Organic Chemistry of Coal - American Chemical Society

16 Characterization of Coal Products by Mass Spectrometry H. E. LUMPKIN and THOMAS ACZEL

Downloaded by UNIV OF ARIZONA on November 12, 2012 | http://pubs.acs.org 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

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 .


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




218

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


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 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



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


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.


16.

LUMPKIN AND ACZEL

Characterization

of Coal

Products

221

Table V


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.


222


Literature Cited (1) (2) (3) (4) (5) Downloaded by UNIV OF ARIZONA on November 12, 2012 | http://pubs.acs.org 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


Organic Chemistry of Coal - American Chemical Society

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