Organosulfur Constituents in Rasa Coal - ACS Symposium Series

Jun 29, 1990 - Curt M. White1, L. J. Douglas1, R. R. Anderson1, C. E. Schmidt1, and R. J. Gray2. 1 Pittsburgh Energy Technology Center, U.S. Departmen...
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Chapter 16

Organosulfur Constituents in Rasa Coal 1

1

1

1

Curt M . White , L. J . Douglas , R. R. Anderson , C. E. Schmidt , and R. J. Gray 2

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1

Pittsburgh Energy Technology Center, U.S. Department of Energy, P.O. Box 10940, Pittsburgh, PA 15236 Ralph Gray Services, 303 Drexel Drive, Monroeville, PA 15146 2

The petrographic, proximate, and ultimate analyses of Rasa coal are reported, along with information on the v i t r i n i t e reflec­ tance, carbon aromaticity, sulfur and carbon isotopic abundances, ash analysis and forms of sulfur. A Rasa coal containing 11.79% sulfur was extracted with a pyridine/toluene azeotrope and the extract was analyzed by low-voltage, high-resolution mass spec­ trometry. The molecular ions of 1440 indi­ vidual compounds were detected, and using this precise mass information, molecular formulae were assigned. The average deviat­ ion between the measured and theoretical masses was 0.0003 amu. Many homologous series of organosulfur compounds were detected. Some families of organosulfur com­ pounds contained two or three sulfur atoms per molecule. The degree of alkylation of many homologous series maximized at either three, four, or five alkyl carbons. Rasa c o a l h a s g e n e r a t e d s u b s t a n t i a l i n t e r e s t o v e r t h e years because o f i t s h i g h o r g a n i c s u l f u r content. I n f o r m a t i o n c o n c e r n i n g t h e n a t u r e and d i s t r i b u t i o n o f organic sulfur moieties i n coal i s desirable f o rthe design and e v a l u a t i o n of coal de s u Ifuriζ a t i o n processes. A major impediment to the character0097-6156/90/0429-0261$07.50/0 © 1990 AmericanChemicalSociety

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

262

GEOChemISTRY OF SULFUR IN FOSSIL FUELS

ization

of

sulfur

coals

which

organosulfur is

interferes

organosulfur

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point.

in

same in

having

much

Rasa

coal

Peninsula, roundings

in

were

formed

of

occurs

the

Cretaceous. under with

seawater.

marine Rasa

coals

faulting Hamrla under

(1-3) .

completely

He

noted

i.e.,

that

i t

large

of

tistical van

the

coal

i s aromatic

Kavcic

plants

Rasa

coal

the

The

inundated

beds

are

region

mainly

where

the

folding

or

maceral coals

coal

content,

were

ring

analysis that

was

waxes,

exhibits

low-

tests in

grew

conditions.

Rasa

coal

both

seam Upper

formed

conditions.

that

computed

forming

the

coal the

vigorous

s u l f u r present

structural

Krevelen

of

no

Rasa

occurs

lowest

the

the

Rasa

brackish

periodically

studying

sur-

Hamrla,

and

In

Chemical

amount

The

saprope 1 i t e s ,

exhibits

teristics. amount

no

to

the

anaerobic

and

constitute

of

that

reported

contained

Hamrla

flysch.

After

concluded

Istrian

that

coal

was

to

coals

the

conditions

was

there

guide in

on

surface

roofs

and

occur,

Kreulen and

The

a

Cretaceous.

brackish

debris

limestone

be

seams

Paleocene.

and/or

plant

other

organosulfur

to

lacustrine

the

coal

of

those

According

Apparently,

starting

contents.

seams

erosion

lacustrine

resulting

10

the

sulfur

Rasa

compounds

being

are

Upper the

for

in

the

sulfur

(1-3).

strata

on

of

of

suffer

good

to,

several

the

a

expected

geologic

which

coal-bearing

is

seam

the

not

Thus,

is

similar

in

lowest

described

facies

coal

organic

occurs

the

does

constituents

organosulfur

lower

organic

background,

observation

coal

probleM.

or

coal

of

lower

characterizing organic

Rasa

as,

Rasa

analysis

coals

in

coal,

spectral

Characterization

compounds

has

this

in

hydrocarbon

Rasa

organosulfur

the

coals. the

the

from

The

be

with

interested

components may

high

compounds.

significantly scientist

constituents

the

and

a or

humic

coal

resins

(4).

dual

character,

high-rank

charac-

indicated

that

is

chains,

in

side

structures. method 59%

of

Using

based the

a

on

small and a

a

sta-

density,

carbon

in

Rasa

(4).

treated

several

hydrogenated

Rasa

coal,

acetophenone

extraction

and of

samples the Rasa

of

residue coal

Rasa left with

coal, after methyl-

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

16.

WHITE ET A L

Organosulfur Constituents in Rasa Coal

263

i o d i d e to d i f f e r e n t i a t e between the t y p e s of s u l f u r present. Results i n d i c a t e d t h a t about 751 of the sulfur was thiophenic and 25% was reactive with methyliodide (5). Kavcic later investigated the r a t i o o f 32s/34s i n a R a s a c o a l and f o u n d i t t o be 22.9 ( 6 3 4 s = -30.1) (6) .

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C D T

K a v c i c s ' r e s u l t s on t h e f o r m s o f o r g a n i c s u l f u r were c o n f i r m e d by I g n a s i a k e t a l . ( 7 ) , who determined t h a t about one t h i r d o f t h e s u l f u r i n R a s a c o a l i s i n thioether links. T h i s r e s u l t was determined using two independent techniques. Ignasiak et a l . a l s o c o n c l u d e d t h a t m e r c a p t a n i c s u l f u r was absent from Rasa c o a l because u n s p e c i f i e d Chemical tests failed to r e v e a l i t s presence. U n t i l r e c e n t l y , l i t t l e was known w i t h c e r t a i n t y about the Chemical i d e n t i t y o f o r g a n o s u l f u r compounds in coal. W h i t e and c o w o r k e r s c h a r a c t e r i z e d some organosulfur constituents extractable from both Homestead, Kentucky, c o a l (8>) and Bevier seam c o a l ( 9 ) . Boudou e t a l . have s t u d i e d t h e organosulfur components i n t h e C u r r i e p o i n t p y r o l y s i s products from Provence, Muskingum, and Meigs coals by GC-MS ( J J ) ) . Many organosulfur compounds were tentatively identified. N i s h i o k a p u b l i s h e d an e x c e l l e n t paper d e s c r i b i n g the c h a r a c t e r i z a t i o n of organosulfur constituents extracted f r o m a Rock Springs No. 7 c o a l t a k e n f r o m S w e e t w a t e r , Wyoming (jJL) . Even though s i g n i f i c a n t p r o g r e s s has been made on the characterization of organosulfur constituents from c o a l , almost nothing i s known w i t h c e r t a i n t y c o n c e r n i n g the n o n t h i o p h e n i c c o n s t i t u e n t s i n c o a l . One purpose of the p r e s e n t m a n u s c r i p t i s t o b e g i n to d e f i n e the p o s s i b l e n a t u r e of n o n t h i o p h e n i c s u l f u r moeities i n coal.

Experimental A s i n g l e lump, a p p r o x i m a t e l y 2 k g , o f R a s a c o a l was o b t a i n e d f r o m M. E c k e r t - M a k s i c o f t h e R u d j e r B o s k o v i c Institute of Zagreb, Y u g o s l a v i a . The lump was r a n d o m l y s e l e c t e d , and no s p e c i a l s t o r a g e conditions

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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were u s e d . The c o a l was ground i n a i r u n t i l i t p a s s e d t h r o u g h a minus 60-mesh s c r e e n . Pétrographie s t u d i e s were c o n d u c t e d u s i n g t h e a i r d r i e d p u l v e r i z e d c o a l m i x e d w i t h a n o n r e a c t i v e epoxy binder. A i r d r y i n g was p e r f o r m e d a t a m b i e n t temperature. The ASTM method s p e c i f i e s minus 20 mesh (minus 850μπι) . The Rasa c o a l sample was f i n e r . The mixture, which contained about 18 to 25 percent plastic, was briquetted in a one-inch-internaldiameter cylindrical mold using pressures up to 5000 p s i . The mold c o n t a i n e d t o p and b o t t o m p l u g s . The b r i q u e t t e was g r o u n d and p o l i s h e d f o r m i c r o s c o p i c examination a c c o r d i n g t o ASTM D2797-85 ( 1 2 ) . One p e l l e t o f Rasa c o a l was prepared using a Buehler Automet p o l i s h i n g d e v i c e . The c o a l macérais were d e f i n e d a c c o r d i n g t o ASTM D2796-88 ( 1 3 ) . Use of b r a n d names f a c i l i t a t e u n d e r s t a n d i n g and does not n e c e s s a r i l y i m p l y e n d o r s e m e n t by t h e U.S. Department of Energy. A L e i t z O r t h o l u x m i c r o s c o p e was u s e d t o d e t e r m i n e the maceral content of Rasa c o a l . The m i c r o s c o p e was f i t t e d w i t h an o i l - i m m e r s i o n 60X f l u o r i d e o b j e c t i v e and 10X h i g h e y e p o i n t o c u l a r s t o g i v e an e f f e c t i v e m a g n i f i c a t i o n o f 720 d i a m e t e r s . A p o i n t count system o f a n a l y s i s was u s e d f o r t h e m a c e r a l d e t e r m i n a t i o n . F o u r p o i n t s were i d e n t i f i e d p e r f i e l d , and a t o t a l o f 1000 counts were d e t e r m i n e d f o r R a s a c o a l . This s y s t e m employs a p o i n t c o u n t s t a g e and an ocular graticule. The volume p e r c e n t o f macérais was calc u l a t e d a c c o r d i n g t o ASTM D2799-86 ( 1 4 ) . E l e m e n t a l a n a l y s i s o f t h e minus 60-mesh c o a l was p e r f o r m e d u s i n g ASTM methods D3177, D3178, and D3179 (15-17) . M o i s t u r e and ash were d e t e r m i n e d by ASTM methods D3173 and D3174 ( 1 8 , 1 9 ) , v o l a t i l e m a t t e r by ASTM method D3175 (20) , and forms o f s u l f u r by ASTM method D2492 ( 2 J J . E l e m e n t a l a n a l y s i s o f t h e a s h was p e r f o r m e d u s i n g ASTM method D3682 (22.) . Carbon a r o m a t i c i t y was d e t e r m i n e d u s i n g 13e NMR CP-MAS p r o cedures described elsewhere (H) . X-ray powder diffraction a n a l y s i s of the m i n e r a l matter i n the whole c o a l was p e r f o r m e d u s i n g a R i g a k u powder d i f -

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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16. WHITE ET AL.

Organosulfur Constituents in Rasa Coal

265

fTactometer. The d i f f r a c t i o n l i n e s were compared w i t h t h o s e i n t h e Powder D i f f r a c t i o n F i l e (2_4) . The ) . A complete d e s c r i p t i o n of the d i r e c t - i n s e r t ion probe technique, and an a u x i l i a r y c o m p u t a t i o n method t o i m p r o v e the interpolation of sample p e a k m a s s e s , h a v e also been r e p o r t e d (27.) .

R e s u l t s and

Discussion

Pétrographie e x a m i n a t i o n o f t h e R a s a c o a l shows i t t o be p r e d o m i n a t e l y v i t r i n i t e a n d / o r b i t u m i n i t e (90+%) w i t h some l i p t i n i t e (2-3%) and v e r y l i t t l e i n e r t i n i t e (2-3%). The vitrinite occurs as subangular to r o u n d e d p a r t i c l e s s u r r o u n d e d by an eucollinitic-toresinous material. The e u c o l i n i t e groundmass has no s p e c i f i c m o r p h o l o g y and f i t s t h e d e s c r i p t i o n f o r t h e m a c e r a l b i t u m i n i t e . T h e r e a r e some f u n g a l s p o r e s and a s m a l l amount o f m i c r i n i t e , m a c r i n i t e , and i n e r t o detrinite. The c o a l has an abundance o f v e r y s m a l l pyrite c r y s t a l s r e l a t i v e to North American coals. Many of these crystals appear to be euhedral ( o c t a h e d r o n s ) , and most o f t h e p y r i t e i s h i g h l y d i s seminated and less than 5 microns. Microscopic e x a m i n a t i o n r e v e a l e d c a l c i t e , much o f w h i c h e x h i b i t s c r y s t a l twinning. T h e r e i s a l s o some d o l o m i t e and a s m a l l amount o f s i d e r i t e . X - r a y d i f f r a c t i o n a n a l y s i s o f Rasa c o a l i n d i c a t e d t h a t c a l c i t e and d o l o m i t e were the major m i n e r a l c o n s t i t u e n t s . The r e s u l t s o f t h e p r o x i m a t e and u l t i m a t e a n a l y s i s o f Rasa c o a l a p p e a r i n T a b l e I . The r e s u l t s o f t h e f o r m s o f s u l f u r a n a l y s i s and c a r b o n a r o m a t i c i t y are also included i n Table I. The t o t a l s u l f u r on an asr e c e i v e d b a s i s was 10.77 w e i g h t p e r c e n t , and includes 0.02 weight percent s u l f a t e , 0.30 weight percent pyrite, and 10.45 weight percent organic sulfur. Organic sulfur is calculated as the difference

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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b e t w e e n t o t a l s u l f u r and t h e sum o f t h e p y r i t i c and sulfate sulfur. T a b l e I I i n d i c a t e s t h a t t h e ash cont a i n e d 5.23 w e i g h t p e r c e n t Fe2Û3, on an a s - r e c e i v e d basis. T h u s , t h e r e i s more i r o n i n t h e ash t h a n i s a c c o u n t e d f o r by t h e p y r i t e . T h e r e f o r e , the p y r i t e v a l u e r e p o r t e d i n T a b l e I i s p r o b a b l y low. If a l l t h e Fe i n t h e ash was present as p y r i t e , as i s p r o b a b l y t h e c a s e , t h e n t h e c o a l w o u l d have c o n t a i n e d 0.63 w e i g h t p e r c e n t p y r i t e on an a s - r e c e i v e d b a s i s . Because the pyrite was highly disseminated and present i n p a r t i c l e s of 5 microns o r l e s s , i t may have been i n c o m p l e t e l y l e a c h e d f r o m t h e c o a l d u r i n g nitric acid treatment, resulting i n a low pyrite value. TABLE I .

P r o p e r t i e s o f Rasa C o a l

As-Received Basis

MoistureFree B a s i s

M o i s t u r e - and Ash-Free Basis

Moisture V o l a t i l e Matter F i x e d Carbon Ash

0.68 48.00 43.34 7.98

N/A 48.33 43.63 8.04

N/A 52.55 47.45 N/A

Hydrogen Carbon Nitrogen Sulfur Oxygen*

4.34 73.29 1.12 10.77 2.01

4.79 73.79 1.13 10.84 1.42

5.21 80.23 I . 23 I I . 79 1.54

S u l f u r Forms Sulfate Pyritic Organic

0.02 0.30 10.45

0.02 0.30 10.52

0.02 0.33 11.44

N/A

N/A

f a by 13C NMR CP-MAS *By

0.65

difference.

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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GEOChemISTRY O F SULFUR IN FOSSIL FUELS

The c a r b o n a r o m a t i c i t y o f R a s a c o a l was 0.65, which i s not s i g n i f i c a n t l y different from van K r e v e l e n ' s f i n d i n g t h a t 591 o f t h e c a r b o n i n Rasa c o a l was a r o m a t i c ( 4 ) . Rasa c o a l i s d i f f i c u l t t o c l a s s i f y a c c o r d i n g t o rank. Some l i t e r a t u r e a r t i c l e s r e f e r t o i t as a l i g n i t e . The h i g h s u l f u r c o n t e n t o f Rasa c o a l t e n d s t o skew t h e q u a n t i t a t i v e r e s u l t s f o r the o t h e r e l e m e n t s . The v i t r i n i t e r e f l e c t a n c e v a l u e s range f r o m 0.60% t o 0.77%. Rasa v i t r i n i t e has a mean maximum r e f l e c t a n c e i n g r e e n l i g h t o f 546 nm and i n o i l o f 0.682%. These v a l u e s a r e o v e r t w i c e t h o s e r e p o r t e d f o r l i g n i t e s , and t h e mean maximum r e f l e c ­ t a n c e i s s i m i l a r t o t h a t o f many I l l i n o i s and O h i o h i g h - v o l a t i l e Β o r C rank b i t u m i n o u s c o a l s . Rasa c o a l i s h i g h i n v o l a t i l e m a t t e r as e x p e c t e d f o r a lignite. T h i s i s due i n s m a l l p a r t t o t h e l a r g e amounts o f c a l c i t e and d o l o m i t e ( c a r b o n a t e s ) i n Rasa coal. C a r b o n a t e s y i e l d c a r b o n d i o x i d e when h e a t e d , g i v i n g an e r r o n e o u s l y h i g h v o l a t i l e m a t t e r v a l u e , making t h e c o a l a p p e a r t o be o f l o w e r r a n k . B a s e d on the v i t r i n i t e r e f l e c t a n c e v a l u e and t h e c a r b o n v a l u e , Rasa c o a l a p p e a r s t o be a r e l a t i v e l y m a t u r e c o a l . The major e l e m e n t s p r e s e n t i n Rasa c o a l a s h were d e t e r m i n e d . The r e s u l t s a r e i n T a b l e I I . The m a j o r e l e m e n t s p r e s e n t i n t h e a s h , Ca and Mg, a r e c o n ­ sistent with the X-ray diffraction findings of c a l c i t e and d o l o m i t e . The w e i g h t p e r c e n t v a l u e s i n T a b l e I I do n o t and s h o u l d n o t add t o 100%. The sum of a l l the values reaches 100% when t h e w e i g h t p e r c e n t o f t h e minor elements a r e i n c l u d e d . Rasa c o a l i s exceptional because of i t s high s u l f u r c o n t e n t , most o f w h i c h a p p e a r s t o be o r g a n i c sulfur. The h i g h o r g a n i c s u l f u r c o n t e n t i s c h a r a c ­ t e r i s t i c o f m a r i n e - i n f l u e n c e d b i t u m i n o u s c o a l s . Rasa c o a l a p p e a r s t o have been formed i n a h i g h - p H m a r i n e e n v i r o n m e n t where b a c t e r i a t h r i v e d . This hypothesis i s s u p p o r t e d by t h e p r e s e n c e o f s u b s t a n t i a l amounts of b o t h c a l c i t e and d o l o m i t e i n Rasa c o a l . The c a l c i u m - and m a g n e s i u m - r i c h environment where Rasa c o a l formed i s e x p e c t e d t o have been a l k a l i n e . The

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

16.

WHITE ET AL.

Organosulfur Constituents in Rasa Coal TABLE I I .

Major Elements i n Ash

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Si0

2

Ti0 CaO MgO Na 0 K0 S0 2

2

2

3

Rasa C o a l Ash

269

Analysis

Wt.% o f E l e m e n t O x i d e i n Ash, As-Received B a s i s 5.63 7.07 5.23 0.28 33.03 10.15 1.00 0.42 37.16

a l k a l i n e marine environment, having r e l a t i v e l y high concentrations o f Group I I i o n s , f o s t e r e d b a c t e r i a l growth i n which p r o d u c t s of b a c t e r i a l a c t i o n cont r i b u t e d t o c o a l f o r m a t i o n and s u l f u r f i x a t i o n . This s c e n a r i o f i t s w e l l w i t h the d e s c r i p t i o n p r o v i d e d by H a m r l a (1-3) c o n c e r n i n g the e n v i r o n m e n t a l conditions that existed on the Istrian Peninsula during coalif icat ion. The p r e s e n c e o f l a r g e amounts o f o r g a n i c s u l f u r and s m a l l amounts o f p y r i t e i n R a s a c o a l i s a l s o c o n s i s t e n t w i t h the e a r l y i n f l u e n c e of a marine e n v i r o n ment t h a t was low i n i r o n and h i g h i n s u l f a t e . The a b n o r m a l l y h i g h s u l f u r c o n t e n t o f Rasa c o a l s u g g e s t s a source of s u l f u r other than t h a t o r i g i n a l l y i n the p l a n t s , t h a t became i n c o r p o r a t e d i n the vegetable d e b r i s t h a t formed t h e c o a l . P l a n t s do not typically c o n t a i n enough s u l f u r t o a c c o u n t f o r t h e v e r y high v a l u e s f o u n d i n Rasa c o a l . The s u l f u r i n Rasa c o a l i s p r e s e n t as a r e s u l t o f b a c t e r i a l r e d u c t i o n of m a r i n e s u l f a t e and subsequent i n c o r p o r a t i o n of the reduced s u l f u r i n t o the o r g a n i c matrix. The low p y r i t e c o n t e n t o f t h e Rasa c o a l i s c o n s i s t e n t with minimal input of t e r r e s t r i a l i r o n by f r e s h water. The observed f a c t s are consistent with the early

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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270

GEOChemISTRY O F SULFUR IN FOSSIL FUELS

d e p o s i t i o n a l environment o f Rasa c o a l b e i n g p r i m a r i l y m a r i n e and a l k a l i n e . An a l k a l i n e marine environment h i g h i n and HS" i s favorable f o r incorporation of sulfur into o r g a n i c m a t t e r ; HS" i s an a g g r e s s i v e nucleophile. Such c o n d i t i o n s a l s o w o u l d have been f a v o r a b l e f o r the f o r m a t i o n o f p o l y s u l f i d e s and e l e m e n t a l s u l f u r . A l l o f these species, e i t h e r alone o r i n combination, are expected t o have played a role i n the incorporation of sulfur into the vegetable debris that u l t i m a t e l y formed R a s a c o a l . Many o f t h e s e s p e c i e s a r e known t o be r e a c t i v e w i t h h y d r o c a r b o n s a t mild temperatures. Elemental sulfur reacts with h y d r o c a r b o n s t o f o r m o r g a n o s u l f u r compounds, i n c l u d ing thiophenes at mild temperatures (28,29). Polys u l f i d e s r e a c t w i t h c o n j u g a t e d ene c a r b o n y l s a t room temperature t o form t h i o p h e n e s and o t h e r sulfur heterocycles (30). The isotopic abundances o f 13c a n d 34s were measured. D e t e r m i n a t i o n o f t h e 634SCDT c a n p r o v i d e insight into the o r i g i n of sulfur i n coal. Theref o r e , t h e 6l3CpDB and 634SCDT were e a c h measured i n duplicate. The 6l3CpDB d u p l i c a t e v a l u e s were -23.98, and -24.02, w h i l e t h e Ô34SCDT d u p l i c a t e v a l u e s were +7.8 and +7.9. The fi34s v a l u e s a r e r e l a t i v e t o Canyon Diablo t r i o l i t e (CDT), w h i l e t h e 6l3c v a l u e s a r e r e l a t i v e t o Peedee b e l e m i n i t e (PDB). The 6l3CpDB v a l u e s a r e t y p i c a l o f t h o s e f o u n d f o r many c o a l s . The $34SCDT v a l u e s a r e a l s o t y p i c a l o f many c o a l s and a r e c o n s i s t e n t w i t h t h e s u l f u r i n Rasa c o a l h a v i n g a marine o r i g i n . The 634SÇDT o f s e a w a t e r s u l f a t e h a s r a n g e d f r o m about +10 t o +23 o v e r t h e l a s t 250 m i l l i o n yearfc ( 3 1 ) . Thus, Rasa c o a l i s d e p l e t e d i n 34s r e l a t i v e t o s e a w a t e r s u l f a t e . A fractionation of at l e a s t 14 p e r m i l u s u a l l y o c c u r s d u r i n g b a c t e r i a l sulfate reduction i f the available sulfate source a p p r o a c h e s i n f i n i t y , as i t does i n t h e o c e a n . In 1957, K a v c i c r e p o r t e d t h e i s o t o p i c abundance o f 34s i n Rasa c o a l as a 32s/34s r a t i o o f 22.9 + 0.04 ( 0-0027 f o r C H S , and 0 . 0 0 4 0 f o r C 3 H ) . Even t h o u g h t h e m e a s u r e d mass i s c l o s e r t o t h a t o f ^20^16^> t h e C^ H oS2 f o r m u l a c a n n o t be e l i m i n a t e d b e c a u s e l o w e r m o l e c u l a r w e i g h t homologs o f C ^ H Q S were c l e a r l y p r e s e n t i n t h e s a m p l e . Further, the assignment o f t h e peak a t m/e 2 8 8 . 0 9 7 9 i n part to C H Q S i s s u p p o r e d by o b s e r v a t i o n a 34s p e a k . The peak a t m/e 2 8 8 . 0 9 7 9 i s b e s t a s s i g n e d t o b o t h s u l f u r containing molecular formulae. The peak a t m/e 288.1899 c o u l d be a s s i g n e d to either C^g^gS or C H 4 or both. U s i n g a dynamic r e s o l u t i o n o f one part i n 2 5 , 0 0 0 , t h e s e two i o n s a r e n o t b a s e - l i n e s e p a r a t e d , and t h u s i t i s d i f f i c u l t to distinguish between t h e s e two p o s s i b i l i t i e s . I t s h o u l d be 2

0

C

H

Γ

I

Η

1

S

1 7

7

2 0

2

2

1

7

2 2

2

2

2

7

1

6

n

2

2

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

2

2

16.

emphasized, however, t h a t base-line peaks i s n o t always n e c e s s a r y .

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TABLE I V .

Calculated Mass

Molecular Formula

288.1899

288.1911 288.1878 288.1514 288.1350 288.1150 288.0973 288.1006

C

288.1514 288.1357 288.1113 288.0979

288.0939 288.0774 288.0609 288.0101

288.0781 288.0606 288.0085

2 8

1 9

2 2

2 8

2 4

2 1

2 0

H

1 8

1 8

C

2 2

2 2

S

H

S

2 0

C

1 6

H

S

20 16°2> 2 0 1 6 20 16 > 17 20 2 20 16 > 23 12 17 20 2> 23 12 20 16 > 2 0 1 4 C H 34 , C H OS C H 0S, C H S

C

H

S

C

C

C

H

S

C

H

S

C

H

S

2 0

1 4

l g

1 2

C

H

2 8

16. 53

S

22 24 21 20° . Ci H 2° 20 16°2 20 16 17 20 2

3 4 s

8

C

2

H

C

H

C

H

C

S

6. 92 0. 81 2. 38 28. 67

S

H

23 12_ C H 34 2 0

C C

% of Base Peak

1 9

1 4

H H

1 2

OS S

15 12 3

S

5. 81 17. 84 1. 33

Resolution

C H S, C H C H S, C H O 21 20°> C H 0 3 4 C H 034 , C H 0 C

H

of

Approximate R e s o l u t i o n Required t o Achieve B a s e - L i n e S e p a r a t i o n o f t h e Ions Observed at m/e 288 and L i s t e d i n TABLE IV

Doublet

1 9

H

1 9

C

resolution

a t m/e 288

Multiplet

Measured Mass

TABLE V.

273

Organosulfur Constituents in Rasa Coal

WHITE E T AL.

H

H

C

C

S

S

H

H

3 4 s

1 9

1 5

1 2

1 2

3

2

Required

87,270 7,250 17,560 14,400 16,270 87,270 84,700 42,990 14,470 17,450 5,670

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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274

GEOChemISTRY OF SULFUR IN FOSSIL FUELS

The use of LVHRMS t o determine organosulfur constituents in a coal containing a significantly l o w e r amount o f o r g a n i c s u l f u r t h a n t h a t i n R a s a c o a l i s much more d i f f i c u l t and l e s s r e l i a b l e b e c a u s e t h e l a r g e hydrocarbon background i n t e r f e r e s w i t h obser­ v a t i o n o f the o r g a n o s u l f u r compounds. Furthermore, the o r g a n o s u l f u r compounds a r e u s u a l l y p r e s e n t in s u c h low c o n c e n t r a t i o n s t h a t o b s e r v a t i o n o f a 34s i s o t o p e peak i s r a r e . I n most c o a l s , t h e m u l t i p l e t at m/e 288 w o u l d have c o n t a i n e d large hydrocarbon i o n s f o r C22H24 and C23H12 a t p r e c i s e masses of 288.1878 and 288.0939, r e s p e c t i v e l y . I f present i n s i g n i f i c a n t amounts, t h e s e i o n s w o u l d have obscured t h e s u l f u r - c o n t a i n i n g compounds. The C22H24 w o u l d have i n t e r f e r e d w i t h C ^ g ^ g S , and t h e ^23^12 l d have i n t e r f e r e d w i t h b o t h C2Q 16^ * ^17 20^2· r e s o l u t i o n required to achieve b a s e - l i n e separation o f t h e C 2H24> 1 9 2 8 d o u b l e t i s 87,000, w h i l e t h e r e s o l u t i o n needed t o a c h i e v e b a s e - l i n e s e p a r a t i o n o f the C 3H > 2 0 1 6 doublet i s 84,700. In fact, b a s e d on t h e r e s u l t s o b t a i n e d , t h e p r e s e n c e o f t h e s e h y d r o c a r b o n i o n s c a n n o t be r u l e d o u t . However, i f t h e y were p r e s e n t i n s i g n i f i c a n t amounts, e x p e r i e n c e has shown t h a t t h e measured mass w o u l d have been c l o s e r to t h a t of the h y d r o c a r b o n i o n s r a t h e r than the s u l f u r - c o n t a i n i n g i o n s . w

H

C

H

a n c

Η

o

u

T n e

S

2

C

2

H

S

12

T a M e VI c o n t a i n s a p o r t i o n o f t h e low-voltage, high-résolut i o n mass spectrometric information o b t a i n e d d u r i n g a n a l y s i s o f t h e Rasa c o a l e x t r a c t (127 o f t h e 1440 peaks observed) . The s t r u c t u r e s shown i n T a b l e VI a r e i n c l u d e d t o show some o f t h e kinds of p o s s i b l e types of o r g a n o s u l f u r compounds t h a t c o u l d be p r e s e n t . These s t r u c t u r e s a r e c o n s i s t e n t w i t h the observed m o l e c u l a r formulae. The s t r u c t u r e s drawn have n o t been i d e n t i f i e d i n t h e c o a l extract. Many o t h e r s t r u c t u r e s a r e c o n s i s t e n t w i t h the observed molecular formulae. In f a c t , the t h i o l s are p a r t i c u l a r l y s u s p i c i o u s because Ignasiak et a l . f a i l e d t o f i n d t h i o l s i n Rasa c o a l ( 7 ) . T h r o u g h o u t T a b l e V I , i t i s c l e a r t h a t t h e mass measurements a r e made w i t h e x t r e m e l y h i g h accuracy.

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

η

R

r^i—r^s

r^sl

Ο

ι

SR

Possible Compound Type

T A B L E VI.

124.0347

4

310.1755 324.1912

380.2537 394.2694

282.1435 296.1590 310.1744 324.1917 338.2056 352.2199 366.2375 380.2536 394.2704

7 8 9 10 11 12 13 14 15

366.2369

352.2224

338.2069

282.1442 296.1598

268.1282

268.1285

254.1129

240.0973

226.0816

212.0659

6

254.1125

226.0813 240.0968

3 5

212.0666

2

198.0503

2.20

10.90

11.81

8.14

22.16

16.98

28.39

33.57

52.80

49.25

55.52

55.36

74.55

51.94

23.81

5.99

218.1130

218.1115

6

184.0347

20.36

204.0973

204.0971

5

184.0347

4

16.90

190.0816

190.0816

4

198.0509

3

15.19

176.0657

176.0652

3

1

14

12

15.86

162.0503

162.0500

0

12

5.24 16.15

148.0346

148.0346

1 2

ie

ie

10

28

M

24

22

1s

ie

14

12

10

M

32

S

NO

NO

NO

NO

NO

NO

YES

NO

YES YES YES YES YES YES

NO

NO

NO

NO

NO

NO

NO

NO

NO

NO

NO

NO

M

Continued on next page.

CMHMS

25

24

C H S C H S

CMHJOS

22

2

20

19

ie

1S

3

12

C H,S Ci H S Ci4H S C H S C H S CuH S CieHjoS C H S C H S C iH S C H S

10

C.H.S C H S C„H S C H S Ci H S Ci H S

10

2.95

166.0816 180.0973

14

10

180.0957

0

2.62 4.54

7

e

4.00

C H,S CH S Ci H S CnH S

Molecular Formula

166.0802

138.0503

% of Base Peak

4

138.0503

Calculated M.W.

5

124.0352

1

Measured M.W.

2

Number of Alkyl Carbons

PARTIAL L V H R M S DATA F R O M R A S A C O A L EXTRACT

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In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

Q

SR



R

Possible Compound Type

240.0067 254.0225 268.0380 282.0537 296.0693 310.0851 324.1006 338.1162 352.1319 366.1476 380.1633

240.0067 254.0225 268.0380 282.0531 296.0716 310.0851 324.1015 338.1157 352.1297

0 1 2 3 4 5 6 7 8 9 10

366.1478 380.1622

174.0503 188.0659 202.0816 216.0973 230.1129 244.1285 258.1442 272.1599 286.1755

174.0508 188.0661 202.0797 216.0970 230.1100 244.1261 258.1445 272.1586 286.1726

3 4

1 2 3 4 5 6 7 8 9

186.0503 200.0659 214.0816 228.0973 242.1129

Calculated M.W.

186.0506 200.0657 214.0816 228.0961 242.1138

Measured M.W.

0 1 2

Number of Alkyl Carbons

T A B L E VI. C O N T I N U E D

42.45 75.53 100.00 88.26 32.61 40.83 26.01 26.69 10.79 6.10 8.64

ie

ie

14

2e

2e

2

23

24

24

22

21

22

ie

20

2

2

2

2

2

2

H S H S H S H S H S H ,S

ie

14

9

e

20

Ci C C C C C

2

2

C, H S

2

CuH S

10

12

5

e

2

2

S S S S S S S S

C H,S Ci H S Ci H S 14

24

ie

22

19

20

ie

17

ie

14

13

15

12

12

H H H H H H H H

1 0

18

YES YES YES YES YES YES YES NO NO NO NO

NO NO NO YES YES YES YES YES NO

C„H S C C C C C C C C

3.32 4.15 9.96 11.71 56.56 45.95 16.41 30.50 23.68

ie

15

14

12

13

14

10

12

NO NO NO NO YES

S

S S S S S

M

C C C C C

H H H H H

Molecular Formula

4.10 5.90 6.19 19.35 10.77

% of Base Peak

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ο

1

η

Ο

es

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

236.0660

33.72

26.79 26.13

322.1755 336.1912

298.0850 312.1014

238.0817 252.0959 266.1124 280.1283 294.1443 308.1595 322.1761 336.1906 350.2040

242.0205 256.0364 270.0524 284.0669 298.0830 312.1010 326.1153 340.1352

2 4 5 6 7 8 9 10

0 1 2 3 4 5 6 7

340.1353

6.09

17.37

21.32

284.0693

326.1163

11.26

5.12

4.44

4.25

15.23

13.04

20.88

32.38

42.59

45.73

35.99

25.23

270.0537

256.0380

242.0224

350.2068

308.1598

294.1443

280.1286

266.1129

252.0972

238.0816

6.89

3

224.0660

2.31

31.50

34.68

210.0498

210.0450

32.94 63.72

224.0674

292.1286

278.1129

264.0973

250.0816

5.56

3.70

1

292.1286

6

208.0357 222.0503

0

264.0976 278.1124

250.0812

2 3 5

236.0661

1

4

208.0352 222.0487

0 e

ie

ie

14

12

10

S S S S S

NO

NO

2

2

2

Ci H S Ci H S IE

14

24

22

M

te

2

2

2

2

NO

YES YES YES

NO

NO

NO

NO

NO

NO

Continued on next page.

2

1 9

e

Ci H S C H S C2oH S C iH S

7

9

1 2

2

1 S

CI H S 1 0

2

2e

24

22

C H S

4

23

22

21

20

20

18

ie

14

NO NO

7

19

ie

12

10

C H ,S

YES YES YES YES YES YES

YES

NO

NO

YES YES

NO

S S S S S S S S S 15

4

Ci H C H C H C, H Ci$H C H C H C H C H

CJOHJOS

9

e

7

ie

5

Ci H C H Ci H Ci H Ci H

14

C HS

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In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

Q

Possible Compound Type

Measured M.W. 216.0076 230.0228 244.0377 258.0542

218.0221 232.0379 246.0530 260.0680 274.0840 288.0979 302.1140 316.1337 330.1466

213.0625 227.0766 241.0932 255.1081 215.0417 229.0565 243.0719 257.0882 271.1010 285.1178 299.1354

Number of Alkyl Carbons 0 1 2 3

0 1 2 3 4 5 6 7 8

1 2 3 4 0 1 2 3 4 5 6

215.0429 229.0561 243.0717 257.0875 271.1031 285.1187 299.1344

213.0612 227.0769 241.0925 255.1082

218.0224 232.0381 246.0537 260.0693 274.0849 288.1006 302.1163 316.1354 330.1476

216.0068 230.0224 244.0380 258.0537

Calculated M.W.

T A B L E VI. C O N T I N U E D

9.22 15.40 10.22 8.32 4.82 3.19 2.76

3.40 12.39 13.40 7.07

4.47 12.00 16.18 24.29 48.00 28.67 24.24 34.79 25.30

1.31 4.08 3.14 7.72

% of Base Peak 2

2e

24

22

20

18

ie

14

12

10

H H H H H H H H

S S S S S S S S

2

2

2

2

2

2

2

2

2

13

15

17

19

21

14

15

16

17

ie

12

15

17

19

ie

C H,NOS CHnNOS C H NOS C H NOS C H NOS C H NOS C H NOS

13

14

C„H„NS C H NS C H NS C H NS

20

19

e

7

e

9

4

3

12

Ci Ci Ci Ci Ci Ci C C

2

2

2

2

C H S

12

14

4

10

5

3

C, H,S Ci H S Ci H S Ci H S

Molecular Formula

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S

NO NO NO NO NO NO NO

NO NO NO NO

NO NO YES YES YES YES YES NO YES

NO NO NO NO

M

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

224.0276 238.0472 252.0607 266.0764 280.0922 294.1069 308.1226 322.1418 234.0512 248.0659 262.0819 276.0976 290.1133 304.1282 318.1446 332.1609 346.1747 360.1909 250.0431 264.0606 278.0770 292.0933 306.1075 320.1232 334.1404 348.1528

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 250.0453 264.0609 278.0775 292.0922 306.1078 320.1232 334.1392 348.1548

234.0503 248.0659 262.0816 276.0972 290.1129 304.1285 318.1442 332.1598 346.1755 360.1912

224.0296 238.0452 252.0609 266.0766 280.0922 294.1079 308.1235 322.1444

2.41 5.12 5.83 7.43 7.94 7.17 5.10 2.76

49.06 92.77 76.73 69.16 41.47 32.23 33.60 18.04 11.97 8.64

1.18 6.97 12.62 22.42 23.94 18.91 15.11 5.43 14

19

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NO NO YES YES NO NO NO NO

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280

GEOChemISTRY OF SULFUR IN FOSSIL FUELS

On a v e r a g e , t h e d e v i a t i o n b e t w e e n t h e m e a s u r e d and c a l c u l a t e d masses was 0.0003 amu. Further support f o r t h e a s s i g n e d f o r m u l a e comes f r o m t h e f a c t t h a t an e n t i r e homologous s e r i e s was o b s e r v e d where t h e mass o f each homolog was m e a s u r e d w i t h h i g h a c c u r a c y . In many c a s e s , final c o n f i r m a t i o n of the assigned m o l e c u l a r f o r m u l a r e s u l t s f r o m o b s e r v a t i o n o f t h e 34s i s o t o p e peak two amu h i g h e r a t t h e c o r r e c t p r e c i s e mass and a p p r o x i m a t e l y c o r r e c t intensity. A 34s i s o t o p e peak was n o t o b s e r v e d f o r e a c h sulfur-con­ t a i n i n g i o n . F a i l u r e t o o b s e r v e a 34s i s o t o p e peak was due t o e i t h e r l o w i n t e n s i t y o f t h e i s o t o p e peak or t o t h e p r e s e n c e o f an i n t e r f e r i n g i o n . A summary o f t h e LVHRMS r e s u l t s o b t a i n e d on t h e Rasa c o a l e x t r a c t a p p e a r s i n T a b l e V I I . T h i s summary was o b t a i n e d by t a k i n g d a t a f r o m e i g h t individual s c a n s a c q u i r e d a t d i f f e r e n t t e m p e r a t u r e s and a d d i n g them t o g e t h e r . The d a t a a r e s u m m a r i z e d a c c o r d i n g t o t h e method o f A c z e l e t a l . ( 3 2 ) . T a b l e V I I i n d i c a t e s t h a t 24 d i f f e r e n t homologous s e r i e s c o n t a i n i n g one s u l f u r atom were o b s e r v e d . Among t h e s e m o n o s u l f u r containing families o f compounds, 181 different homologs (not i n c l u d i n g positional isomers) were o b s e r v e d t h a t - c o n t a i n e d f r o m 6 t o 36 c a r b o n s . The range i n Ζ i s a l s o l i s t e d i n T a b l e V I I , where Ζ i s d e f i n e d as CNH2N-Z and i s a measure o f h y d r o g e n deficiency. N e a r l y 50% o f t h e m o l e c u l a r formulae d e t e c t e d by LVHRMS c o n t a i n e d a t l e a s t one s u l f u r atom. I n a l l , 219 d i s t i n c t s t r u c t u r a l s e r i e s were d e t e r m i n e d i n t h e R a s a c o a l e x t r a c t by LVHRMS; 1440 i n d i v i d u a l m o l e c u l a r f o r m u l a e were i d e n t i f i e d . Commonly, t h e most abundant homolog o f e a c h s e r i e s possessed t h r e e , f o u r , or f i v e a l k y l carbons. The o b s e r v a t i o n o f s e v e r a l homologous s e r i e s o f a l k y l a t e d thiophenes and o t h e r o r g a n o s u l f u r compounds is s i m i l a r t o t h a t o f S i n n i n g h e Damste' e t a l . (33). They observed multiple homologous series of thiophenes i n p y r o l y s a t e s of s u l f u r - r i c h kerogens. Many o f t h e f a m i l i e s o f compounds found i n T a b l e V I a p p e a r t o be r e l a t e d t o one a n o t h e r . For e x a m p l e , t h e sample c o n t a i n s f a m i l i e s o f compounds

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

1440

4-50 0-58 10-44 6-52 5-55 9-45 10-48 14-50 20-38 10-34 22-38 20-42 0-58

24 30 18 24 24 20 19 19 10 12 9 10 219

31.6 31.1 10.9 8.8 4.0 3.8 3.6 2.4 1.6 0.9 0.7 0.6 100.0

Formula C l a s s

M o n o s u l f u r compounds Hydrocarbons D i s u l f u r compounds Monoxygenates Nitrogenates N i t r o g e n - o x y g e n compounds S u l f u r - o x y g e n compounds Dioxygenates D i s u l f u r o x y g e n compounds Trioxygenates T r i s u l f u r compounds D i o x y g e n - s u l f u r compounds

Summary

181 328 136 178 138 110 92 114 67 47 22 27

Ζ Number Range

Number o f Homologous Series

Number o f Individual Homologs Observed

Summary o f Compound Types D e t e r m i n e d by LVHRMS i n a P y r i d i n e / T o l u e n e E x t r a c t From Rasa C o a l

Relat ive Mole Percent o f Those Compounds That Ionized

TABLE V I I .

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5-42

6-36 5-42 9-32 6-39 6-39 10-37 9-35 14-38 15-27 14-23 17-26 16-31

Carbon Number Range

282

GEOChemISTRY OF SULFUR IN FOSSIL FUELS

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Η

a n (

H

having formulae of £ΐ2 10^ * ^12 8^ (dibenzothiophenes). The d i b e n z o t h i o p h e n e s c o u l d have been formed by i n t e r n a l c y c l i z a t i o n and d e h y d r o g e n a t i o n o f the C ^ H I Q S family o f compounds. Several other examples o f one homologous s e r i e s b e i n g formed from a n o t h e r by d e h y d r o g e n a t i o n a r e p o s s i b l e . Dehydrogenation of organic compounds i s promoted by elemental s u l f u r . The s u l f u r c o n t e n t o f t h e e x t r a c t was so h i g h t h a t f a m i l i e s o f compounds c o n t a i n i n g two and t h r e e d i f ­ ferent heteroatoms per molecule were observed. Bodzek and M a r z e c have o b s e r v e d compounds f r o m c o a l extracts t h a t c o n t a i n e d b o t h n i t r o g e n and sulfur, b o t h n i t r o g e n and o x y g e n , and b o t h s u l f u r and o x y g e n (34). The d a t a i n T a b l e VI show t h a t t h e R a s a c o a l c o n t a i n e d f a m i l i e s o f compounds t h a t c o n t a i n e d b o t h n i t r o g e n and s u l f u r , both s u l f u r and oxygen, and s u l f u r , n i t r o g e n , and o x y g e n . I t i s rare to observe a homologous s e r i e s o f compounds f r o m c o a l t h a t c o n ­ t a i n s three d i f f e r e n t heteroatoms. The Rasa c o a l appeared t o be susceptible to oxidation. The o r g a n o s u l f u r compounds i n t h e c o a l a p p e a r e d t o be o x i d i z e d when e x p o s e d t o a i r . Thus, f o r many homologous s e r i e s o f compounds t h a t con­ t a i n e d o n l y s u l f u r , t h e r e was a c o r r e s p o n d i n g s e r i e s t h a t c o n t a i n e d b o t h s u l f u r and o x y g e n . The f o r m a t i o n o f s u l f u r o x y g e n b o n d i n g was o b s e r v e d by electron spectroscopy f o r Chemical analysis (ESCA) when t h e Rasa coal was exposed to oxygen (Baltrus, J., Pittsburgh Energy Technology Center, Personal Communication, 1989). No s p e c i f i c compounds have y e t been identified. A l t h o u g h t h e s t r u c t u r e s drawn i n T a b l e VI a r e con­ sistent w i t h the observed molecular formulae, at p r e s e n t no o t h e r e v i d e n c e suggests that they are valid. The t h i o l f u n c t i o n a l i t i e s are particularly suspicious. N e v e r t h e l e s s , the molecular formulae assigned are c o r r e c t . This i n v e s t i g a t i o n represents a s t a r t i n g p o i n t f o r more d e t a i l e d study of the m o l e c u l a r components p r e s e n t i n R a s a and o t h e r c o a l s , and has d e f i n e d some p o s s i b i l i t i e s concerning the

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

16. WHITE ET AL.

Organosulfur Constituents in Rasa Coal

283

n a t u r e o f o r g a n o s u l f u r compounds i n c o a l . Lastly, i t i s p o s s i b l e , but not l i k e l y , t h a t t h e s u l f u r com­ pounds i n t h e c o a l were t h e r m a l l y a l t e r e d e i t h e r d u r ­ ing t h e 110OC e x t r a c t i o n o r d u r i n g volatilization i n t o t h e mass s p e c t r o m e t e r .

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Acknowledgment The a u t h o r s a r e i n d e b t e d t o M . E c k e r t - M a k s i c f o r p r o ­ v i d i n g a sample o f Rasa c o a l , t o J o s e p h M a l l i , J r . , f o r o p e r a t i n g t h e h i g h - r e s o l u t i o n mass spectrometer, t o F r a n c i s McCown f o r p e r f o r m i n g t h e S o x h l e t e x t r a c ­ t i o n s , t o R i c h a r d F . S p r e c h e r f o r p e r f o r m i n g t h e 13c NMR, t o S i d n e y P o l l a c k f o r o b t a i n i n g t h e X - r a y d i f ­ f r a c t i o n r e s u l t s , and t o t h e C o a l A n a l y s i s B r a n c h o f PETC for performing the ultimate and p r o x i m a t e a n a l y s i s o f t h e Rasa c o a l .

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March 5, 1990

In Geochemistry of Sulfur in Fossil Fuels; Orr, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.