Reduction and Phenol Acid Depolymerization of Colorado Oil Shale

21 Reduction and Phenol Acid Depolymerization of Colorado Oil Shale Kerogen J. SOLASH, D. C. CRONAUER, and T. P. KOBYLINSKI

Downloaded by UNIV OF OTTAWA on October 3, 2016 | http://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch021

G u l f Research & Development C o m p a n y , Pittsburgh, PA 15230

Colorado oil shale kerogen has been chemically altered to promote its solubility. Reductive alkylation using Na-HMPA was attempted. While some kerogen alkylation occurred, little increase in toluene solubility was noted. Ether and ester cleavage reagents also failed to promote an increase in kerogen solubility. Phenol-tosyl acid treatment of kerogen resulted in large product weight gains. The toluene soluble product fractions were analyzed by IR, NMR, and MS techniques. The results indicate that aryl-alkyl bonds are important crosslinks for these kerogens.

The c h e m i c a l s t r u c t u r e o f U.S. W e s t e r n o i l s h a l e k e r o g e n i s n o t known w i t h c e r t a i n t y . Many s t r u c t u r e s t u d i e s e m p l o y e d s t r o n g l e - o x i d a n t s t o d e g r a d e k e r o g e n ( l ^ ) * A c i d i c p r o d u c t s were i s o l a t e d and analyzed. I n most c a s e s , r e l a t i v e l y s m a l l amounts o f m a t e r i a l were a n a l y z e d . S t r u c t u r a l i n f e r e n c e s from a n a l y s i s o f s m a l l q u a n t i t i e s ( g e n e r a l l y l e s s than 20% o f kerogen) of degraded m a t e r i a l a r e a p t t o be m i s l e a d i n g . The l i t e r a t u r e i s i n c o n f l i c t r e g a r d i n g e v e n b a s i c s t r u c t u r a l f e a t u r e s o f kerogen. Y e n a n d c o - w o r k e r s have u s e d X - r a y a n a l y s i s t o deduce t h a t k e r o g e n s c o n t a i n v e r y l i t t l e a r o m a t i c m a t e r i a l ( 5 ) . However, ^ C CP/MAS NMR measurements show t h a t W e s t e r n k e r o g e n s a r e 20-30% a r o m a t i c c a r b o n (6,_7)» The s t r u c t u r e o f n i t r o g e n c o n t a i n i n g m o i e t i e s i s a l s o i n doubt. I t h a s b e e n s u g g e s t e d (8) that t e t r a p y r r o l e s i n kerogen pyrolyze t o y i e l d p y r i d i n e s , quinol i n e s , a n d o t h e r c l a s s e s o f n i t r o g e n e o u s compounds f o u n d i n s h a l e oil. No q u a n t i t a t i v e d a t a were g i v e n . P y r o l y s i s o f simple p y r r o l e s was f o u n d t o g i v e l o w y i e l d s o f p y r i d i n e s (9). Pyridines and q u i n o l i n e s a r e t h e major n i t r o g e n - c o n t a i n i n g species i n d i s t i l l a t e shale o i l s .

0097-6156/ 83/0230-0397S06.00/0 © 1983 A m e r i c a n C h e m i c a l S o c i e t y

Miknis and McKay; Geochemistry and Chemistry of Oil Shales ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


398

GEOCHEMISTRY AND CHEMISTRY OF OIL SHALES

A b e t t e r a p p r o a c h w o u l d be t o d e g r a d e W e s t e r n U.S. o i l s h a l e k e r o g e n under m i l d c o n d i t i o n s . T h e r e h a s been a r e p o r t o f r e d u c i n g kerogen using d i s s o l v i n g metals ( 1 0 ) . Jones and D i c k e r t reported that t r e a t i n g Colorado o i l shale kerogen w i t h l i t h i u m aluminum h y d r i d e , H I , o r l i t h i u m i n e t h y l e n e d i a m i n e were a l l i n e f f e c t i v e i n i n c r e a s i n g kerogen s o l u b i l i t y (10). I n t e r e s t i n g l y , HI h a s been r e p o r t e d t o c o n v e r t k u k e r s i t e ( E s t o n i a n o i l s h a l e ) t o 100% e t h e r a n d benzene s o l u b l e s ( 1 1 ) . No d a t a were r e p o r t e d on the p o s s i b l e extent of r e d u c t i o n w i t h l i t h i u m i n ethylene diamine. We w o u l d l i k e t o r e p o r t o u r r e s u l t s o f t r e a t i n g k e r o g e n w i t h two known r e a g e n t s y s t e m s : sodium-hexamethylphosphoric triamide (Na-HMPA) and p h e n o l - j ^ - t o l u e n e s u l f o n i c a c i d ( p h e n o l - t o s y l a c i d ) . R e d u c t i v e l y a l k y l a t i n g k e r o g e n u s i n g Na-HMPA s h o u l d r e s u l t i n a more e x t e n s i v e l y r e d u c e d p r o d u c t . Na-HMPA h a s been r e p o r t e d t o be a s u p e r i o r medium t o p r o d u c e s o l v a t e d e l e c t r o n s ( 1 2 ) . Na/HMPA i s capable of reducing i s o l a t e d d o u b l e bonds o r h i g h l y hindered aromatics (13). Using a " s o l v a t e d e l e c t r o n " system t o r e d u c t i v e l y a l k y l a t e avoids the complications of adding elements of the s o l v e n t o r e l e c t r o n t r a n s f e r agent t o t h e s u b s t r a t e (14). There i s a r i c h l i t e r a t u r e d e a l i n g w i t h s i m i l a r r e d u c t i o n s o f c o a l and m o d e l compounds ( 1 5 - 1 8 ) . P r o d u c t s r e s u l t i n g from p h e n o l - t o s y l a c i d r e a c t i n g w i t h c o a l have been s t u d i e d ( 1 9 ) . S o l u b i l i z i n g of c o a l i s thought t o r e s u l t f r o m a n a t t a c k o f p h e n o l on a r y l - a l k y l bonds ( 1 9 ) . The r e a c t i o n i s Lewis or Bronsted a c i d c a t a l y z e d . An i m p o r t a n t f e a t u r e o f t h i s chemistry i s the apparent f a c i l e a t t a c k of phenol a t b e n z y l i c sites. Experimental G e n e r a l Methods. The k e r o g e n s used i n t h i s s t u d y were d e r i v e d from Colorado o i l s h a l e . The o i l s h a l e s used w e r e : A, a 95.0 L / t s h a l e ; B, a 84 L / t s h a l e ; a n d C, a 198 L / t p r e t r e a t e d s h a l e . These o i l s h a l e s were a l l mined f r o m t h e G u l f C-a t r a c t . A isa Mahogany Zone o i l s h a l e o f unknown g e o g r a p h i c o r i g i n . The B a n d C s a m p l e s were m i n e d f r o m t h e P a r a c h u t e C r e e k member o f t h e G r e e n River formation. S h a l e B i s a c o m p o s i t e o f Mahogany t h r o u g h R-4 zones. (20). S h a l e C i s a c o m p o s i t e f r o m t h e R-4 z o n e . The C s a m p l e was b e n e f i c i a t e d by g r a v i t y methods (1.60 s p . g r . f l o a t ) p r i o r to our treatment. M i n e r a l s were removed f r o m t h e o i l s h a l e s by s e q u e n t i a l HC1 t h e n HF t r e a t m e n t . B i t u m e n was removed f r o m t h e k e r o g e n s by e x t r a c t i n g w i t h b e n z e n e - m e t h a n o l ( 7 : 3 ) p r i o r t o t h e i n i t i a l HC1 t r e a t m e n t . The s h a l e was f u r t h e r e x t r a c t e d w i t h b e n z e n e : m e t h a n o l b e f o r e and a f t e r HF t r e a t m e n t . Elemental analys e s o f t h e t h r e e k e r o g e n s used a r e p r e s e n t e d i n T a b l e I . O t h e r s at our l a b o r a t o r i e s a r e i n v e s t i g a t i n g the nature of r e s i d u a l mineral matter i n kerogen a f t e r various b e n e f i c i a t i o n treatments.


21.

SOLASH ETAL.

Colorado

399

Oil Shale Kerogen

Table I ELEMENTAL ANALYSES OF KEROGEN CONCENTRATES


Sample

H

C

N

Elemental S

Analysis, wt% 0 F CI

Ash

A

69.35

8.75 1.61 4.84 5.90

6.44

B

65.12

8.15 2.10 4.59 10.21 0.77

1.03

11.03

C

65.40

8.79 2.05 3.24 5.37 1.49

0.22

13.57

1.16

Elemental a n a l y s e s were d e t e r m i n e d by M i c r o a n a l y s i s I n c . , W i l m i n g t o n , D e l a w a r e ; o x y g e n was d i r e c t l y d e t e r m i n e d by a m o d i f i e d Unterzaucher technique. I R s p e c t r a were r e c o r d e d o n a D i g i l a b M o d e l 15C i n t e r f e r o m e t e r u s i n g K B r p e l l e t s . NMR s p e c t r a w e r e r e c o r d e d o n a V a r i a n XL-200. D i s s o l v i n g Metal Reduction. A t y p i c a l experiment i s as f o l l o w s : a 100 mL r o u n d - b o t t o m f l a s k , e q u i p p e d w i t h p r e s s u r e e q u a l i z i n g a d d i t i o n f u n n e l , e f f i c i e n t c o n d e n s e r , a n d g a s a d d i t i o n t u b e was u s e d . The a p p a r a t u s was o v e n - d r i e d , a s s e m b l e d h o t , a n d a l l o w e d t o c o o l under d r y N . The f l a s k was c h a r g e d w i t h 15 mL o f f r e s h l y d i s t i l l e d HMPA. Sodium ( a b o u t 1.5 g ) was f r e s h l y c u t i n t o s m a l l pieces. S e v e r a l p i e c e s o f sodium w e r e a d d e d t o t h e HMPA w i t h stirring. A f t e r s e v e r a l minutes, the s o l u t i o n turned blue. About 1 g o f k e r o g e n was added; 5 mL o f HMPA were u s e d t o r i n s e a n y kerogen adhering to the sides of the flask. The b l u e c o l o r d i s a p p e a r e d upon a d d i n g k e r o g e n . A f t e r s o l v a t e d e l e c t r o n s reapp e a r e d , t h e a d d i t i o n f u n n e l was c h a r g e d w i t h t h e c a l c u l a t e d q u a n t i t y o f quencher (methanol o r a l k y l i o d i d e s ) . The q u e n c h e r was added d r o p w i s e u n t i l t h e b l u e c o l o r was removed; when s o l v a t e d e l e c t r o n s r e a p p e a r e d more q u e n c h e r was added. Sodium was added a s required. T y p i c a l l y , 24 h was a l l o w e d f o r t h e a d d i t i o n o f t h e q u e n c h e r . The q u a n t i t y o f q u e n c h e r was c a l c u l a t e d o n t h e b a s i s o f t h e a r o m a t i c c o n t e n t (assume f a » .25) a n d t h e o x y g e n c o n t e n t . A f t e r a l l q u e n c h i n g a g e n t was a d d e d , t h e m i x t u r e was p o u r e d i n t o 50 mL o f w a t e r a n d f i l t e r e d . The s o l i d s were washed w i t h l a r g e v o l u m e s o f w a t e r , d r i e d i n v a c u o (85°C, 24-48 h , 300-400 t o r r ) , and w e i g h e d . The s o l i d s were t h e n S o x h l e t - e x t r a c t e d w i t h t o l u e n e and submitted f o r elemental a n a l y s i s . Incorporated ^ C (from e t h y l i o d i d e - l - C ) was d e t e r m i n e d by G l o b a l G e o c h e m i s t r y , I n c . , Canoga P a r k , C a l i f o r n i a , u s i n g a c o m b u s t i o n method. 2

1 3

Phenol-p-Toluene S u l f o n i c A c i d Depolymerization. The k e r o g e n s were t r e a t e d w i t h phenol-tosyl acid according to literature methods ( 2 4 ) . A f t e r r e a c t i n g , e x c e s s p h e n o l was removed by steam distilling. The p r o d u c t s were f i l t e r e d , washed w i t h w a t e r , a n d d r i e d i n vacuo. The p r o d u c t s were t h e n S o x h l e t - e x t r a c t e d w i t h t o l u e n e , m e t h a n o l , and f i n a l l y p y r i d i n e . E x t r a c t s were i s o l a t e d ,


400

GEOCHEMISTRY A N D CHEMISTRY OF OIL SHALES

weighed, and a n a l y z e d as o u t l i n e d i n t h e t e x t . Product r e c o v e r i e s a r e o u t l i n e d i n F i g u r e 1. F o r i n s t a n c e , f o r t h e B k e r o g e n , 3.87 g o f s o l i d s were r e c o v e r e d f r o m 2.00 g o f s t a r t i n g k e r o g e n ( 1 9 3 % yield). From t h e r e c o v e r e d ( p h e n o l a t e d ) p r o d u c t , 4 6 % was s o l u b l e i n toluene. The t o l u e n e - s o l u b l e p r o d u c t s f r o m e a c h r e a c t e d k e r o g e n were s u b j e c t e d t o SARA a n a l y s i s ( s a t u r a t e s , a r o m a t i c s , r e s i n s , a s p h a l t e n e s ) ( 2 2 ) . The B t o l u e n e s o l u b l e s gave a l m o s t 9 1 % a s p h a l t e n e s . The C k e r o g e n t o l u e n e s o l u b l e s were a l m o s t 8 1 % a s p h a l t e n e s . The C t o l u e n e s o l u b l e s were more d i f f i c u l t t o h a n d l e ; 1 4 . 5 % o f t h e m a t e r i a l was u n r e c o v e r e d f r o m t h e c h r o m a t o g r a p h i c c o l u m n .


R e s u l t s and D i s c u s s i o n Reductive A l k y l a t i o n . The k e r o g e n s d e s c r i b e d i n t h e e x p e r i m e n t a l s e c t i o n were r e d u c t i v e l y a l k y l a t e d by c o n t i n u a l l y q u e n c h i n g t h e intermediate anions. The method r e q u i r e s t h a t t h e d a r k b l u e s o l u t i o n ( s o l v a t e d e l e c t r o n s ) be s t o i c h i o m e t r i c a l l y quenched w i t h a l k y l a t i n g agent. When t h e d a r k b l u e s o l u t i o n r e a p p e a r s , more a l k y l a t i n g a g e n t i s a d d e d . The r e s u l t s o f r e d u c t i v e l y a l k y l a t i n g t h r e e kerogens w i t h methanol ( p r o t o n a t e ) and e t h y l - , b u t y l - , and o c t y l i o d i d e a r e presented i n Table I I . Table I I ELEMENTAL ANALYSES FOR Na/HMPA TREATED KEROGENS

Sample A (1) (2)

£

Elemental A n a l y s i s , wt% iL 2L ^ £ — 9.61

2

AA

#Gp/ 100 C Recovery

1

65.35 71.22

8.97 9.4

2.94 2.34

— 2.59

M 0

(3) (4) (5) (6) (7) (8)

63.79 64.95 64.08 66.67 65.76 66.61

8.40 8.36 8.37 8.82 8.75 8.95

2.15 2.50 2.34 2.34 2.35 2.45

4.32 11.45 M 5.88 8.75 M 2.14 — E 3.04 7.95 E - C 3.60 8.94 B 2.31 8.24 B

(9) (10) (11) (12) (13)

64.96 62.45 66.24 65.61 63.54

8.75 7.95 9.01 8.89 8.85

2.48 2.30 3.40 2.12 3.00

1.51 2.54 1.93 2.66 1.79

2

14 3.3

97.6% 105

B 8 4 2.8 3.6 4.4 4.9

93.5 83.5 88.3 97.4 106 95

5.75 M 0.0 9.10 M -8 — E 0.8 5.10 E - C 0.4 — B 2.7

91.8 88.7 108 97 108

1 3

C

1 3

AA - a l k y l a t i n g a g e n t ; M - m e t h a n o l , E - e t h y l i o d i d e , B butyl iodide, 0 - octyl iodide. A l l e n t r i e s i n t h i s c o l u m n r e f e r t o t h e c a l c u l a t e d number o f a l k y l g r o u p s i n c o r p o r a t e d p e r 100 atoms C o f s u b s t r a t e ( s e e text for details).


21.

SOLASH ET AL.

Colorado

401

Oil Shale Kerogen

KEROGEN (BUM FREE; MM FREE) UNREACTED PHENOL


2.00g

STEAM DISTILL PRODUCTS

(SOLIDS) 1. WASH WITH H 0 2. DRY IN VACUUM 2

SOLIDS 3.87g C *3.66g SEQUENTIAL SOXHLET EXTRACT | a. TOLUENE

r

| c. Py

b. MeOH

0.77g (20%) C - 1.53g (42%)

0.28g (7.6%)

0.45g (12.3%)

SARA (HEX)

* SAT* AROM* RESIN B - 9.3 C - 4.7

INSOL 90.7 80.5 (14.5% UNRECOVERED) Figure 1. Phenol-TsOHreaction

with kerogen.


402

G E O C H E M I S T R Y A N D C H E M I S T R Y OF OIL

SHALES

T a b l e I I p r e s e n t s t h e r e c o v e r y and e l e m e n t a l a n a l y s i s d a t a o f the s o l i d s recovered a f t e r r e d u c t i v e l y a l k y l a t i n g . I n a number o f c a s e s , t h e r e c o v e r y o f m a t e r i a l was g r e a t e r t h a n 100% b a s e d on s t a r t i n g kerogen. N i t r o g e n l e v e l s i n the recovered products are a b o u t t h e same as i n s t a r t i n g m a t e r i a l i n most c a s e s . This i n d i c a t e s t h a t o n l y s m a l l q u a n t i t i e s o f HMPA r e m a i n e d on t h e k e r o g e n . U s i n g t h e e l e m e n t a l a n a l y s i s d a t a i n T a b l e s I and I I , we c a l c u l a t e d t h e number o f a l k y l ( o r p r o t o n ) g r o u p s added t o t h e k e r o g e n s . The A and B k e r o g e n s i n c o r p o r a t e d more p r o t o n s and a l k y l g r o u p s than the C kerogen. I n two e x p e r i m e n t s ( T a b l e I I , Runs 6 and 12) we used l a b e l l e d e t h y l i o d i d e as a l k y l a t i n g a g e n t and m e a s u r e d incorporated i n the product s o l i d s . We f o u n d t h a t t h e B k e r o g e n i n c o r p o r a t e s a l m o s t t w i c e t h e number o f e t h y l g r o u p s as t h e C k e r o g e n (2.44 v s 1.25 e t h y l g r o u p s / 1 0 0 atoms C) b a s e d on C labelling data. T h i s compares f a i r l y w e l l w i t h t h e e l e m e n t a l a n a l y s i s d a t a i n T a b l e I I (Runs 6 and 1 2 ) . W h i l e k e r o g e n c a n be a l k y l a t e d , t h e a l k y l a t e d p r o d u c t s were o n l y s l i g h t l y (

Reduction and Phenol Acid Depolymerization of Colorado Oil Shale

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