Liquefaction of Western Subbituminous Coals with Synthesis Gas

Subbituminous coals from four major coal-bearing regions of. Wyoming: Hams Fork, Green River, Hanna and Powder River Coal. Basin having ash from 4 to ...
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27 L i q u e f a c t i o n of W e s t e r n S u b b i t u m i n o u s Coals w i t h Synthesis G a s

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CHARANJIT RAI University of Wyoming, Laramie, WY 82071 HERBERT R. APPELL and E. G. ILLIG Pittsburgh Energy Research Center (ERDA), 4800 Forbes Ave., Pittsburgh, PA 15213 The r e c e n t energy c r i s i s on t h e e a s t c o a s t and c o n t i n u e d c o n c e r n r e g a r d i n g e n v i r o n m e n t a l e f f e c t s have once a g a i n emphas i z e d t h e importance o f p r o d u c i n g l o w - s u l f u r f u e l s by l i q u e f a c t i o n . Most l i q u e f a c t i o n p r o c e s s e s i n v o l v e some form o f hydrogen t r a n s f e r , where c o a l i s h e a t e d and l i q u e f i e d a t 400500°C i n a s o l v e n t . Falkum and G l e n (JL) suggested t h a t t h e i n i t i a l r e a c t i o n o f c o a l w i t h m o l e c u l a r hydrogen i n v o l v e d d e a l k y l a t i o n t o r e a c t i v e unsaturated m a t e r i a l s which a r e e i t h e r s t a b i l i z e d b y hydrogénation o r r e p o l y m e r i z e . Van K r e v e l e n (2.) r e p o r t e d t h a t c o a l p y r o l y s i s i n v o l v e d d e p o l y m e r i z a t i o n and d i s p r o p o r t i o n a t i o n i n w h i c h f r e e r a d i c a l s a r e formed. Hill e t a l . (3) d i s c u s s e d t h e l i q u e f a c t i o n o f a h i g h v o l a t i l e b i t u m i n o u s c o a l i n t e t r a l i n i n terms o f d i s s o l u t i o n and s t a t e d t h a t "the hydrogen t r a n s f e r r e a c t i o n a t 350-450°C i s a second o r d e r p r o c e s s , i n w h i c h t h e a c t i v a t i o n energy i n c r e a s e s as t h e r e a c t i o n p r o c e e d s . " C u r r a n e t a l . (4) d e s c r i b e d t h e t r a n s f e r of hydrogen from t e t r a l i n t o c o a l as a f r e e r a d i c a l r e a c t i o n i n v o l v i n g thermal cleavage of the c o a l molecules. Heredy and Neuworth (5) were a p p a r e n t l y t h e f i r s t i n v e s t i g a t o r s t o report the depolymerization of coal using F r i e d e l - C r a f t s c a t a l y s t s . They o b s e r v e d t h a t t h e s o l u b i l i t y o f c o a l c o u l d be c o n s i d e r a b l y i n c r e a s e d by t r e a t m e n t w i t h boron t r i f l u o r i d e i n p h e n o l a t 100°C. Subsequent s t u d i e s (6) i n d i c a t e d t h a t p a r a - t o l u e n e s u l f o n i c a c i d i n p h e n o l was t h e most e f f i c i e n t c a t a l y s t f o r t h e d e p o l y m e r i z a t i o n r e a c t i o n a t 185°C. Lower rank c o a l s were found t o be more r e a c t i v e r e s u l t i n g i n higher s o l u b i l i t y (T). More r e c e n t l y S t e r n b e r g (8) has s t u d i e d t h e d i s s o l u t i o n o f c o a l by r e d u c t i v e a l k y l a t i o n , w h i c h i n v o l v e s a v a r i e t y o f r e a c t i o n s , i n c l u d i n g f r e e r a d i c a l and e l i m i n a t i o n r e a c t i o n s . The r e d u c t i v e a l k y l a t i o n proceeds by t h e a d d i t i o n o f e l e c t r o n s t o t h e a r o m a t i c n u c l e i t o form t h e c o r r e s p o n d i n g a n i o n s f o l lowed by C - a l k y l a t i o n . Cleavage o f e t h e r bonds r e s u l t s i n p h e n o l a t e a n i o n s and subsequent O - a l k y l a t i o n o f t h e a n i o n s s o l u b i l i z e s c o a l . C o a l has a l s o been s o l u b l i z e d by a g r a f t i n g 438

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

27.

RAI

ET

AL.

Liquefaction

of Subbituminous

Coals

439

t e c h n i q u e w h i c h c a n be c a r r i e d o u t a t m i l d temperatures (140150°C) and a t m o s p h e r i c p r e s s u r e (£). P u l v e r i z e d b i t u m i n o u s o r a n t h r a c i t e c o a l i s mixed w i t h a c h e m i c a l g r a f t i n i t i a t o r and an a p p r o p r i a t e monomer, and t h e r e a c t i o n p r o d u c t i s l i q u e f i e d e i t h e r by h e a t i n g o r by a d d i t i o n o f s o l v e n t s d e r i v e d from c o a l o r p e t r o l e u m . N o n - p o l a r a l k y l monomer s u b s t i t u e n t s enhance the s o l u b i l i t y o f c o a l i n a l i p h a t i c h y d r o c a r b o n s ; whereas a r o m a t i c s u b s t i t u e n t s make c o a l s o l u b l e i n a r o m a t i c s o l v e n t s . The p o l a r groups make the g r a f t e d c o a l s more s o l u b l e i n p o l a r s o l v e n t s such as k e t o n e s and a l c o h o l s . V i g o r o u s e f f o r t s a r e b e i n g made t o d e v e l o p c a t a l y t i c hydrogénation p r o c e s s e s f o r p r o d u c i n g l i q u i d f u e l s from c o a l . The r o l e o f hydrogen i n l i q u e f a c t i o n o f c o a l i s t o s a t u r a t e t h e f r e e r a d i c a l s formed by bond c l e a v a g e o f c o a l a t r e a c t i o n temperature. T h i s can o c c u r d i r e c t l y o r through hydrogénation o f s m a l l e r s o l v e n t m o l e c u l e s w h i c h then donate t h e i r hydrogen t o r e a c t i v e c o a l s p e c i e s . D e s u l f u r i z a t i o n and s a t u r a t i o n o f d o u b l e bond and a r o m a t i c r i n g s t r u c t u r e s a l s o occurs i n t h e p r e s e n c e of hydrogen. Enormous amounts o f hydrogen a r e needed f o r h y d r o génation p r o c e s s e s and w i t h o u t a t e c h n o l o g i c a l b r e a k t h r o u g h f o r p r o d u c t i o n o f hydrogen a t low c o s t s , an e c o n o m i c a l p r o c e s s f o r l i q u e f a c t i o n w i l l n o t be a c h i e v e d . An a l t e r n a t i v e approach has been i n v e s t i g a t e d by A p p e l l e t a l . (10) c o n s i s t i n g o f l i q u e f y i n g l i g n i t e and b i t u m i n o u s c o a l w i t h low c o s t s y n t h e s i s g a s . Fu and I l l i g (11) have attempted l i q u e f a c t i o n and d e s u l f u r i z a t i o n o f h i g h s u l f u r b i t u m i n o u s c o a l s w i t h s y n t h e s i s gas a t temperat u r e s o f 400-450°C, and o p e r a t i n g p r e s s u r e s o f 3000-4000 p s i i n the presence o f c o b a l t molybdate and sodium c a r b o n a t e c a t a l y s t s , steam and a r e c y c l e o i l . The e f f e c t o f m i n e r a l m a t t e r p r e s e n t i n w e s t e r n c o a l s was i n v e s t i g a t e d i n an a t t e m p t t o d e v e l o p an e c o n o m i c a l n o n - c a t a l y t i c l i q u e f a c t i o n p r o c e s s u s i n g low c o s t s y n t h e s i s gas. The m i n e r a l s p r e s e n t i n the subbituminous c o a l s o f f e r an adequate, i n e x p e n s i v e and n a t u r a l l y o c c u r i n g source o f c a t a l y t i c m a t e r i a l s f o r l i q u e f a c t i o n and h y d r o d e s u l f u r i z a t i o n r e a c t i o n s i n v o l v e d i n c o a l conv e r s i o n . M i t c h e l l and G l u s k o t e r (12) have i d e n t i f i e d b a s s a n i t e , q u a r t z , k a o l i n i t e , c a l c i t e and p y r i t e i n the Rocky M o u n t a i n subb i t u m i n o u s c o a l s by low temperature a s h i n g t e c h n i q u e . Morooka and Hamrin (13) o b s e r v e d t h a t t h e m i n e r a l m a t t e r from two Kentucky c o a l s e x h i b i t e d c a t a l y t i c a c t i v i t y f o r t h e d e h y d r o s u l f u r i z a t i o n o f t h i o p h e n e and butene i s o m e r i z a t i o n . I n t h i s s t u d y subbituminous c o a l s were l i q u e f i e d and d e s u l f u r i z e d e f f e c t i v e l y by h y d r o t r e a t i n g w i t h s y n t h e s i s gas a t moderate o p e r a t i n g c o n d i t i o n s i n the p r e s e n c e o f steam and a n t h r a c e n e o i l used as a s o l v e n t . The d a t a were compared when the same c o a l s were l i q u e f i e d w i t h pure hydrogen under s i m i l a r e x p e r i m e n t a l c o n d i t i o n s . P y r i t i c and o r g a n i c s u l f u r p r e s e n t i n t h e s e c o a l s appear t o be r e s p o n s i b l e f o r t h e f o r m a t i o n o f c a t a l y t i c a c t i v e form o f i r o n s u l f i d e t h a t f u n c t i o n s as an e f f e c t i v e h y d r o t r e a t i n g c a t a l y s t ( 1 4 ) . The presence o f

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

440

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

a l u m i n o s i l i c a t e s and c a r b o n a t e s i n these c o a l s promote t h e con­ v e r s i o n o f complex o r g a n i c s t r u c t u r e s t o s o l u b l e l i q u i d p r o d u c t s . The water-gas s h i f t r e a c t i o n and the r e d u c t i o n o f c a r b o n y l groups i n the c o a l s t r u c t u r e s a r e c a t a l y z e d by a l k a l i m e t a l c a r b o n a t e s . The r e d u c t i o n o f c a r b o n y l groups proceeds v i a d o n a t i o n o f t h e a l d e h y d i c hydrogen i n the formate i o n t o the c a r b o n y l group. The formate i o n i s c o n t i n u a l l y r e g e n e r a t e d by the r e a c t i o n o f carbon monoxide w i t h a l k a l i n e m a t e r i a l s present i n coal ash. M >C = 0

+

+

+

OH"

+

CO

Η(φ>©

H-C-0 M —>· -C-0 M

+

C0

H 0 ® -Ç-0 Μ

+

Η 0

, H-C-OH

θ

+

OH

o

A

1

Φ

+

M

Experimental Equipment. The l i q u e f a c t i o n o f c o a l was s t u d i e d i n a 1 l i t e r m a g n e t i c a l l y s t i r r e d s t a i n l e s s s t e e l a u t o c l a v e . The a u t o ­ c l a v e was equipped w i t h a t h e r m o w e l l ; a gas i n l e t p o r t connected to a s y n t h e s i s gas (H :C0 r a t i o o f 1:1), o r t o a hydrogen c y ­ l i n d e r ; and t o a p r e s s u r e gauge; a p o r t f o r c o n n e c t i o n t o a r u p t u r e d i s k assembly; and a p o r t f o r gas d i s c h a r g e . The v e r ­ t i c a l magentic r o d w i t h dashers s t i r r e d the c o a l , s o l v e n t and a s h o r c a t a l y s t p a r t i c l e s . The a u t o c l a v e temperature was measured by a thermocouple p l a c e d i n t o the t h e r m o w e l l . 9

M a t e r i a l s . Twelve subbituminous c o a l s from f o u r major c o a l - b e a r i n g r e g i o n s o f Wyoming were s t u d i e d i n t h i s program. Chemical and p h y s i c a l a n a l y s e s o f these c o a l s a r e p r e s e n t e d i n T a b l e I . The c o a l samples were b a l l - m i l l e d t o minus 100 mesh under n i t r o g e n and s t o r e d i n a r e f r i g e r a t o r b e f o r e u s e . A C o - M o - A l 0 c a t a l y s t (Harshaw CoMo 0402T, 3% CoO - 15% Mo0 ) was used i n some experiments e i t h e r w i t h o r w i t h o u t p o t a s ­ sium c a r b o n a t e . P y r i t e i s o l a t e d from c o a l was a l s o used as a c a t a l y s t w i t h p o t a s s i u m c a r b o n a t e i n some e x p e r i m e n t s . An­ t h r a c e n e o i l o b t a i n e d from Crowley T a r P r o d u c t s Company was used as the s t a r t - u p s o l v e n t . I n the r e c y c l e runs w i t h S h e r i d a n F i e l d C o a l (W-74-45), 80% o f the a n t h r a c e n e o i l was g r a d u a l l y r e p l a c e d by c o a l - d e r i v e d o i l a f t e r n i n e r e c y c l e s . The benzene and pentane used f o r s e p a r a t i o n o f o i l , and a s p h a l t e n e were F i s h e r s o l v e n t grade. 3

3

3

P r o c e d u r e . I n a t y p i c a l e x p e r i m e n t , the a u t o c l a v e was charged w i t h subbituminous c o a l (80-110g), a n t h r a c e n e o i l ( 1 4 0 g ) , w a t e r as needed t o p r o v i d e 25 w t % o f t h e c o a l charge w i t h s y n ­ t h e s i s gas o r hydrogen as the r e d u c i n g a g e n t , and w i t h o r w i t h o u t

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

COAL NAME

ADAVILLE # 6

2

16.7

20.3

20.9

23.8

22.1

19.1

18.3

18.0

19.5

21.1

Ar 12.4 Maf

Ar 19.5 Maf

1

Ar Maf Ar Maf Ar Maf Ar Maf Ar Maf

POWDER RIVER COAL BASIN Ar WYO-74-40 WYODAK Maf (Anderson-Canyon) Ar WYO-74-45 UNNAMED DIETZ Maf (Sheridan F i e l d ) Ar WYO-74-50 MONARCH (Upper Bench) Ar WYO-74-52 MONARCH (Lower M i d d l e Bench) Maf Ar WYO-74-53 MONARCH Maf (Lower Bench)

HANNA COAL FIELD WYO-74-24 BED #80

WYO-74-19 ADAVILLE # 1 (Elkol) GREEN RIVER REGION WYO-74-20 DEADMAN

WYO-74-14 ADAVILLE # 3

WYO-74-12 ADAVILLE # 4

WYO-74-4

HAMS FORK COAL REGION WYO-74-3 ADAVILLE #10

SAMPLE NO.

35.0 47.7 32.9 50.0 36.8 49.6 37.5 51.0 28.3 48.0

38.4 52.3 32.8 50.0 37.4 50.4 36.1 49.0 30.7 52.0

39.6 50.3

42.0 56.2

32.6 43.8 39.2 49.7

37.9 54.9 37.8 53.3 41.2 54.9 37.8 50.5 42.8 54.0

31.1 45.1 33.1 46.7 34.0 45.1 37.1 49.5 36.5 46.0

21.9

8.1

7.8

14.8

5.5

8.8

5.9

4.0

4.8

3.9

5.3

8.9

PROXIMATE ANALYSIS (PERCENT) VOLATILE FIXED CARBON ASH MATTER MOISTURE

54.9 74.8 48.0 73.1 53.6 72.3 53.7 72.9 42.1 71.4

5.9 4.9 5.9 5.7 6.3 5.8 6.1 5.5 5.4 5.5

5.7 5.5

0.9 1.2 1.1 1.6 1.3 1.7 1.2 1.6 1.0 1.7

1.3 1.7

1.1 1.5

5.6 4.6 55.6 74.6 59.7 75.7

1.4 2.1 1.4 2.0 1.5 1.9 1.4 1.9 0.9 1.2 6.1 5.3 6.1 4.9 6.1 5.1 6.1 5.2 6.2 5.5

50.8 73.6 50.7 71.5 55.9 74.3 56.3 75.1 60.1 75.8

32.3 18.4 28.0 16.2 29.8 18.6 28.9 17.2 27.7 18.3

0.5 0.7 2.2 3.4 1.2 1.6 2.0 2.8 1.9 3.1

1.2 1.5

9480 12920 8560 13040 9450 12750 9600 13030 7380 12520

10450 13260

9270 12440 0.5 0.6 31.3 18.7 23.3 15.6

8980 13010 8560 12070 9750 12960 9780 13050 10530 13270 1.8 2.6 0.6 0.9 0.4 0.5 0.3 0.4 1.3 1.6

ΒTU/ LB

31.0 16.4 35.9 20.7 32.2 18.2 31.1 17.4 27.5 15.9

ULTIMATE ANALYSIS (PERCENT) s Ν 0 H c

TABLE I . ANALYSES OF SUBBITUMINOUS COALS FROM MAJOR WYOMING COAL FIELDS

Η-'

Ο

ο

CO

1* ο

1"

S 5-

C/3

Ο

δ"

Ci

442

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

c a t a l y s t s . The a u t o c l a v e w i t h t h e r e a c t a n t s was f l u s h e d w i t h n i t r o g e n f o l l o w e d by s y n t h e s i s gas o r hydrogen and charged w i t h the a p p r o p r i a t e gas w i t h a n i n i t i a l p r e s s u r e o f 1600 t o 2000 p s i . The a u t o c l a v e temperature was t h e n i n c r e a s e d t o t h e d e s i r e d o p e r a t i n g temperature (400° t o 450°C) o v e r a p e r i o d o f 50 t o 60 m i n u t e s , m a i n t a i n e d a t t h e temperature from 15 t o 75 min. After the experiment was c o m p l e t e d , r a p i d i n t e r n a l c o o l i n g o f t h e a u t o c l a v e t o the ambient temperature was a c h i e v e d by c o l d w a t e r . The f i n a l p r e s s u r e i n t h e a u t o c l a v e was r e c o r d e d t h e n e x t d a y , the d i f f e r e n c e i n p r e s s u r e i n d i c a t i n g t h e volume o f gas consumed i n t h e e x p e r i m e n t . The p r o d u c t s were f i l t e r e d a t ambient or h i g h e r temperatures t o o b t a i n l i q u i d o i l s . F i l t e r cakes c o n t a i n i n g u n r e a c t e d c a r b o n , a s h and w a t e r were e x t r a c t e d w i t h benzene o r a c e t o n e . The w a t e r was removed by d i s t i l l a t i o n and the r e m a i n i n g o i l was r e c o v e r e d by removing t h e s o l v e n t i n a r o t a r y vacuum e v a p o r a t o r . Gaseous p r o d u c t s were a n a l y z e d by mass s p e c t r o m e t r y . Data on c o n v e r s i o n , o i l y i e l d and gas consumption a r e g i v e n as w e i g h t p e r c e n t based on m o i s t u r e - f r e e and a s h - f r e e (maf) c o a l . R e s u l t s and D i s c u s s i o n L i q u e f a c t i o n w i t h S y n t h e s i s Gas (1H :1C0) and Hydrogen. Subbituminous c o a l s from f o u r major c o a l - b e a r i n g r e g i o n s o f Wyoming: Hams F o r k , Green R i v e r , Hanna and Powder R i v e r C o a l B a s i n h a v i n g a s h from 4 t o 22 wt%, m o i s t u r e from 12 t o 25 w t % and s u l f u r from 0.6 t o 3.4 w t % (maf) were l i q u e f i e d and des u l f u r i z e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and i n absence of added c a t a l y s t s . The major elements p r e s e n t i n the m i n e r a l m a t t e r o f t h e s e c o a l s a r e shown i n T a b l e I I ( 1 5 ) . Some o f these m e t a l s a c t as c a t a l y s t s f o r d e p o l y m e r i z i n g and l i q u e f y i n g c o a l s . When Monarch (Lower Bench) c o a l (W-74-53) was h y d r o t r e a t e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and 25 w t % m o i s t u r e a t 425 + 5°C, an o p e r a t i n g p r e s s u r e o f 3900-4000 p s i , and a r e a c t i o n time o f one h o u r , a 99/o c o n v e r s i o n and 72% s e l e c t i v i t y t o o i l on a m o i s t u r e - and a s h - f r e e b a s i s was o b s e r v e d . The v i s c o s i t y o f the c o a l o i l i n a n t h r a c e n e s o l v e n t was r e m a r k a b l y low, 53 c e n t i p o i s e s a t 6 0 ° C A t l o w e r r e s i d e n c e time from 15 min. t o 30 min., t h e p r o d u c t o i l r e s u l t e d i n a h i g h v i s c o s i t y , eventhough t h e c o n v e r s i o n s were n o t g r e a t l y a f f e c t e d . These d a t a are shown i n T a b l e I I I and F i g u r e 1. E s s e n t i a l l y a l l the subbituminous c o a l s when h y d r o g r e a t e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and adequate amounts o f m o i s t u r e r e s u l t e d i n h i g h c o n v e r s i o n s v a r y i n g from 90 t o 99% on m o i s t u r e - and a s h - f r e e b a s i s a t a temperature o f 425 + 5°C, an o p e r a t i n g p r e s s u r e o f 3500 t o 4500 p s i g , and a r e s i d e n c e time o f a n h o u r . The p r o d u c t o i l i n v a r i a b l y had a low v i s c o s i t y . These a r e optimum c o n d i t i o n s f o r a u t o c l a v e e x p e r i m e n t s . H i g h e r temperatures r e s u l t e d i n i n c r e a s e d gas consumption, l o w e r conv e r s i o n s , and a p r o d u c t o i l o f low v i s c o s i t y . Likewise, Q

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

ADAVILLE #10 Kemmerer ADAVILLE # 6 Kemmerer ADAVILLE # 4 Kemmerer ADAVILLE # 3 Kemmerer ADAVILLE # 1 Kemmerer DEADMAN Rock S p r i n g s BED #80 Hanna WYODAK Powder R i v e r UNNAMED DIETZ Sheridan MONARCH (Upper Bench) Sheridan MONARCH (Lower M i d d l e Bench) Sheridan MONARCH (Lower Bench) Sheridan

WYO-74-3

WYO-74-53

WYO-74-52

WYO-74-50

WYO-74-45

WYO-74-40

WYO-74-24

WYO-74-20

WYO-74-19

WYO-74-14

WYO-74-12

WYO-74-4

COAL NAME COAL FIELD

SAMPLE NO.

0.012 0.019 0.017 0.032