l i t e o x i d a n t , t h e v a r i a t i o n i n the y i e l d o f t o l u e n e c a r b o x y l i c a c i d s h a s added s i g n i f i c a n c e i n terms o f the c h e m i s t r y o f l o w - t e m p e r a t u r e h e a t i n g e f f e c t . During heat t r e a t m e n t , p r e s u m a b l y , a m e t h y l e n e o r m e t h i n e group i s c o n v e r t e d to methyl group which o c c u p i e s r e l a t i v e l y l e s s a c t i v e p o s i t i o n to s u r v i v e o x i d a t i o n . We b e l i e v e t h a t t h e s e v a r i a t i o n s i n y i e l d and d i s t r i b u t i o n

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

Figure 2.

Yield of total carboxylic acids as methyl esters from variously samples

heat-treated

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

136

Figure 3.

ORGANIC CHEMISTRY OF COAL

Yield of complex acids as methyl esters, M.W. > 600 from variously heattreated samples

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

CHAKRABARTTY AND BERKOWITZ

Coal

Carbonization:

Isomerization

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

9.

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50

Figure 5.

100

150

200

250

300

350

400 ° C

Yield of simple acids as methyl esters from variously heat-treated samples

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

140

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch009

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Coal Carbonization: Isomerization

141

of c a r b o x y l i c acids are best understood in terms o f lowtemperature i n t r a - m o l e c u l a r i s o m e r i z a t i o n r e a c t i o n s which modify the i n i t i a l carbon-hydrogen c o n f i g u r a t i o n s o f the coal w e l l be­ fore i t begins to undergo thermal c r a c k i n g . Of the two s p e c i f i c processes that could be postulated as e f f e c t i n g such i s o m e r i z a ­ t i o n , one i s trans-annular bond formation and the other i s i s o m e r i z a t i o n o f b e n z y l i c carbon to methyl phenyl d e r i v a t i v e s and more complex r i n g systesm (Figure 8). E i t h e r change could r e a d i l y occur at temperatures as low as 150°C and c r e a t e s t r u c ­ tures s u s c e p t i b l e to o x i d a t i o n by sodium h y p o c h l o r i t e . We note, i n t h i s c o n n e c t i o n , that ether-oxygen a l s o appears to play a major r o l e i n the behaviour o f coal a t elevated temp­ eratures (4); but whether o r not i s o m e r i z a t i o n and/or cleavage of ether-1inkages a l s o occurs a t low temperatures could not be determined in t h i s study, s i n c e h y p o c h l o r i t e o x i d a t i o n e a s i l y degrades h e t e r o c y c l i c f u n c t i o n a l elements under a c i d i c as w e l l as b a s i c c o n d i t i o n s . Abstract D e t a i l e d study o f the o x i d a t i o n products obtained by r e ­ a c t i o n o f preheated coals w i t h sodium h y p o c h l o r i t e shows signi­ ficant, though complex, changes in the yields o f various benzene and toluene p o l y c a r b o x y l i c acids. These observations can be accounted f o r by p o s t u l a t i n g a s e r i e s o f t r a n s - a n u l a r bond formations at 170-200°C and i s o m e r i z a t i o n o f b e n z y l i c carbon with formation o f methyl-phenyl d e r i v a t i v e s between 200° and 300°C. Literature Cited 1. 2. 3.

4.

K i r o v , Ν. Y . and Stephens, J. N.; P h y s i c a l Aspects o f Coal Carbonization Research Monograph, U . o f New South Wales, Sydney, Australia, Chap. 12 (1967) Chakrabartty, S. K. and Kretschmer, H . O.; Fuel (Lond.) 53. 132 (1974) Whitehurst, D. D. and Mitchell, T. O.; ACS D i v . Fuel Chem. P r e p r i n t s 21 (5), 127 (1976) F a r c a s i u , Μ., Mitchell, T. O. and Whitehurst, D.D.;ACS Div. Fuel Chem. P r e p r i n t s 21 (7), 11 (1976) Lazarov, L . and Angelova, G.; Fuel (Lond.) 50, 338 (1971) Szladow, A . J. and Ignasiak, B.; Fuel (Lond.) 55, 253 (1976) Ignasiak, B . and Gawlak, M.; Fuel (Lond.) 56, 216 (1977)

RECEIVED February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10 Electron Spin Resonance Studies of Coals and Coal­ -Derived Asphaltenes H. L. RETCOFSKY, G. P. THOMPSON, M. HOUGH, and R. A. FRIEDEL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

U.S. Department of Energy, Pittsburgh Energy Research Center, 4800 Forbes Avenue, Pittsburgh,PA15213

The discovery of e l e c t r o n s p i n resonance (esr) absorption i n n a t u r a l carbons by Uebersfeld (1) and Ingram (2) prompted a number of i n v e s t i g a t o r s to apply the technique to c o a l and m a t e r i a l s derived from c o a l . At l e a s t three e x c e l l e n t review articles d e s c r i b i n g the e a r l y esr s t u d i e s o f c o a l s have been published (3-5). Although the exact nature of the species r e s p o n s i b l e f o r the esr absorption has not been e s t a b l i s h e d unambiguously, it is g e n e r a l l y thought that the unpaired e l e c trons, at l e a s t i n n o n - a n t h r a c i t i c and p o s s i b l y young anthracitic c o a l s , are a s s o c i a t e d with organic f r e e r a d i c a l s t r u c t u r e s . One group of i n v e s t i g a t o r s , however, has proposed that charge-transfer complexes r a t h e r than s t a b l e f r e e r a d i c a l s may be r e s p o n s i b l e f o r the absorption (6). During the present i n v e s t i g a t i o n , esr spectra were obt a i n e d f o r v i t r a i n s and f u s a i n s from a l a r g e number of c o a l s . For most ranks of c o a l , samples of both l i t h o t y p e s were studi e d . The o b j e c t i v e s of the i n v e s t i g a t i o n were: 1) to b e t t e r c h a r a c t e r i z e the immediate chemical environment o f the unpaired e l e c t r o n s ; 2) to deduce information about the metamorphic changes that occur during vitrinization and f u s i n i z a t i o n ; and 3) to provide needed background information f o r future s t u d i e s of the r o l e of f r e e r a d i c a l s i n c o a l l i q u e f a c t i o n . To f u r t h e r pursue the l a t t e r o b j e c t i v e , esr s p e c t r a of asphaltenes, which are considered by many c o a l researchers to be intermediates i n the conversion of c o a l to liquid f u e l s , were a l s o obtained. A secondary purpose f o r examining the asphaltenes was to explore the recent hypothesis (7) that charge-transfer i n t e r a c t i o n s may be important binding f o r c e s between the a c i d / n e u t r a l and base components i n these m a t e r i a l s . EXPERIMENTAL Samples.

Most of the v i t r a i n s and

f u s a i n s studied were o f

0-8412-0427-6/78/47-071-142$05.00/0 This chapter not subject to U.S. copyright. Published 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

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AL.

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Spin Resonance

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143

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high pétrographie p u r i t y , although s e v e r a l of the v i t r a i n s are more a p p r o p r i a t e l y described as v i t r a i n - r i c h samples. Sixtythree v i t r a i n s , i n c l u d i n g samples from A n t a r c t i c a , A u s t r i a , Canada, Germany, Japan, P a k i s t a n , Peru, the United States, and Yugoslavia, and 30 f u s a i n s , most of which were separated from U. S. c o a l s , were i n v e s t i g a t e d . Pétrographie c h a r a c t e r i z a t i o n and other p r o p e r t i e s of many of these samples were published p r e v i o u s l y (8). The asphaltene samples were d e r i v e d from products from the P i t t s b u r g h Energy Research Center's SYNTHOIL (9) c o a l l i q u e f a c t i o n Process Development Unit using a r e c e n t l y described s o l vent s e p a r a t i o n method (10). The a c i d / n e u t r a l and base components of the asphaltenes were prepared according to published procedures (11). S p e c t r a l Measurements. The esr measurements were made over a p e r i o d of approximately ten years. The experimental techniques were e s s e n t i a l l y those published e a r l i e r (12) except for minor m o d i f i c a t i o n s that were made over the years to f a c i l i t a t e the measurements.^ A l l esr measurements were made on evacuated samples (*°10 t o r r ) to prevent l i n e broadening by oxygen i n the a i r . The e l e c t r i c a l p r o p e r t i e s of many of the higher rank samples n e c e s s i t a t e d that the samples be dispersed i n a non-conducting medium to avoid microwave s k i n e f f e c t s . RESULTS AND

DISCUSSION

V i t r a i n s and F u s a i n s . ESR data obtained f o r v i t r a i n s and f u s a i n s during the present i n v e s t i g a t i o n are f a r too numerous to t a b u l a t e here; complete l i s t i n g s of the data are a v a i l a b l e from the authors upon request. The p l o t s of Figures 1-6 show some of the more s i g n i f i c a n t c o r r e l a t i o n s of the data with c o a l composition or c o a l rank. The concentrations of unpaired e l e c t r o n s i n the v i t r a i n s , as estimated by comparing the esr i n t e n s i t y of each sample with that of a standard sample of d i p h e n y l p i c r y l h y d r a z y l , are shown as a f u n c t i o n of the carbon contents of the samples i n F i g u r e 1 The r e l a t i o n s h i p of F i g u r e 1 i s s i m i l a r to those from e a r l i e r s t u d i e s (3-5, 12), although the s c a t t e r of the data p o i n t s i s more pronounced i n the present work. These data show t h a t , i n general, the concentrations of unpaired e l e c t r o n s i n c r e a s e with i n c r e a s i n g c o a l rank up to a carbon content of approximately 94% a f t e r which the s p i n concentrations decrease r a p i d l y . The i n i t i a l , crudely exponential i n c r e a s e i n s p i n c o n c e n t r a t i o n i s g e n e r a l l y a t t r i b u t e d to the formation of organic f r e e r a d i c a l s during v i t r i n i z a t i o n . The f r e e r a d i c a l e l e c t r o n s are thought to be d e l o c a l i z e d over aromatic r i n g s and thus s t a b i l i z e d by resonance. Resonance s t a b i l i z a t i o n of the r a d i c a l s i s g r e a t e r for the v i t r a i n s from higher rank c o a l s s i n c e these presumably c o n t a i n the l a r g e r polynuclear condensed aromatic r i n g systems.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

ORGANIC CHEMISTRY OF COAL

Figure 1. Concentrations of unpaired electrons as a function of carbon content for vitrains from selected coals

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

10.

RETCOFSKY ET

AL.

Electron

Spin Resonance

Studies

The p r e c i p i t o u s decrease i n s p i n c o n c e n t r a t i o n above 94% C r e s u l t s from the increased c o n d u c t i v i t y of the samples. In c o n t r a s t to the r e s u l t s f o r v i t r a i n s , the s p i n concent r a t i o n s of the f u s a i n s (Figure 2) e x h i b i t no r e a d i l y d i s c e r n able dependence on carbon content. The wide v a r i a t i o n i n thermal h i s t o r y experienced by f u s a i n s during t h e i r formation i s the most l i k e l y explanation f o r t h i s behavior (13). The changes that occur i n esr l i n e w i d t h s and g values during v i t r i n i z a t i o n and f u s i n i z a t i o n are shown i n F i g u r e s 3-6. The a b s c i s s a used i n these f i g u r e s i s based on the c o a l i f i c a t i o n p l o t s of Schopf (14) with s l i g h t m o d i f i c a t i o n s by Parks (15) and the present authors. The ranks shown on the p l o t s are those of the parent c o a l s as determined by standard procedures (16) . For the v i t r a i n s , an i n c r e a s e i n esr l i n e w i d t h with i n c r e a s i n g rank i s f i r s t observed (Figure 3); t h i s trend i s reversed at the low rank bituminous stage. The r a t e of decrease becomes l a r g e r as c o a l i f i c a t i o n progresses through the higher rank bituminous stages to the e a r l y a n t h r a c i t i c stages. Some of the a n t h r a c i t e s and most of the meta-anthracites exh i b i t very broad l i n e s (not shown i n the f i g u r e ) ; a l i n e w i d t h i n excess of 60 gauss was observed f o r one such c o a l . The l i n e w i d t h r e s u l t s can be i n t e r p r e t e d as f o l l o w s : Nuclear broadening, i . e . , unresolved p r o t o n - e l e c t r o n h y p e r f i n e i n t e r a c t i o n s , plays an important r o l e i n the observed l i n e w i d t h s of peats, l i g n i t e s , and bituminous c o a l s . The r e l a t i v e l y narrow l i n e s observed i n the s p e c t r a of some of the a n t h r a c i t e s probab l y r e s u l t from the smaller number of protons i n the samples, although exchange narrowing of the esr resonances may a l s o be o c c u r r i n g . The proton l i n e broadening hypothesis i s supported by a recent esr study of c o a l s before and a f t e r c a t a l y t i c dehydrogenation (17). The very l a r g e l i n e w i d t h s of the highest rank m a t e r i a l s are undoubtedly due to the presence of g r a p h i t e l i k e s t r u c t u r e s which form during the latt,er stages of c o a l i f i cation. The d i f f i c u l t y i n d i f f e r e n t i a t i n g between a n t h r a c i t e s and meta-anthracites (18) may be r e s p o n s i b l e f o r the apparent l a c k of p r e d i c t a b i l i t y of l i n e w i d t h s i n v i t r a i n s from c o a l s of these ranks. The esr l i n e w i d t h s f o r the f u s a i n s (Figure 4) are very small, f r e q u e n t l y l e s s than one gauss, except f o r samples from the lowest rank c o a l s . U n l i k e the r e s u l t s f o r the v i t r a i n s , no evidence was found f o r the formation of g r a p h i t i c s t r u c t u r e s during the l a t t e r stages of f u s i n i z a t i o n . In a d d i t i o n , the gradual decrease i n l i n e w i d t h s of v i t r a i n s as c o a l i f i c a t i o n proceeds from the low rank bituminous stages to the e a r l y a n t h r a c i t i c stages (Figure 3) appears as a very r a p i d change i n the f u s i n i z a t i o n p l o t (Figure 4 ) . This i s i n accord with S c h o p f s (14) r e p r e s e n t a t i o n of f u s i n i z a t i o n as a process which has an e a r l y i n c e p t i o n and progresses r a p i d l y i n the peat and l i g n i t i c stages, a f t e r which the metamorphic changes become 1

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

145

ORGANIC CHEMISTRY OF COAL

Ί

Γ

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

°

° ο ο ο

° ο

ο

ο ο ο ο

_L 50

60 CARBON

70

80

CONTENT,

90

100

percent m a f

Figure 2. Concentrations of unpaired electrons as a function of carbon content for fusains from selected coals

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

s

σ

s

«

s

CO C3 ^ --s Ο ?= £5 3

l à

Figure 3.

bituminous"

Bituminous -

Electron spin resonance linewidths as a function of coal rank for vitrains from selected coals

coal

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Figure 4.

bituminous"

Bituminous-

-Anthracite-

-anthracite —

Electron spin resonance linewidths as a function of coal rank for fusains from selected coals

coal y

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

r

I

Ο

a

ο » ο > 2

00

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

10.

RETCOFSKY ET

AL.

Electron

Spin Resonance

Studies

149

n e a r l y imperceptible. V i t r i n i z a t i o n , on the other hand, i n v o l v e s a p r o g r e s s i v e change throughout a l l stages of rank development. The r e l a t i o n s h i p between the g values of the l i t h o t y p e s and c o a l rank (Figures 5 and 6) a l s o supports S c h o p f s t h e o r i e s of v i t r i n i z a t i o n and f u s i n i z a t i o n . The l a r g e g values found f o r the v i t r a i n s from meta-anthracites i s i n accord with the f i n a l step i n v i t r i n i z a t i o n being the f u s i n g of aromatic r i n g s i n t o g r a p h i t e - l i k e s t r u c t u r e s . The g value of each of the v i t r a i n s and f u s a i n s i s higher than that of the f r e e e l e c t r o n and l i e s i n the s p e c t r a l r e g i o n expected f o r simple organic free radicals. The only exceptions are v i t r a i n s from the more h i g h l y metamorphized c o a l s , one of which e x h i b i t e d a g value of 2.011. The f a c t that esr g values of organic f r e e r a d i c a l s are g r e a t e s t f o r r a d i c a l s i n which the unpaired e l e c t r o n i s l o c a l i z e d or p a r t i a l l y l o c a l i z e d on atoms having high s p i n - o r b i t coupling constants can be used to e x p l a i n the g value r e s u l t s for vitrains. Since the heteroatom contents of c o a l s decrease w i t h i n c r e a s i n g rank, the high g values f o r peats and l i g n i t e s can be i n t e r p r e t e d i n terms of aromatic r a d i c a l s with some p a r t i a l l o c a l i z a t i o n of the unpaired e l e c t r o n s on heteroatoms, p a r t i c u l a r l y but not e x c l u s i v e l y oxygen. As c o a l i f i c a t i o n progresses the g values decrease, suggesting that the r a d i c a l s become more "hydrocarbon-like. The g values of many of the v i t r a i n s from bituminous and young a n t h r a c i t i c c o a l s compare f a v o r a b l y with those e x h i b i t e d by aromatic hydrocarbon r a d i c a l s . During the f i n a l stages of c o a l i f i c a t i o n , the g values become q u i t e l a r g e as one would expect i f continued condensat i o n of the aromatic r i n g s i n t o g r a p h i t e s t r u c t u r e s occurs. The o b s e r v a t i o n of a s m a l l , but r e p r o d u c i b l e , anisotropy i n the g value of c e r t a i n a n t h r a c i t e s (Figure 7) suggests that some o r d e r i n g of the polynuclear condensed aromatic r i n g s i s o c c u r r i n g . 11

Coal-Derived Asphaltenes. To b e t t e r understand the chemist r y of c o a l l i q u e f a c t i o n , an esr i n v e s t i g a t i o n of c o a l - d e r i v e d asphaltenes was i n i t i a t e d . P r e l i m i n a r y r e s u l t s are presented here. Of p a r t i c u l a r concern was the temperature v a r i a t i o n of the esr i n t e n s i t i e s of asphaltenes and t h e i r a c i d / n e u t r a l and base components (Figure 8). The most s i g n i f i c a n t f i n d i n g to date i s that the weighted average of the temperature dependencies of the two components reproduces the temperature dependence of the t o t a l asphaltene (before separation) e x c e p t i o n a l l y w e l l . T h i s suggests that charge t r a n s f e r i n t e r a c t i o n s , at l e a s t i n the M u l l i k a n sense, are r e l a t i v e l y unimportant b i n d i n g f o r c e s between the a c i d / n e u t r a l and base components of the asphaltenes.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

ι ι ι ι—Γ

\ *

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•

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—

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innitp L , g n , t e

spin resonance g values as a function of coal rank for vitrains from selected coals

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

RETCOFSKY E T AL.

Electron

Spin Resonance

2.0070 Γ

Ί

151

Studies

Γ

I

I I

I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

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Electron spin resonance g values as a function of coal rank for fusains from selected coals

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

152

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

2.003001

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Figure 7.

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OF

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T H E C O A L , degrees

Value anisotropy in Huber Mine anthracite

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Electron

RETCOFSKY ET AL.

Spin Resonance

Studies

153

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

10.

Aspholtene acid/neutral components Q

ο

2

t

η

ft

n

|

ο—ο- j

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4 6 8 10 RECIPROCAL TEMPERATURE x I0' deg K~' 3

Figure 8.

Variable temperature ESR data for asphaltenes and components

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

12

154

ORGANIC CHEMISTRY OF COAL ACKNOWLEDGMENTS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

The authors gratefully acknowledge gifts of samples from M. Teichmuller (Geologisches Landesamt Nordrhein-Westfalen), B. N. Nandi (Department of Energy, Mines and Resources - Canada), H. Honda (Resources Research Institute - Japan), K. F. Schulz (Research Council of Alberta - Canada), P. M. Yavorsky (U. S. DOE), and B. C. Parks and H. J. O'Donnell (U. S. Bureau of Mines). Separation of the asphaltenes into acid/neutral and base components was carried out by F. K. Schweighardt (U. S. DOE).^ By acceptance of this article, the publisher and/or recipient acknowledges the U. S. Government's right to retain a non-exclusive, royalty-free license in and to.any copyright covering this paper. LITERATURE CITED 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

J. Uebersfeld, A. Étienne, and J. Combrisson, Nature, 174, 614 (1954). D. J. E. Ingram, J. G. Tapley, R. Jackson, R. L. Bond, and A. R. Murnahgan, ibid., 174, 797 (1954). H. Tschamler and E. De Ruiter, "Chemistry of Coal Utiliza­ tion," Suppl. Vol., H. H. Lowry, Ed., Wiley, New York, 1963, p. 78. W. R. Ladner and R. Wheatley, Brit. Coal Util. Res. Assoc. Monthly Bull., 29, 202 (1965). D. W. Van Krevelen, "Coal", Elsevier, Amsterdam, 1961, p. 393. R. M. Elofson and K. F. Schulz, Preprints, Am. Chem. Soc. Div. Fuel Chem., 11, 513 (1967). I. Schwager and T. F. Yen, Preprints, Am. Chem. Soc. Div. Fuel Chem., 21, 199 (1976). B. C. Parks and H. J. O'Donnell, U. S. Bureau of Mines Bull. 550 (1956), 193 pp. P. M. Yavorsky, S. Akhtar, J. J. Lacey, M. Weintraub, and A. A. Reznik, Chem. Eng. Prog., 71, 79 (1975). F. K. Schweighardt and Β. M. Thames, Manuscript in prepara­ tion. H. W. Sternberg, R. Raymond, and F. K. Schweighardt, Science, 188, 49 (1975). H. L. Retcofsky, J. M. Stark, and R. A. Friedel, Anal. Chem., 40, 1699 (1968). D. E. G. Austin, D. J. E. Ingram, P. H. Given, C. R. Binder, and L. W. Hill, "Coal Science," R. F. Gould, Ed., Amer. Chenu Soc., Washington, D. C., 1966, p. 344. J. M. Schopf, Econ. Geol., 43, 207 (1948). B. C. Parks, "Chemistry of Coal Utilization," Suppl. Vol., H. H. Lowry, Ed., Wiley, New York, 1963, p. 6. Standard Specifications for Classification of Coals by

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

17. 18.

RETCOFSKY ET AL.

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Spin Resonance

Studies

155

Rank (D 388-66), 1975 Annual Book of ASTM Standards, ASTM, P h i l a d e l p h i a , 1975. H. L. Retcofsky, G. P. Thompson, R. Raymond, and R. A. F r i e d e l , F u e l , 54, 126 (1975). M. Mentser, H. J . O'Donnell, and S. Ergun, F u e l , 41 153 (1962). 1978

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch010

RECEIVED March 6,

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11 Photochemistry Hydrogen Atoms as a Structural Probe of the Surface of Coal

1

GILBERT

J.

MAINS,

MUTHU

SP.

SUNDARAM,

and

JOSEPH

SOLOMON

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

Department of Chemistry, Oklahoma State University, Stillwater, OK 74074

Considerable interest in the interaction of hydrogen atoms with coal surfaces has been evident for over twenty-five years (l), resulting in a review of the literature (2) in 1965 and recent research by N. Berkowitz, et al (3, 4). Despite this intense interest the data are conflicting, and range all the way from reports of no reaction at ambient temperature to complete gasification. Some of these discrepancies arise from the discharge technique used to generate the H atoms; coal dust probably found its way into the discharge itself in some instances. Photochemical production of H atoms was mentioned and dismissed as being too inefficient (2). Because of the experimental discrepancies and their probably cause, the system H · atoms + coal was reinvestigated with photochemically generated H atoms. Experimental In work reported elsewhere in this symposium it was found that cryocrushing was the grinding method of choice if the surface of the coal was to represent bulk coal more accurately. The grinding techniques are reported elsewhere (5) and will not be described here. The bituminous coals were dried at 200°C in an oven through which N gas was passed continuously. The subbituminous Wyoming-Wyodak coal was dried in a vacuum oven at 100°C. Illinois No. 6, Pittsburgh Seam, Utah-Emery, and Wyodak coal samples were then cryocrushed, sieved, and stored in a nitrogen environment. Only the -53/+38 micron fractions were used in these studies. 2

1

B a s e d i n p a r t on d a t a t o be s u b m i t t e d by Muthu Sp. Sundaram a s a Ph.D. D i s s e r t a t i o n .

2

0 n s a b b a t i c a l l e a v e , P h i l a d e l p h i a C o l l e g e o f Pharmacy and S c i e n c e , P h i l a d e l p h i a , Pa. 0-8412-0427-6/78/47-071-156$05.00/0 © 1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

MAINS ET AL.

Photochemical

Hydrogen

157

Atoms

F i f t e e n grams o f c o a l were mixed w i t h an e q u a l w e i g h t o f g r o u n d g l a s s , +50 m i c r o n s i z e s , a n d p l a c e d on a f r i t , F F i g u r e 1, f o r d i s p e r s a l i n t h e q u a r t z r e a c t o r . T h e m e r c u r y s a t u r a t o r was h e a t e d t o n e a r 100°C a n d a m b i e n t c o n d e n s e r w a t e r u s e d t o p r o d u c e s a t u r a t i o n . T h e r e a c t o r w a l l s were h e a t e d by p a s s i n g c u r r e n t through t h e nichrome h e a t e r s . The s i x , m e t e r - l o n g , g e r m i c i d a l lamps, 36 w a t t s e a c h , were c o o l e d w i t h r a p i d l y f l o w i n g , f i l t e r e d a i r and t u r n e d on. Next, a stream o f H s u f f i c i e n t t o d i s p e r s e the c o a l d u s t ( a b o u t 300 l i t e r s / m i n ) was i n i t i a t e d . T r a p s T and T 3 , p a c k e d w i t h 1/4" g l a s s b e a d s , were p r e c o o l e d i n l i q u i d n i t r o g e n f o r n i n e t y m i n u t e s b e f o r e t h e e x p e r i m e n t a n d were by­ passed i n i t i a l l y . When t h e t e m p e r a t u r e i n t h e q u a r t z r e a c t o r r e a c h e d 2 0 0 ° C , t h e l i q u i d - N - c o o l e d t r a p s were opened and t h e gas b y - p a s s c l o s e d . T h r o u g h o u t t h i s p e r i o d and t h e r e m a i n d e r o f t h e e x p e r i m e n t , t h e f i n e r c o a l d u s t , w h i c h t e n d e d t o a c c u m u l a t e on the M i l l i p o r e f i l t e r , F on F i g u r e 1, was r e c y c l e d u s i n g a mechan­ i c a l v i b r a t o r . A t t h e e n d o f an h o u r , d u r i n g w h i c h t h e t e m p e r a ­ t u r e sometimes d r o p p e d as l o w a s 1 8 5 ° C , t h e f l o w was d i s c o n t i n u e d and t h e t r a p s were i s o l a t e d f o r a n a l y s e s . In t h e a c t i n o m e t r y e x p e r i m e n t s , t h e i d e n t i c a l p r o c e d u r e was f o l l o w e d e x c e p t t h a t t h e c o a l was o m i t t e d and t h e c a r r i e r g a s c o n t a i n e d 2% e t h y l e n e . The t r a p s were d i s c o n n e c t e d f r o m t h e a p p a r a t u s and t h e e x c e s s H was pumped away a t l i q u i d n i t r o g e n t e m p e r a t u r e . The r e s i d u a l g a s e s , a f t e r t h e t r a p s were warmed t o a m b i e n t t e m p e r a t u r e f o r s e v e r a l h o u r s , were sampled w i t h a 2 5 - c c sample l o o p and i n j e c t e d on t o a gas c h r o m a t o g r a p h i c column a t 6 0 ° C , 1/8" χ 1 0 ' , p a c k e d w i t h n - C ^ / P o r a s i l C, i n a P e r k i n - E l m e r Model 990 gas c h r o m a t o g r a p h e q u i p p e d w i t h a t h e r m a l c o n d u c t i v i t y d e t e c t o r u s i n g 8% H i n He c a r r i e r g a s . T h e r e s u l t a n t gas c h r o m a t o g r a m s a r e r e p r o d u c e d i n F i g u r e s 2 t h r o u g h 5, i n c l u s i v e . T e n t a t i v e p r o d u c t i d e n t i f i c a ­ t i o n s , b a s e d on e l u t i o n t i m e s , a r e i n c l u d e d on F i g u r e 2. l t

2

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

2

4

2

2

R e s u l t s and D i s c u s s i o n Because t h e v a p o r p r e s s u r e o f Hg was h i g h , p r o b a b l y n e a r a m i l l i t o r r , most o f t h e 2537A r e s o n a n c e r a d i a t i o n was a b s o r b e d w i t h i n 0.2 cm. o f t h e q u a r t z w a l l . However, t h e r e s u l t a n t e x c i t e d ^ H g atoms, τ = 1 0 * s e c , were e s s e n t i a l l y c o m p l e t e l y quenched by t h e a t m o s p h e r e o f H and t h u s g e n e r a t e d two Η atoms p e r p h o t o n i n t h i s 240 c m z o n e . T h e e x t e n t t o w h i c h t h e r a p i d l y moving Η atoms a t t a i n e d a u n i f o r m c o n c e n t r a t i o n t h r o u g h o u t t h e v e s s e l i s not known, n o r i s t h e r a t e a t w h i c h t h e y were removed a t t h e q u a r t z r e a c t o r s u r f a c e by r e c o m b i n a t i o n . When 2% e t h y l e n e was added t o t h e f l o w s t r e a m i n t h e a b s e n c e o f c o a l and t h e r e s u l t a n t b u t a n e , e t h a n e , e t h y l e n e m i x t u r e a n a l y z e d , a r a t e o f Η atom f o r ­ m a t i o n o f 2 . 9 0 x l 0 a t o m s / s e c i n t h e r e a c t o r was i n d i c a t e d . I f t h e s e were u n i f o r m l y d i s t r i b u t e d , 5 . 4 x l 0 a t o m s / c c / s e c was t h e s t a t i o n a r y s t a t e r a t e o f h y d r o g e n atom p r o d u c t i o n a n d an o v e r a l l 7

0

2

3

1 8

1 4

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

ROOF VENT

V M

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

5

'

3

c v,^/2

V

4

!t V

5

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UV L A M P S (6-36WATTS) THERMOMETER

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STAINLESS

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ROUNDING T H E W H O L E REACTOR AIR

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MERCURY

SATURATOR

FROM AND

H

2

CYLINDERS

FLOWMETERS

Figure 1. Photoreactor: C = couplings, F = frits/filter, V = stopcocks, Τ = traps. Products collected in T and T . 2

s

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

MAINS ET AL.

Photochemical

Hydrogen

159

Atoms 1 3

3

s t e a d y s t a t e c o n c e n t r a t i o n o f a b o u t 2 x 1 0 H a t o m s / c m can be c a l c u l a t e d , w h i c h compares w e l l w i t h t h o s e g e n e r a t e d by d i s c h a r g e techniques. A l t h o u g h no c o a l d u s t d e p o s i t e d on t h e w a l l s o f t h e q u a r t z r e a c t o r , i t d i d c o l l e c t on t h e p y r e x thermometer, t h e M i l l i p o r e f i l t e r p a p e r , F , and i n t h e l o w e r u n - i r r a d i a t e d z o n e . T h i s d e p o s i t i o n precluded a q u a n t i t a t i v e determination of the p a r t i c l e c o n c e n t r a t i o n . S w i r l i n g c o a l d u s t i n t h e r e a c t o r zone i s v i s i b l e t o a c u t e eyes and i s i n f e r r e d r e a d i l y by l i g h t s c a t t e r i n g when He-Ne l a s e r beam i s d i r e c t e d t h r o u g h t h e r e a c t o r . A c o a r s e ( a n d , p r o b a b l y , h i g h ) e s t i m a t e o f t h e p a r t i c l e c o n c e n t r a t i o n can be made i f one assumes t h a t 0.01% o f t h e c o a l i s d i s p e r s e d i n t h e f l o w i n g H a t any g i v e n t i m e ; making t h i s a d m i t t e d l y p o o r a s s u m p t i o n , we c a l c u l a t e 6 x l 0 coal p a r t i c l e s / c c i n the r e a c t o r . This suggests a b o u t A v o g a r d r o ' s Number o f c o l l i s i o n s p e r s e c o n d between a t o m i c H and c o a l d u s t , and t h e y i e l d s s u g g e s t e d i n F i g u r e s 2 t o 4 a r e c o n s i s t e n t with the formation of 1 0 - 1 0 product molecules per second. T h i s suggests a c o l l i s i o n e f f i c i e n c y o f the order o f 1 0 " t o 1 0 " w h i c h i s below t h e 7 x 1 0 " v a l u e o b s e r v e d by S n e l s o n (6) f o r g r a p h i t e ; t h e e s t i m a t e d c o a l p a r t i c l e c o n c e n t r a t i o n must be f a r t o o h i g h a n d / o r t h e p r o f i l e o f a t o m i c h y d r o g e n n o t u n i f o r m a c r o s s t h e r e a c t o r . Based on t h e o v e r a l l p r o d u c t y i e l d e s t i m a t e s and t h e a c t i n o m e t r y f o r t h e e n t i r e r e a c t o r , t h e p r o d u c t e f f i c i e n c y p e r hydrogen atom must be i n t h e 1 0 " t o 1 0 " r a n g e . C l e a r l y , f u r t h e r e x p e r i m e n t a t i o n , e s p e c i a l l y p r o d u c t i d e n t i t y and q u a n t i f i c a t i o n , i s r e q u i r e d to decrease the u n c e r t a i n t y i n the y i e l d per H atom. E x a m i n a t i o n o f F i g u r e s 2, 3, and 4 shows t h a t t h e gas c h r o m a t o g r a p h i c t r a c e s a r e e x t r e m e l y s i m i l a r f o r t h e hydrogénation p r o d u c t s f r o m I l l i n o i s No. 6, P i t t s b u r g h Seam, and Utah-Emery c o a l s . Although a l l three are indeed bituminous c o a l s , they are p h y s i c a l l y v e r y d i f f e r e n t and one would be s u r p r i s e d i f t h e y had i d e n t i c a l s u r f a c e c o m p o s i t i o n s . The " f i n g e r p r i n t s " do show s u b t l e d i f f e r e n c e s but, i n view o f the u n c e r t a i n t i e s j u s t d i s c u s s e d , one i s s t r u c k more by t h e i r s i m i l a r i t y t h a n a n y t h i n g e l s e . ( A t t h i s w r i t i n g , p r o d u c t i d e n t i f i c a t i o n i s based on e l u t i o n t i m e s . I t i s hoped t h a t GC-MS i d e n t i f i c a t i o n w i l l be made on e v e r y peak l a t e r . ) E i t h e r t h e s u r f a c e s t r u c t u r e s w h i c h can be " c r a c k e d o f f " by H atoms a t 185°-200°C a r e t h e same f o r t h e s e t h r e e c o a l s o r a l l t h e p r o d u c t s r e p r e s e n t e d by peaks have common p r e c u r s o r s which are l i b e r a t e d from the c o a l s i n the experiment, e.g. some c o m b i n a t i o n o f a r o m a t i c f r e e r a d i c a l s . Worth m e n t i o n i n g i s one e x p e r i m e n t i n w h i c h He c a r r i e r gas was used i n s t e a d o f H . O n l y v e r y s m a l l y i e l d s o f benzene (-17 m i n u t e e l u t i o n t i m e ) and t h e p r o d u c t w i t h 3 5 - m i n u t e r e t e n t i o n t i m e were f o u n d i n t h e t r a p s , p r e s u m a b l y p h o t o - d e t a c h e d f r o m t h e c o a l s u r f a c e . The y i e l d s were f a r t o o s m a l l t o a c c o u n t f o r a l l t h e o t h e r p r o d u c t s by hydrogen atom c r a c k i n g o f t h e s e compounds. B l a n k e x p e r i m e n t s u s i n g H b u t l e a v i n g t h e u l t r a v i o l e t l i g h t s o f f gave no d e t e c t a b l e p r o d u c t s i n an hour. W h i l e c o n s i d e r a b l e e x p e r i m e n t a t i o n r e m a i n s t o be done, 4

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

6

1 I +

9

8

1 5

3

2

3

2

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Figure 2. 185°-200°C.

2

Gas chromatogram of Η-atom produced gaseous products from Illinois No. 6 coal at Peak identifications are by retention times and are tentative. η-OCT/PORACIL C, Ve " X JO' column; 60°C; 8% H in He carrier gas; 25 cc injection loop.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

11.

MAINS E T AL.

Photochemical Hydrogen Atoms

161

UJ >

It

Ζ

ο

(Λ

ο 5

Lu

oc κ

LU LU χ Q

40

30

20

10

TIME (MINUTES)

Figure 3. Gas chromatogram of Η-atom produced gaseous products from Pittsburgh Hi-Seam Coal at 185°-200°C. V -OCT/PORACIL C, X 10' column; 60°C; 8% Η in He carrier gas; 25 cc injection loop. 2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

162

ORGANIC CHEMISTRY OF COAL

the s i m i l a r i t y o f the products from the three bituminous c o a l s s u g g e s t t h e f o l l o w i n g mechanism: Hg + hv Hg* + H

+ Hg* 2

3

(P)

Hg + 2H

(2)

H + coal

-> P r e c u r s o r s + ?

H + Precursors

+ C , C , C\, C , C 2

3

hydrogénation

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

(1)

X

5

(3) 6

(4)

products

In o t h e r w o r d s , t h e s i m i l a r i t y o f t h e p r o d u c t d i s t r i b u t i o n s f r o m t h e d i f f e r e n t b i t u m i n o u s c o a l s i s p r o p o s e d t o be a r e s u l t o f t h e s i m i l a r i t y o f s e c o n d a r y H atom c r a c k i n g o f t h e p r o d u c t p r e c u r s o r s f r o m r e a c t i o n (3) u n d e r t h e i d e n t i c a l r e a c t o r c o n d i t i o n s , r a t h e r t h a n an i n d i c a t i o n t h a t t h e s e t h r e e c o a l s , w i t h d i f f e r e n t h i s t o r i e s and d i f f e r e n t p h y s i c a l p r o p e r t i e s , have s u r f a c e s t h a t a r e s i m i l a r . A t t h i s p o i n t , t h e o n l y l i k e n e s s i n s u r f a c e t h a t can be i n f e r r e d i s t h e a b i l i t y o f H atoms t o l i b e r a t e t h e h y d r o g é n a t i o n p r e c u r s o r s f r o m t h e s u r f a c e o f I l l i n o i s #6, P i t t s b u r g h Hi-Seam, and Utah-Emery b i t u m i n o u s c o a l s . R e a c t i o n (3) must be s i m i l a r i n r a t e arid r e a c t i o n p r o d u c t s t o a c c o u n t f o r t h e s i m i l a r i t y o f F i g u r e s 2, 3, and 4. K i n e t i c i n f o r m a t i o n a b o u t r e a c t i o n (4) i s a p p e a r i n g (7_, 8) and s h o u l d a i d i n t h e i n t e r p r e t a t i o n o f f u t u r e e x p e r i m e n t s i n v o l v i n g more u n i f o r m c o n c e n t r a t i o n s . F i n a l l y , t h e f a i l u r e o f Wyoming-Wyodak c o a l t o r e a c t u n d e r i d e n t i c a l c o n d i t i o n s must be a t t r i b u t e d t o a s l o w n e s s o f r e a c t i o n (3). A g r e a t e r d i v e r s i t y of products from a sub-bituminous coal m i g h t have been e x p e c t e d s i n c e i t s o r g a n i c s t r u c t u r e s had been s u b j e c t e d t o l e s s s t r i n g e n t c o a l i f i c a t i o n c o n d i t i o n s and i t c o n t a i n s more v o l a t i l e o r g a n i c m a t t e r . S i n c e F i g u r e 5 l o o k s r e m a r k a b l y s i m i l a r to r e s u l t s from experiments e a r l y i n t h i s program u s i n g I l l i n o i s #6 c o a l a t a m b i e n t t e m p e r a t u r e , one m i g h t e x p e c t a g r e a t l y e n h a n c e d ESR s p e c t r u m s u c h as was o b s e r v e d t h e n . That i s , a r e s u l t o f H atom bombardment i s t h e p r o d u c t i o n o f n o n v o l a t i l e f r e e r a d i c a l s . F u r t h e r work i s c l e a r l y w a r r a n t e d . N o n e t h e l e s s , i t has now been d e m o n s t r a t e d t h a t p h o t o - p r o d u c e d H atoms do i n t e r a c t w i t h t h e s u r f a c e o f b i t u m i n o u s c o a l s a t 200°C t o y i e l d C t o C h y d r o c a r b o n s . However, t h e a u t h o r s f e e l t h a t f u r t h e r e x p e r i m e n t s , some a l t e r i n g t h e s t e a d y s t a t e H atom c o n c e n t r a t i o n and a d d i n g s u s p e c t e d p r e c u r s o r s , a r e r e q u i r e d t o e l u c i d a t e t h e mechanisms. A l s o , an a c c u r a t e method f o r d e t e r m i n i n g c o a l p a r t i c l e c o n c e n t r a t i o n s i n t h e p h o t o r e a c t o r needs t o be f o u n d b e f o r e r e l i a b l e r a t e d a t a can be f o r t h c o m i n g . F i n a l l y , o t h e r s u b - b i t u m i n o u s c o a l s need t o be examined t o see i f t h e Wyodak r e s u l t s , r e p r o d u c e d s e v e r a l t i m e s , a r e common t o t h i s r a n k o f c o a l . Whether H atoms w i l l p r o v e an e f f e c t i v e c o a l s u r f a c e 2

8

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

11.

MAINS ET AL.

Photochemical

TIME

Hydrogen

163

Atoms

(MINUTES)

Figure 4. Gas chromatogram of Η-atom produced gaseous products from Emery-Utah Coal at 185°-200°C. V-OCT/PORACIL C, Va" χ IV column; 60°C; 8% Η in He carrier gas; 25 cc injection loop. 2

>H Lu

Ρ ο *

< o

S LU oc i 40

LU Lu Χ Ω

30

20

10

TIME (MINUTES) Figure 5. Gas chromatogram of Η-atom produced gaseous products from Wyodak-Wyoming Coal at 185°-200°C. η -OCT/PORACIL C, Vs" χ 10' column; 60°C; 8% H in He carrier gas; 25 cc injection loop. 2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

164

ORGANIC CHEMISTRY OF COAL

probe remains to be proven. couraging i n some r e s p e c t s .

These p r e l i m i n a r y r e s u l t s are en­

Acknowledgments We wish to thank Dr. Fred Radd, Continental O i l Company, who e n t h u s i a s t i c a l l y encouraged us to begin coal r e s e a r c h , and Mr. Ed O b e r m i l l e r , CONOCO Coal Development, f o r both encouragement and the coal samples. L a s t , but c e r t a i n l y not l e a s t , we thank E . R . D . A . f o r a research grant that supported these experiments. Abstract Hydrogen atoms, produced by the mercury p h o t o s e n s i t i z a t i o n of H , were made to i n t e r a c t with coal d u s t , -53 to +38 microns, at 200°C i n a flow r e a c t o r . Illinois No. 6, P i t t s b u r g h Seam, and Utah-Emery c o a l s produced a l a r g e number o f saturated hydrocarbon products i n the C to C range. Wyoming-Wyodak coal was c o n s i d ­ e r a b l y l e s s r e a c t i v e . The kinetic, q u a n t i t a t i v e , and s t r u c t u r a l i m p l i c a t i o n s o f these r e s u l t s are d i s c u s s e d . Experimentation with d i f f e r e n t r e a c t o r c o n d i t i o n s c o n t i n u e s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch011

2

2

8

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8)

Avaremko, V. J., J. Phys. Chem. (U.S.S.R.), (1946), 20, 1299. P i n c h i n , F. T., Brit. Coal Util. Res. A s s o c . , Monthly Bulletin, (1965), 29, 105. Sanada, Y., B e r k o w i t z , N., F u e l , (1969), 48, 375. Kobayashi, K., B e r k o w i t z , N., F u e l , (1971), 50, 254. Solomon, J. Α., Mains, G. J., F u e l , (1977), 56, 302. S n e l s o n , Α., A . C . S . D i v . Fuel Chem. P r o c . , (1973), 18, 101. Kim, P., Lee, J., Bonnano, R . , Timmons, R . , J. Chem. P h y s . , (1973), 59, 4593. Amano, Α . , H o r i e , O., Hanh, W., I n t . J. Chem. Kinetics, (1976), 8, 321.

RECEIVED March 13, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

12 Isotopic Studies of Thermally Induced Reactions of Coal and Coal-Like Structures CLAIR J. COLLINS, BEN M. BENJAMIN, VERNON F. RAAEN, PAUL H. MAUPIN, and W. H . ROARK (1)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, T N 37830

We r e c e n t l y (2) reported that under c o n d i t i o n s o f coal conv e r s i o n (tetralin, 400°) several d i a r y l a l k a n e s undergo carbon-carbon cleavage, and that the scission o f carbon-carbon bonds must t h e r e f o r e be considered as an important process i n asphaltene formation ( 3 ) . We also reported (2) t h a t vitrinite (from Illinois No. 6 c o a l ) was a " b e t t e r hydrogen t r a n s f e r agent" than tetralin itself f o r the hydrogenolysis o f 1 , 1 , 2 - t r i p h e n y l e t h a n e t o diphenylmethane and toluene. We have now extended these s t u d i e s to e s t a b l i s h a) t h a t vitrinite i s indeed a b e t t e r hydrogen donor than tetralin toward several organic s t r u c t u r e s ; b) that tetralin, i n a d d i t i o n t o its f u n c t i o n as a hydrogen donor, can undergo c e r t a i n other r e a c t i o n s w i t h coal and coal-like s t r u c t u r e s which i n v o l v e both carbon-carbon bond formation and bond cleavage. A Comparison o f T etralin an d V itrinite as H-donors When 1 , 2 - d i p h e n y l - 1 - p - t o l y l e t h a n e i s heated a t 400° ( e i t h e r i n g l a s s capillaries or i n s t a i n l e s s s t e e l tubes) w i t h an excess of tetralin, the major products are toluene and phenyl-p-tolylmethane. The same products are obtained when 1 , 2 - d i p h e n y l - l - p t o l y l e t h a n e i s heated a t 400° i n the presence o f an excess o f v i t r i n i t e (handpicked from I l l i n o i s No. 6 c o a l ) . Given i n Table I i s a comparison o f the extent r e a c t i o n - as determined by g . c . a n a l y s i s o f the products - a f t e r various contact times with t e t r a l i n or w i t h v i t r i n i t e . Another d i a r y l a l k a n e which i s e a s i l y decomposed i n the presence o f excess t e t r a l i n o r excess v i t r i n i t e i s 1,3-diphenylpropane. The major products i n both cases are toluene and e t h y l benzene, although a m u l t i p l i c i t y o f minor products are produced. Also given i n Table I are comparisons o f the extent r e a c t i o n o f 1,3-diphenylpropane (400° f o r 30 minutes) a) with excess t e t r a l i n ; b) with excess t e t r a l i n and v i t r i n i t e ; and c) with excess v i t r i n i t e . The extent r e a c t i o n i n each case was estimated from the g . c . t r a c e .

0-8412-0427-6/78/47-071-165$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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ORGANIC CHEMISTRY OF COAL

Table I A Comparison o f T e t r a l i n and I l l i n o i s No. 6 V i t r i n i t e as Hydrogen Donors

Reactants

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

1,2-Diphenyl-1-ptolylethane

Conditions 400°, 5 min tetralin

Percent Reaction 2%

a

II

4 0 0 ° , 30 m i n tetralin

II

400°, 5 min vitrinite 4 0 0 ° , 30 m i n tetralin

b

50%

a

1 , 3 - d i p h e n y l propane

b

23%

b

43%

b

65%

II

4 0 0 ° , 30 m i n tetralin & vitrinite

II

4 0 0 ° , 30 m i n vitrinite

The oven was a t 4 0 0 ° , b u t t h e warm-up t i m e i s 15 m i n u t e s , t h e a c t u a l t e m p e r a t u r e was c o n s i d e r a b l y l e s s t h a n 4 0 0 ° . b

94%

thus

3 0 m i η i n c l u d e d warm up t i m e .

S i n c e t h e r e a c t i o n s were m o n i t o r e d by g . c , w h i c h would d e t e c t n e i t h e r n o n v o l a t i l e polymeric m a t e r i a l , nor high molecular weight products o f r e a c t i o n with v i t r i n i t e , i t i s p o s s i b l e t h a t t h e v i t r i n i t e i s a c t i n g n o t as a hydrogen d o n o r , b u t m e r e l y as a c a t a l y s t , and t h a t t h e s o u r c e o f t h e h y d r o g e n f o r t h e h y d r o g e n o l y s e s comes f r o m t h e 1 , 2 - d i p h e n y l - l - £ - t o l y l e t h a n e or from the 1,3-diphenylpropane. To c i r c u m v e n t t h i s p r o b l e m , we h e a t e d benzophenone t o 4 0 0 ° f o r one hour a) i n t h e p r e s e n c e o f e x c e s s t e t r a l i n , and b) i n t h e p r e s e n c e o f e x c e s s v i t r i n i t e . The m a j o r p r o d u c t s a r e d i p h e n y l m e t h a n e and w a t e r , w i t h t r a c e s o f t o l u e n e and benzene. The r e a c t i o n i n t e t r a l i n p r o c e e d e d t o t h e e x t e n t o f o n l y 12%, whereas i n t h e p r e s e n c e o f v i t r i n i t e 35% r e a c t i o n had o c c u r r e d . (6,7) R e a c t i o n s o f T e t r a l i n o t h e r t h a n Hydrogen D o n a t i o n T e t r a l i n - l - ^ C r e a c t s w i t h Wyodak c o a l a t 4 0 0 ° (1 hour) t o the extent t h a t the p y r i d i n e - i n s o l u b l e r e s i d u e c o n t a i n s c h e m i c a l l y bound c a r b o n - 1 4 e q u i v a l e n t t o 5% t e t r a l i n by w e i g h t . F u r t h e r , when t h e r e s i d u e was r e h e a t e d i n normal t e t r a l i n ( 4 0 0 ° , one h o u r ) t h e r e i s o l a t e d s o l v e n t c o n t a i n e d no m e a s u r a b l e amount o f e i t h e r

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

12.

Isotopic

COLLINS ET AL.

Studies of Thermally

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

l l f

Induced

Reactions

167

ll

t e t r a l i n - C o r o f n a p h t h a l e n e - * C . T h e r e were, however, t r a c e s o f l a b e l e d a l k y l a t e d n a p h t h a l e n e s , w h i c h were i d e n t i f i e d by g.c. r e t e n t i o n t i m e s as 1- and 2 - s u b s t i t u t e d m e t h y l - and e t h y l n a p h t h a l e n e s . These p r o d u c t s u n d o u b t e d l y a r i s e as a r e s u l t o f f r e e r a d i c a l i n t e r m e d i a t e s . We t h e r e f o r e i n v e s t i g a t e d t h e p o s s i b i l i t y t h a t m e t h y l - o r e t h y l n a p h t h a l e n e s c o u l d be p r o d u c e d by t h e r e a c tion of t e t r a l i n with structures containing aromatic moieties s e p a r a t e d by two o r more m e t h y l e n e g r o u p s , o r w i t h a r y l a l k y l e t h e r s . Both t y p e s o f s t r u c t u r e (4,5) a r e known t o be p r e s e n t i n d i f f e r e n t k i n d s and r a n k s o f c o a l . We h e a t e d s e v e r a l d i a r y l a l k a n e s and a r y l a l k y l o r a r a l k y l e t h e r s t o 4 0 0 ° i n t e t r a l i n f o r v a r y i n g p e r i o d s o f t i m e . Many o f t h e s e r e a c t i o n s y i e l d e d m e a s u r a b l e q u a n t i t i e s o f m e t h y l - and ethyl naphthalenes i n a d d i t i o n to other products. Typical are the r e a c t i o n s o f 1 , 3 - d i p h e n y l p r o p a n e and o f p h e n e t o l e , b o t h o f w h i c h were i n v e s t i g a t e d w i t h c a r b o n - 1 4 — l a b e l e d s p e c i e s . The p r o d u c t s were a n a l y z e d a) by gas c h r o m a t o g r a p h y combined w i t h r a d i o a c t i v i t y m o n i t o r i n g o f c a r b o n - 1 4 — l a b e l e d p r o d u c t s ; b) by gas c h r o m a t o g r a phy e q u i p p e d w i t h mass s p e c t r o g r a p h s a n a l y z e r s ; and c ) by i s o l a t i o n o f s p e c i f i c p r o d u c t s u s i n g p r e p a r a t i v e g.c. f o l l o w e d by nmr a n a l y s i s ( V a r i a n XL-100 S p e c t r o m e t e r ) . G i v e n i n T a b l e s II and I I I a r e t h e m a j o r p r o d u c t s o b t a i n e d - t o g e t h e r w i t h a p p r o p r i a t e y i e l d s - f r o m t h e r e a c t i o n s o f 1 , 3 - d i p h e n y l propane and phenetole, respectively, with t e t r a l i n . T a b l e II 3

M a j o r P r o d u c t s and Y i e l d s O b t a i n e d on H e a t i n g 1 , 3 - D i p h e n y l propane w i t h T e t r a l i n One Hour a t 4 0 0 °

Toluene E t h y l benzene 1- and 2 - ( 2 - P h e n y l e t h y l ) t e t r a l i n s 1,4-Diphenylbutane 1- and 2 - M e t h y l n a p h t h a l e n e s Styrene 1,3-Diphenylpropene Methyldi hydronaphthalenes 1,2-Diphenylethane 1- and 2 - ( 2 - P h e n y l e t h y l ) n a p h t h a l e n e s Other a

B a s e d on 1 , 3 - d i p h e n y l p r o p a n e

28% 19 8 5 3 1. 1. 34

consumed.

The 1- and 2 - m e t h y l n a p h t h a ! e n e s were i s o l a t e d and i d e n t i f i e d by nmr a n a l y s i s . T h e i r g e n e s i s f r o m t h e r e a c t i o n o f 1 , 3 - d i p h e n y l p r o p a n e - 2 - C ( C=*) and t e t r a l i n was d e t e r m i n e d as follows: lif

llf

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

168

ORGANIC CHEMISTRY OF COAL

CH P h C H C H C H P h + (0Q 2

2

-

2

00}

CH CH Ph

3

2

+

2

00)

Table III

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

M a j o r P r o d u c t s and Y i e l d s O b t a i n e d on H e a t i n g P h e n e t o l e w i t h T e t r a l i n E i g h t e e n Hours a t 4 0 0 °

Phenol M e t h y l n a p h t h a l enes Toluene E t h y l benzene Ethylnaphthalenes Methyltetralins Ethyl phenol Ethyltetralins E t h y l m e t h y l benzene Methylindane B u t y l benzene

37J » 7 ' 7

3 / 0

4 3 3 %

From D e c o m p o s i t i o n of Tetralin

The m i x t u r e o f e t h y l n a p h t h a l e n e s was i d e n t i f i e d by g . c . r e t e n t i o n t i m e s and r a d i o a c t i v i t y a s s a y by means o f t h e g . c . r a d i o a c t i v i t y m o n i t o r . T r a c e s o f m e t h y l i n d a n e and o f b u t y l benzene were a l w a y s p r e s e n t a f t e r r e a c t a n t s were h e a t e d w i t h t e t r a l i n . T h a t t h e s e l a t t e r two p r o d u c t s were d e r i v e d f r o m t e t r a l i n was d e m o n s t r a t e d by t h e f a c t t h a t t h e y c o n t a i n e d c a r b o n - 1 4 when t e t r a l i n - * C was u s e d i n t h e r e a c t i o n . In l i k e manner, l a b e l e d p h e n e t o l e and t e t r a l i n were s u b j e c t e d t o t h e c o n d i t i o n s o f r e a c t i o n w i t h t h e f o l l o w i n g results: l l

It i s c l e a r from the i s o t o p i c l a b e l i n g experiments t h a t t e t r a l i n has e n t e r e d i n t o t h e r e a c t i o n b o t h w i t h 1 , 3 - d i p h e n y l p r o p a n e and w i t h p h e n e t o l e . The r e s u l t s a r e n i c e l y accommodated by t h e p o s t u l a t i o n o f r a d i c a l i n t e r m e d i a t e s . A p o s s i b l e mechanism f o r t h e r e a c t i o n o f 1 , 3 - d i p h e n y l p r o p a n e i s i n d i c a t e d i n T a b l e IV.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

COLLINS ET AL.

12.

Isotopic Studies of Thermally Induced Reactions

169

TABLE IV P o s s i b l e Mechanism f o r t h e R e a c t i o n o f T e t r a l i n w i t h 1 , 3 - D i p h e n y l propane PhCH CH CH Ph

>• PhCH -

+

PhCH -

*

+

2

2

2

+

2

PhCH

3

PhCH CH - +

*• PhC,H CH

2PhCH CH -

*~

2

2

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

2

2

2

(00

PhCH CH - + 2

2

CH CH Ph 2

2

-CH CH Ph 2

2

+

3

PhCH CH CH CH Ph 2

2

2

2

CH CH Ph

-

®3 ©0

2

2

CH '

?

2

+

PhCH 2

α & g

€0

CH 2

+

.

CH

0D - OO^eO ^ .CHs 3

a

α,β A c k n o w l e d g e m e n t s : We a c k n o w l e d g e w i t h t h a n k s t h e a s s i s t a n c e o f Mr. L. L. Brown i n r u n n i n g t h e nmr s p e c t r a , and o f Dr. W. T. R a i n e y , Mr. Ε. H. McBay and Mr. D. C. Canada o f t h e A n a l y t i c a l C h e m i s t r y D i v i s i o n , f o r c a p i l l a r y g . c . a n d mass s p e c t r o g r a p h ! c a n a l y s e s o f s e v e r a l o f t h e h y d r o g e n o l y s i s p r o d u c t s . We thank t h e S a h a r a M i n i n g Co., H a r r i s o n b u r g , 111., f o r a g e n e r o u s sample o f I l l i n o i s No. 6 c o a l ; t h a n k s a r e a l s o due D r s . L. A. H a r r i s and A. S. Dworkin f o r a f i e l d t r i p t o t h e mine s i t e .

Literature Cited 1. 2.

Research sponsored by the Division o f Basic Energy Sciences of the Department o f Energy under contract with the Union Carbide Corporation. C o l l i n s , C. J., Raaen, V. F., Benjamin, Β. M . , and Kabalka, G. W., Fuel (1977), 56, 107.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

170

3.

4. 5. 6.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch012

7.

ORGANIC CHEMISTRY OF COAL

S e e also S h o z d a , R. J., Depp, Ε. Α . , Stevens, C. Μ . , and Neuworth, M. B., J. Amer. Chem. S o c . ( 1 9 5 6 ) , 78, 1716; Depp, Ε . Α . , Stevens, C. Μ . , and Neuworth, M. B., Fuel ( 1 9 5 6 ) , 35, 437. H e r é d y , L. Α . , K o s t y o , A. E . , and Neuworth, M. B., Fuel ( 1 9 6 5 ) , 44, 125. Brücker, R. a n d Kölling, G., Brennst. Chem. ( 1 9 6 5 ) , 46, 4 1 ; Kölling, G. a n d H a u s i g k , D., ibid. (1969) 50, 1. For information on "Catalylic D e h y d r o g e n a t i o n of Coal" s e e R e g g e l , L . , Wender, I., a n d Raymond, R., Fuel ( 1 9 7 3 ) , 52. 162-163 (1973) a n d the previous six papers in this series cited therein. C o a l s have previously been d e h y d r o g e n a t e d w i t h p - b e n z o q u i n o n e , P e o v e r , M. E . , J. Chem. S o c . (London) ( 1 9 6 0 ) , 5020.

RECEIVED February 10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

13 Supercritical Solvents and the Dissolution of Coal and Lignite JAMES E. BLESSING and DAVID S. ROSS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025

The unique solvent properties of supercritical fluids suggest their use in coal extraction as a novel scheme for isolating syncrude-like materials. One advantage such a process might offer is the ease of separating solvent from extract. We have studied the degree of coal dissolution possible with a number of solvents in the supercritical state and examined the importance of system parameters, such as solvent type, density, and temperature, on the success of extractions. Shortly after we began our work, Bartle, Martin, and Williams of the National Coal Board of Britain reported a 17% yield of low­ -ash, high-H/C material from the extraction of coal with superc r i t i c a l toluene at 350°C (1). Since then, Maddocks and Gibson have reported greater yields, with up to one-third extraction of an I l l i n o i s No. 6 coal with toluene at 400°C (2). They estimated that their process would be economically competitive with the COED and SRC operations. This paper reviews the fundamentals of supercritical extraction, discusses our data in terms of theoretical expectations, and draws some conclusions regarding the role of extraction per se i n obtaining products from coal. Background A "supercritical" fluid i s one that i s above i t s c r i t i c a l temperature (T ), the point beyond which a phase boundary no longer exists between gas and liquid. In the supercritical region, the density of a f l u i d is a continuous function of i t s pressure, no distinction exists between gas and liquid, and the f l u i d has no surface tension. One hundred years ago, Hannay and Hogarth observed the dissolution of KI in supercritical ethanol (3). Yet, until now, little practical use has been made of supercritical extractants. Paul and Wise have described the theoretically based expectations of the use of supercritical fluids as solvents or extractants, both c

0-8412-0427-6/78/47-071-171$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

172

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

g e n e r a l l y and with some emphasis on c o a l d i s s o l u t i o n (4). Given below are some of the p r o p e r t i e s of s u p e r c r i t i c a l f l u i d s , d i s cussed i n t h e i r monograph: •

At low d e n s i t i e s , gases have no solvent power, and the concentration of a compound s o l u t e i n the gas phase i s described by i t s p a r t i a l pressure. However, at a given temperature, the solvent power of any gas increases d r a m a t i c a l l y as i t s density approaches that of l i q u i d s .

•

For a given pressure, a gas i s at i t s highest d e n s i t y near i t s c r i t i c a l temperature, where i t i s l e a s t i d e a l .

•

For a given gas density, the concentration of a s o l u t e i n a gas increases with i n c r e a s i n g temperature due to increased s o l u t e v o l a t i l i t y , but solvent pressures r i s e r a p i d l y as the temperature exceeds T and the solvent gas becomes more i d e a l . Theory p r e d i c t s that the solvent power of such a gas i s p r i m a r i l y a f u n c t i o n of i t s p h y s i c a l p r o p e r t i e s and i s r e l a t i v e l y independent of i t s chemical s t r u c t u r e and f u n c t i o n a l i t y . c

•

Because a gas i s g e n e r a l l y l e s s viscous than a l i q u i d , i t can b e t t e r penetrate porous substrates, such as coal.

•

Though the solvent power of a dense gas may not be high compared with l i q u i d s , the gas i s more e a s i l y separated from m a t e r i a l s l i k e c o a l , and solvent r e c o v e r i e s can therefore be b e t t e r .

The conclusions of Paul and Wise thus suggest that superc r i t i c a l e x t r a c t i o n i s a promising procedure f o r c o a l conversion. The r e s u l t s of our research v e r i f y the a p p l i c a b i l i t y of these p r i n c i p l e s to c o a l e x t r a c t i o n , but a l s o point to the importance of processes other than simple e x t r a c t i o n s i n the production of c o a l products. Experimental Procedures A v a r i e t y of experiments were performed using s e v e r a l s o l vents over a range of c o n d i t i o n s to e x t r a c t samples of I l l i n o i s No. 6 c o a l and North Dakota l i g n i t e . The coals are c h a r a c t e r i z e d i n Table I. A l l experiments were done i n batch mode, i n a 300 cm , 316 SS AE MagneDrive autoclave. Most experiments were run f o r 90 min at 335°C. The run procedure i s summarized i n Figure 1. The workup procedure i s shown i n Figure 2. Each r e a c t i o n product i s separated i n t o a f i l t r a t e and a s o l i d s f r a c t i o n . In every case, the f i l t r a t e s were f u l l y p y r i d i n e s o l u b l e . The p y r i d i n e s o l u b i l i t i e s of the s o l i d s were determined by s t i r r i n g 0.5 g s o l i d i n 50 ml p y r i d i n e f o r 1 hr at room temperature, and 3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

COAL OR LIGNITE

Figure 1.

Run procedure

CAREFULLY COLLECT REACTOR CONTENTS

HEAT-UP (50 MIN) HOLD COOL-DOWN (60 MIN)

FILL AND V E N T 1000 psig OF NITROGEN, TWICE

3

A E MAGNEDRIVE 300 c m , 316 SS AUTOCLAVE STIRRING 1500 rpm

DRY A T 120°C, < 1 TORR

REACTION SOLVENT

Figure 2.

Low melting solids. Typical MW_ « 450

Wt% Filt. based on MAF starting coal.

REACTION MIXTURE

"SOLIDS"

Workup procedure

Typical MW

n

* 1100

Wt% solids pyr. sol based on MAF 0.5 g sample

EVAPORATE SOLVENT AND DRY, 120°C, < 1 TORR

MED. POROSITY FILTER

STIR 0.5 g IN 50 ml PYRIDINE FOR 1 HOUR A T ROOM T E M P E R A T U R E

DRY, 120°C, < 1 TORR

MEDIUM POROSITY FRITTED FILTER (10-15 Mm)

EVAPORATE SOLVENT AND DRY, 120°C, < 1 TORR

"FILT"

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

174

ORGANIC CHEMISTRY OF COAL

Table I CHARACTERISTICS OF COAL AND LIGNITE SAMPLES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

Analyses

Beneficiated I l l i n o i s No. 6 Coal Dried Over­ night at 120°C and < 1 t o r r . ASTM HVC (PSOC-26?

%C %H Molar H/C %N %S org %S. morg %0 Δ %Ash % Pyridine solubility % Solubility i n a l l reac­ tion solvents

North Dakota L i g n i t e Dried Overnight a t 120°C and < 1 t o r r (PSOC-246)'

77.2 5.1 0.79 1.7 2.1

62.0 4.5 0.87 1.0 0.7

b

% 0 11.9

14.8

2.0 13

17 2

Λ

<

1

^Pennsylvania State U n i v e r s i t y d e s i g n a t i o n . Organic and inorganic s u l f u r combined. then f i l t e r i n g (Figure 2). Included i n Figure 2 are t y p i c a l number-average molecular weights f o r f i l t r a t e s and p y r i d i n e s o l ­ uble p o r t i o n s of the s o l i d s . The p y r i d i n e s o l u b i l i t y (PS) of the e n t i r e r e a c t i o n product i s the appropriate a l g e b r a i c composite of the f i l t r a t e f r a c t i o n and the p y r i d i n e s o l u b i l i t y of the s o l i d s :

PS = {% F i l t j

+

ft.00% - F i l t \ / % p y r i d i n e s o l u b i l i t y \ 100 Λ of s o l i d s /

I n i t i a l l y , we found i t necessary to separate any m a t e r i a l s d i s s o l v e d i n the media from the m a t e r i a l that was i n s o l u b l e during the experiment. We took t h i s precaution to e l i m i n a t e any confu­ s i o n of r e s u l t s where a s i g n i f i c a n t f r a c t i o n of the c o a l would be s o l u b l e under s u p e r c r i t i c a l c o n d i t i o n s but i n s o l u b l e when the system was brought back to ambient temperature and pressure. Accordingly, we designed a c o a l f i l t e r "basket" f o r these e x p e r i ­ ments (see Figure 3). The procedure was to place the s t a r t i n g c o a l between two s i n t e r e d - g l a s s d i s c s w i t h i n the autoclave so that any m a t e r i a l d i s s o l v e d under s u p e r c r i t i c a l c o n d i t i o n s would be c a r r i e d through these d i s c s and recovered outside the basket a f t e r the experiment, whether or not t h i s m a t e r i a l was s t i l l s o l u b l e .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

13.

BLESSING AND Ross

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

Results and

Supercritical

Solvents

175

Discussion

I n i t i a l E x t r a c t i o n s . We performed s e v e r a l experiments using the e x t r a c t i o n apparatus of Figure 3. Table I I compares the r e s u l t s of these experiments with those of experiments run i d e n t i c a l l y but without the e x t r a c t i o n apparatus ( i . e . , with the c o a l dispersed i n the r e a c t o r ) . The f i l t r a t e y i e l d s are comparable, and i n the basket runs, l i t t l e i f any s o l i d m a t e r i a l i s recovered outside the basket.* Thus, no more m a t e r i a l i s s o l u b l e i n the s u p e r c r i t i c a l media at 335°C than i n the solvent at ambient c o n d i t i o n s a f t e r the run. In l i g h t of these r e s u l t s , a l l subsequent work was done without the e x t r a c t i o n apparatus. The f i l t r a t e y i e l d s are much greater than the s o l u b l e s of the untreated c o a l i n these same s o l v e n t s at ambient c o n d i t i o n s (Table I ) . The s o l u b l e m a t e r i a l , t h e r e f o r e , e i t h e r was p h y s i c a l l y entrapped i n the c o a l and r e q u i r e d s u p e r c r i t i c a l treatment to l i b e r a t e i t , or was not i n i t i a l l y s o l u b l e , but a r e s u l t of some chemical change i n the c o a l during s u p e r c r i t i c a l treatment. We b e l i e v e the l a t t e r to be the case, as w i l l be discussed l a t e r . The high p y r i d i n e s o l u b i l i t i e s obtained with isopropanol are due to hydride donation chemistry, and are discussed elsewhere (5). The experiments described above might be considered as continuous e x t r a c t i o n s c a r r i e d out w i t h i n a batch r e a c t o r . There can be l i m i t a t i o n s imposed on r e s u l t s acquired i n batch type experiments, perhaps the most important of which i s the l a c k of f r e s h solvent continuously e n t e r i n g the r e a c t o r and removing d i s solved m a t e r i a l . T h i s c o n s t r a i n t could r e s u l t i n a s a t u r a t i o n of the s o l v e n t , thereby l i m i t i n g e x t r a c t i o n y i e l d s . To determine i f we were encountering solvent s a t u r a t i o n s , we performed two experiments i n 0.62 g/cm benzene at 335°C f o r 3 hr, one w i t h 1 g of c o a l and the other w i t h 5 g. The amount of f i l t r a t e found i n the r e a c t i o n solvent was 12% of the s t a r t i n g c o a l i n both cases. Furthermore, the r e a c t i o n s o l i d s of both runs were found to be completely i n s o l u b l e i n f r e s h solvent a f t e r r e a c t i o n , i n d i c a t i n g that these runs were not s a t u r a t i o n - l i m i t e d . These b a t c h - r e a c t i o n r e s u l t s , though not i d e n t i c a l with continuous e x t r a c t i o n r e s u l t s , lead to conclusions that may apply to continuous u n i t operations as w e l l as batch operations. 3

The e x t r a c t i o n r e s u l t s f o r the i - P r O H / l i g n i t e / b a s k e t run are s i g n i f i c a n t l y low, perhaps because the l i g n i t e tended to agglomerate under these c o n d i t i o n s , thereby r e s t r i c t i n g the c i r c u l a t i o n of i-PrOH through the basket.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

0

0

(0.2,320) (0.2,320) (0.1,253) (0.1,253)

(0.3,253) (0.3,253) (0.6,289) (0.6,289) (0.4,240) (0.4,240)

b

3 4 5 12

11 11 12 13 12 8

—

0

—

0

—

2

—

1

—

0

Solids Recovered Outside Basket (%)

— — — —

— —

45 40 14 18

PS (%)

Percent of s t a r t i n g c o a l or l i g n i t e recovered.

^1 g c o a l i s used.

1 g c o a l i s used, f o r 3 hr.

'Density of media during run, and c r i t i c a l temperature of solvent (°C).

Reaction volume i s * 280 ml.

Basket No Basket Basket No Basket

Basket No Basket Basket No Basket Basket No Basket

Mode

5 g c o a l or l i g n i t e i s used.

Lignite: Toluene Toluene iPrOH iPrOH

d

Coal: iPrOH iPrOH Benzene Benzene MeOH MeOH

c

Medium , (g/ml,T )

Dissolved i n the Medium (% F i l t r a t e )

3

87 88 86 85

97 97 95 92 97 94

Mass Recovered (%)

THE EFFECTIVENESS OF SUPERCRITICAL EXTRACTION OF ILLINOIS NO. 6 COAL AND NORTH DAKOTA LIGNITE AT 335°C FOR 90 MINUTES

Table I I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

13.

BLESSING AND Ross

Supercritical

Solvents

STIRRING (304 SS)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

STIRRER (316 SS)

SHAFT

PROPELLER

EXTRACTOR (316 SS)

BODY

CUP C O V E R COMPRESSION S P R I N G (316 SS) C U P C O V E R (M P O R O S I T Y G L A S S FRIT) COAL CUP (GLASS, WITH M POROSITY BOTTOM) CUP H O L D - D O W N RING (316 SS) H O L D - D O W N R I N G L O C K PIN (316 SS) EXTRACTOR SUPPORTER (316 SS) —

AUTOCLAVE (316 SS)

AUTOCLAVE

Figure 3.

BODY

CAVITY

Basket assembly in autoclave

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

178

ORGANIC CHEMISTRY OF COAL

E f f e c t s of the State, Temperature and Density of the Medium. We performed one s e t of experiments to determine i f increased d i s s o l u t i o n r e q u i r e s a solvent that i s s t r i c t l y s u p e r c r i t i c a l . In these runs, toluene was used a t f i f t e e n degrees above and below i t s c r i t i c a l temperature ( T = 320°C ). To account f o r simple thermal e f f e c t s , we used benzene a t these same temperatures. Since the T of benzene i s 288°C, benzene was s u p e r c r i t i c a l i n both runs. The r e s u l t s of these experiments are presented i n Table I I I . c

c

Table I I I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

EXPERIMENTS ON ILLINOIS NO. 6 COAL WITH TOLUENE BELOW AND ABOVE ITS CRITICAL TEMPERATURE FOR 90 MINUTES Experimental Conditions Solvent Density Temp Solvent (g/ml) (°C)

Solubility

(%)

a

psig

Filt

PS

305

2400

8

13

Toluene (subcritical)

0.65

Toluene (supercritical)

0.65

335

3400

13

24

Benzene (supercritical)

0.70

305

3400

8

13

Benzene (supercritical)

0.70

335

4100

10

20

b

The c r i t i c a l temperatures f o r toluene and benzene are 320°C and 288°C, r e s p e c t i v e l y . 'The l i q u i d has expanded to f i l l the e n t i r e r e a c t o r and thus t h i s d e n s i t y i s the same as i n the s u p e r c r i t i c a l experiment. The r e s u l t s show that toluene a t 15°C above i t s c r i t i c a l temperature e x t r a c t s s i g n i f i c a n t l y more m a t e r i a l from the c o a l than i t does a t 15°C below i t s c r i t i c a l temperature. The comparable runs using benzene, however, show p a r a l l e l i n c r e a s e s . Thus, a s u p e r c r i t i c a l c o n d i t i o n has no s i g n i f i c a n t e f f e c t on d i s s o l u tion. Simple thermal e f f e c t s must be p r i m a r i l y r e s p o n s i b l e f o r these increased s o l u b i l i t i e s . To i n v e s t i g a t e f u r t h e r the e f f e c t s of temperature on these y i e l d s , we performed one experiment w i t h toluene a t a higher temperature. The r e s u l t s f o r three temperatures a r e compiled i n Table IV.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

13.

BLESSING AND Ross

Supercritical

179

Solvents

Table IV EFFECTS OF VARYING TEMPERATURE ON 0.65 g/ml TOLUENE/COAL TREATMENTS FOR 90

Reaction Temperature (°C)

Filt (%) 8 13 17

305 335 375

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

PS (%) 13 24 28

MIN

Reaction Pressure (psig) 2400 3400 4800

C l e a r l y , the f i l t r a t e y i e l d i s s t r o n g l y temperaturedependent. The amount of toluene s o l u b l e m a t e r i a l obtained from the 375°C r e a c t i o n exceeds the p y r i d i n e s o l u b i l i t y of the unt r e a t e d c o a l , and the p y r i d i n e s o l u b i l i t y of the e n t i r e product i s more than twice that of the untreated c o a l . Thus, thermal processes are probably breaking down the c o a l to s o l u b l e materials. Considerations of bond strengths and thermal cleavage k i n e t i c s do not p r e d i c t much thermal a c t i v i t y at 335°C. For example, given the r e l a t i v e l y weak C-C bond i n 1,2-diphenylethane (57 kcal/mol), the h a l f - l i f e f o r i t s thermal cleavage at 335°C PhCH -CH Ph + 2PhCH · 2

2

2

i s 160 hr (6). On t h i s b a s i s , l i t t l e thermal fragmentation should occur i n 90 min at t h i s temperature. On the other hand, the h a l f l i f e value i s f o r a gas-phase, low-density system and may not s t r i c t l y apply here. When c o a l i t s e l f i s heated i n n i t r o g e n at 335°C f o r 90 min, i t s pyridine s o l u b i l i t y declines s l i g h t l y . In the presence of s o l v e n t , however, the p y r i d i n e s o l u b i l i t y of a product c o a l i n c r e a s e s , as we have j u s t seen. The r e s u l t s of a b r i e f s e r i e s of experiments i n which only the d e n s i t y of the s o l v e n t was v a r i e d are presented i n Table V. This table reveals a clear i n c r e a s e i n both the f i l t r a t e y i e l d and the product p y r i d i n e s o l u b i l i t y w i t h i n c r e a s i n g s o l v e n t d e n s i t y , as when the temperature was v a r i e d . Thus, a dense s o l v e n t must p l a y some p a r t i n the p r o d u c t i o n of i n c r e a s e d f i l t r a t e y i e l d s and p y r i d i n e s o l u b i l i t i e s at these temperatures. The s o l v e n t may be a c t i n g simply as a s o l v e n t , where the s o l v e n t power i s changing with d e n s i t y , or i t may be r e a c t i n g with the c o a l , or both.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

180

Table V

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

EFFECTS OF VARYING SOLVENT DENSITY IN TOLUENE/COAL TREATMENTS AT 335°C FOR 90 Solvent Density (g/ml)

Filt (%)

PS (%)

0.21 0.60 0.65

5 11 13

9 18 24

MIN

Filt Molar H/C

Reaction Pressure (psig)

0.98 0.93

600 2150 3400

—

The Hildebrand s o l u b i l i t y parameter 6 i s a measure of the cohesive f o r c e s i n a solvent and has been considered i n terms of polar and nonpolar c o n t r i b u t i o n s (7). The a p p l i c a t i o n of the s o l u b i l i t y parameter to c o a l processing has been discussed by Angelovich et a l . , who concluded that solvents with a nonpolar s o l u b i l i t y parameter of about 9.5 are most e f f e c t i v e i n c o a l d i s s o l u t i o n (8). The polar/nonpolar e f f e c t s should d i m i n i s h above the c r i t i c a l temperature of a solvent as i t becomes more l i k e an i d e a l gas. Giddings et a l . (9) found a c o r r e l a t i o n between the solvent c a p a b i l i t i e s and the δ values of a number of s u p e r c r i t i c a l f l u i d s at l i q u i d d e n s i t i e s . T h e i r expression f o r the parameter, the one we are using, i s δ = 1.25

P^ p / p r

,

£

where P i s the c r i t i c a l pressure of the medium i n atmospheres, P i s i t s reduced d e n s i t y ( p r i t i c a l ) > * £ the duced d e n s i t y of l i q u i d s , taken to be about 2.66. Thus δ i s a l i n e a r f u n c t i o n of the experimental d e n s i t y , a l l other v a r i a b l e s i n the equation being constant f o r any given s o l v e n t . Product p y r i d i n e s o l u b i l i t y versus δ i s p l o t t e d i n F i g u r e 4. The data f o r a l l the s o l v e n t s appear to f a l l about a l i n e . * Regardless of t h e i r s t r u c t u r a l d i f f e r e n c e s , a l l these compounds l a r g e l y perform i n accordance with t h e i r solvent c a p a b i l i t i e s . Thus, the media are a c t i n g simply as solvents and are apparently not chemically a c t i v e . Since the p y r i d i n e s o l u b i l i t y of the s t a r t i n g c o a l i s 13%, the use of these solvents at lower den­ s i t i e s i s a c t u a l l y counterproductive. c

a n c

r

p

i s

r e

C

A comparable run with T e t r a l i n and c o a l y i e l d s a product that i s about 50% p y r i d i n e s o l u b l e .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

BLESSING AND Ross

Figure 4.

Supercritical

Solvents

Product pyridine solubilities vs. 8 (reaction conditions: 90 min, 335°C, approx. 500-5000 psig)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

182

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

Conclusion The conclusions presented here are based on the r e s u l t s of our experiments with c o a l . On the b a s i s of some l i m i t e d research with l i g n i t e , we suggest that these conclusions a l s o apply to lignite. The y i e l d s f o r l i g n i t e , however, were g e n e r a l l y lower than those f o r c o a l under comparable c o n d i t i o n s . The c o r r e l a t i o n of p y r i d i n e s o l u b i l i t y of the c o a l products with the Hildebrand s o l u b i l i t y parameter coupled with the tempera­ ture dependence of the product y i e l d s leads us to suggest that the s o l u b l e product m a t e r i a l s r e s u l t from an i n i t i a l , thermally induced fragmentation of the c o a l i n v o l v i n g the a c t i o n of a dense solvent. Thermochemical c o n s i d e r a t i o n s suggest that the r a t e of thermal fragmentation i s too slow to account f o r the r e s u l t s . As s t a t e d , however, these thermochemical c a l c u l a t i o n s are f o r a gas phase system, a t d e n s i t i e s s e v e r a l orders of magnitude lower than those used i n our experiments. Wiser has suggested that c o a l thermolysis r a t e s may be s i g n i f i c a n t l y enhanced i n the presence of a s o l v e n t (10). Although n e i t h e r t h e o r e t i c a l nor independent experimental j u s t ­ i f i c a t i o n e x i s t s f o r t h i s suggestion,* our data, and p a r t i c u l a r l y , our f i n d i n g of a correspondence between the d e n s i t y of the medium and the conversion to p y r i d i n e - s o l u b l e products, are best explained that way. Thus, a model c o n s i s t e n t with the data i s

c

_

c

solvent participation 1

c

m

2

C-0 bonds can be considered s i m i l a r l y .

(i)

Hydrogen-transfer coal, —C-

(ii)

conversion to s t a b l e products

Step (2) may i n v o l v e e i t h e r

from a hydrogen-rich p o r t i o n of the

+ RH—^R- +

—CH

D i s p r o p o r t i o n a t i o n of the r a d i c a l s p e c i e s , 2

—CH-CH

3

—*~

—CH=CH

2

+ —CH -CH 2

3

or ( i i i ) β-scission, s p l i t t i n g o f f a s m a l l , r e l a t i v e l y f r e e r a d i c a l (R=H, a l k y l , benzyl) —C-C-R — — C = C

stable

+ R-

* For the simple, thermal homolysis, R-R 2R«, no evidence e x i s t s that the r a t e i s s i g n i f i c a n t l y enhanced by the presence o f s o l ­ vent. Moreover, i f the process i s s t r i c t l y one i n which no charge s e p a r a t i o n occurs i n the t r a n s i t i o n s t a t e , there i s no t h e o r e t i c a l expectation of a s i g n i f i c a n t solvent e f f e c t .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

13.

BLESSING AND Ross

Supercritical

183

Solvents

(An a l t e r n a t i v e mechanism i s discussed i n the Appendix.) S u p e r c r i t i c a l s o l v e n t s , t h e r e f o r e , c l e a r l y can provide moderate y i e l d s of s y n c r u d e - l i k e m a t e r i a l s from c o a l , and these y i e l d s are not p r i m a r i l y due to any unique c h a r a c t e r i s t i c s of s u p e r c r i t i c a l c o n d i t i o n s . Since high solvent d e n s i t i e s are d e s i r a b l e , solvents that are l i q u i d at l i q u e f a c t i o n temperatures could prove at l e a s t as e f f e c t i v e as those that are s u p e r c r i t i c a l , and at lower pressures. L i q u i d s , however, are subject to the l i m i t a t i o n s of surface t e n s i o n and higher v i s c o s i t i e s , which dimi n i s h t h e i r usefulness i n t h i s scheme. A d d i t i o n a l l y , s o l v e n t s that are l i q u i d at l i q u e f a c t i o n temperatures are very d i f f i c u l t to separate from c o a l products. Thus, s u p e r c r i t i c a l s o l v e n t s o f f e r solvent f l u i d i t y , a r e l a t i v e l y wide range of usable types of compounds, and e a s i l y o b t a i n a b l e high solvent r e c o v e r i e s i n the e x t r a c t i o n of low molecular weight m a t e r i a l s from c o a l . An understanding of the importance of the thermal processes i n v o l v e d i n the treatment of c o a l with hot, dense solvents and the p r i n c i p l e s of s u p e r c r i t i c a l e x t r a c t i o n , as enumerated at the outset of t h i s paper, could l e a d to an e f f e c t i v e use of s u p e r c r i t i c a l solvents i n c o a l and l i g n i t e processing.

Appendix An a l t e r n a t i v e scheme i n v o l v i n g charge s e p a r a t i o n i s suggested f o r c o a l t h e r m o l y s i s : coal + coal ^ ± r w

+· coal

/

.+· (coal ....coal

solvent )

solvent ^ separated

pair

+·

> coalH coal or H-donor

2

As u n l i k e l y as t h i s suggestion may seem at the o u t s e t , the propos i t i o n i s c o n s i s t e n t with the f o l l o w i n g : •

As discussed i n the t e x t , an i n c r e a s e i n d e n s i t y of the media increases the degrees of c o a l conversion. The conversion process, i n turn, e n t a i l s i r r e v e r s i b l e changes i n the c o a l , and thus i s not j u s t a simple s o l v e n t - s o l u t e interaction.

•

Wiser s t a t e s that c o a l p y r o l y s i s i n the absence of T e t r a l i n i s second order i n c o a l , and when T e t r a l i n i s present the process i s f i r s t order i n both T e t r a l i n and c o a l (10).

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

184

ORGANIC CHEMISTRY OF

COAL

•

T e t r a l i n r e a d i l y donates hydrogen to electron-poor systems at 50 to 160°C. T y p i c a l Η-acceptors are quinones. The r e a c t i o n i s a c c e l e r a t e d by electron-withdrawing subs t i t u e n t s on the quinone, i s a c c e l e r a t e d by polor s o l v e n t s , and i s unaffected by f r e e r a d i c a l i n i t i a t o r s (11) .

•

R a d i c a l cations r e a d i l y accept H (12) .

•

The e s t a b l i s h e d acid-base character of c o a l - d e r i v e d asphaltenes (13) suggests that charge separation, i . e . , donor-acceptor complexes, e i t h e r are present i n c o a l i t ­ s e l f or form thermally.

•

Poly-condensed aromatic s t r u c t u r e s , l i k e those i n c o a l , are known to form r e a d i l y both r a d i c a l c a t i o n s and r a d i c a l anions (15) .

2

from hydrocarbon donors

This suggested model could provide p r a c t i c a l i n s i g h t i n t o the a c t i o n of c a t a l y s t s i n conversion processes. One might consider, thus, the use of c a t a l y s t s that promote C-C s c i s s i o n by r a d i c a l c a t i o n intermediates.* The i m p l i c a t i o n s of t h i s scheme await the r e s u l t s of f u r t h e r research i n t o the Η-donor process and c o a l con­ v e r s i o n chemistry. Acknowledgment We acknowledge the support of the Department o f Energy f o r t h i s work on Contract EF-76-C-01-2202. Literature Cited 1. 2. 3. 4.

B a r t l e , K e i t h D., Martin, Terence G., and Williams, Dereck F., F u e l (1975), 54, 226. Maddocks, R. R., and Gibson, J . , Chem. Eng. Prog. (June 1977), 73, 6, 59-63. Hannay, J . B., and Hogarth, J . , Proc. Roy. Soc. (London), Ser. A (1879), 29, 324-26. Paul, P.F.M., and Wise, W.S., "The P r i n c i p l e s of Gas E x t r a c t i o n , " M i l l s and Boon Limited, London, 1971.

*Trahanovsky and B r i x i u s have shown that at temperatures below 100°C, Ce(IV) promotes the cleavage of PhCH -CH Ph, y i e l d i n g o x i d a t i o n products by way of a r a d i c a l c a t i o n intermediate (16). I t would be of i n t e r e s t to c a r r y out the r e a c t i o n with H-donor solvents present. 2

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

BLESSING AND Ross 5.

6.

7. 8. 9.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch013

10. 11. 12.

13. 14.

15.

16.

Supercritical

Solvents

185

Ross, D. S., and B l e s s i n g , J . Ε., " I s o r p o p y l A l c o h o l as Coal L i q u e f a c t i o n Agent," F u e l D i v i s i o n P r e p r i n t s f o r the 173rd N a t i o n a l Meeting of the Amer. Chem. Soc., New Orleans, LA, (March 1977). Manuscript i n p r e p a r a t i o n . Benson, S. W., and O'Neal, Η., N a t i o n a l Standard Refer­ ence Data S e r i e s — NBS 21, U.S. Government P r i n t i n g O f f i c e , Washington, D.C., 1970. Blanks, R., and Peausnitz, J . , Ind. Eng. Chem. Funda­ mentals (1964), 3, 1. Angelovich, J . , Pastor, G., and S i l v e r , Η., Ind. Eng. Chem. Process Des. Dev. (1970), 9, 160. Giddings, J . , Myers, Μ., McLaren, L., and K e l l e r , R., Science (4 October 1968), 162, 67. Wiser, N., F u e l (1968), 47, 475. Braude, Ε. Α., Jackman, L., and L i n s t e a d , R., J . Chem. Soc. (1954), 3548, 3564, 3569. Doepker, R., and Ausloos, P., J . Chem. Phys. (1960), 44 (5), 1951; Kramer, G., and Pancirov, R., J . Org. Chem. (1973), 38, 349. Sternberg, Η., Raymond, R., and Schweighardt, F., Science (4 April 1975), 188, 49. F r a n k l i n , J . , Dillard, S., Rosenstock, Η., Herron, J . , and D r a x l , Κ., " I o n i z a t i o n P o t e n t i a l s , Appearance P o t e n t i a l s , and Heats of Formation of Gaseous P o s i t i v e Ions," N a t i o n a l Standard Reference Data S e r i e s — NBS 26, U.S. Government P r i n t i n g O f f i c e , Washington, D.C., 1969. Compton, R., and Huebner, R., in "Advances in R a d i a t i o n Chemistry," Burton, Μ., and Magee, J . , Ed., V o l . 2., 1970 p. 281; Christophorou, L., and Compton, R., Heath P h y s i c s (1967), 13, 1277. Trahanovsky, W., and B r i x i u s , W., J . Amer. Chem. Soc. (1973), 95 (20), 6778.

RECEIVED February 10,

1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

14 Homogeneous Catalytic Hydrogenations of Complex Carbonaceous Substrates J. L. COX, W. A. WILCOX, and G. L. ROBERTS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

Battelle, Pacific Northwest Laboratories, Richland, WA 99352

Hydrogenation of unsaturated organic compounds with homogeneous catalysts has been known and practiced for some time. Such hydrogenations have been of both an academic and commercial interest. Some of the more extensively studied catalysts include Co(CN) (1), RhCl (ΡΦ ) (2), Ir(CO)Cl(ΡΦ ) (3,4), IrH(CO)(PΦ ) (3,4), OsHCl(CO)(PΦ ) (3,4) and Ziegler-type catalysts (5,6). These catalysts, except for the Ziegler-type, have not been observed to hydrogenate aromatics. In fact, very few homogeneous catalysts have been reported that will hydrogenate aromatics. Wender, et al. (7) have shown that polynuclear aromatics are partially hydrogenated with Co (CO) Efimov, et al., (8,9) have observed rapid hydrogenation of polynuclear aromatics in the presence of a rhodium complex of N-phenylanthranilic acid (NPAA), formulated as (RhNPAA) . This rhodium catalyst is more active than the dicobalt octacarbonyl and shows a greater hydrogenation activity toward polynuclear aromatics than the Ziegler catalyst. Holly et al. (10) investigated the use of this rhodium complex and other homogeneous catalysts for coal liquefaction, concluding that such catalysts do not appear to offer a viable route to coal liquefaction. Muetterties and Hirsekorn (11) have reported the hydrogenation of benzene to cyclohexane at 25°C and 1 atm pressure in the presence of n -allylcobalt phosphite; n -C H Co[P(0CH ) ] . Here we report the results of homogeneous catalytic hydrogénation of complex unsaturated substrates including coal and coal-derived materials. -35

3

3

3

3

2

3

3

2

8

·

2

3

3

3

5

3

3

3

Hydrogénations U s i n g o r g a n i c s o l u b l e m o l e c u l a r c o m p l e x e s as c a t a l y s t s , a number o f h y d r o g é n a t i o n s o f v a r i o u s o r g a n i c s u b s t r a t e s (a Hvab c o a l , s o l v e n t r e f i n e d c o a l (SRC) and COED p y r o l y s a t e ) were p e r f o r m e d . The a n a l y s i s o f t h e s e f e e d m a t e r i a l s i s c o n t a i n e d i n T a b l e I . The h y d r o g é n a t i o n s were c a r r i e d o u t i n a 300 c c s t i r r e d a u t o c l a v e by m i x i n g c o a l w i t h c a r r i e r s o l v e n t c o n t a i n i n g s o l u b i 0-8412-0427-6/78/47-071-186$05.00/0 This chapter not subject to U.S. copyright. Published 1978 American Chemical Society

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3

14.

Homogeneous

COX ET AL.

Catalytic

Hydrogénations

187

1 i z e d c a t a l y s t u n d e r p r e s c r i b e d c o n d i t i o n s . Upon c o m p l e t i o n o f the r u n t h e g a s e s were m e a s u r e d w i t h a c a l i b r a t e wet t e s t m e t e r and a n a l y z e d b y r o u t i n e g a s c h r o m a t o g r a p h y p r o c e d u r e s . T h e s o l i d c a r b o n a c e o u s r e s i d u e was s e p a r a t e d f r o m c a r r i e r s o l v e n t by f i l t r a t i o n , t h e n t h o r o u g h l y washed w i t h benzene and f i n a l l y d r i e d i n a vacuum o v e n .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

TABLE I . A n a l y s i s o f Feed M a t e r i a l s Hydrogenated Coal C o a l (a) Run 25 SRC COED As R e c e i v e d Vacuum D r i e d Moisture Ash H C 0 Ν S

1.1 14.5 4.8 68.8 6.0 1.2 4.6

0.0 14.7 4.6 68.3 6.1 1.2 4.6

0.0 0.3 5.6 87.7 4.0 2.2 0.5

0.0 0.1 7.3 85.0 7.2 1.1 1.3

1.8 27.0 4.4 55.0 5.9 0.2 4.0

B o t h samples were -200 mesh. A l l catalysts except the Ni-Ziegler are commercially available and were u s e d w i t h o u t f u r t h e r p u r i f i c a t i o n . The N i - Z i e g l e r was p r e p a r e d u n d e r a n i t r o g e n a t m o s p h e r e b y r e a c t i n g 4 moles o f t r i e t h y l aluminum w i t h 1 m o l e o f n i c k e l n a p h t h e n a t e i n a n h y d r o u s η - h e p t a n e . T h e a c t i v i t y o f t h i s c a t a l y s t was f i r s t t e s t e d w i t h b e n z e n e b e f o r e p r o c e e d i n g t o more complex s u b s t r a t e s . Hence, 10 ml benzene were h y d r o g e n a t e d i n 40 ml η - h e p t a n e c o n t a i n i n g 4 χ 1 0 " m o l e s o f t h e N i - Z i e g l e r c a t a l y s t f o r 1 hour a t 150°C and 1000 p s i g H ( a m b i e n t t e m p e r a t u r e ) . Even t h o u g h t h e h y d r o g é n a t i o n c o v e r e d a 1 hour p e r i o d t h e a u t o c l a v e p r e s s u r e r a p i d l y d r o p p e d t o 650 p s i g once 150°C was r e a c h e d , s i g n a l i n g r a p i d h y d r o g é n a t i o n o f t h e benzene. L i q u i d p r o d u c t a n a l y s i s by gas c h r o m a t o g r a p h y r e v e a l e d 9 9 % c o n v e r s i o n o f t h e benzene t o c y c l o hexane. H y d r o g é n a t i o n c o n d i t i o n s and r e s u l t s f o r c o a l and c o a l d e r i v e d m a t e r i a l s a r e summarized i n T a b l e I I . The change i n a t o m i c h y d r o g e n - c a r b o n r a t i o (Δ) i s t h e p r i n c i p a l c r i t e r i o n f o r c o m p a r i n g c a t a l y s t a c t i v i t y and e x t e n t o f h y d r o g é n a t i o n . S i n c e no a t t e m p t has been made t o a c c o u n t f o r t h e l i g h t e r h y d r o c a r b o n s t h a t were removed w i t h t h e c a r r i e r s o l v e n t by f i l t r a t i o n t h e h y d r o g é n a t i o n c r i t e r i o n i s v e r y c o n s e r v a t i v e . The Δ v a l u e has been o b t a i n e d b y s u b t r a c t i n g t h e e x p e r i m e n t a l l y d e t e r m i n e d atomic hydrogen-carbon r a t i o o f carbonaceous s u b s t r a t e from that o f t h e p r o d u c t . The c a r b o n - h y d r o g e n a n a l y s i s was p e r f o r m e d on a P e r k i n E l m e r model 240 e l e m e n t a l a n a l y z e r . S i n c e a s m a l l amount 3

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5.7 mmole N i - Z i e g l e r / 1 7 . 2 g COED/THF

40

(e)

(d)

(c)

(b)

8 mmole N i - Z i e g l e r / 1 0 g

38 200/3850/21

200/1200/23

200/1300/22

200/2770/2

8.28

7.29

5.88

74. .8

77. .1

63. ,6

55. ,8

70. ,7

4.94

220/2720 V2

4.48

65. ,9

(E

4.56

71. ,8

5.26

200/2830^/2

69. ,0

67. .4

68. .6

Ç_

5.16

4.69

4.64

H

c

?

0.291 0.377 0.290

1.13 1.32

V a r i a b l e s temperature, pressure and time reported as °C, psig and h r . , r e s p e c t i v e l y .

2

Gas composition of 25%C0, 75%H , used i n h y d r o g é n a t i o n .

Pressures are those at r e a c t i o n temperature and due to hydrogen and solvent unless otherwise stated.

Δ, i s the change i n atomic H/C r a t i o between substrate and product.

0.148 1.10

0.957

0.021

0.015

0.824 0.833

0.064

0.082

0.891 0.873

0.020

-0.003

Δ(atomic

0.829

0.806

At.H/C

Feed materials i n c l u d e : C o n s o l i d a t i o n coal (C), 4.64%H, 68.3%C, At.H/C = 0.809; Solvent Refined Coal (SRC), 5.55%H, 87.7%C, At.H/C = 0.753; FMC p y r o l y s a t e (COED), 7.32%H , 85.0%C, At.H/C = 1.03.

SRC/THF

C/heptane

8 mmole N i - Z i e g l e r / 1 5 g

?

36

c

C/decalin

?

7 mmole N i - Z i e g l e r / 1 5 g

c

25

0

7 mmole N i [ ( P h O ) , P ] ( C O ) / 1 5 g C/ decalin

C/decalin

19

3

8

13 mmole Fe (C0)-j /30g

2

Q

2

400/3400^/2

7 mmole C o ( C 0 ) / 1 5 g C / d e c a l i n

20

18

300/3080^/2

2

200/2950^/2

7 mmole C o ( C 0 ) / 1 5 g C / d e c a l i n

8

21

2

14 mmole C o ( C 0 ) / 3 0 g C / d e c a l i n

300/2880/2

17

C/decalin

P r e s s u r e ^ V"Time^

Temperature/

No c a t a l y s t / 1 5 g

Catalyst/Feed^ Vsol vent a

31

Run No.

TABLE I I . Summary o f Homogeneous C a t a l y t i c H y d r o g é n a t i o n s o f Carbonaceous Substrates

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

H/C)

(c)

1

î

ο

i

W

00

14. COX ET AL.

Homogeneous

Catalytic

189

Hydrogénations

o f unremoved s o l v e n t i n t h e p r o d u c t c a n s e r i o u s l y a f f e c t t h e i n t e r p r e t a t i o n o f r e s u l t s , extreme p r e c a u t i o n was t a k e n t o ensure i t s complete removal. T h i s was a c c o m p l i s h e d by w a s h i n g w i t h a v o l a t i l e s o l v e n t ( t e t r a h y d r a f u r a n ) f o l l o w e d by vacuum d r y i n g w i t h a n i t r o g e n b l e e d a t 1 1 0 ° C f o r a t l e a s t 24 h o u r s . I n o r d e r t o c h e c k t h o r o u g h n e s s o f s o l v e n t removal a d r i e d sample showing H/C o f 1.10 was f u r t h e r d r i e d and r e a n a l y z e d . T h e r e was e s s e n t i a l l y no change i n t h e H/C ( i . e . , 1.10 v e r s u s 1.09). I t i s apparent from T a b l e II t h a t t h e N I - Z i e g l e r c a t a l y s t i s more a c t i v e t h a n C o ( C 0 ) , N i [ ( P h 0 ) P ] ( C 0 ) and F e ( C 0 ) . In Run 25 a Δ o f 0.148 f o r t h e Hvab c o a l was o b s e r v e d o v e r a 2-hour r e a c t i o n t i m e a t 200°C and 2770 p s i g . T h i s change i n a t o m i c H/C r a t i o f r o m hydrogénation c o r r e s p o n d s t o a hydrogen usage o f o n l y 0.85% (w/w) o f c o a l . Even i n Run 36 where a Δ o f 0.291 was e f f e c t e d a t 200°C a n d 1300 p s i g H a f t e r 22 h o u r s o n l y 1.7% (w/w) H i s consumed i n t h e h y d r o g é n a t i o n . T h e s e h y d r o g é n a t i o n s may be compared t o Run 31 where a s l i g h t d e c r e a s e i n Δ, -0.003, was o b s e r v e d i n t h e hydrogénation o f t h e Hvab c o a l w i t h no c a t a l y s t f o r 2 hours a t 300°C a n d 2880 p s i g . I n c o n t r a s t t o t h e s e h y d r o g e n c o n s u m p t i o n s a b o u t 2% H (w/w maf c o a l b a s i s ) i s used i n t h e SRC p r o c e s s , 2.5% i n S y n t h o i l and 4% f o r Η - C o a l . Homogeneous c a t a l y t i c h y d r o g é n a t i o n s were a l s o c o n d u c t e d on s o l i d p r o d u c t s f r o m t h e SRC a n d COED c o a l l i q u e f a c t i o n p r o c e s s e s . The a n a l y s e s o f t h e s e s u b s t r a t e s a r e c o n t a i n e d i n T a b l e I . E x a m i n a t i o n o f t h e hydrogénation r e s u l t s summarized i n T a b l e I I r e v e a l s t h a t t h e e a s e o f hydrogénation under t h e s e homogeneous c a t a l y t i c c o n d i t i o n s i s SRC > COED > Hvab, a l t h o u g h some r e s e r v a t i o n must be made s i n c e t h e hydrogénations were n o t made under i d e n t i c a l c o n d i t i o n s . That the c o a l - d e r i v e d substrates a r e more r e a d i l y h y d r o g e n a t e d t h a n t h e c o a l i s n o t t o o s u r p r i s i n g s i n c e t h e y a r e l i q u i d s a t r e a c t i o n t e m p e r a t u r e s (>200°C) and quite soluble i n carrier solvent permitting effective catalysts u b s t r a t e i n t e r a c t i o n . D i f f u s i o n a l r e s i s t a n c e s t o hydrogénation a r e a l s o e x p e c t e d t o be l e s s f o r t h e s e m a t e r i a l s t h a n t h e s o l i d coal. P r o d u c t g a s a n a l y s i s o n each e x p e r i m e n t a l hydrogénation r u n r e v e a l e d p r e d o m i n a n t l y r e a c t a n t g a s e s . In Runs 17, 18, 19, 20 and 21 t h e p r o d u c t gas c o n s i s t e d o f >98% H and CO, w h i l e Runs 25, 3 1 , 36, 38 a n d 40 showed a t l e a s t a s g r e a t a c o n c e n t r a t i o n o f h y d r o g e n . E x c e p t f o r Run 20, C 0 a n d CH4 c o n t r i b u t e d <0.2% t o t h e g a s b a l a n c e . The g a s c o m p o s i t i o n o f Run 20 was d i f f e r e n t from t h e o t h e r s i n t h a t low b u t n o t i c e a b l e c o n c e n t r a t i o n s o f l i g h t h y d r o c a r b o n s i n c l u d i n g CH^, C H , and C H were f o u n d . The o b s e r v e d l i g h t h y d r o c a r b o n s i n t h i s r u n a r e u n d o u b t e d l y due t o t h e h i g h e r t e m p e r a t u r e (400°C v e r s u s < 3 0 0 ° C ) employed, w h i c h was h i g h enough t o a f f e c t h y d r o g e n o l y s i s . The g a s a n a l y s i s o f Runs 2 5 , 36, 38 a n d 40 e m p l o y i n g t h e N i - Z i e g l e r c a t a l y s t were u n i q u e i n t h a t a p p r e c i a b l e c o n c e n t r a t i o n s (1 t o 2%) o f e t h a n e were o b s e r v e d . T h e e t h a n e i s a t t r i b u t e d t o l o s s o f e t h y l g r o u p s from t h e N i - Z i e g l e r c a t a l y s t o r decomposition o f excess 2

8

3

2

2

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

2

2

2

2

2

2

6

3

8

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1 2

190

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

t r i e t h y l a l u m i n u m w h i c h was used i n i t s p r e p a r a t i o n . Even though t h e r e i s no k i n e t i c d a t a t o s u p p o r t a p r o p o s e d mechanism f o r t h e o b s e r v e d homogeneous c a t a l y t i c hydrogénation o f a r o m a t i c s t h e f o l l o w i n g mechanism i s c o n s i s t e n t w i t h t h e c h e m i s t r y o f analogous systems. In t h i s p r o p o s e d mechanism L r e p r e s e n t s c o o r d i n a t e d l i g a n d s and s o l v e n t and M i s t h e t r a n s i t i o n metal. T h i s proposed mechanism d e p i c t s t h a t g e n e r a l l y a c c e p t e d f o r t h e hydrogénation o f o l e f i n s ( i n c l u d i n g c y c l o h e x e n e ) by a number o f group V I I I m e t a l c o m p l e x e s .

We know f o r i n s t a n c e t h a t m o l e c u l a r hydrogen w i l l undergo o x i d a t i v e a d d i t i o n r e a c t i o n s w i t h a number o f t r a n s i t i o n metal complexes as shown i n t h e f i r s t e q u a t i o n ( 1 2 ) . The metal m i g r a t i o n s d u r i n g hydrogénation may o c c u r t h r o u g h a π - a l l y l c o m p l e x . F i n a l l y , intermediates s i m i l a r to those postulated i n t h i s mechanism have been s u p p o r t e d by c h e m i c a l e v i d e n c e and i n c l u d e t h e two f o l l o w i n g compounds ( 1 3 ) .

Even though t h e a b o v e mechanism has been w r i t t e n w i t h benzene as t h e s u b s t r a t e i t i s r e l a t i v e l y e a s y t o w r i t e a n a l o g o u s mechanisms f o r y e t more complex a r o m a t i c s u b s t r a t e s . Product C h a r a c t e r i z a t i o n s The p r o d u c t s f r o m t h e hydrogénation o f t h e c o a l and c o a l d e r i v e d m a t e r i a l s were a l l s o l i d g l o s s y b l a c k m a t e r i a l s a t room

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

14.

COX ET AL.

Homogeneous

Catalytic

191

Hydrogénations

t e m p e r a t u r e , e x c e p t i n Run 20 where t h e t e m p e r a t u r e r e a c h e d 4 0 0 ° C and a b l a c k v i s c o u s l i q u i d was o b t a i n e d . The c a r b o n and hydrogen a n a l y s e s o f these hydrogénation products are c o n t a i n e d in Table II. W i t h r e s p e c t t o t h e s e complex c a r b o n a c e o u s s u b s t r a t e s h y d r o g é n a t i o n i s o f t e n f a l s e l y t a k e n t o be synonymous w i t h l i q u e f a c t i o n . The p o l y m e r i c s t r u c t u r e o f c o a l {H ]S) i m p l i e s t h a t complete s a t u r a t i o n with hydrogen would not a l t e r i t s p h y s i c a l s t a t e . An a p p r o p r i a t e a n a l o g y would be t h e h y d r o g é n a t i o n o f p o l y s t y r e n e to produce the s o l i d s a t u r a t e d polymer.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

9

Even t h o u g h p o l y e t h y l e n e has a n H/C r a t i o o f 2.0, i t i s a l s o s o l i d . Hence w i t h r e s p e c t t o c o a l l i q u e f a c t i o n , u n d o u b t e d l y t h e h y d r o g e n o l y s i s r e a c t i o n s and n o t h y d r o g é n a t i o n a r e r e s p o n s i b l e f o r c o n v e r t i n g the s o l i d to a l i q u i d by c o n v e n t i o n a l p r o c e s s i n g schemes. The l i q u e f a c t i o n t h a t o c c u r r e d i n Run 20 was u n d o u b t e d l y due t o h y d r o g e n o l y s i s a s a c o n s e q u e n c e o f t h e h i g h t e m p e r a t u r e (400°C) employed. Again using p o l y s t y r e n e f o r analogy, the h y d r o g e n o l y s i s may be r e p r e s e n t e d b y t h e f o l l o w i n g r e a c t i o n i n w h i c h t h e p r o d u c t e t h y l benzene i s c l e a r l y a l i q u i d . + nH.

C o a l h y d r o g e n o l y s i s has been c o n t r a s t e d w i t h i t s h y d r o g é n a t i o n by c a r r y i n g o u t a m a t e r i a l b a l a n c e e s t i m a t i o n on t h e S y n t h o i l p r o c e s s a s shown i n T a b l e I I I . T h e s e r e s u l t s show t h a t one net r e s u l t o f c a t a l y t i c hydrogenolysis i s a decrease i n the p r o d u c t ( c h a r + c r u d e o i l ) H/C r a t i o (0.765 v e r s u s 0.883), d e s p i t e t h e a d d i t i o n o f 9000 s c f H p e r t o n o f c o a l ( m a f ) . T h e d e c r e a s e i n t h e H/C r a t i o i s a d i r e c t c o n s e q u e n c e o f t h e h y d r o g e n o l y s i s r e a c t i o n w h i c h b r e a k s s t r u c t u r a l bonds i n t h e s o l i d s u b s t r a t e and adds h y d r o g e n t o t h e f r a g m e n t s . Hence, a l a r g e h y d r o g e n c o n s u m p t i o n i s seen i n removing oxygen and s u l f u r from t h e c o a l a s H 0 and H S, r e s p e c t i v e l y . C o n s i d e r a b l e h y d r o g e n i s a l s o consumed b y t h e f o r m a t i o n o f l i g h t h y d r o c a r b o n gases ( C i - C ) a s a r e s u l t o f h y d r o g e n o l y s i s r e a c t i o n s . On t h e o t h e r hand, h y d r o g e n consumed b y h y d r o g é n a t i o n goes d i r e c t l y t o i n c r e a s e t h e s u b s t r a t e H/C r a t i o . T h i s i s why t h e H/C r a t i o i s r e l a t i v e l y h i g h i n t h e p r o d u c t f o r t h e amount o f h y d r o g e n consumed i n t h e homogeneous c a t a l y t i c h y d r o g é n a t i o n s . O f c o u r s e , from a p r a c t i c a l viewpoint i t i s h i g h l y d e s i r a b l e , i f not necessary, to a t l e a s t remove t h e s u l f u r w h i c h i s i n v a r i a b l y a c c o m p a n i e d by oxygen removal and l i g h t h y d r o c a r b o n gas p r o d u c t i o n . 2

2

2

3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

TABLE I I I .

Synthoil Material

M a t e r i a l s Charged Coal^

lb-moles

lb

(atomic H/C = 0.883)

2000

C

1117.90

1416

H

104.20

105

0

22.50

360

S

3.00

96

Ν Hydrogen Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

Balance

7.50 (b)

(Η)

105

50.04

50.5 2050.5

M a t e r i a l s Out C -C }

Hydrocarbons^

3

100

C

6.52

78.3

Η

21.53

Heteroatoms H 0

( d )

H S

( e )

2

2

Product^

21.7 467.8

21.25

382.8

2.5

85.0

(atomic H/C = 0.765)

1482

C

111.4

1338

Η

85.3

86

0

1.2

20

S

0.5

16

Ν

1.6

22 2049.8

^maf

basis.

(^50.04 lb-moles Η e q u i v a l e n t t o 9000 s c f H 2

(^Amount t o 5 wt% o f maf coal charged w i t h estimated composition o f 60% C ^ 30% C and 10% C 2

3

d )

( 3 4 0 l b 0 + 42.8 l b H.. (^80 l b S + 5.04 l b H. f

( ) c r u d e o i l + char.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

14.

cox ET AL.

Homogeneous Catalytic

Hydrogénations

Complete hydrogénation o f t h e u n s a t u r a t e d c a r b o n - c a r b o n bonds i n t h e complex c a r b o n a c e o u s s u b s t r a t e s i s e s t i m a t e d t o r e s u l t i n a H/C r a t i o o f a t l e a s t 1.5. The maximum v a l u e we have o b t a i n e d i s 1.32 f o r t h e COED p y r o l y s a t e . The f a i l u r e t o o b t a i n more e x t e n s i v e hydrogénation may be due t o t h e c a t a l y s t ' s i n a b i l i t y t o a c t i v a t e t h e more complex a r o m a t i c s . A l s o , a p o r t i o n o f the s u b s t r a t e ' s u n s a t u r a t i o n i s undoubtedly very f a c i l e and a p o r t i o n i s v e r y i n e r t t o w a r d hydrogénation. A s noted e a r l i e r , the N i - Z i e g l e r v e r y r a p i d l y hydrogenates mononuclear a r o m a t i c s b u t i s much more s l u g g i s h toward t h e p o l y n u c l e a r a r o m a t i c s . F o r example, a t 100 p s i g H , phenol i s 92% c o n v e r t e d t o c y c l o h e x a n o l i n 0.2 h o u r s a t 150°C i n t h e p r e s e n c e o f 5 m o l e % N i - Z i e g l e r c a t a l y s t , w h i l e o n l y 12.5% n a p h t h a l e n e i s c o n v e r t e d t o d e c a l i n i n 18 hours a t 210°C i n t h e p r e s e n c e o f 2.5 m o l e % N i Z i e g l e r ( 5 J . The more complex p o l y n u c l e a r a r o m a t i c s , such a s p h e n a n t h r e n e and p y r e n e t h a t a r e c o n t a i n e d i n c o a l a l o n g w i t h t h e h e t e r o p o l y n u c l e a r a r o m a t i c s such a s i n d o l e s and d i b e n z o t h i p h e n e s w i l l u n d o u b t e d l y be even more s l u g g i s h toward hydrogénation. A n o t h e r p o s s i b l e c a u s e o f low hydrogénation l e v e l s i s t h e i n a c c e s s i b i l i t y o f c a t a l y s t to s u b s t r a t e . T h i s i s a n t i c i p a t e d t o be more o f a p r o b l e m f o r c o a l t h a n f o r c o a l - d e r i v e d p r o d u c t s , due t o t h e i r d i f f e r e n c e s i n p h y s i c a l p r o p e r t i e s , p a r t i c u l a r l y p o r e s i z e d i s t r i b u t i o n s and s o l u b i l i t y i n c a r r i e r s o l v e n t . T h e moderate to high s o l u b i l i t y o f the c o a l - d e r i v e d m a t e r i a l s w i l l u n d o u b t e d l y e n h a n c e c a t a l y t i c hydrogénation o v e r t h e r e l a t i v e l y i n s o l u b l e c o a l i n a c a r r i e r s o l v e n t . The c o a l i t s e l f , h a v i n g an e x t e n s i v e pore s t r u c t u r e , w i l l undoubtedly c o n t a i n a s i g n i f i c a n t number o f m i c r o p o r e s t h a t a r e t o o s m a l l f o r a c c e s s o f t h e c a t a l y s t (16). To o b t a i n i n f o r m a t i o n on t h e r e a c t i v i t y o f t h e s o l i d h y d r o g e n a t e d p r o d u c t , t h e r m o g r a v i m e t r i c a n a l y s e s were run and compared t o t h o s e o f t h e u n h y d r o g e n a t e d c o a l . The r e s u l t s a r e shown i n F i g u r e 1 f o r hydrogénation p r o d u c t s o f Runs 25 and 36 a s w e l l a s t h e p a r e n t c o a l . T h e s e t h e r m o g r a v i m e t r i c c u r v e s were a l l r e c o r d e d w i t h a duPont model 900 a n a l y z e r o n 19-23 mg samples under a h i g h - p u r i t y a r g o n atmosphere à t 20°C/min h e a t i n g r a t e , f r o m a m b i e n t t o 8 0 0 ° C . A l t h o u g h t h e sample f r o m Run 25 had a H/C o f 0.148, g r e a t e r t h a n t h e p a r e n t c o a l , t h e r e i s no q u a l i t a t i v e d i f f e r e n c e i n t h e i r thermogravimetric curves except f o r the s m a l l amount o f m o i s t u r e d e v o l a t i l i z e d f r o m t h e p a r e n t c o a l a t a b o u t 125°C. T h i s t y p e o f thermogram i s t y p i c a l o f many t h a t have been r e p o r t e d f o r d i f f e r e n t r a n k s o f c o a l (17_). I n s h a r p c o n t r a s t , t h e sample f r o m Run 36 w h i c h had a H/C i n c r e a s e o f 0.291 o v e r t h e p a r e n t c o a l r e v e a l s c o n s i d e r a b l e s t r u c t u r e i n i t s d e r i v a t i v e thermogram. In a d d i t i o n t o t h e m a j o r peak a t a b o u t 475°C w h i c h was a l s o o b s e r v e d f o r t h e c o a l and sample f r o m Run 25, two a d d i t i o n a l peaks were o b s e r v e d a t c o n s i d e r a b l y l o w e r t e m p e r a t u r e s - - o n e a t 360°C and t h e o t h e r a t 275°C. The v o l a t i l e m a t t e r from t h i s sample was 54% ( a s h - f r e e b a s i s ) w h i l e t h a t 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

193

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

194

ORGANIC CHEMISTRY OF COAL

f r o m Run 25 and t h e p a r e n t c o a l was 42% and 37% r e s p e c t i v e l y (ash-free basis). I t i s n o t s u r p r i s i n g t h a t t h e sample from Run 36 showed more s t r u c t u r e i n i t s thermogram and a l a r g e r amount o f v o l a t i l e m a t t e r p r o d u c t i o n t h a n t h e p a r e n t c o a l s i n c e i t does have a s i g n i f i c a n t l y g r e a t e r hydrogen c o n t e n t t h a n t h e p a r e n t c o a l . What i s somewhat s u r p r i s i n g i s t h a t t h e sample f r o m Run 25 a c t e d v e r y s i m i l a r t o t h e p a r e n t c o a l d u r i n g t h e r m o l y s i s even though i t s H/C r a t i o l i e s between t h a t o f p r o d u c t f r o m Run 36 and t h e p a r e n t c o a l . The h y d r o g é n a t i o n i n Run 36 i s a p p a r e n t l y e x t e n s i v e enough t o s a t u r a t e key u n s a t u r a t e d g r o u p s i n c o a l l e a d i n g to decreased thermal s t a b i l i t y . I t i s g e n e r a l l y recogn i z e d t h a t c l e a v a g e o f s a t u r a t e d g r o u p s i s much more f a c i l e t h a n u n s a t u r a t e d g r o u p s under t h e r m o l y s i s c o n d i t i o n s . To p r o j e c t t h e y i e l d o f l i q u i d p r o d u c t f r o m t h e t h e r m o g r a v i m e t r i c a n a l y s i s we have assumed t h a t a l i n e a r r e l a t i o n s h i p e x i s t s between t h e p e r c e n t v o l a t i l e m a t t e r and l i q u i d y i e l d . T h i s i m p l i e s t h a t i f a c o a l i s 25% v o l a t i l i z e d and y i e l d s 10% o i l t h e n 35% d e v o l a t i l i z a t i o n o f t h i s c o a l a f t e r p r e t r e a t m e n t s u c h as h y d r o g é n a t i o n w i l l y i e l d 0.35/0.25 χ 10% = 14% o i l . U s i n g t h i s a p p r o x i m a t i o n one can r e a d i l y e s t i m a t e t h a t p r e h y d r o g e n a t i o n o f t h e c o a l i n Run 36 has i n c r e a s e d y i e l d o f o i l by 46% o v e r t h e u n h y d r o g e n a t e d c o a l upon p y r o l y s i s . In p r a c t i c a l terms t h i s means t h a t t h e p r e h y d r o g e n a t i o n c o u l d be used t o s i g n i f i c a n t l y i n c r e a s e t h e y i e l d o f l i q u i d s from c o a l by p y r o l y s i s . F o r i n s t a n c e , t h e o i l y i e l d f r o m t h e COED p r o c e s s (18) w h i c h uses m u l t i p l e s t a g e p y r o l y s i s t o p r o d u c e g a s e s , l i q u i d s and c h a r w o u l d be i n c r e a s e d f r o m 1.5 b b l / t o n t o a b o u t 2.2 b b l / t o n . Hydrogenolysis A h y d r o g e n o l y s i s e x p e r i m e n t was c o n d u c t e d w i t h t h e Hvab c o a l and i t s h y d r o g e n a t e d p r o d u c t under i d e n t i c a l e x p e r i m e n t a l c o n d i t i o n s . The a n a l y s i s o f t h e s e -200 mesh f e e d m a t e r i a l s was r e p o r t e d i n T a b l e I . H y d r o g e n o l y s i s was c a r r i e d o u t i n t h e p r e v i o u s l y d e s c r i b e d 300 c c m a g n e d r i v e a u t o c l a v e . In t h e h y d r o ­ g e n o l y s i s o f Hvab, 10.0 g were c h a r g e d t o t h e a u t o c l a v e a l o n g w i t h 30.0 g (32 ml) t e t r a l i n and 0.5 g -100 mesh Co-Mo c a t a l y s t (Harshaw HT-400 c o n t a i n i n g 3% c o b a l t o x i d e and 15% molybdenum d i o x i d e on a l u m i n a ) . In t h e h y d r o g e n o l y s i s o f t h e p r e h y d r o g e n a t e d c o a l f r o m Run 25 t h e same q u a n t i t y o f c a r b o n a c e o u s f e e d and t e t r a l i n were c h a r g e d , b u t no c a t a l y s t was added. A f t e r m a t e r i a l s were c h a r g e d , t h e a u t o c l a v e was p u r g e d t w i c e w i t h h i g h - p u r i t y h y d r o g e n and t h e n p r e s s u r i z e d w i t h hydrogen t o 1500 p s i g . E x p e r i m e n t a l h y d r o g e n o l y s i s c o n d i t i o n s were 0.5 hour a t 4 0 0 ° C , 2700 p s i g (1500 p s i g H a m b i e n t ) and 300 rpm. The a u t o c l a v e was b r o u g h t up t o r e a c t i o n t e m p e r a t u r e and c o o l e d a f t e r t h e d e s i g n a t e d r e a c t i o n t i m e as r a p i d l y as p o s s i b l e . I t r e q u i r e d a b o u t 30 m i n u t e s t o r e a c h 4 0 0 ° C f r o m ambient and 10 m i n u t e s t o c o o l f r o m 4 0 0 ° C t o 60°C. However, t h e t i m e r e q u i r e d t o h e a t f r o m 200°C t o 2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

14.

cox ET AL.

Homogeneous

Catalytic

Hydrogénations

195

4 0 0 ° C and c o o l f r o m 400°C t o 200°C was o n l y a b o u t 2 m i n u t e s ; i . e . , t h e time spent a t temperatures s u f f i c i e n t l y high t o potent i a l l y c o n t r i b u t e t o h y d r o g e n o l y s i s was s i g n i f i c a n t l y s h o r t e r t h a n t h e o v e r a l l h e a t - u p and c o o l - d o w n t i m e . Once t h e r u n was c o m p l e t e d and t h e t e m p e r a t u r e had c o o l e d t o a m b i e n t t h e e x p e r i m e n t was worked up a c c o r d i n g t o t h e d i a g r a m i n F i g u r e 2. T h e g a s volume was measured w i t h a wet t e s t m e t e r and i t s c o m p o s i t i o n d e t e r m i n e d by g a s c h r o m a t o g r a p h y . T h e l i q u i d and s o l i d p r o d u c t s were e m p t i e d i n t o a t a r e d e x t r a c t i o n t h i m b l e whence t h e f i l t r a t e f r o m t h e t h i m b l e was c o l l e c t e d and s a v e d . T h e a u t o c l a v e was r i n s e d w i t h benzene i n t o t h e same e x t r a c t i o n t h i m b l e . T h e s o l i d s were t h e n e x t r a c t e d w i t h t h e r i n s e benzene f o r 8 h o u r s i n a s o x h l e t a p p a r a t u s whence t h e e x t r a c t i o n t h i m b l e was vacuum d r i e d a n d w e i g h e d . The benzene s o l u t i o n f r o m t h e e x t r a c t i o n was combined w i t h t h e p r e v i o u s l y s a v e d t e t r a l i n - l a d e n f i l t r a t e . T o t h i s s o l u t i o n was added a t h r e e - f o l d excess o f pentane, t o p r e c i p i t a t e a s p h a l t e n e s which were t h e n s e p a r a t e d by f i l t r a t i o n and vacuum d r i e d . T h i s f i l t r a t e was t h e n vacuum d i s t i l l e d (-25 mm Hg, 4 0 - 8 0 ° C ) t o remove t h e p e n t a n e and benzene f r o m t h e t e t r a l i n s o l u b l e p r o d u c t ( l i g h t o i l ) . T h e y i e l d s o f t h e v a r i o u s f r a c t i o n s o b t a i n e d by f o l l o w i n g t h i s p r o c e d u r e a r e a l l summarized on a maf c h a r g e b a s i s i n T a b l e IV f o r t h e Hvab c o a l a n d t h e p r e h y d r o g e n a t e d c o a l . The t a b u l a t e d r e s u l t s ( T a b l e I V ) f o r t h e h y d r o g e n o l y s i s o f the c o a l a n d h y d r o g e n a t e d c o a l c l e a r l y i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e i n t h e i r p r o d u c t y i e l d s . T h e y i e l d o f g a s and l i g h t o i l was g r e a t e r f o r t h e h y d r o g e n a t e d t h a n t h e n o n h y d r o g e n a t e d c o a l ( 3 0 % a n d 4 9 . 0 % v e r s u s 3 1 % and 4 8 . 6 % ) . P e r h a p s even more s i g n i f i c a n t i s t h e lower a s p h a l t e n e y i e l d observed f o r t h e h y d r o g e n a t e d sample ( 3 . 0 % v e r s u s 1 0 . 3 % ) . T h e o v e r a l l c o n v e r s i o n was e s s e n t i a l l y t h e same f o r b o t h samples (90 v e r s u s 89%) and t h e r e was l i t t l e d i f f e r e n c e i n t h e i r p r o d u c t g a s c o m p o s i t i o n s . In e x a m i n i n g t h e d i f f e r e n c e s between t h e s e two h y d r o g e n o l y s i s e x p e r i m e n t s o n e i s r e m i n d e d t h a t w h i l e a Co-Mo c a t a l y s t was u s e d w i t h t h e c o a l , t h e r e was no a d d i t i o n o f c a t a l y s t t o t h e h y d r o g e n a t e d c o a l . However, t h e h y d r o g e n a t e d c o a l d i d c o n t a i n n i c k e l t h a t was a p p a r e n t l y d e p o s i t e d o n t h e c o a l f r o m t h e N i - Z i e g l e r c a t a l y s t d u r i n g t h e homogeneous c a t a l y t i c h y d r o g é n a t i o n . T h i s nickel undoubtedly p a r t i c i p a t e d as a c a t a l y s t i n the hydrogenolysis o f t h e sample. So i n e s s e n c e , we a r e c o m p a r i n g t h e h y d r o g e n o l y s i s o f t h i s h y d r o g e n a t e d sample c o n t a i n i n q n i c k e l w i t h t h e Hvab c o a l t o w h i c h was added a c o n v e n t i o n a l Co-Mo c a t a l y s t . An a n a l y s i s ^ ) o f t h e nickel content i n t h e hydrogenated coal The a n a l y s i s o f t h e h y d r o g e n a t e d sample was p e r f o r m e d b y f i r s t a s h i n g t h e sample a t 850°C i n a m u f f l e f u r n a c e . T h i s r e v e a l e d 2 7 . 0 % a s h . T h e a s h was t h e n d i g e s t e d i n h o t aqua r e g i a s o l u t i o n a n d f i l t e r e d . T h e f i l t r a t e was t h e n d i l u t e d w i t h w a t e r a n d a n a l y z e d f o r n i c k e l by a t o m i c a d s o r p t i o n s p e c t r o s c o p y t o g i v e 1.2% Ni i n t h e h y d r o g e n a t e d sample.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

196

COAL/CATALYST. TETRALIN/H

2

I 400°C, 2700 psi. 1 / 2 hr

ι ι

GASES

LIQUIDS/SOLIDS I FILTRATION

I

FILTRATE

SOLIDS BENEZEN EXTRACTION J

Γ

FILTRATE I PENTANE EXTRACTION

CHAR/CATALYST

ι

1 FILTRATE I VACUUM DISTILLATION

ASPHALTENES

I PENTANE/ BENZENE

Figure 2.

Schematic and workup of hydrogenolysis experiments

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

LIQUIDS/ TETRALIN

COX ET AL.

Homogeneous

Catalytic

Hydrogénations

TABLE I V . H y d r o g e n o l y s i s E x p e r i m e n t a l R e s u l t s

Hvab Coal

Hydrogenated Coal Run 25

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

Reaction C o n d i t i o n s feed, g

10.0

10.0

tetralin, g

30.0

30.0

catalyst, g

0.5

temperature, °C pressure, psig

400 2660

none 400 2770

time, hr

1/2

1/2

Conversion, %

90.0

88.9

30.8

38.0

58.8

52.1

48.6

49.0

Product Y i e l d s , % gas oil light o i l asphaltenes char

10.2

3.0

10.3

9.9

91.2

87.7

Gas Composition, mole % H

2

C0

2

C H^ 2

C H 2

0 N

6

2

2

CH

4

CO C,H

Q

0.5

0.4

trace

trace

2.4

2.6

trace

0.3

0.5

2.5

4.1

3.9

0.1

0.2

1.3

2.3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

198

ORGANIC CHEMISTRY OF COAL

r e v e a l e d 1.2% N i w h i c h c a n be compared t o 5% Co-Mo c a t a l y s t i n t h e Hvab c o a l . S i n c e t h e n i c k e l c a t a l y s t was a p p a r e n t l y decomposed on t h e h y d r o g e n a t e d c o a l sample i t a l m o s t c e r t a i n l y had b e t t e r c a t a l y s t - s u b s t r a t e c o n t a c t i n g t h a n t h e Co-Mo w h i c h was m i x e d w i t h t h e Hvab c o a l . T h i s i n i t s e l f c o u l d a c c o u n t f o r t h e h i g h e r h y d r o g e n o l y s i s y i e l d s o f g a s and l i g h t o i l and l o w e r a s p h a l t e n e s t h a n w i t h t h e Co-Mo c a t a l y s t . In a d d i t i o n , n i c k e l c a t a l y s t s g e n e r a l l y show h i g h e r g a s y i e l d s under h y d r o g e n o l y s i s t h a n s u p p o r t e d Co-Mo c a t a l y s t s . F i n a l l y , t h e h y d r o g e n a t e d sample i s e x p e c t e d t o p r o d u c e h i g h e r y i e l d s o f g a s e s a n d l i g h t o i l s and lower a s p h a l t e n e s under h y d r o g e n o l y s i s simply because i t has been h y d r o g e n a t e d . In an a t t e m p t t o b e t t e r d e f i n e t h e n a t u r e o f t h e l i q u i d p r o d u c t f r o m t h e h y d r o g e n o l y s i s o f t h e s e two samples t h e i r l i g h t o i l f r a c t i o n s were s u b j e c t e d t o g a s c h r o m a t o g r a p h i c - m a s s s p e c t r a l a n a l y s i s . T h e more p r o m i n e n t components o f t h e t e t r a l i n s o l u b l e f r a c t i o n ( l i g h t o i l ) f r o m h y d r o g e n o l y s i s o f t h e two samples were a n a l y z e d on a H e w l e t t - P a c k a r d (HP) 5980A q u a d r u p l e mass s p e c t r o ­ m e t e r w i t h a HP 571 OA GC and HP 5934A d a t a s y s t e m . Chroma­ t o g r a p h y was p e r f o r m e d on a 6 - f o o t SP 2250 column t e m p e r a t u r e programmed f r o m 80 t o 250°C a t 8 ° C / m i n u s i n g He c a r r i e r a t 40 m l / m i η . Mass s p e c t r o m e t r y was c o n d u c t e d w i t h e l e c t r o n i m p a c t a t 60 e l e c t r o n v o l t s . A d d i t i o n a l chromatography o f t h e l i g h t o i l f r o m e a c h sample was p e r f o r m e d on an HP 5830A GC e q u i p p p e d w i t h an HP 18850A t e r m i n a l a t t h e p r e v i o u s l y d e s c r i b e d r u n c o n d i t i o n s . A t y p i c a l c h r o m a t o g r a m o f t h e s e samples i s shown i n F i g u r e 3 a l o n g w i t h r e t e n t i o n t i m e s w h i l e T a b l e V c o n t a i n s t h e mass s p e c t r a l i d e n t i f i c a t i o n o f t h e more p r o m i n e n t components o f b o t h s a m p l e s . Upon c o m p a r i n g t h e c h r o m a t o g r a p h d a t a t h e i r s i m i l a r i t y i s p a r t i c u l a r l y s t r i k i n g . When t h e s o l v e n t ( t e t r a l i n ) i s sub­ t r a c t e d f r o m b o t h samples a s has been done i n t a b u l a t i n g t h e a r e a p e r c e n t i n T a b l e VI we q u i c k l y r e a l i z e t h a t o n l y a few o f t h e more t h a n 22 i n t e g r a t e d peaks a c c o u n t f o r t h e m a j o r i t y o f t h e sample. In f a c t , t h e r e a r e o n l y f i v e compounds, a l l w i t h two o r g r e a t e r a r e a p e r c e n t , t h a t a c c o u n t f o r g r e a t e r t h a n 90 a r e a p e r c e n t o f t h e e n t i r e sample. T h e s e compounds a r e common t o e a c h sample and i n c l u d e t h e f o l l o w i n g i n d e s c e n d i n g o r d e r o f a b u n d a n c e : n a p h t h a l e n e ( 0 0 ) >methyl i n d a n ( C O — C H ) >benzene ( Q ) , C^-benzene ( Q — C ^ H g ) > d e c a l i n ( 0 0 ) . O f t h e s e f i v e compounds t h e f i r s t t h r e e a c c o u n t f o r a t l e a s t 8 0 % o f t h e l i g h t o i l i n e a c h sample. T h e b r o a d n e s s o f many o f t h e chromatogram peaks, p a r t i c u l a r l y those a t t h e l o n g e r r e t e n t i o n t i m e , i s a good i n d i c a t i o n t h a t t h e y c o n s i s t o f more t h a n one component. Hence, t h e number o f c h e m i c a l compounds a c t u a l l y i n t h e l i g h t o i l sample i s p r o b a b l y a t l e a s t t w i c e t h e number o f i n t e g r a t e d gas c h r o m a t o g r a p h peaks. 3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

cox ET AL.

Homogeneous

Catalytic

Hydrogénations

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

14.

Figure 3.

Gas chromatogram of light oil from hydrogenolysis of hydrogenated Hvab coal

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

199

ORGANIC CHEMISTRY OF COAL

200

TABLE V. G. C. Mass S p e c t r a l A n a l y s i s o f L i g h t O i l

G. C. Retention Time, Area %

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

Hvab Coal

H -Hvab Coal 2

Mass Spec Assignments

18.59

0.58

16.02

benzene

0.44

0.93

0.52

toluene

0.15

1.19

0.20

0.67

1.59

1.32

xylene

0.35

2.17

0.52

xylene

0.46

2.97

0.68

C^-benzene

2.06

4.39

2.03

decalin

8.10

5.78

10.37

C^-benzene

20.47

7.51

22.74

1-methylindane

0.93

8.41

1.04

40.54

12.35

40.61

0.80

13.17

0.49

0.50

14.12

0.14

0.82

14.67

0.60

0.65

15.33

0.29

0.42

16.17

0.05

1.17

17.18

0.54

0.32

17.88

0.08

0.68

18.53

0.10

18.95

0.03

0.31

19.47

0.10

0.04

20.40

0.12

0.04

20.93

0.12

0.05

21.87

0.07

0.29

22.89

0.28

0.12

24.28

0.27

0.66

25.20

0.52

0.00

26.19

0.02

0.18

28.07

0.12

naphthalene methyl-tetrahydronaphthalene

methyl-naphthalene

C -tetralin 2

methyl-biphenyl

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

14.

cox ET AL.

Homogeneous

Catalytic

Hydrogénations

201

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

Utility Even t h o u g h homogeneous c a t a l y t i c h y d r o g é n a t i o n has had c o n s i d e r a b l e p r a c t i c a l u t i l i t y i n the hydrogénation o f s p e c i a l i z e d c h e m i c a l s such a s c e r t a i n f a t s , o i l s and p h a r m a c e u t i c a l s , i t s e c o n o m i c and t e c h n i c a l u t i l i t y i n p r o c e s s i n g c a r b o n a c e o u s f e e d s t o c k s such as c o a l , o i l o r t h e i r d e r i v e d i n t e r m e d i a t e s i s very uncertain. We have seen t h a t p r e h y d r o g e n a t i o n o f c o a l c a n s i g n i f i c a n t l y i n c r e a s e t h e amount o f l i q u i d s o b t a i n e d by p y r o l y s i s compared t o t h e u n h y d r o g e n a t e d c o a l . I t has a l s o been shown t h a t the hydrogenolysis o f prehydrogenated coal produces l e s s a s p h a l t e n e s and more l i g h t o i l and gas t h a n t h e c a t a l y t i c h y d r o g e n o l y s i s o f t h e p a r e n t c o a l . F i n a l l y i t was shown t h a t homogeneous c a t a l y t i c h y d r o g é n a t i o n c a n e f f e c t i v e l y i n c r e a s e t h e atomic hydrogen t o carbon r a t i o o f the carbonaceous m a t e r i a l s i n c l u d i n g c o a l and m a t e r i a l s d e r i v e d from c o a l by p y r o l y s i s and solvent refining. A l t h o u g h t h e amount o f e x p e r i m e n t a l d a t a g e n e r a t e d here i n s u p p o r t o f homogeneous c a t a l y t i c h y d r o g é n a t i o n i s i n f i n i t e s i m a l i n r e g a r d t o t h a t needed f o r a sound t e c h n i c a l j u d g m e n t concerning i t s u t i l i t y i n the area of f u e l s processing, there i s a c l e a r i n d i c a t i o n t h a t t h e a p p r o a c h has m e r i t . The e x t r a p o l a t i o n o f t h e e x p e r i m e n t a l d a t a i n d i c a t e s t h a t homogeneous c a t a l y t i c h y d r o g é n a t i o n has c o n s i d e r a b l e p o t e n t i a l a s a p r e l i m i n a r y p r o c e s s i n g s t e p f o r i n c r e a s i n g t h e a t o m i c H/C r a t i o o v e r c o n v e n t i o n a l methods f o r c a r b o n a c e o u s m a t e r i a l s such a s c o a l , and p o s s i b l y o i l s h a l e and t a r s a n d s . T h e d e r i v e d b e n e f i t from s u c h a u n i t o p e r a t i o n a s i d e from t h e a d d i t i o n o f h y d r o g e n t o t h e s e h y d r o g e n - d e f i c i e n t m a t e r i a l s i s t o i n c r e a s e t h e y i e l d and q u a l i t y o f t h e p r o d u c t s o v e r t h a t now o b t a i n a b l e b y c o n v e n t i o n a l p r o c e s s i n g techniques a t such m i l d c o n d i t i o n s . Y e t another p o t e n t i a l a p p l i c a t i o n o f homogeneous c a t a l y t i c h y d r o g é n a t i o n i s as a n i n t e r m e d i a t e s t e p i n f u e l p r o c e s s i n g o r c o n v e r s i o n schemes i n w h i c h t h e H/C r a t i o i s i n c r e a s e d t o p r o d u c e a s u p e r i o r q u a l i t y p r o d u c t . F i n a l l y , p o t e n t i a l a p p l i c a t i o n s o f homogeneous c a t a l y t i c hydrogénation a r e foreseen i n the area o f b a s i c r e s e a r c h s t u d i e s where i t i s used a s a n a n a l y t i c a l t o o l o r t e c h n i q u e f o r i n v e s t i g a t i n g complex c a r b o n a c e o u s s u b s t r a t e s . Much o f t h e i m p e t u s f o r t h e u s e o f homogeneous c a t a l y s t s i s t h e p r o s p e c t o f r e d u c i n g t e m p e r a t u r e and p r e s s u r e r e q u i r e d f o r c o n v e r s i o n , i n c r e a s i n g r e a c t i o n s p e c i f i c i t y and o b t a i n i n g t h e most e f f i c i e n t u s e p o s s i b l e o f t h e a c t i v e metal component. I n some i n s t a n c e s o f homogeneous c a t a l y t i c h y d r o g é n a t i o n , a l l t h e s e p r o s p e c t s have been r e a l i z e d . I t i s r e a s o n a b l e t o e x p e c t t h a t homogeneous c a t a l y s t s w i l l e v e n t u a l l y be d e v e l o p e d t h a t a r e c a p a b l e and e f f e c t i v e i n h y d r o g e n o l y s i s r e a c t i o n s o f c a r b o n c a r b o n bonds. T h i s i n d e e d w o u l d be a n e x t r e m e l y s i g n i f i c a n t break-through with respect t o coal l i q u e f a c t i o n . The m a j o r t e c h n i c a l drawback t o t h e u s e o f homogeneous a s well as heterogeneous c a t a l y s t s i s the d i f f i c u l t y o f recovery

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

202

ORGANIC CHEMISTRY OF COAL

f r o m p r o c e s s i n g s t r e a m s and p o i s o n i n g . S i n c e c a t a l y s t s a r e extremely expensive processing m a t e r i a l s , as a r e s u l t o f t h e i r m a n u f a c t u r i n g c o s t s and c o s t o f t h e i r component c o n s t i t u e n t s , o n l y s m a l l l o s s e s c a n be e c o n o m i c a l l y t o l e r a t e d . In homogeneous c a t a l y t i c h y d r o g é n a t i o n Run 25 where 7 mmole o f N i - Z i e g l e r c a t l y s t were employed p e r 15 g c o a l , t h e c o s t o f n i c k e l a l o n e a t z e r o r e c o v e r y ( i . e . , 54.8 l b / t o n c o a l ) w o u l d amount t o a b o u t $110/ton coal hydrogenated. I f t h e c o s t o f t h e t r i e t h y l aluminum and t h e c a r b o x y l a t e o f n i c k e l a r e t a k e n i n t o c o n s i d e r a t i o n t h e c o s t o f c a t a l y s t m a t e r i a l s a l o n e i s estimated t o exceed $150/ton coal hydrogenated. C l e a r l y , i n o r d e r t o c o n t e m p l a t e such a u s e o f t h e s e c a t a l y s t s , t h e y must e i t h e r be r e c o v e r e d o r used i n a much r e d u c e d c o n c e n t r a t i o n o r p r e f e r a b l y b o t h . Even though no a t t e m p t s were made a t c a t a l y s t r e c o v e r y o r u s e o f r e d u c e d amounts i n t h i s s t u d y i t was f o u n d t h a t t h e h y d r o g e n a t e d c o a l i n Run 25 c o n t a i n e d 1.2% N i . T h i s f i g u r e s t o be 3 1 % o f t h e n i c k e l used i n t h e homogeneous c a t a l y t i c h y d r o g é n a t i o n . T h e r e m a i n i n g 6 9 % o f the n i c k e l c a t a l y s t a p p a r e n t l y remained i n t h e c a r r i e r s o l v e n t , w h i c h i n p r a c t i c e w o u l d be r e c y c l e d . O b v i o u s l y , even h i g h e r c a t a l y s t r e c o v e r y i s n e c e s s a r y t o promulgate i t s economic viability. T h a t c a t a l y s t s c a n be used e f f e c t i v e l y and e c o n o m i c a l l y i n b u l k c h e m i c a l p r o c e s s e s i s amply d e m o n s t r a t e d i n t h e h y d r o c a r b o n p r o c e s s i n g i n d u s t r i e s . A l t h o u g h t h e s e c a t a l y s t s have been f o r t h e most p a r t h e t e r o g e n e o u s , homogeneous c a t a l y s t s have f o u n d a home i n a t l e a s t two n o t a b l e a r e a s . One i s t h e u s e o f Z i e g l e r c a t a l y s t s i n c o o r d i n a t i o n p o l y m e r i z a t i o n and t h e o t h e r i s i n t h e h y d r o f o r m y l a t i o n p r o c e s s . T h e s e two examples show t h a t t h e t e c h n i c a l and e c o n o m i c p r o b l e m s so o f t e n a s s o c i a t e d w i t h t h e u s e o f homogeneous c a t a l y s t s i n i n d u s t r i a l p r o c e s s e s c a n be overcome. Acknowledgement The a u t h o r s w i s h t o a c k n o w l e d g e t h e D i v i s i o n o f B a s i c Energy S c i e n c e s , Department o f Energy f o r f i n a n c i a l support o f t h i s work. Literature Cited 1. 2. 3. 4. 5.

K w i a t e k , J., Mador, I . L . , and Seyler, J.K., Adv. in Chem. Ser. (1963) ( 3 7 ) , 201-215. O s b o r n , J.Α., Jardine, F.H., Young,J.F.,a n d Wilkerson, G., J. Chem. S o c . , A, ( 1 9 6 6 ) , 1711-32. V a s k a , L . , a n d Rhodes, R.E., J. Amer. Chem. S o c . , (1965) 87, 4970. V a s k a , L . , Inor. N u c l . Chem. Lett., ( 1 9 6 5 ) , 1, 89. L a p p o r t e , S . J . , A n n . N.Y. A c a d . Sci., ( 1 9 6 9 ) , 158, ( 2 ) , 510.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch014

14.

cox ET AL.

Homogeneous Catalytic Hydrogénations

203

6. Bressan, G . , and Broggi, R., Chem. Abstr., (1969), 70, 37257k. 7. Friedman, S., Metlin, S., Svedi, Α . , and Wender, I., J. Org. Chem., (1959), 24, 1287-89. 8. Efimov, O.N., et al., J. Gen. Chem., USSR, (1968) 38, (12), 2581. 9. Efimov, O.N., et al., Izv. Akad. Nauk. SSSR, Ser. Khim. (1969), (4), 855-8. 10. Holy, Ν . , Nalesnik, T., and McClanahan, s., Fuel, (1977), 56, (10) 272-77. 11. Muetterties, E.L., and Hirsekon, F.J., J. Amer. Chem. Soc. (1974), 96, (12), 4063-7. 12. Cotton, F . Α . , and Wilkinson, G . , "Advanced Inorganic Chemistry", 3rd Edition, 772-6, Interscience Publishers, New York, 1972. 13. Coates, G.E., Green, M.L.H., Powell, P . , and Wade, Κ., "Principles of Organometallic Chemistry", 197-8, Methuen and Co., L t d . , London, 1968. 14. Heredy, L.A., and Neuworth, M.B., Fuel (London), (1962), 41, 221. 15. Ouchi, K . , Imuta, K . , and Yamashita, Y . , Fuel, (London), (1965), 44, 29. 16. Gan,H.,Nandi, S.P., and Walker, P.L. Jr., Fuel (London) (1972), 51, (10), 272-77. 17. Howard, H . C . , in "Chemistry of Coal Utilization, Supplemental Volume", H.H. Lowry, e d . , 363-70, John Wiley & Sons, New York, 1963. 18. Jones, J.F., "Project COED: Clean Fuels from Coal Symposium" Institute of Gas Technology, Chicago, Ill., September 1014, 1973. RECEIVED February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

15 Hydrotreatment of Coal with AlCl /HCl and Other 3

Strong Acid Media J. Y. LOW

and D. S. ROSS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025

Most current processes for upgrading coal to cleaner fuels require stringent reaction conditions of high temperatures and pressure. Less severe reaction conditions are needed to make coal upgrading economically feasible. The objective of this work was to investigate catalyst systems for upgrading coal to clean fuels under moderated conditions. In this work, homogeneous acid catalysts are of particular interest because they allow intimate contact with the coal and are not liable to coal ash founding. The most common homogeneous catalysts studied i n coal upgrading belong to the general class of molten salt catalyst (1-5) and include halide salts of antimony, bismuth, aluminum, and many of the transition metals. Most often, these molten salts have been studied at high temperature and i n massive excess (1-5). We have performed a systematic study of the use of some of these molten salts as homogeneous acid catalysts for upgrading of coal at relatively low temperatures and i n moderate quantities. In our i n i t i a l work to establish relatively mild reaction conditions that would still give relatively good conversions, we conducted a series of experiments to determine the role of HCl, A1C1 , and H i n coal hydrocracking. We examined the effects of temperature and residence time, studied catalyst/coal weight ratios of 1/1 to 3/1, then chose the standard reaction conditions for the screening of several acid catalysts. The effectiveness of the catalysts was judged by the solubility of the treated coal in THF and pyridine or both, and by the gas yields. In some cases where gasification was significant, gas yields were the only c r i t e r i a used. 3

2

Experimental Studies We used I l l i n o i s No. 6 coal pulverized by b a l l milling under nitrogen to -60 mesh and then usually dried i n a vacuum oven at 115°C overnight. Pennsylvania State University supplied beneficiated coal samples (PSOC-26) as well as an unbeneficiated sample (PSOC-25) for use i n some experiments. The beneficiated 0-8412-0427-6/78/47-071-204$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

15.

LOW AND ROSS

Hydrotreatment

of

205

Coal

c o a l has the f o l l o w i n g elemental a n a l y s e s : C, 77,2%; H, 5.05% N, 1.69%; S, 2.08%; ash, 2.0%. The experiments were c a r r i e d out i n e i t h e r a r o c k i n g 500-ml autoclave f u l l y l i n e d w i t h T e f l o n or i n a 300 m l - H a s t e l l o y C MagneDrive s t i r r e d autoclave from Autoclave Engineers. In general, the r e a c t o r was charged with c o a l and c a t a l y s t , evacuated, then f i l l e d with 0.7 mole of HC1 ^~ 500 p s i ) and 800 p s i of hydrogen. The r e a c t i o n mixture was heated to and kept a t the r e a c t i o n temperature f o r a given p e r i o d . A f t e r the r e a c t i o n , the r e a c t o r was cooled slowly to room temperature. The gases were analyzed by gas chromatography to determine hydrogen, methane, ethane, and propane contents. The r e a c t o r was then depressurized and the r e a c t i o n mixture washed w i t h water u n t i l the washings were neutral. The f i l t e r e d c o a l products were then allowed to dry i n a vacuum oven at 115°C overnight. The t r e a t e d product c o a l was u s u a l l y c h a r a c t e r i z e d by elemental analyses (C, Η, Ν ) , by molecular weight determinations, and by s o l u b i l i t i e s i n THF and p y r i d i n e . THF and p y r i d i n e s o l u b i l i t i e s were determined by s t i r r i n g a 0.50 g sample of the product c o a l i n 50 ml THF or p y r i d i n e at room temperature f o r 1 hr, f i l t e r i n g the mixture i n a medium p o r o s i t y s i n t e r e d g l a s s f i l t e r , and then washing the r e s i d u e with f r e s h solvent (~ 50 ml) u n t i l the washings were c l e a r . Results and D i s c u s s i o n AlCl /HCl. In a s e r i e s of runs i n a r o c k i n g T e f l o n - l i n e d autoclave, we f i r s t studied the r o l e of HC1, A1C1 , and H i n c o a l hydrocracking using 5 g each of A1C1 and c o a l , at 190°C ( j u s t above the melting point of A1C1 ), f o r 15 hr. As shown i n Figure 1, one or more of the three components were absent i n Runs 1 to 6 and i n Run 9, and i n each case, no i n c r e a s e i n THF and p y r i d i n e s o l u b i l i t i e s was observed. In Run 10, where a l l three components were present, s o l u b i l i t i e s increased s u b s t a n t i a l l y , suggesting that the A1C1 /HC1 system was a c t i v e . The purpose of Runs 7 and 10 was to assess the importance of HC1 i n the system under these c o n d i t i o n s ; however, the r e s u l t s are not unequivocal. Here, the presence i n the c o a l of proton sources, such as phenolic groups and traces of water, undoubtedly hydrolyzes some of the A1C1 , producing HC1. These runs i n d i c a t e that no added HC1 i s r e q u i r e d f o r c o a l hydrocracking at these lower temperatures At higher r e a c t i o n temperatures (210°C) and shorter r e a c t i o n time (5 h r ) , the added HC1 c l e a r l y i n c r e a s e s the conversion (Runs 21 and 25), suggesting that the e f f e c t i v e c a t a l y s t i n the system must c o n t a i n the elements of HCl and A1C1 . We a l s o studied the e f f e c t of p o t e n t i a l Η-donor hydrocarbons and temperature. We based our work on the r e s u l t s of S i s k i n (6), who found that saturated, t e r t i a r y hydrocarbons serve as e f f e c t i v e hydride donors i n the strong acid-promoted hydrogenolysis of benzene. In our system, they proved i n e f f e c t i v e (Runs 17, 22, 24, a

3

2

3

3

3

3

3

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978. IS

THF Solubility

50 60

RUN NO.

2

3

2

a) DMB = 2,3-Dimethylbutane b) MCP = Methylcyclopentane

AICI3/H2

AICI /H /HCI

H

Figure 1.

a

a

2

3

2

AICI /H /HCI/MCP

AICI3/H2

3

b

a

210°C, 5 hr

X

30

40

S O L U B I L I T Y (%) 20

1 9 5 C , 15 hr

10

Acid-catalyzed hydrocracking of beneficiated Illinois No. 9 coal

Pyridine Solubility

2

AICI /N /HCI/DMB

3

AICI /N /DMB

Coal Heated Alone In Evacuated Bulb

2

AICI /H /HCI 3

2

2

2

AICI3

AICI3/HCI

3

AICI /HCI/N

3

3

3

AICI /H /HCI

AICI /H /HCI (5 hr)

190 C, 15 hr

40

HCI/H

2

30

SOLUBILITY (%) 20

AICI /H /HCI/DMB

2

10

HCI

Untreated Coal

RUN| NO.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

50

60

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

15.

LOW AND ROSS

Hydrotreatment

of

Coal

207

and 26, Figure 1). Higher temperatures allowed s h o r t e r r e a c t i o n times. The r e s u l t s f o r Run 17 (only 5 hr at 195°C) are comparable to those f o r Runs 7 and 10 (15 hr, 190°C). Runs at 195°C f o r 15 hr were f a r more e f f e c t i v e , and the conversion f o r Run 15 at 210°C f o r 5 hr i s about the same as that f o r Run 16 at 195°C f o r 15 hr. Next, we s t u d i e d the e f f e c t s of the c a t a l y s t / c o a l weight r a t i o on product character and c o a l product y i e l d s i n both the T e f l o n - l i n e d and the H a s t e l l o y C a u t o c l a v e s . At a weight r a t i o of 1.0, the two systems y i e l d e d products w i t h s t r i k i n g l y d i f f e r e n t pyridine s o l u b i l i t i e s : about 13% and 60% with the metal and Tefl o n equipment, r e s p e c t i v e l y (Figure 2). Increasing the c a t a l y s t / c o a l r a t i o to 2.0 increased s o l u b i l i t i e s to above 90% f o r both systems, but a f u r t h e r r a t i o increase a c t u a l l y caused s o l u b i l i t i e s to decrease s l i g h t l y . The s o l i d product recovery a l s o decreased with i n c r e a s i n g c a t a l y s t / c o a l r a t i o . As shown i n Figure 2, at a 2.0 r a t i o only about h a l f the c o a l was recovered as a s o l i d product. The other h a l f was converted to a mixture of methane and ethane. The s o f t e n i n g p o i n t f o r the THF-soluble fraction was about 150°C; however, the p y r i d i n e - s o l u b l e f r a c t i o n d i d not melt even a t temperatures up to 280°C. Figure 3 presents data on the H/C r a t i o s f o r products from both systems. The c o a l products from the T e f l o n - l i n e d r e a c t o r have c o n s i s t e n t l y higher H/C r a t i o than those from the H a s t e l l o y C reactor. R e s u l t s i n the H a s t e l l o y C autoclave were unchanged when a l o o s e l y f i t t i n g T e f l o n l i n e r was used. We have no d e t a i l e d explanation f o r the e f f e c t of autoclave s u r f a c e on the r e s u l t s , but p a s s i v a t i o n of the metal s u r f a c e by some minimum q u a n t i t y of c a t a l y s t i s part of the answer. Whatever the mechanism, the Teflon surface i s h e l p f u l . The c a t a l y s t system g a s i f i e s some of the c o a l d i r e c t l y to methane and ethane. This r e s u l t and the e f f e c t s of temperature on c o a l conversion are shown i n Table I. The t a b l e shows data from runs at 210°C f o r r e a c t i o n times from 45 min to 5 hr, and at 300°C f o r a 90 min r e a c t i o n time. The 210°C data are from an e a r l i e r phase of our work, where the g a s i f i c a t i o n was not q u a n t i f i e d , and the g a s i f i c a t i o n was determined by d i f f e r e n c e . For the 300°C work, the q u a n t i t i e s of gases and r e s i d u e were determined independently, and thus, the mass balances f o r these runs are not e x a c t l y 100%. The 300°C runs are a l l f o r 90 min, and Runs 83 and 85 show s t r i k i n g degrees of g a s i f i c a t i o n . More than 90% of the carbon i n the c o a l was converted to a 50/50 mixture of methane and ethane i n these experiments. In the next three runs, no HC1 was present, and we observe a cumulative e f f e c t of i t s absence. The degrees of g a s i f i c a t i o n d e c l i n e s e v e r e l y , and a l l the s o l i d c o a l products recovered have d e c l i n i n g p y r i d i n e s o l u b i l i t i e s and H/C r a t i o s . Kawa et a l . (2) observed a s i m i l a r e f f e c t f o r HC1.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

208

ORGANIC CHEMISTRY OF COAL

CATALYST/COAL

Figure 2.

(wt/wt)

Effect of autoclave surface and catalyst I coal ratio on coal conversion.

The AlClj/HCl system was used with reaction temperature of 210°C, for 5 hr in a stirring Hastelloy C autoclave or rocking Teflon-lined autoclave.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

LOW AND ROSS

Hydrotreatment

of

Coal

2 CATALYST/COAL

3 (wt/wt)

Figure 3. Comparison of H/C atomic ratio of treated product coal vs. effects by different reactors and catalyst/coal ratios. For runs at 210°Cand5hr.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

210

Table I THE EFFECT OF RESIDENCE TIMES ON COAL GASIFICATION (4 g I l l i n o i s No. 6 c o a l , 8 g A1C1 , 500 p s i HC1, 800 p s i H , i n 2 300 ml s t i r r e d H a s t e l l o y C autoclave) 3

2

Run

Residence Time

67

5 hr

Coal Residue %Recovered %Pyridine Solubility a

% H/C

Coal , Gasified

0.83

61

b

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

210°C

46

C

39

97

5 hr

48

87

0.82

52

b

41

4 hr

49

91

0.84

51

b

66

90 min

47

96

0.85

53

b

45 min

72

93

0.82

28

b

71

45 min

66

97

0.82

34

b

83

90 min

18

78

0.72

96

d

85

90 min

18

83

0.74

90

d

69

C

300°C

86

e

90 min

30

60

0.75

72

d

87

e

90 min

49

31

0.68

56

d

88

e

90 min

68

28

0.64

36

d

°Based on 4 g of c o a l . ^Based on unaccounted f o r s o l i d product. Run with 3 g c o a l and 6 g A1C1 . 3

^Determined independently. CHz,/C H - 1/1. Traces of propane were seen i n Runs 86, 87, and 88. 2

e

6

Run without HC1

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

15.

LOW AND ROSS

Hydrotreatment

of

211

Coal

These data can be explained by the f o l l o w i n g scheme: 1 Coal H/C = 0.79

2 Coal product

<

Ha/catalyst

•

Ci + C

2

H /catalyst 2

Char

3 ' H/C

H /no c a t a l y s t 2

= 0.75

-^0.64^

Steps 1 and 2 are important i n the presence of an e f f e c t i v e c a t a l y s t and step 3 becomes competitive with no e f f e c t i v e c a t a l y s t present. At lower temperatures, k i > k . Thus, the hydrogenr i c h , p y r i d i n e - s o l u b l e c o a l product accumulates and can be i s o l a t e d . At higher temperatures, the r e l a t i v e r a t e s of steps 1 and 2 are reversed, k > k i , and g a s i f i c a t i o n i s the major e f f e c t . C l e a r l y , both A1C1 and HC1 are necessary f o r e f f e c t i v e catalysis. When HC1 i s e l i m i n a t e d , c a t a l y s t e f f e c t i v e n e s s i s reduced, steps 1 and 2 are suppressed, and step 3 becomes dominant. With the l e s s e n i n g degrees of g a s i f i c a t i o n , the c o a l r e s i d u e appear to be i n c r e a s i n g l y c r o s s - l i n k e d and depleted i n hydrogen, p o s s i b l y a r e s u l t of chemistry at the autoclave s u r f a c e . HC1 alone (Figure 1) not only i s i n e f f e c t i v e , but a l s o promoted char formation. 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

2

3

Other Lewis/Bronsted Combinations. Several a c i d c a t a l y s t s were screened i n two s e r i e s of t e s t s at two c a t a l y s t concentrat i o n l e v e l s , 210°C, 5 hr, 800 p s i H ( c o l d ) , and 0.7 mole HX (X = Br, CI, or F ) . We found c a t a l y s t a c t i v i t y to vary c o n s i d e r ably from one s e r i e s to the next (Figure 2). C a t a l y s t / c o a l weight r a t i o f o r the f i r s t s e r i e s was 1/1. A l l catalysts studied at t h i s r a t i o , except A l B r and A1C1 , were i n e f f e c t i v e , reducing THF and p y r i d i n e s o l u b i l i t i e s s i g n i f i c a n t l y , perhaps because of i n t e r n a l condensation i n the s t a r t i n g c o a l . The c o a l products i n these runs are probably h i g h l y c r o s s - l i n k e d . A1C1 was c o n s i d e r ably more e f f e c t i v e than A l B r , and HBr alone (Run 30) was, not surprisingly, ineffective. These r e s u l t s i n d i c a t e a c a t a l y s t e f f e c t i v e n e s s of A1C1 > A l B r » S b C l = SbF * Z n C l - T a F - N i S 0 - C 0 S O 4 - HBr. In the second s e r i e s , a constant molar q u a n t i t y of c a t a l y s t was used: 0.045 moles c a t a l y s t /4 g c o a l , equivalent to 6 g A l C l / 4 g c o a l . The o r d e r i n g here i s SbBr - S b C l > A l B r > A1C1 > N i ( A A ) > T a F » SbF - M0CI5 - WC1 (AA = a c e t y l a c e t o n a t e ) . Thus T a F , which S i s k i n (6) found e f f e c t i v e l y hydrocracked benzene to mixed hexanes, i s not at a l l e f f e c t i v e under our c o n d i tions. S i m i l a r l y , Z n C l , the w e l l known c o a l conversion c a t a l y s t , 2

3

3

3

3

3

3

3

3

2

2

5

5

4

3

3

3

3

3

6

5

2

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5

212

ORGANIC CHEMISTRY OF

COAL

i s not e f f e c t i v e under these c o n d i t i o n s , perhaps because under our r e l a t i v e l y mild c o n d i t i o n s , Z n C l i s not molten (mp 283°C). F i n a l l y , the favorable antimony bromide and c h l o r i d e r e s u l t s are s i m i l a r to those reported by S h e l l (1). In Run 35 (Table I I ) , with A1C1 /HC1, we used unbeneficiated c o a l . Here, the THF s o l u b i l i t y of the product c o a l increased by almost a f a c t o r of 2, to 40%. The p y r i d i n e s o l u b i l i t y increased s l i g h t l y , to 66%. Since p y r i d i n e i s g e n e r a l l y a b e t t e r solvent f o r c o a l l i q u i d s than i s THF, the considerable increase i n THF s o l u b i l i t y suggests that more lower molecular weight products are obtained when u n b e n e f i c i a t e d c o a l i s used. A l s o , the mineral matter present i n the unbeneficiated c o a l c l e a r l y aids the hydro­ cracking process, suggesting that the mineral matter i n the c o a l i s an e f f e c t i v e c a t a l y s t under a c i d c o n d i t i o n s . 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

3

Summary In s t u d i e s with mixtures of Lewis and Bronsted (proton) a c i d s as c a t a l y s t s , we have found that with hydrogen some mixtures con­ v e r t I l l i n o i s No. 6 c o a l to f u l l y p y r i d i n e - s o l u b l e products and 50/50 mixtures of methane and ethane. The A1C1 /HC1 system was studied most e x t e n s i v e l y , and i t was found that at 210°C (410°F) and 45 min residence time, about 70% of the c o a l was converted to a hydrogen-enriched, f u l l y p y r i d i n e - s o l u b l e product and the remainder, to methane and ethane. A 90 min or longer residence time y i e l d e d 50% gases. At 300°C (572°F), more than 90% of the carbon i n the s t a r t i n g c o a l was converted to methane and ethane. Neither HC1 nor A1C1 alone was e f f e c t i v e ; when used along, e i t h e r system y i e l d e d a s o l i d product r e l a t i v e l y low i n p y r i d i n e s o l ­ u b i l i t y and depleted i n hydrogen r e l a t i v e to the s t a r t i n g c o a l . Reaction runs i n an autoclave f u l l y l i n e d with T e f l o n gave f a r b e t t e r r e s u l t s than those i n a H a s t e l l o y C autoclave. A screening study of s e v e r a l acids showed that at a 1/1 c a t a l y s t / c o a l weight r a t i o , the order of e f f e c t i v e n e s s i s A1C1 > AlBr » SbCl - SbF κ Z n C l - T a F - NiSO^ - CoS0 . With a constant r a t i o of a given molar quantity of c a t a l y s t to mass of c o a l , the order i s SbBr * S b C l > A l B r > A1C1 > N i ( A A ) > TaF » SbF « MoCl - WC1 . (AA = acetonylacetonate.) 3

3

3

3

3

2

3

5

3

3

3

4

3

2

5

s

5

6

Acknowledgment

No.

The f i n a n c i a l support f o r t h i s work from DOE EF-76-C-01-2202 i s g r a t e f u l l y acknowledged.

under

Contract

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

15.

LOW AND ROSS

Hydrotreatment

213

of Coal

Table I I TREATMENT OF ILLINOIS NO. 6 COAL WITH H /STRONG ACID SYSTEMS 2

Run No.

Catalyst

Pressurel ( p s i ) HX H

System

2

(a) Constant Weight

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

28

AICI3/HCI/H2

a

800

500

23

58

800

500

40

66

35

A1C1 /HC1/H

29

AlBr /HB /H

27

AlBr /HBr/H

30

HBr/H

31

SbCl /HCl/H

32

TaF /HF/H

2

1100

33

SbF /HF/H

2

1100

44

ZnCl /HCl/H

56

CoS0 /H S0*/H

2

1300

57

NiS0 /H S0z,/H

2

1300

3

3

2

C 2

2

3

2

980

33g

9

27

820

50g

11

32

1000

2

3

5

3

2

4

800

2

2

A

800

2

2

S o l u b i l i t i e s (%)b THF Pyridine

2

6

-

1

22g

-

13

16g

< 1

4

-

9

68. 6g

< 1

< 1

68.6g

< 1

< 1

25

47

30

59

-

95

31g 500

500

(b) Constant Molar Quantity* 1

45

A1C1 /HC1/H

48

AlBr /HBr/H

2

1100

49

SbCl /HCl/H

2

800

50

3

3

3

800

2

500 70g 500

TaF /HF/H

2

900

14g

11

20

52

SbF /HF/H

2

1150

14g

< 1

< 1

54

MoCl /H

1300

-

8

16

55

WC1 /H

1300

-

6

12

61

SbBr /HBr

43

95

62

Ni(AA) /HCl/H

70

MoCl /HCl/H

5

5

5

6

2

2

850

3

2

5

2

2

59g

800

500

ND

800

500

< 1

e

+

+

38 4

In t h i s s e r i e s of experiments, 5 g of c o a l was t r e a t e d a t 210°C f o r 5 hr i n a rocking T e f l o n - l i n e d autoclave. > c Moisture-ash-free b a s i s . Unbeneficiated c o a l was used. Srhese experiments used 0.045 moles of c a t a l y s t per 4 g c o a l . A s t i r r e d H a s t e l l o y C autoclave was used. ND = Not determined.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

214

Literature Cited 1. Wald, Μ., U.S. Patent 3,543,665 (November 24, 1970). 2. Kawa, W., S. Freidman, L. V. Frank, and R. W. Hiteshue, Amer. Chem. Soc., Div. Fuel Chem. (1968), Preprint 12 (3), 43-7. 3. Qader, S., R. Haddadin, L. Anderson, and G. Hill, Hydrocarbon Process (1969), 48 (9), 147. 4. Kiovsky, Τ. Ε., U.S. Patent 3,764,515 (October 9, 1973). 5. Zielke, C. W., R. T. Struck, J. M. Evans, C. P. Costanza, and E. Gorin, I & Ε C Process Design and Development (1969), 5, (2), 151, and references therein. 6. Siskin, M., J. Amer. Chem. Soc. (1974), 95, 3641. February 10,

1978

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch015

RECEIVED

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16 Characterization of Coal Products by Mass Spectrometry H. E. LUMPKIN and THOMAS ACZEL

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Exxon Research and Engineering Co., P.O. Box 4255, Baytown, TX 77520

I.

Introduction and Background

In studies on the organic chemistry of coal, the researcher, unfortunately, i s unable to examine a complete coal molecule. He must instead be content to analyze bits and pieces of coal molecules produced by solvent refining, liquefaction, pyrolysis, or extraction. Knowledge of the composition of these pieces helps in understanding the organic chemistry of coal and i s v i t a l for the development of coal liquefaction processes and the further upgrading of the liquefaction products. Mass spectrometry i s the prime technique used in our laboratories (1,2) and in other laboratories (3) to determine the composition of the very complex mixtures derived from coal. Petroleum fractions have been analyzed by mass spectrometry (MS) for over 30 years. As heated inlet systems evolved (4,5) and instrumental resolving power increased, MS was applied to higher boiling ranges and more complex mixtures. When research in coal liquefaction began in our laboratories about 10 years ago, we had well-developed instrumentation, data handling procedures, and quantitative analyses for petroleum (6,7). Extension of these techniques to coal products required only minor changes and extensions (8,9) · In this paper we describe some of the MS procedures we use and give some typical examples of analyses. II.

Equipment and Data Handling Procedures

A very repeatable low resolution instrument is used for streams in which the major components have been previously identified. The unseparated naptha boiling range, separated saturate fractions, and mid-boiling range samples (when detailed knowledge of the hetero-atom components i s not required) f a l l in this category. For mid-boiling and high-boiling fractions requiring more complete breakdown of aromatic, hydroaromatic, and aromatic hetero-compounds, spectra are obtained on a high-resolution double focusing instrument. 0-8412-0427-6/78/47-071-215$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

216

Both of the instruments are automated. A d i g i t a l readout system senses peaks and converts analog s i g n a l s to d i g i t a l s i g n a l s , records d i g i t a l data on p r i n t e d paper tape and on magnetic tape, and a l a r g e r computer reads the data from the magnetic tape and f u r t h e r processes i t employing p r o p r i e t a r y computer programs. A l i s t of the equipment i s shown below: Item

Manufacturer

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Low R e s o l u t i o n MS High R e s o l u t i o n MS MS Readout System Printer Computer III·

Model

Cons. Electrodynamics Corp. Assoc. E l e c . I n d u s t r i e s , L t d . Columbia S c i e n t i f i c Ind. Mohawk Data Systems I n t e r n a t i o n a l Bus. Machines

21-103C MS50 CSI-260 2016 370

Methods and Results

A. Naphtha B o i l i n g Range. High i o n i z i n g v o l t a g e , low r e s o l u t i o n spectra are adequate to determine p a r a f f i n s , naphthenes, 2-ring naphthenes, C - C n benzenes, C - C indanes and t e t r a l i n s , C9-C10 indenes, C i - C n naphthalenes, and C - C i phenols i n the C to 450°F b o i l i n g range. The c a l i b r a t i o n data were derived p r i m a r i l y from scans of pure compounds and assembled i n a 20 component matrix. A summary a n a l y s i s i s given i n Table I . 6

9

0

1 0

1 0

2

5

Table I Component T o t a l Saturates T o t a l Benzenes Indanes/Tetralins Indenes Naphthalenes T o t a l Phenols Total Wt.% Carbon Wt.% Hydrogen Wt.% Oxygen

Wt.% 76.6 13.9 2.3 0.1 0.0 7.1 100 ·0 85.80 13.09 1.11

With some assumptions regarding the molecular weight d i s t r i b u t i o n s of the p a r a f f i n s and naphthenes, a u s e f u l elemental a n a l y s i s can be r e a d i l y c a l c u l a t e d . O c c a s i o n a l l y more d e t a i l e d data f o r the saturated components i s d e s i r a b l e . A 42 component combined MS and gas chromatographic procedure determines the aromatic and phenolic components l i s t e d p r e v i o u s l y and f u r t h e r breaks down the p a r a f f i n s i n t o i s o - and normal types by carbon number and the naphthenes i n t o cyclohexanes and cyclopentanes by carbon number. C a l i b r a t i o n data were

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16.

LUMPKIN AND ACZEL

Characterization

of

Coal

Products

obtained from pure compounds and from concentrates separated molecular s i e v e and gas chromatography.

217

by

B. Higher B o i l i n g Range Saturate F r a c t i o n . F r a c t i o n s b o i l ­ ing above the naphtha range can be separated i n t o s a t u r a t e , aromatic and p o l a r f r a c t i o n s employing a modified v e r s i o n of the c l a y - g e l adsorption chromatographic method, ASTM D-2007. The saturate f r a c t i o n i s analyzed by the high i o n i z i n g voltage MS method, ASTM D-2786. A t y p i c a l a n a l y s i s of a 430-950°F s a t u r a t e f r a c t i o n from a S y n t h o i l product (10) i s given i n Table I I .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Table I I Compound Type

Wt.%

Paraffins 1-Ring Naphthenes 2-Ring Naphthenes 3-Ring Naphthenes 4-Ring Naphthenes 5-Ring Naphthenes 6-Ring Naphthenes Monoaromatics

34.2 18.4 16.3 14.6 10.3 3.0 1.1 2.1

Normal p a r a f f i n s g e n e r a l l y comprise the major p a r t , 80-90%, of the t o t a l p a r a f f i n s i n c o a l l i q u e f a c t i o n products and a l e s s e r part i n c o a l e x t r a c t s . When a s p l i t between i s o - and normalp a r a f f i n s i s d e s i r e d , gas chromatography r a t h e r than mass spectrometry i s normally the method of preference i n higher b o i l i n g f r a c t i o n s . I s o - p a r a f f i n s are not u s u a l l y i d e n t i f i e d . However, we have r e c e n t l y i d e n t i f i e d the i s o p r e n o i d p a r a f f i n s p r i s t a n e , 2, 6, 10, 14-tetramethyl pentadecane, and phytane, 2, 6, 10, 14-tetramethyl hexadecane i n c o a l e x t r a c t s and l i q u e f a c ­ t i o n products. These components were separated and i d e n t i f i e d by gas chromatography, corroborated by MS (10). Isoprenoid p a r a f f i n s are used i n organic geochemistry to group o i l s i n t o " f a m i l i e s " (11). It i s p o s s i b l e that c o a l s from different seams or deposits might be d i f f e r e n t i a t e d by the r e l a ­ t i v e r a t i o s of these isoprenoids or by the i s o p r e n o i d to η-paraffin r a t i o . P r i s t a n e i s thought to be derived from the d i t e r p e n i c a l c o h o l p h y t o l (12), that comprises about 30% of the c h l o r o p h y l l molecule, and i t s presence and concentration might be r e l a t e d to the environment of the marsh i n which a p a r t i c u l a r c o a l bed or seam was formed. C. Higher B o i l i n g Range Aromatic and Polar F r a c t i o n s . If data on the saturate p o r t i o n are not r e q u i r e d , the aromatic and p o l a r aromatic components are determined on the unseparated sam­ ple. This i s done with a high r e s o l u t i o n instrument operated i n the low i o n i z i n g voltage mode (13)· The same procedure can be

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

218

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

a p p l i e d to separated aromatic and p o l a r f r a c t i o n s , and t h i s i s p r e f e r r e d i f there i s a s i g n i f i c a n t c o n c e n t r a t i o n of polar components · With low i o n i z i n g v o l t a g e e l e c t r o n s only those components c o n t a i n i n g double bonds, such as aromatics and o l e f i n s , are i o n i z e d and only the molecular i o n i s produced. Thus, the s p e c t r a , the s p e c t r a l i n t e r p r e t a t i o n , and the c a l i b r a t i o n data are s i m p l i f i e d , as there i s no i n t e r f e r e n c e between components. A f u l l d i s c u s s i o n of high r e s o l u t i o n mass spectrometry i s beyond the scope of t h i s paper, so the technique w i l l be des c r i b e d here only b r i e f l y . D i f f e r e n t combinations to form molecules of the atomic species found i n c o a l products w i l l have d i f f e r e n t molecular weights. For example, from the atomic weights of the most abundant species given below one c a l c u l a t e s the molecular weight of methyl Atomic Species Carbon Hydrogen Oxygen Nitrogen Sulfur

Atomic Weight 12.000 1.0078 15.9949 14.0031 31.9721

acenaphthene, C H , to be 168.0939, and the molecular weight of dibenzofuran, C H 0 , to be 168.0575. The high r e s o l u t i o n MS r e s o l v e s these two peaks having the same nominal molecular weight and the r e s o l v i n g power required i s 4615 (Mass/AMass = 168/0.0364 = 4615). Other molecules r e q u i r e even greater r e s o l v i n g power to separate, p a r t i c u l a r l y those c o n t a i n ing n i t r o g e n or s u l f u r (14)· The MS and i t s a u x i l i a r y apparatus must a l s o provide data from which p r e c i s e mass measurements can be c a l c u l a t e d . By measuring the time at which each peak occurs i n a repeatable l o g a r i t h m i c scan of the s p e c t r a and by i n t r o ducing compounds having peaks at known masses, the masses of the sample peaks can be determined very p r e c i s e l y , and the mass determines the molecular formula. The scheme we use from mass spectrometer to f i n a l q u a n t i t a t i v e a n a l y s i s i s given i n the data flow scheme below. The MS, MS readout system, p r i n t e r , computer, computer programs, and people are r e q u i r e d . 1 3

l 2

l2

e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16.

LUMPKIN AND ACZEL

Characterization

of

Coal

Sample and r e f e r e n c e compounds charged

219

Products

to h i g h r e s o l u t i o n

MS

f Peak heights and times p r i n t e d on paper tape

* Peak heights and times w r i t t e n on mag tape

Reference peak times recognized and cards punched by hand

Mag tape read and cards punched by computer

τ

Cards read, masses c a l c u l a t e d , molecular formulas assigned, output p r i n t e d , cards punched by computer

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Formulas checked

and c o r r e c t i o n cards punched by hand

ί Cards read, q u a n t i t a t i v e a n a l y s i s , average molecular weight, carbon number, and r i n g d i s t r i b u t i o n s , elemental analyses, d i s t i l l a t i o n c h a r a c t e r i s t i c s , p r e d i c t e d composition of narrow cuts c a l c u l a t e d and p r i n t e d by computer. The most d e t a i l e d i n f o r m a t i o n c a l c u l a t e d from the high r e s o l u t i o n s p e c t r a i s the q u a n t i t a t i v e amount of each compound type at each carbon number. This t a b u l a t i o n i s p r i n t e d on 6 pages, 50 rows and 12 columns per page. This i s more data than most engineers care to examine; t h e r e f o r e , summary t a b l e s , d i s ­ t r i b u t i o n s and other items are c a l c u l a t e d from these d e t a i l e d data. Excerpts from the compound type summary of a S y n t h o i l product (10) are given i n Table I I I . This i s the i n i t i a l summary made from the d e t a i l e d data. Table I I I

Compound Type A l k y l Benzenes Naphthalenes Dibenzothiophenes Fluorenothiophenes Benzofurans Dibenzofurans

Wt.% 1.74 11.02 0.33 0.16 0.56 2.55

Average Mol.Wt. 160.8 176.4 210.9 241.2 210.9 255.0

Average Carbon No. 11.9 13.5 13.9 16.4 14.6 16.1

C Atoms i n Sidechains 5.9 3.5 1.9 2.4 6.6 4.1

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

220

The d i s t r i b u t i o n of aromatic r i n g s i s a f u r t h e r summary which may be of value i n r e f i n i n g of c o a l products. The r i n g d i s t r i b u t i o n f o r the same product of Table I I I i s shown i n Table IV normalized to 100%, but the program a l s o c a l c u l a t e s and p r i n t s the same d i s t r i b u t i o n normalized to the percent aromatics i n the sample. Table IV

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Hydrocarbons Nonaromatics 1-Ring Aroms 2-Ring Aroms 3-Ring Aroms 4-Ring Aroms 5-Ring Aroms 6-Ring Aroms 7+Ring Aroms Totals

0.0 20.960 36.919 15.644 12.388 1.997 0.856 0.068 88.832

Sulfur Comp.

Oxygen Comp.

0.144 0.517 0.611 0.153 0.067 0.020

0.0 2.235 3.465 2.202 1.470 0.208 0.084

1.512

9.664

Totals 0.144 23.712 40.996 17.999 13.925 2.225 0.940 0.068 100.008

A d d i t i o n a l c a l c u l a t e d items, such as d i s t i l l a t i o n characteri s t i c s (15), can be of great value to a researcher. I f there i s i n s u f f i c i e n t sample a v a i l a b l e f o r a c t u a l d i s t i l l a t i o n , say from a bench-scale experiment, a few milligrams w i l l s u f f i c e f o r a high r e s o l u t i o n MS run. The c a l c u l a t e d MS values, GC d i s t i l l a t i o n , and 15/5 d i s t i l l a t i o n are i n good agreement. The same high r e s o l u t i o n scheme can also be applied to the p o l a r f r a c t i o n s from the c l a y - g e l separation. But the a n a l y s i s of polars can become very t e d i o u s — t h e composition i s much more complex as the polars contain many of the same hydrocarbon spec i e s as the aromatic f r a c t i o n s i n a d d i t i o n to the p o l a r heteroaromatic oxygen, n i t r o g e n , and s u l f u r compounds. In a d d i t i o n , our computer programs f o r some of these c l a s s e s of components are not yet f u l l y i n t e g r a t e d i n t o the f i n a l q u a n t i t a t i v e a n a l y s i s program, and separate programs must be run and the r e s u l t s meshed. An i n d i c a t i o n of the complexity of the p o l a r components i n c o a l products i s provided by a very small p o r t i o n of spectra of the p o l a r f r a c t i o n of a S y n t h o i l product given i n Table V, i n which some t y p i c a l m u l t i p l e t s resolved by the high r e s o l u t i o n MS are shown. The data were obtained at a r e s o l v i n g power of about 40,000.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16.

LUMPKIN AND ACZEL

Characterization

of Coal

Products

221

Table V

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

Mass

Formula

General Formula

Intensity

Possible Structure

254.0764

C H SO

230

254.1306

C

17 18°2

H

822

C

n 2n-16°2

254.1671

C

18 22°

H

511

C

n 2n-14°

381.1517

C

2 9

H

1 9

N

337

C

n 2n-39

381.1729

C

2 6

H

2 3

N0

219

C

n 2n-29 °2

381.2092

C H NO

363

C

n 2n-27

381.2456

C

267

C

n 2n-25

394.1357

C

30 18°

H

110

C

n 2n-42°

394.1569

C

27 22°3

H

225

C

n 2n-32°3

394.1933

C

28 26°2

H

275

C

n 2n-30°2

C

29 30°

H

507

C

n 2n-28°

394.2295

III.

1 6

1 4

27

2 8

27

H

3 1

N

2

C H S0 η 2n-18 0

1 Q

H

H

H

H

H

N

N O

N

H

H

H

H

2

C^-Dihydroxyfluorene C^-Hydroxyacenaphthene C^-Dibenzoperylenide

N

H

C -Hydroxythiophenoacenaphthene

C^-Dihydroxybenzochrysenide C^-Hydroxydibenzcarbazole Cg-Chloranthridine C ~Hydroxybenz ocoronene 2

C^-Trihydroxybenzoperylene C^-Dihydroxybenzochrysene C^-Hydroxybenzopyrene

Conclusions

The n a t i o n a l need to develop l i q u i d f u e l s from c o a l to augment d i m i n i s h i n g petroleum f u e l s i s a challenge to the c o a l chemist. A n a l y t i c a l c h a r a c t e r i z a t i o n of these c o a l l i q u i d s i s a challenge to the a n a l y t i c a l chemist. We b e l i e v e that mass spec­ trometry, both low r e s o l u t i o n and h i g h r e s o l u t i o n , p l a y s an important r o l e i n responding to t h i s c h a l l e n g e , and have given examples of the a p p l i c a t i o n of the technique to v a r i o u s c o a l product samples. More d e t a i l e d i n f o r m a t i o n on the use of high r e s o l u t i o n mass spectrometry to analyze hetero-compounds i n c o a l e x t r a c t s and l i q u e f a c t i o n products i s given i n our paper i n the "Symposium on R e f i n i n g of Coal and Shale L i q u i d s , " D i v i s i o n of Petroleum Chemistry, N a t i o n a l ACS meeting, Chicago, 1977.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

222

ORGANIC CHEMISTRY OF COAL

Literature Cited (1) (2) (3) (4) (5)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch016

(6) (7) (8)

(9)

(10)

(11) (12) (13) (14)

(15)

Aczel, T., Foster, J. Q., and Karchmer, J. Η. Paper presented at the 157th National Meeting of the American Chemical Society, Minneapolis, Minnesota, April 1969. Aczel, T., Reviews of Analytical Chemistry, 1, 226 (1971). Sharkey, A. G., Schultz, Janet, Friedel, R. Α., Fuel, 38, 315 (1959). Lumpkin, Η. E. and Johnson, Β. H., Anal. Chem., 26, 1719 (1954). O'Neal, M. J., Jr. and Weir, T. P., Jr., Anal. Chem., 23, 830 (1951). Aczel, T., Allan, D. E., Harding, J. H., and Knipp, Ε. Α., Anal. Chem., 42, 341 (1970). Johnson, Β. H. and Aczel, T., Anal. Chem., 39, 682 (1967). Aczel, T. and Lumpkin, H. E., "MS Analysis of Coal Lique­ faction Products," presented at 23rd Annual Conference on Mass Spectrometry and Allied Topics, Houston, Texas, May 25, 1975. Aczel, T. and Lumpkin, H. E., "Mass Spectral Characteriza­ tion of Heavy Coal Liquefaction Products," presented at 24th Annual Conference on Mass Spectrometry and Allied Topics, San Diego, California, May 9, 1976. Aczel, T., Williams, R. B., Pancirov, R. J., and Karchmer, J. H., "Chemical Properties of Synthoil Products and Feeds," Report prepared for U.S. Energy Research and Development Administration, FE8007, 1977. Barbat, W. N., American Association Petroleum Geologists Bulletin, 51, 1255 (1967). Bendoraitis, T. G., Brown, B. L., and Hepner, L. S., Anal. Chem., 34, 49 (1962). Lumpkin, H. E., Anal. Chem., 36, 2399 (1964). Lumpkin, H. E., Wolstenholme, W. Α., Elliott, R. Μ., Evans, S., and Hazelby, D., "The Application of Ultra High Resolution Dynamic Scanning to the Analysis of Sulfur Containing Petrochemicals," presented at 23rd Annual Conference on Mass Spectrometry and Allied Topics, Houston, Texas, May 25, 1975. Aczel, T. and Lumpkin, Η. E., "Simulated Distillation by High Resolution-Low Voltage Mass Spectrometry," presented at 18th Annual Conference on Mass Spectrometry and Allied Topics, San Francisco, California, June 14, 1970.

RECEIVED February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

17 Field Ionization and Field Desorption Mass Spectrometry Applied to Coal Research G . A . ST. J O H N , S. E. B U T T R I L L ,

JR., and M . A N B A R

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

Stanford Research Institute, Mass Spectrometry Research Center, Menlo Park, C A 94025

Mass spectrometry offers a unique way to characterize coal liquefaction products. Molecular weight profiles of such complex mixtures of organic materials may be considered as the first step in the understanding of their nature in molecular terms. Molecular weight profiles may be produced by nonfragmenting mass spectrometry, which almost exclusively yields molecular ions. Field ionization produces molecular ions from most organic compounds (1). When a complex mixture is analyzed by this mass spectrometric technique, we obtain a single peak for each constituent or for a groups of constituents that shares the same nominal molecular weight. By repeated multiscanning, we can obtain a quantitative molecular weight profile of complex mixtures (2). The detailed molecular weight profiles attainable by field ionization mass spectrometry are much more informative than molecular weight profiles obtained by gel permeation chromatography (GPC). Moreover, GPC is subject to artifacts caused by associations of solutes or by solute-solvent complex formations. The average molecular weight profiles obtained by vapor phase osmosis (VPO) contain minimal chemical information and are useful mainly in conjunction with prior chromatographic separation. The cost per mass spectrometric analysis is higher than by these two techniques, but the information obtained on each individual constituent or group of constituents would cost much more i f obtained separately by other techniques. The advantage of the mass spectrometric technique is its universality; for the same sample, the same molecular weight profile will be obtained by different investigators using different mass spectrometers. Low energy electron impact ionization, which induces relatively l i t t l e fragmentation, has been proposed as an appropriate alternative technique for the analysis of complex organic mixtures (3,4) including fuels (5). However, an excellent systematic study by Scheppele ejt al (6), has shown that field ionization is by far superior for this purpose. This 0-8412-0427-6/78/47-071-223$05.00/0 © 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

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recent study has shown that the r e l a t i v e i o n i z a t i o n e f f i c i e n c i e s by f i e l d i o n i z a t i o n of many d i f f e r e n t c l a s s e s of organic com­ pounds are very s i m i l a r , ranging only over a f a c t o r of two. This can be compared with a range of over an order of magnitude for low energy e l e c t r o n impact on the same s u b s t r a t e s . Moreover, i t has shown (6) that once c o r r e c t e d f o r the small d i f f e r e n c e s i n i o n i z a t i o n e f f i c i e n c i e s , which can be programmed and c a l ­ c u l a t e d f o r known homologous s e r i e s , the a n a l y s i s of complex mixtures, l i k e f u e l s , can produce q u a n t i t a t i v e r e s u l t s with a s i g n i f i c a n t l y lower v a r i a n c e than o b t a i n a b l e with low energy e l e c t r o n impact, f o l l o w i n g an i d e n t i c a l computational c o r r e c t i o n . Without such a c o r r e c t i o n , when d e a l i n g with unknown c o n s t i t u e n t s , f i e l d i o n i z a t i o n i s by f a r a s u p e r i o r technique f o r o b t a i n i n g s e m i q u a n t i t a t i v e i n f o r m a t i o n on the composition of h i g h l y com­ plex mixture. F i e l d i o n i z a t i o n i s f a c i l i t a t e d by the high f i e l d gradient that can be produced with very high curvatures. A cathode with a r a d i u s of curvature of about 0.1 μ r e q u i r e s l e s s than 1000 V to produce f i e l d i o n i z a t i o n . Such a c o n f i g u r a t i o n i s r e a d i l y a t t a i n a b l e i n a r e p r o d u c i b l e manner by the a p p r o p r i a t e t e c h ­ nology. At SRI, we have developed a novel f i e l d i o n i z a t i o n source, the p r e a c t i v a t e d f o i l s l i t type source (7). T h i s source i s s u p e r i o r to the now c l a s s i c a l SRI m u l t i p o i n t source (2 8) because of i t s lower s e n s i t i v i t y to d e a c t i v a t i o n i n the presence of oxygen-, s u l f u r - , or halogen-carbonaceous d e n d r i t e s are deposited from p y r i d i n e vapor a t high temperature under a high electrostatic field (2). The mass analyzer used by us f o r multicomponent a n a l y s i s i s a 60° s e c t o r , 25 cm instrument and has been described before (£) . The temperature of the sample can be c o n t r o l l e d inde­ pendently of the temperature of the source. The temperature of the source i s maintained constant and higher than the maximum temperature the sample i s subjected t o ; t h i s prevents memory e f f e c t s and r e s u l t s i n more c o n t r o l l e d i o n i z a t i o n c o n d i t i o n s . This i o n i z a t i o n source, which may be operated up to 400°C, may thus handle thermally s t a b l e compounds of very low v o l a t i l i t y P

(9). The i o n i z a t i o n e f f i c i e n c y of our sources i s 5 χ 10~* or higher, (10) which i s comparable to that of advanced e l e c t r o n impact sources. However, owing to the r e l a t i v e l y l a r g e area of our i o n i z a t i o n source, the high energy of the ions produced, and t h e i r divergence, l e s s than 10Γ * of the ions produced are detected a f t e r mass s e p a r a t i o n . The o v e r a l l e f f i c i e n c y of the present generation of f i e l d i o n i z a t i o n mass spectrometers i s about 2 χ 10~~ ions/molecule f o r instruments w i t h a magnetic sector analyzer ànd a r e s o l u t i o n of 700. Since most organic compounds have s i m i l a r f i e l d i o n i z a t i o n e f f i c i e n c i e s (6), the molecular weight p r o f i l e obtained by i n t e g r a t i n g a l l the s p e c t r a while evaporating the sample to completion t r u l y represents the composition of the mixture. A 1

8

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number of examples of molecular weight p r o f i l e s of d i f f e r e n t c o a l l i q u e f a c t i o n products have been presented elsewhere (9)· These s p e c t r a were obtained on our mass s p e c t r o m e t r i c system before i t was i n t e r f a c e d with a PDP-11 computer. In t h i s mode of o p e r a t i o n , the mass range of i n t e r e s t was scanned repeatedly and synchronized with a 4096-multichannel analyzer o p e r a t i n g i n the m u l t i s c a l e r mode ( 8 ) . The instrument i n t e g r a t e s the s p e c t r a produced i n such scan i n t o a composite mass spectrum. The i n t e g r a t i o n over time i s necessary because the sample i s evaporated slowly and the composition of the vapor phase changes because of the wide range of v o l a t i l i t y of the d i f f e r e n t com­ ponents. T h i s f i e l d i o n i z a t i o n mass s p e c t r o m e t r i c system thus f a c i l i t a t e s the q u a n t i t a t i v e a n a l y s i s of molecular weight pro­ f i l e s of mixtures that may c o n t a i n c o n s t i t u e n t s v a r y i n g i n t h e i r vapor pressure by many orders of magnitude (estimated range, Ι Ο ) over a mass range up to 2000 amu with a r e s o l u t i o n of Μ/ΔΜ = 800.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

1 0

Computer C o n t r o l l e d F I Multicomponent A n a l y s i s The p u b l i s h e d f i e l d i o n i z a t i o n s p e c t r a of c o a l l i q u e f a c t i o n products (9) a r e j u s t the f i r s t step i n the f u l l u t i l i z a t i o n of f i e l d i o n i z a t i o n mass s p e c t r o m e t r i c multicomponent a n a l y s i s . These a r e chart r e c o r d i n g s from a 4096-channel analyzer and, although the i n f o r m a t i o n i n each channel i s d i g i t i z e d , these s p e c t r a give us only a means of v i s u a l i n s p e c t i o n of the gross f e a t u r e of the s p e c t r a . Accurate mass assignment and the i n t e g r a t e d i o n counts under each peak are l a c k i n g , and these a r e necessary f o r any d e t a i l e d q u a n t i t a t i v e i n t e r p r e t a t i o n of these complex s p e c t r a . We would a l s o l i k e to know the " h i s t o r y " of each p e a k — t h e a c t u a l r a t e of accumulation of the ions of a given nominal molecular weight as a f u n c t i o n of time and temperature of the analyzed sample. This i n f o r m a t i o n i s necessary f o r e s t i m a t i n g the number of m a t e r i a l s of the same nominal molecular weight that c o n t r i b u t e d to a given peak. Moreover, from the tem­ perature p r o f i l e of a given peak, i t may be p o s s i b l e to deduce whether some of the c o n t r i b u t i n g ions o r i g i n a t e from a chemical process (e.g., p y r o l y s i s , dehydrogenation) that took p l a c e i n the sample while the sample probe was being heated. Obtaining, f o r i n s t a n c e , a m a t e r i a l with a molecular weight of only 150 when the probe temperature reaches 300°C suggests that i t may be a secondary p y r o l y t i c decomposition product. The temperature p r o f i l e a n a l y s i s may help us to d i s t i n g u i s h between these two p o s s i b i l i t i e s and even determine the a c t i v a t i o n energy f o r the appearance of the given s p e c i e s . To achieve these g o a l s , we have i n t e r f a c e d our mass spec­ t r o m e t r i c system w i t h a PDP 11/10 dedicated computer ( F i g . 1 ) . The computer c o n t r o l s the magnet scan of the mass spectrometer by means of the 1 2 - b i t d i g i t a l - t o - a n a l o g converter (DAC). The

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data a c q u i s i t i o n program increments the input to the DAC at p r e c i s e l y c o n t r o l l e d time i n t e r v a l s so that each channel i s r e c e i v i n g ions counted f o r e x a c t l y the same amount of time. At the end of each time i n t e r v a l , the computer causes the i o n counts accumulated by the 10-MHz counter to be t r a n s f e r r e d to the 12-bit b u f f e r r e g i s t e r . The counter i s c l e a r e d and r e s t a r t e d i n l e s s than one microsecond, so the i n t e r f a c e has a n e g l i g i b l e dead-time and no i o n counts are missed. The DAC input i s incremented by one u n i t , and the i o n count i n the b u f f e r i s t r a n s f e r r e d to the computer and added to the previous i o n counts f o r that channel. The time spent at each channel, or i n other words, the scan r a t e of the mass spectrometer, i s v a r i a b l e and i s c o n t r o l l e d by the operator through the data a c q u i s i t i o n software. A c t u a l time i n t e r v a l s are measured w i t h i n the computer by a programmable c l o c k based on a very s t a b l e quartz c r y s t a l o s c i l l a t o r . The output from the DAC i s a l i n e a r v o l t a g e ramp, s i n c e each of the 4096 p o s s i b l e channels i s a c t i v e f o r an equal amount of time. Since the mass of the ions focused on the mass spectrometer's d e t e c t o r v a r i e s as the square root of the magnet current, the magnet scan c o n t r o l u n i t i s used to convert the l i n e a r v o l t a g e ramp i n t o a s i g n a l that d r i v e s the magnet power supply to produce a l i n e a r mass scan. The 12-bit a n a l o g - t o - d i g i t a l converter (ADC) i s connected to a temperature programmer f o r the s o l i d s probe. At the end of each mass spectrometer scan, the temperature of the probe i s recorded f o r l a t e r use i n the p r i n t e d r e p o r t s or data a n a l y s i s . Since the temperature programmer i s d i g i t a l l y d r i v e n , a given temperature program can be very p r e c i s e l y reproduced to allow meaningful comparisons between samples. Our experience i n d i c a t e s that most pure compounds are v o l a t i l i z e d over a narrow temperature range of 10-30°C. Thus, separate peaks w i l l be observed i n the temperature p r o f i l e of a s i n g l e mass i f there i s more than one component of the sample with that p a r t i c u l a r molecular weight. I t i s p o s s i b l e to d i s t i n g u i s h between genuine low molecular weight components of a sample and those r e s u l t i n g from the thermal decomposition of much l a r g e r molecules because these two d i f f e r e n t types of species appear at very d i f f e r e n t temperat u r e s . Our experiments show no i n d i c a t i o n of s i g n i f i c a n t p y r o l y s i s of c o a l l i q u e f a c t i o n products or of crude o i l s . The r e p o r t program produces r e p o r t s l i s t i n g the masses and t o t a l i o n counts f o r each peak i n the spectrum. Two d i f f e r e n t formats are a v a i l a b l e : one i s a simple t a b l e of the peak mass and i n t e n s i t y , and the other i s the same i n f o r m a t i o n arranged i n a f i x e d format with 14 masses i n each row. The advantage of t h i s second format i s that homologs are a l l l i s t e d i n the same column, making i t easy to p i c k out groups of peaks that may have s i m i l a r chemical s t r u c t u r e s . The p l o t t i n g program produces simple bar graphs of the mass spectra on the X-Y r e c o r d e r . F u l l - s c a l e i n t e n s i t y i s a r b i t r a r i l y chosen as 50 and the e n t i r e spectrum i s a u t o m a t i c a l l y

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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PDP-11/10 COMPUTER

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

12-BI Τ

12-BIT A D C

DAC

S C A N C(D N T R O L UIS IT

12-BIT BUFFER

MASS SPECTROMETER

10 M H z COUNTER

Figure 1.

Mass spectrometer-computer

16 A N A L O G INPUT CHANNELS

SOLID SAMPLE PROBE T E M P E R A T U R E PROGRAMMER

interface

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ORGANIC CHEMISTRY OF COAL

FRACIS.000 SF = 3 3 4-3 7°C

FRACIS.001 SF = 4 37-36°C

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

JL

FRACIS.002 SF = 3 37-3 6°C

FRACIS.003 SF = 4 36-5 0°C

JL

FRACIS.004 SF = 5 51-57°C

FRACIS.005 SF = 4 59-68°C

FRACIS.006 SF = 4 6 9-8 0°C

J 100

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I

I 500

I

L 700

100

300

500

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Figure 3A. Fractions 1 and 2 from hydrogen-coal product 177-57-49 by column chromatography (source: Arco)

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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ST. JOHN ET AL.

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FRACIS.014 SF = 2 165-179°C

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FRACIS.019 SF = 2 250-265°C FRACIS.020 SF = 1 267-285°C

1

FRACIS.015 SF = 2 180-197°C

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

FRACIS.021 SF = 1 286-305

1 FRACIS.022 SF = 1 305-324°C

.jLiiJHHHHhii FRACIS.023 SF = 1

FRACIS.024 SF = 1 325-324°C FRACIS.025 SF = 1 325-325°C J 100

300

500

700

100

I 300

L 500

700

F R A C T I O N S 1-2 BASIC C O M P O U N D S H C O A L P R O D U C T 19531 S U M O F FRACIS.000 — .025 FRACIS.026 SF = 22 34-325°C 94% V O L A T I L I Z E D 100

300

500

700

Figure 3B. Fractions 1 and 2 from hydrogen-coal product 177-57-49 by column chromatography (source: Arco)

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s c a l e d , i f necessary, by d i v i d i n g a l l peak i n t e n s i t i e s by an i n t e g e r . F i g u r e 2 i s an example of a spectrum p l o t obtained i n t h i s manner. These s p e c t r a are e v i d e n t l y s u p e r i o r i n q u a l i t y to those obtained with the multichennel analyzers ( 9 ) . A d d i t i o n a l programs are a v a i l a b l e f o r performing simple but u s e f u l data handling t a s k s . These i n c l u d e programs f o r l i s t i n g on the t e r m i n a l the i o n counts i n each channel of a raw data f i l e and a program f o r summing the data i n s e v e r a l f i l e s i n t o a composition spectrum. The l a t t e r program i s u s e f u l f o r o b t a i n ­ ing the molecular weight p r o f i l e of a complex multicomponent mixture by adding together a l l the s p e c t r a obtained from a sample. A d d i t i o n a l examples of the types of i n f o r m a t i o n c u r r e n t l y a v a i l a b l e from the combination of FIMS and the PDP 11/10 com­ puter are shown i n F i g s . 3a and 3b. The sample was f r a c t i o n s 1 and 2 of b a s i c compounds from an Η-coal product and was pro­ vided to us by the A t l a n t i c R i c h f i e l d Company. The e v o l u t i o n of t h i s spectrum as a f u n c t i o n of temperature i s presented i n F i g s . 3a and 3b. This f i g u r e presents the p l o t t e d s p e c t r a i n t e g r a t e d w i t h i n the d i f f e r e n t temperature ranges during the evaporation of a s i n g l e sample. The f i r s t three s p e c t r a i n F i g u r e 3a show v o l a t i l e com­ ponents of the sample that came o f f as soon as the sample was introduced i n t o the mass spectrometer. When the s i g n a l produced by these v o l a t i l e m a t e r i a l s began to decrease, the operator s t a r t e d the temperature program, heating the sample at about 2°C per minute. The heating r a t e was increased twice during the run to maintain a reasonably high s i g n a l as the l e s s v o l a t i l e com­ ponents were being analyzed. F i n a l l y , three s p e c t r a were recorded a t 325°C, (Figure 3b) which was the f i n a l probe tem­ perature f o r t h i s sample. Weighing the sample before and a f t e r a n a l y s i s showed that 94% of t h i s m a t e r i a l was v o l a t i l i z e d . These r e s u l t s i l l u s t r a t e the v a s t amount of i n f o r m a t i o n to be obtained by combining chemical separations with nonfragmenting FIMS i n the a n a l y s i s of c o a l l i q u e f a c t i o n products. F i g u r e 4 i s an example of a spectrum of a crude o i l analyzed by computer i n the same manner as the samples presented i n F i g u r e s 2 and 3. The only d i f f e r e n c e was that the crude o i l sample was "weathered" i n the probe at room temperature to remove the most v o l a t i l e c o n s t i t u e n t s . The same sample was analyzed 5 times to assess the v a r i a n c e of the a n a l y t i c a l pro­ cedure. F i g u r e 5 presents the standard d e v i a t i o n of each of the mass peaks as a f u n c t i o n of molecular weight. One can see here that the c o n s t i t u e n t s below 250 amu have a high v a r i a n c e due to i r r e p r o d u c i b l e preevaporation ("weathering") but i n the mass range 250 to 550, the standard d e v i a t i o n i s i n the range of 3 to 6%, which i s very s a t i s f a c t o r y f o r such a complex a n a l y s i s . I t should be noted that even the most abundant c o n s t i t u e n t s i n our complex mixture amount to j u s t about 0.6% of the t o t a l . At higher molecular weights, there i s an i n c r e a s e i n the v a r i a n c e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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predominantly because of the lower abundance of these constitu*ents and p o s s i b l y a l s o because of some i r r e p r o d u c i b l e p y r o l y s i s or p o l y m e r i z a t i o n of such minor components. The e f f e c t of abundance on the v a r i a b i l i t y of the i n d i v i d u a l c o n s t i t u e n t s can be seen i n F i g u r e 6 which a l s o presents the t h e o r e t i c a l lower l i m i t of v a r i a n c e due to s t a t i s t i c a l f l u c t u a t i o n s of the ions counted. The two l i n e s "200" and "800" designate the t h e o r e t i c a l l i m i t f o r these two extreme cases of molecular weights. The l i m i t s are d i f f e r e n t because of the d i f f e r e n c e i n the monitoring time per amu during the magnetic scanning. The a c t u a l v a r i a n c e i s about 2 to 3 times higher than the t h e o r e t i c a l lower l i m i t . This i s f a i r l y s a t i s f a c t o r y i n view of the complexity of the sample and the a n a l y t i c a l procedure.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

F i e l d Desorption Experiments Two years ago, we developed at SRI a novel type of f i e l d desorbing source that used a broken metal t i p (11). We have a l s o shown that i o n i c and other p o l a r substances f i e l d desorb more r e a d i l y when d i s s o l v e d i n an a p p r o p r i a t e n o n v o l a t i l e matrix. Our p r e l i m i n a r y t e s t s on low molecular weight hydrocarbon polymers were h i g h l y encouraging (9) . Recently, we have extended our experiments, using broken g r a p h i t e rods and bundles of g r a p h i t e rods and bundles of g r a p h i t e f i b e r s as f i e l d desorbing sources, with even greater success. We a p p l i e d these sources to the a n a l y s i s of asphaltenes. F i g u r e 7 shows a f i e l d desorption spectrum (obtained on a multichannel analyzer) of the asphaltenes of SRC produced from I l l i n o i s No. 6 c o a l . The spectrum was obtained from a g r a p h i t e f i b e r f i e l d desorbing bundle at 205°C. An example of a computer handled FD spectrum of ashphaltenes (produced from Kentucky c o a l ) i s presented i n F i g . 8. In order to provide a d i r e c t comparison of the c h a r a c t e r i s t i c s of FD and FI s p e c t r a c u r r e n t l y a v a i l a b l e , F i g u r e s 8-12 show the raw data as i t was acquired by the computer, r a t h e r than the normal bar-graphs. The r e s o l u t i o n of the FD spectrum i s i n f e r i o r to that obtained by F I of the same sample ( F i g . 9), probably due to the wider energy spread of the f i e l d desorbed i o n s , as w e l l as to the f l u c t u a t i n g nature of the FD i o n beam. Note, however, the s i g n i f i c a n t mass peaks at about 395 amu i n the FD spectrum which are absent i n the FI spectrum. T h i s f e a t u r e appears again at somewhat higher temperatures (157-158°C) as shown i n F i g u r e 10. F i g u r e 11 a-d present FD spectra i n the temperature range 160 to 187°C. Comparison of these s p e c t r a with the FI spectrum over the same temperature range ( F i g . 9) and over a higher temperature range ( F i g . 12) shows that under FD, one i o n i z e s the same c o n s t i t u e n t s , or other compounds of comparable molecular weight, a t s i g n i f i c a n t l y lower temperatures. The r e p r o d u c i b i l i t y and r e s o l u t i o n obtained by FD are, however, major l i m i t i n g f a c t o r s i n the a p p l i c a t i o n of t h i s technique as a q u a n t i t a t i v e

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Figure 7.

Asphaltenes from Illinois No. 6 coal, SRC product, Arco sample No. 9634, graphite fibers source—FDMS

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FD 132° - 154°C 100 SCANS X 1

100

200

Figure 8.

300

400

Field desorption mass spectrum of Kentucky

KENTUCKY ASPHALTENES

100

Figure 9.

200

Field ionization

500

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SRC asphaltenes,

700

132°-154°C

FI SPECTRA 133° - 188° 40 SCANS

Τ " 300

400

mass spectrum of Kentucky

600

SRC asphaltenes,

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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133°-188°C

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FD 157° - 158° 30 S C A N S X 1

1

1

1

!

1

1

100

200

300

400

500

600

Figure 10.

Field desorption of mass spectrum of Kentucky SRC asphaltenes,

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1 700

157°-158°C

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

ORGANIC CHEMISTRY OF COA

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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SPECTRA

189° -

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

230

100

Figure

200

12.

300

400

500

Field ionization mass spectrum of Kentucky 350°C

237

350°C

SCANS

600

SRC asphaltenes,

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

189°-

ORGANIC CHEMISTRY OF COAL

238

way to characterize coal products. Some of these limitations could be overcome by focal plane simultaneous ion collection techniques (e.g., photoplate mass spectrography).

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

Summary We have shown that mass spectrometric multicomponent analysis techniques are ideal for the characterization of coal liquefaction and fuel products. These include the capability of determining molecular weight profiles up to 1000 amu with unit amu resolution and the ability to obtain and record molecular weight profiles as a function of sample temperature during a temperature programmed evaporation of the analyzed sample. Combined with appropriate liquid chromatographic separation techniques or certain fast and quantitative derivatization pro­ cedures to separate coal liquefaction products into families of compounds, advanced FIMS offers an unprecedented, precise and meaningful analytical methodology for the characterization of coal products. The field ionization technique described in this paper is not yet perfect, and i t requires some further development in the areas of instrumentation, sample pretreatment, and data handling. However, there is sufficient evidence that this technique can provide the basis for one of the most comprehensive analytical methodologies ever available to coal research. Literature Cited 1. 2. 3. 4. 5.

6.

Beckey, H. D., Field Ionization Mass Spectrometry, Pergamon Press, Elmsford, N.Y., 1971. Anbar, M. and Aberth, W. H., "Field Ionization Mass Spectrometry--A New Tool for the Analytical Chemist," Anal. Chem. 46, 59A (1974). Lumpkin, H. E. and Aczel, T., "Low Voltage Sensitivities of Aromatic Hydrocarbons," Anal. Chem. 36, 181 (1964). Schultz, J. L., Sharkey, Jr., A. G. and Brown, R. Α., "Determination of Mass Spectrometric Sensitivity Data for Hydroaromatic Compounds," Anal. Chem. 44, 1486 (1972). Aczel, T. and Lumpkin, Η. E., "MS Analysis of Coal Liquefaction Products," 23rd Annual Conference on Mass Spectrometry and Allied Topics, Houston, Texas (1975), p. 228. Scheppele, S. E., Grizzle, P. L., Greenwood, G. J., Marriott, T. D. and Perreira, Ν. B., "Determination of Field Ionization Relative Sensitivities for the Analysis of Coal-Derived Liquids and Their Correlation with Low Voltage Electron Impact Relative Sensitivities," Anal. Chem. 48, 2105 (1976).

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

17.

ST. JOHN ET AL.

Field

Ionization

and Field

Desorption

MS

239

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch017

7. Cross, R. H., Brown, H. L. and Anbar, Μ., "Preactivated Highly Efficient Linear Field Ionization Source," Rev. Scien. Instrum. 47, 1270 (1976). 8. Scolnick, M. E., Aberth, W. H. and Anbar, Μ., "An Integrat­ ing Multiscanning Field Ionization Mass Spectrometer," Int. J. Mass Spectrom. Ion Phys. 17, 139 (1975). 9. Anbar, M. and St. John, G. Α., "Characterization of Coal Liquefaction Products by Molecular Weight Profiles Produced by Field Ionization Mass Spectrometry," Fuel, in press (1977). 10. Brown, H. L., Cross, R. H. and Anbar, Μ., "Characterization of Multipoint Field Ionization Sources," Int. J. Mass Spectrom. Ion Phys. 23, 63 (1977). 11. Anbar, M. and St. John, G. Α., "FI-FD Source for Nonfragmenting Mass Spectrometry," Anal. Chem. 48, 198 (1976). RECEIVED February 10, 1978

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

18 Heteroatom Species in Coal Liquefaction Products F. K. SCHWEIGHARDT, C. M . WHITE, S. FRIEDMAN, and J. L. SHULTZ

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

U.S. Department of Energy, Pittsburgh Energy Research Center, 4800 Forbes Avenue, Pittsburgh, PA 15213

An assessment of the nitrogen and oxygen heteroatom species in coal-derived products is a complex yet important analytical problem in fuel chemistry. Principally, this is because the system is a multifarious molecular mixture that does not easily lend itself to direct analysis of any one component or functional group. Albeit this problem is not new, the characterization of these heteroatoms is of immediate importance to further processing of these fuels. Methods and techniques used to rapidly isolate and/or characterize both nitrogen and oxygen heteromolecular species are described. Utilization is made of solvent separations, functional group type separation, chemical derivatization, HCl salt formation and the use of chromatographic and spectrometric analytical methods to quantitate results. Specifically, the kind and distribution of nitrogen and oxygen heteromolecules in a coal liquefaction product and in a recycle solvent used in solvent refined coal (SRC) processing were determined. The coal liquefaction product was first solvent separated into oils, asphaltenes, preasphaltenes and ash, while low boiling oils (light oils) trapped from knock-out tanks and the SRC recycle solvent were treated directly. Nitrogen bases were complexed as HCl adducts or separated on ionexchange resins. Hydroxyl-containing species from the separated fractions were quantitated by infrared spectroscopy or by formation of a trimethylsilyl ether (TMS) and subsequent analysis by H NMR and mass spectrometry. Hydroxyl species were also isolated on ion-exchange resins or by selective gradient elution from silica gel. EXPERIMENTAL Solvent Separation Coal liquefaction products were solvent separated (1) by 0-8412-0427-6/78/47-071-240$05.00/0 This chapter not subject to U.S. copyright. Published 1978 American Chemical Society In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

18.

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Species

241

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

f i r s t f r e e z i n g the c o a l l i q u i d s i n l i q u i d n i t r o g e n and g r i n d i n g them to f i n e p a r t i c l e s . T h i s f r o z e n o i l can be e a s i l y t r a n s ­ f e r r e d to a s t a i n l e s s s t e e l c e n t r i f u g e tube. P e s t i c i d e grade solvents were then used to s o l u b i l i z e s p e c i f i c f r a c t i o n s — o i l s (pentane), asphaltenes (benzene), preasphaltenes (2) ( t e t r a h y drofuran) and c o a l - d e r i v e d ash ( i n s o l u b l e i n a l l solvents used). By s t a r t i n g with a 3-4 gram sample, one (1) l i t e r of each solvent i n four or f i v e 200 ml p o r t i o n s was u s u a l l y s u f f i c i e n t to e x t r a c t tlje s o l u b l e s . Insolubles were removed by c e n t r i f u g a t i o n at 10 rpm at 6°C f o r 10 minutes. Solvents were removed by n i t r o g e n f l u s h on a Rotovap using a water bath (65-85°C). Asphaltenes were treated d i f f e r e n t l y at the f i n a l solvent r e ­ moval step; a 20 ml s o l u t i o n of benzene/asphaltenes was s w i r l e d i n a f l a s k and flaslji frozen i n l i q u i d n i t r o g e n , and the solvent was sublimed at 10 -10 t o r r f o r 2-3 hours. HC1

Treatment

The o b j e c t i v e of t h i s procedure was to separate and/or concentrate both n i t r o g e n heteromolecules and hydroxyl-containing species from c o a l - d e r i v e d m a t e r i a l (3). Gaseous HC1 was bubbled through a benzene or pentane s o l u t i o n of the c o a l product to form an i n s o l u b l e HC1 adduct with molecules c o n t a i n i n g a b a s i c n i t r o g e n atom. The adduct, a f t e r being washed f r e e of other components, was back t i t r a t e d with d i l u t e NaOH s o l u t i o n to f r e e the base n i t r o g e n i n t o an organic phase, u s u a l l y d i e t h y l ether, methylene c h l o r i d e or benzene. The two f r a c t i o n s recovered c o n t a i n a c i d / n e u t r a l and n i t r o g e n base m a t e r i a l , r e s p e c t i v e l y . Hydroxyl S i l y l a t i o n O i l s , asphaltenes and preasphaltenes were treated with hexamethlydisilazane (HMDS) to form a t r i m e t h y l s i l y l ether (TMS) of a c t i v e hydroxyl groups (4,5). A 50 mg sample of c o a l - d e r i v e d product was d i s s o l v e d i n 25 ml of benzene containing 50 μΐ of p y r i d i n e - d . To t h i s s o l u t i o n 500 μΐ each of HMDS and N - t r i methylsilyldimethylamine were added. This mixture was main­ tained as a closed system except f o r a small Bunsen v a l v e and m i l d l y r e f l u x e d f o r one hour with o c c a s i o n a l s w i r l i n g of the f l a s k . A f t e r the r e a c t i o n was completed, solvents and unreacted reagents were removed under n i t r o g e n f l u s h on a Rotovap and f i n a l l y f r e e z e d r i e d from 5 ml of benzene f o r 30 minutes. A p o r t i o n of the f i n a l product was checked by i n f r a r e d s p e c t r o s ­ copy (IR) f o r disappearance of the OH band at 3590 cm ( 6 ) . The remaining sample was d i s s o l v e d i n benzene-d. and i t s proton NMR spectrum taken and i n t e g r a t e d . From the r e l a t i v e areas of the peaks i n the proton NMR spectrum, a percent H as OH was c a l c u l a t e d (Equation 1) ( 7 ) .

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

242

ORGANIC CHEMISTRY OF COAL

TMS Area. 9 TMS

Area 9

)

+

χ

10

2

=

% H as OH

(1)

(Remaining Proton Area)

From an elemental a n a l y s i s of the o r i g i n a l sample, one can c a l c u l a t e the weight percent oxygen as OH on a moisture and ash f r e e b a s i s (MAF).

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

Combined Gas Chromatography-Mass Spectrometry (GCMS) The combined GCMg analyses were performed u s i n g a Dupont 490 mass spectrometer i n t e r f a c e d to a V a r i a n 1700 Series gas chromatograph, equipped with an 80:20 g l a s s s p l i t t e r and a flame i o n i z a t i o n d e t e c t o r . The spectrometer was a l s o coupled to a Hewlett-Packard 2100A computer used f o r spectrometric data storage and r e d u c t i o n . The mass spectrometer was operated at a r e s o l u t i o n of 600 and an i o n i z i n g v o l t a g e of 70 eV. The i o n source, j e t separator and g l a s s l i n e from the chromatograph to the mass spectrometer were h e l d at 275°C. The chromatographic e f f l u e n t was continuously scanned at a r a t e of four seconds per decade by the mass spectrometer. The gas chromatographic separations were e f f e c t e d u s i n g a v a r i e t y of c o n d i t i o n s . The n i t r o g e n bases and a c i d f r a c t i o n s from the c o a l l i q u e f a c t i o n product were chromatographed on a 10 χ 1/4" OD g l a s s column packed with 100-120 mesh Supelcoport coated with 3% OV-17. Bases from the SRC product were chromato­ graphed on a 10' by 1/8" 0D g l a s s column packed w i t h 100-120 mesh Chromasorb-G coated w i t h 2% OV-17. Gas chromatographic s e p a r a t i o n of bases from the l i g h t o i l was achieved using a 10 χ 1/8" OD g l a s s column c o n t a i n i n g a c i d washed and s i l y l t r e a t e d 100-120 mesh Supelcoport coated with 3% Carbowax 20M. In each case the He flow r a t e was 30 cc/min and the analyses were per­ formed using a p p r o p r i a t e temperature programming c o n d i t i o n s . 1

1

Column Chromatographic Separation Coal-derived l i q u i d s , s o l u b l e i n pentane, were separated i n t o f i v e f r a c t i o n s : a c i d s , bases, n e u t r a l n i t r o g e n , s a t u r a t e hydrocarbons and aromatic hydrocarbons. Acids were i s o l a t e d using anion-exchange r e s i n s , bases with cation-exchange r e s i n s , and n e u t r a l n i t r o g e n by complexation with f e r r i c c h l o r i d e ad­ sorbed on Attapulgus c l a y . Those pentane s o l u b l e hydrocarbons remaining were separated on s i l i c a g e l to give the non-adsorbed saturates and the moderately r e t a i n e d aromatics. This method i s commonly r e f e r r e d to as the SARA technique (8). RESULTS AND

DISCUSSION

The c e n t r i f u g e d c o a l l i q u i d product (CLP) was

produced

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

18.

scHWEiGHARDT ET AL.

Heteroatom

243

Species

using I r e l a n d Mine, P i t t s b u r g h seam, West V i r g i n i a c o a l i n the 1/2 ton per day SYNTHOIL Process Development Unit (PDU) (9). Operating c o n d i t i o n s f o r t h i s experiment were 4000 p s i hydrogen pressure, 450°C and no added c a t a l y s t . The l i g h t o i l s were derived from a c a t a l y t i c experiment (Harshaw 0402T) using Homestead Mine, Kentucky c o a l , under 4000 p s i pressure and 450°C. The coal l i q u e f a c t i o n product was solvent separated by the method p r e v i o u s l y described to y i e l d the d i s t r i b u t i o n of f r a c t i o n s given i n Table I. F i g u r e 1 gives the atom weight percent d i s t r i b u t i o n of n i t r o g e n and oxygen i n the solvent separated f r a c t i o n s l i s t e d i n Table I . The pentane s o l u b l e o i l s were subsequently separated i n t o f i v e f r a c t i o n s using the SARA chromatographic scheme. Table II l i s t s the weight percents of the i n d i v i d u a l f r a c t i o n s . The asphaltenes were t r e a t e d with HC1 to form a c i d / n e u t r a l and base s u b f r a c t i o n s , 63 and 37 weight percent, r e s p e c t i v e l y . Table I.

Solvent Separation Weight Percent D i s t r i b u t i o n .

Solvent F r a c t i o n Oil Asphaltenes Preasphaltenes Ash Table I I .

Wt.

% of CLP 68.0 26 4 2

SARA Chromatography F r a c t i o n s , Weight Percent D i s t r i b u t i o n .

Chromatography F r a c t i o n Saturates Aromatics Acids Bases N e u t r a l Nitrogen Loss Total O i l

Wt.

% of

CLP

4.1 37.3 6.3 10.2 3.9 7.4 68.8

The a c i d and base f r a c t i o n s from the SARA s e p a r a t i o n of the o i l s were subjected to a n a l y s i s by combined GCMS and low v o l t a g e low r e s o l u t i o n mass spectrometry (LVLR). Figures 2 and 3 r e p r o duce the gas chromatograms of the base and a c i d f r a c t i o n s , r e s p e c t i v e l y . The oxygen c o n t a i n i n g species shown i n Figure 3 have been c l a s s i f i e d as a l k y l a t e d phenols, i n d a n o l s / t e t r a l i n o l s , phenylphenols, and cyclohexylphenols. Table I I I l i s t s the carbon number range and t e n t a t i v e compound type assignments f o r the n i t r o g e n heteromolecules i n the a c i d and base f r a c t i o n s as determined by LVLR mass spectrometry (10) . Table IV l i s t s the

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

244

ORGANIC CHEMISTRY OF COAL

Nitrogen

Figure 1.

Oxygen

Atom percent distribution of heteroatoms: (A) oils, (B) asphaltenes, (C) preasphaltenes, and (D) residue.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

0

I

250°

52 4

250°

499

250°

47.4

250°

44.9 250

42.4 250°

39.9 240°

37.4 230°

34.9 220° 210° 200° TEMPERATURE ,*C

32.4 29.9 27.4 TIME, minutes 190°

24.9 180°

22.4 170°

19.9 160°

17.4 150°

14.9

9.9

140° 130°

12 4

120°

7.4

110°

4.9

e

0 1 0 0 100°

24

I

55.5

250°

I

58.0

250°

250°

53.0

I

250°

50 5

I

I

250°

45.5

Figure 3.

250°

48.0

I

I

250°

I

240°

38.0

I

230°

35.5

I

220°

33.0

I

I

I

TEMPERATURE, t

190

e

25.5 TIME, minutes

28.0 210° 200°

30.5

I

e

180

23.0

I

e

170

20.5

I

e

160

18.0

ι

ι

13.0 150° 140°

15.5

Gas chromatogram of acid fraction from a coal liquefaction product

250°

43.0 40.5

I

130°

10.5

ι

120°

8.0

ι

ι

3.0 110° 100°

5.5

ι

Gas chromatogram of nitrogen-base fraction from a coal liquefaction product. Table IV identifies major components.

250°

250°

Figure 2.

54 9

57 4

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

100°

0

ι

1

^

t"

In Organic Chemistry of Coal; Larsen, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

- 5 - 7 - 9 -11 -13 -15 -17 -19 -21 -23 -25 -27 -29 -31 -33 -35 -37 -39

z#

Bases Typical Structural Nitrogen Analogs

Pyridines, Anilines Azaindans Dihydroquinolines, Indols Quinolines Phenylpyr i d ines Azafluorenes Acridines Benzo[ghi]azafluorenes Azapyrenes Benzacridines Benzo[ghi]azafluoranthenes Benzazapyrenes Dibenzacridines Azaanthanthrenes Dibenzazapyrenes Azacoronenes

— —

6-12 8-13 9-15 9-15 11-17 12-19 13-19 14-21 15-21 17-26 17-26 19-26 21-26 21-26 23-26 23-27

— —

— — — —

— — — — 12-20

—

20-29 22-29 22-29 24-29 26-29 28-29 28-30

—

Dibenzocarbazoles Naphthylcarbazoles Naphthobenzo[def]carbazoles Anthracenocarbazoles Anthranylcarbazoles Anthracenobenzo[def]carbazoles Dinaphthocarbazoles

Carbazoles Phenylindoles Benzo[def]carbazoles Benzocarbazoles Phenylcarbazoles

__

__

14-20 14-22 16-24 18-24

Acids Typical Structural Nitrogen Analogs

LRLV C# Range

Carbon Number D i s t r i b u t i o n f o r the Acid and Base F r a c t i o n s From SARA Chromatography Separation.

LRLV C# Range

Table I I I .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

Ο *1

I

18.

SCHWEIGHARDT ET AL.

Heteroatom

Species

Table IV. Compounds Found i n the Nitrogen Base F r a c t i o n of Figure 2.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0071.ch018

Peak Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Compound Solvent (Carbon D i s u l f i d e ) Phenol Cresol Cresol Tetrahydroquinoline Quinoline 6-Methyltetrahydroquinoline Methylquinoline Isoquinoline Methylquinoline Methylquinoline C -Quinoline C^-Quinoline Octahydro-N-3-Ring (Octahydroacridine) Methyloctahydro-N-3-Ring (Methyloctahydroacr Phenanthridine + A c r i d i n e Methylacridine Azapyrene Methylaza