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
