High-resolution mass spectrometry of nitrogenous compounds of the Colorado Green River Formation oil shale

Chemical Geology - E l s e v i e r Publishing Company, Amsterdam Printed in The Netherlands

H I G H - R E S O L U T I O N MASS S P E C T R O M E T R Y O F NITROGENOUS COMPOUNDS O F T H E C O L O R A D O G R E E N R I V E R F O R M A T I O N OIL SHALE 1

B.R. SIMONEIT, H.K. SCHNOES 2, p. HAUG3 and A.L. BURLINGAME Space Sciences Laboratory, University of California, Berkeley, Calif. (U.S.A.) (Received April 2, 1970) ABSTRACT Simoneit, B.R., Sehnoes, H.K., Haug, P. and Burlingame, A.L., 1971. High-resolution m a s s s p e c t r o m e t r y of nitrogenous compounds of the Colorado Green River Formation oil shale. Chem. Geol., 7: 123-141. Basic nitrogenous compounds isolated from extracts of Green River F o r m a t i o n oil shale were analyzed. The major homologous constituents found were the compositional types CnH2n_ 11N (e.g., quinolines) and CnI-I2n_.7N (e.g., tetrahydroquinolines) with minor amounts of the CnH2n-5 N (e.g., pyridines) and CnH2n_gN (e.g., indoles) s e r i e s and traces of m o r e aromatized nitrogen compounds. These results a r e correlated with the nitrogen compounds isolated from Green River Formation r e t o r t oil and are a survey of the unaltered nitrogen compounds indigenous to the shale. INTROD UC TION Unlike t h e n i t r o g e n o u s c o n s t i t u e n t s of p e t r o l e u m w h i c h h a v e b e e n t h e s u b j e c t of n u m e r o u s i n v e s t i g a t i o n s o v e r t h e p a s t t h i r t y y e a r s , t h e n i t r o g e n c o n t a i n i n g c o m p o u n d s of s e d i m e n t s h a v e r e c e i v e d l e s s a t t e n t i o n f r o m o r g a n i c g e o c h e m i s t s . T h e w o r k on p e t r o l e u m h a s l e d to t h e i d e n t i f i c a t i o n o f a c o n s i d e r a b l e n u m b e r of r e l a t i v e l y s i m p l e a r o m a t i c n i t r o g e n c o m p o u n d s p a r t i c u l a r l y of v a r i o u s p y r i d i n e s a n d q u i n o l i n e s ( L o c h t e a n d L i t t m a n , 1955; L o c h t e a n d P i t t m a n , 1960a, b; D r u s h e l a n d S o m m e r s , 1966; C o n s t a n t i n i d e s and A r i c h , 1967; B r a n d e n b u r g h a n d L a t h a m , 1968). In a d d i t i o n , p r i n c i p a l l y t h r o u g h s t u d i e s i n v o l v i n g m a s s s p e c t r a l t y p e a n a l y s i s , a l a r g e n u m b e r of m o r e c o m p l e x s t r u c t u r a l c a t e g o r i e s h a v e b e e n r e c o g n i z e d ( L a L a u , 1960; J e w e l l and H a r t u n g , 1964; S n y d e r a n d B u e l l , 1965 and 1966; S n y d e r et a l . , 1968; S n y d e r , 1969). T h e e a r l y m o n o g r a p h by L o c h t e and L i t t m a n (1955) a n d s o m e m o r e r e c e n t r e v i e w s and p a p e r s (Dirmeen et a l . , 1961; D r u s h e l a n d 1This represents P a r t XXXIV in the s e r i e s High Resolution Mass Spectrometry in Molecular Structure Studies. F o r P a r t XXXIII, see A.L. Burlingame, Melvin Calvin, J. Han, W. Henderson, W. Reed and B.R. Simoneit. Geochim. Cosmochim. Aeta Suppl. 1, vol. 2:1779-1791 (1970}. 2present address: Department of Biochemistry, University of Wisconsin, Madison, Wisc., 53706 (U.S.A.). 3present address: Department of Chemistry, Rice University, Houston, Texas, 77001 (U.S.A.). Chem. Geol., 7 (1971} 123-141

123

S o m m e r s , 1966; Constantinides and Arich, 1967; B r a n d e n b u r g and L a t h a m , 1968; B u r l i n g a m e and Schnoes, 1969) s u m m a r i z e these r e s u l t s . By c o n t r a s t , few r e c e n t p a p e r s d e s c r i b e the nitrogen compounds in shales and all data thus f a r have been obtained on constituents o f the shale oil p r o d u c e d upon r e t o r t i n g of s e d i m e n t s a m p l e s (Ball et al., 1949; J a n s s e n et al., 1951; Van M e t e r et al., 1952; Lochte and M e y e r , 1956; Dinneen et al., 1958, 1961; Meinschein et al., 1964; Iida et al., 1966; Brown et al., 1970). Although n i t r o g e n compounds r e p r e s e n t ~'ery m i n o r Constituents of the total o r g a n i c s in s h a l e s , a study of these compotmds a p p e a r e d definitely indicated in view of the limited data on t h e i r distribution in s h a l e s and in connection with the c u r r e n t l y r a t h e r active investigations of s e d i m e n t lipid fractions. Consequently, we undertook an a n a l y s i s of nitrogen c o m p o u n d s d i r e c t l y e x t r a c t a b l e f r o m the G r e e n R i v e r deposit and h e r e p r e s e n t c u r r e n t r e s u l t s . Some p r e l i m i n a r y data on this work have been published (Simoneit et al., 1970). The compound m i x t u r e s analyzed w e r e obtained by t h r e e s e q u e n t i a l e x t r a c t i o n s t e p s , namely: (a) extraction of p u l v e r i z e d shale with b e n z e n e / methanol, followed by (b) exhaustive Soxhlet e x t r a c t i o n of a p o r t i o n of this p r e - e x t r a c t e d m a t e r i a l with the s a m e solvent m i x t u r e and, finally, (c) e x t r a c t i o n of the k e r o g e n m a t e r i a l r e m a i n i n g a f t e r t r e a t m e n t of the exhaustively e x t r a c t e d shale s a m p l e s with hydrofluoric and h y d r o c h l o r i c acids. Two different shale s a m p l e s w e r e analyzed. The f i r s t one w a s collected by one of us (B.R.S.) f r o m an outcrop at P a r a c h u t e C r e e k , 8 m i l e s n o r t h w e s t of Grand Valley, Colorado (108°7'W 39°37'N; elevation 7,300 ft.) and the second was obtained f r o m the Colony Mine, 15 m i l e s n o r t h w e s t of Grand Valley, C o l o r a d o (108°3'W 39o37'N; elevation 7,300 ft,). EXPERIMENTAL

Extraction of the shale sample f r om Parachute Creek The e x t r a c t i o n of this s a m p l e has been detailed by Haug (1967) and in our e a r l i e r r e v i e w ( B u r l i n g a m e et al., 1969a). F a i r l y l a r g e s h a l e e x t r a c t i o n of p u l v e r i z e d r o c k with b e n z e n e / m e t h a n o l ( 4 / 1 , v / v ) yielded 1.300 g total e x t r a c t p e r 100 g of shale. F r o m this total e x t r a c t b a s i c m a t e r i a l w a s s e p a r a t e d by e x t r a c t i o n with 1N aqueous H2SO4 yielding a f t e r n e u t r a l i z a t i o n (NaOH) and e x t r a c t i o n into hexane 3.8 m g ' b a s e s " / 1 0 0 g r o c k ( B a s e m i x t u r e A). A 100 g portion of p u l v e r i z e d rock, e x t r a c t e d in the fashion outlined above, was subsequently subjected to f u r t h e r e x t r a c t i o n with a b e n z e n e / methanol m i x t u r e ( 4 / 1 ) in a Soxhlet a p p a r a t u s . T h i s e x t r a c t i o n w a s c o n tinued until no f u r t h e r o r g a n i c s could be solubilized by u l t r a s o n i c a t i o n . T h e total yield was 0.440 g e x t r a c t p e r 100 g of shale a f t e r one w e e k of e x t r a c tion. A b a s e fraction (Base m i x t u r e B) was obtained f r o m this e x t r a c t by t r e a t m e n t as d e s c r i b e d e a r l i e r , yielding 1.4 m g " b a s e s " / 1 0 0 g of r o c k . Finally, a 100 g portion of this exhaustively e x t r a c t e d shale m a t e r i a l was t r e a t e d twice with 250 m l p o r t i o n s of 1 / 1 c o n c e n t r a t e d H F / H C 1 (in Teflon b e a k e r s ) to d i s s o l v e the inorganic m a t r i x . 45 g of r e s i d u e ( k e r o g e n c o n c e n t r a t e ) was obtained which was e x t r a c t e d subsequently with b e n z e n e / m e t h a n o l using r e p e a t e d ultrasonication to yield 190 m g of total organic m a t t e r , f r o m which a b a s i c fraction (Base m i x t u r e C) was obtained as usual. B a s e m i x t u r e C amounted to 0.4 rag. 124

Chem. Geol., 7 (1971) 123-141

Base mixture A was further fractionated by p a s s a g e through a s h o r t (10 cm) activated aluminum oxide column. Seven crude fractions w e r e collected by elution with hexane and h e x a n e / b e n z e n e (1/1). Each of t h e s e fractions was then analyzed by gas chromatography (Varlan A - 9 0 P 3 i n s t r u ment, 10 ft.× 1 / 4 inches column of 5% SE-30 on 100/120 Aeropak 30, p r o g r a m m e d from 75-250°C at 4 ° / m i n , helium flow rate of 50 m l / m i n ) and m a j o r components w e r e collected to be r e c h r o m a t o g r a p h e d on a 6 ft. × 1 / 4 inches column of Carbowax 20 ml/5% KOH, on 100/110 A e r o pak 30, operated i s o t h e r m a l l y depending on the fraction analyzed. M a j o r peaks collected from these runs were subsequently analyzed by low r e s o l u tion m a s s s p e c t r o m e t r y . In addition, the total base mixture A was a n a l y z e d by high-resolution m a s s s p e c t r o m e t r y . Base mixture B was analyzed by high-resolution m a s s s p e c t r o m e t r y as a total mixture. A gas c h r o m a t o g r a m (Varian 204, 10 ft. × 1 / 8 inches column, 3% SE-30 on c h r o m o s o r b , p r o g r a m m e d from 100-250°C at 6 ° / m i n with a helium flow r a t e of 40 m l / m i n ) was also run and is shown in Fig.1.

Fig.1. Gas c h r o m a t o g r a m of base mixture B (run on a Varian Model 204 gas c h r o m a t o g r a p h u s i n g a 10 ft. x 1 / 8 inch column, packed with 3% SE-30 on c h r o m o s o r b , p r o g r a m m e d from 100-250°C at 6 ° / m i n with a He flow rate of 40 m l / m i n ) .

Extraction of the shale from the Colony Mine A sample of pulverized rock was' exhaustively extracted by both Soxhlet extraction (1 w e e k ) a n d repeated u l t r a s o n i c a t i o n s using 3 / 1 b e n z e n e / m e t h a n o l . The combined total e x t r a c t amounted to 2,121..0 mg p e r 100 g of sample. F r o m this extract 5.5 m g b a s e s p e r 100 g of s h a l e (Base mixture D) were isolated in the usual m a n n e r (a subsequent diethyl ether extract yielded an additional 3.0 mg of m o r e polar bases). This sample was then d e m i n e r a l i z e d by the same p r o c e d u r e as d e s c r i b e d e a r l i e r , yielding 674.0 mg total organic m a t t e r per 100 g of shale f r o m which another b a s i c fraction was isolated as usual (Base m i x t u r e E). Base mixture E amounted Chem. Geol., 7 (1971) 123-141

125

to 0.43 m g and a subsequent e t h e r e x t r a c t yielded an additional 2.2 m g of material. E a c h b a s e m i x t u r e was again g a s - c h r o m a t o g r a p h e d and analyzed by h i g h resolution m a s s s p e c t r o m e t r y . The e x p e r i m e n t a l conditions w e r e kept the s a m e as for b a s e m i x t u r e s A - C , in o r d e r to facilitate c o m p a r i s o n s . An •i n f r a r e d s p e c t r u m ( P e r k i n - E l m e r Model 257 i n f r a r e d s p e c t r o p h o t o m e t e r , neat sandwich) of m i x t u r e D is shown in Fig.2. Gas c h r o m a t o g r a p h y w a s p e r f o r m e d on a Varian Model 204B (for a n a l y t i c a l runs) using 1 / 8 inches d i a m e t e r s t a i n l e s s s t e e l columns of 3% SE-30 on c h r o m o s o r b and a V a r i a n Model A90P3 (for p r e p a r a t i v e r u n s ) using 1 / 4 inches columns as specified above. All conventional m a s s s p e c t r a w e r e obtained with a Consolidated E l e c t r o d y n a m i c s C o r p o r a t i o n i n s t r u m e n t , Model 21-110B (electron e n e r g y 70 V, filament c u r r e n t 100 pA). S a m p l e s w e r e introduced via the d i r e c t p r o b e inlet, with the ion s o u r c e o p e r a t e d at 8 0 - 1 1 0 ° C . All h i g h - r e s o l u t i o n m a s s s p e c t r a w e r e obtained on a G E C - A E I i n s t r u m e n t , Model 902, coupled on-line to an XDS Sigma 7 c o m p u t e r ( B u r l i n g a m e et al., 1968; B u r l i n g a m e , 1968; B u r l i n g a m e et al., 1969a), the s a m p l e being introduced v i a d i r e c t introduction probe. Spectra w e r e r e c o r d e d at a r e s o l u t i o n of 10,000 with the following operating conditions: e l e c t r o n e n e r g y 70 V, filament c u r r e n t 450 b'A, ion s o u r c e t e m p e r a t u r e 200°C. Some m i x t u r e s w e r e a l s o a n a l y z e d by G.C.-M.S. techniques using a P e r k i n - E l m e r Model 270 gas c h r o m a t o graphic m a s s s p e c t r o m e t e r s y s t e m on-line to an XDS Sigma 2 c o m p u t e r (Burlingame et al., 1969b). All organic solvents used w e r e A.C.S. r e a g e n t g r a d e and r e d i s t i l l e d b e f o r e use or of nanograde purity. 200 m l of solvent upon e v a p o r a t i o n gave no organic r e s i d u e as judged by gas c h r o m a t o g r a p h y . RESULTS Shale s p e c i m e n collected at Parachute C r e e k H i g h - r e s o l u t i o n m a s s s p e c t r a l data of total f r a c t i o n s and m a s s s p e c t r a of s a m p l e s isolated by gas c h r o m a t o g r a p h y indicate that the m a j o r m o n o nitrogen constituents e x t r a c t a b l e f r o m the s e d i m e n t a r e compounds of g e n e r a l composition Cn H 2 n _ l l N (quinolines, i s o q u i n o l i n e s ) a n d compounds of the s e r i e s CnH2n-7 N, for which the c a r b o n s k e l e t o n s of t e t r a h y d r o quinolines and - i s o q u m o l i n e s , and of d i h y d r o p y r i n d i n e s or c y c l o a l k y l p y r i dines, etc., can be considered, l=~ridines (CnH2n_5N) and the compound c l a s s C_~H2~_9N, (indoles, b i c y c l o a l k a n o p y r i d i n e s ) a r e other i m p o r t a n t constituents which a p p e a r in l o w e r abundance, however. The v a r i o u s homologous s e r i e s and t h e i r r e s p e c t i v e r a n g e s found in the b a s e e x t r a c t s a r e listed in T a b l e I. The following r e p r e s e n t s a d i s c u s s i o n of the data obtained f o r the t h r e e b a s e m i x t u r e s (Base m i x t u r e s A, B and C; s e e s e c t i o n " E x p e r i m e n t a l " ) organized a c c o r d i n g to compound c l a s s . Compounds of composition C nH2 n-5 N (alkylpyridines) B a s e m i x t u r e A, obtained f r o m the initial e x t r a c t s , contains p y r i d i n e type c o m p o n e n t s ranging f r o m C7H9N to C17H29N with a m a x i m u m at CgH13N. In the h i g h - r e s o l u t i o n m a s s s p e c t r u m of this m i x t u r e (Fig.3, 126

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p r e s e n t e d a s h e t e r o a t o m i c plots, B u r l i n g a m e and Smith, 1968), the h o m o logs of this compound c l a s s , a s s u m e d to be m o l e c u l a r ions, c a n be s e e n by i n c r e m e n t i n g the peak indicated by the l e t t e r " P " b y CH2 units. It m u s t be pointed out that t h e s e data a r e b a s e d on 70 eV s p e c t r a and that s o m e of the p e a k s a s s i g n e d to m o l e c u l a r ions of a l k y l p y r i d i n e s could r e p r e s e n t f r a g m e n t ions. T h i s would not affect the c o r r e c t recognition of s t r u c t u r a l type, but would lead to e r r o n e o u s conclusions r e g a r d i n g the r a n g e of t h e s e compounds. T h e CnH2n..5N compounds a p p e a r as m a j o r c o m p o n e n t s but, again, p e a k height m a y be quite m i s l e a d i n g in quantitating. L o w - r e s o l u t i o n data on i s o l a t e d f r a c t i o n s has furnished evidence for alk-ylpyridines, with the C4, C5, C6 and C7 a l k y l p y r i d i n e s as p r o m i n e n t constituents. In addition, s e v e r a l f r a c t i o n s r e v e a l e d ions of m / e 205, 219 and 261, which m a y r e p r e s e n t m o l e c u l a r ions of l a r g e r a l k y l p y r i d i n e s . The s p e c t r u m of b a s e m i x t u r e B (exhaustive e x t r a c t b a s e s ) indicates a s i m i l a r distribution of pyridines. Ions c o r r e s p o n d i n g to the homologous s e r i e s f r o m C7H9 N ( C 2 - a l k y l p y r i d i n e s ) to C14 H25N (C9-alkylpyridines) a r e c l e a r l y o b s e r v e d with a m a x i m u m at C9H15N ( s a m e as for A). By c o n t r a s t , the b a s e f r a c t i o n C (obtained f r o m the d e m i n e r a l i z e d shale) contains few p y r i d i n e s ( s e e Fig.4) and only the ions of c o m p o s i t i o n C5HsN, C7H9N and C 8 H l l N could be c o n s i d e r e d as due to a l k y l p y r i d i n e s .

Compounds of composition C n H ~ _ 7 N (tetrahydroquinolines, dihydropyrindines , cyc loalky lpyridines) This c l a s s is quite abundant in b a s e m i x t u r e s A and B but is a l m o s t absent in the d e m i n e r a l i z e d shale e x t r a c t ( m i x t u r e C). F o r e x a m p l e , the m a s s s p e c t r u m of m i x t u r e A (Fig.3) shows p e a k s of this composition for the homologous s e r i e s CnH2n-TN ranging f r o m n = 8 - 1 9 with a m a x i m u m at n = 13 ( a e r i e s indicated by p e a k s l a b e l l e d "r"). S e v e r a l conventional m a s s s p e c t r a of compounds of this c l a s s isolated by gas c h r o m a t o g r a p h y (see " E x p e r i m e n t a l " section) a r e i l l u s t r a t e d in Fig.5, including t h r e e i s o m e r s of m o l e c u l a r weight 189 (C13 I-I19N), and in Fig.6, including four i s o m e r s of m o l e c u l a r weight 203 (C14 H21N). An i n t e r p r e t a t i o n of t h e s e s p e c t r a is not p o s s i b l e at this stage due to the unavailability of c o m p a r i s o n compounds; the f r a g m e n t a t i o n p a t t e r n s fit too m a n y , and ill-defined, s t r u c t u r a l a r r a n g e m e n t s . A compound (or compounds) of m o l e c u l a r weight 189 (C13H19 N) o c c u r s in c o n s i d e r a b l e abundance and a p p e a r s to be a m a j o r component, not only of this s e r i e s but a l s o in the total b a s e e x t r a c t . B a s e m i x t u r e B contains a s i m i l a r range of CnH2n-7N compounds. P e a k s c o r r e s p o n d i n g to the s e r i e s f r o m C g H l l N to C15 H23N a r e p r e s e n t , showing a m a x i m u m for C13H19 N. In the d e m i n e r a l i z e d shale t h e s e compounds a r e a l m o s t c o m p l e t e l y absent (see Fig.4). A component of c o m p o s i t i o n C13H19 N is the only r e p r e s e n t a t i v e of this c l a s s .

Compounds of composition CnH2n_9 N (indoles, pyrindines, bicvcloalkvH)vridines, cycloalkyltetrahydroquinolines, etc.)

Pe~Lks whi~cll ~could be a s s i g n e d to m o l e c u l a r ions of t h e s e compound c l a s s e s a p p e a r in both m i x t u r e s A and B in s i m i l a r distribution ( s e r i e s inclicated by p e a k s l a b e l l e d " I " Fig.3), a r a n g e f r o m about C8 to C20 is indicated with a m a x i m u m at Cll and C12. Ill b a s e m i x t u r e C (Fig.4) p e a k s due to this s e r i e s a r e e s s e n t i a l l y absent.

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Compounds of composition C n H 2 n _ l l N (quinolines, isoquinolines) This c l a s s is abundantly r e p r e s e n t e d in all extracts. F o r example, the high-resolution m a s s s p e c t r a l data (Fig.3) of mixture A shows the homologs ranging from n = 9 - 2 0 with C12 as m a x i m u m ( s e r i e s indicated by peak labelled "Q"). An essentially s i m i l a r distribution is indicated by the data for base mixture B. C.nIa~n-11 N compounds appear to c o m p r i s e the s e r i e s from the unsubstituted C9H7N skeleton to a p p r o x i m a t e l y C16 H21N, with a distinct maximum at C12 [C3-alkyl(iso)quinoline]. Quinolines or isoquinolines r e p r e s e n t the bulk of the b a s e s of the d e m i n e r a l i z e d shale - m i x 132

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ture C, and in even b r o a d e r range - up to C23. F r o m base m i x t u r e A s e v e r a l quinoline-type compounds w e r e isolated by gas c h r o m a t o g r a p h y . A r e p r e s e n t a t i v e m a s s s p e c t r u m of one of these, the p r e s u m e d C6 -alkylquinoline, is illustrated in Fig.7. F r a g m e n t a t i o n is r e s t r i c t e d essentially to loss of a CH3 radical, usually insufficient for any general s t r u c t u r a l deduction.

More condensed aromatic systems CnH2n_13N (phenylpyridines or cycloalkanoquinolines). In the b a s e m i x t u r e s from the f i r s t two e x t r a c t s (mixtures A and B ) and the d e m i n e r a l i z a t i o n (mixture C) these m o r e condensed a r o m a t i c s y s t e m s appear to be m i n o r contributors (see Fig.3). The homologous s e r i e s CnH2n_13N extends from n = 10-19 (C15 as m a x i m u m ) in both m i x t u r e s A and B. However, the m a s s s p e c t r a l data of base mixture C (Fig.4) - with the exception of a few peaks contains few components with a higher d e g r e e of unsaturation. CnH2n_15 (carbazoles). This homologous s e r i e s , CnH2n_-15N , extends f r o m n = 12-18 with n = 14 as m a x i m u m (cf. Fig.3). This s e r i e s is not found in base mixture C. CnH2n_17 N (acridines). Only in base m i x t u r e s A and B is a m i n o r s e r i e s of acridines indicated. This s e r i e s , CnH2n _17 N, r a n g e s f r o m n = 13-16 with C14 as maximum (cf. Fig.3). T h e s e compounds a r e entirely absent in b a s e mixture C (cf. Fig.4).

CnH2n_19N (c~cloalkylacridines). The homologs of CnH2n_19N a r e limited to two m e m b e r s in both base m i x t u r e s A and B, namely, C15 H l l N and C16 H13N. They a r e lowest in intensity of all the s e r i e s dicussed. N - O compounds B a s e d on h i g h - r e s o l u t i o n m a s s s p e c t r a l data obtained for b a s e m i x t u r e s A (Fig.3) and B, the m a j o r constituents of the C / H NO compound category belong to the s e r i e s C.n H2n_ 7NO, i.e., oxygenated t e t r a h y d r o q u i n o lines, cycloalkylpyridones, etc. Somewhat s u r p r i s i n g l y , m o n o - o x y g e n a t e d compounds of the quinoline type (CnH2n_llNO) a r e not prominent. The range of the CnH2n_7NO s e r i e s (C10-C16) p a r a l l e l s roughly the distribution of the corresponding C~H2n-7N s e r i e s ( c o m p a r e C / H N plot of Fig.3). Another s e r i e s of the composition CnH2n _gNO and ranging from n = 9 - 1 7 with C12 as maximum is p r e s e n t in the b a s e m i x t u r e s A and B. This is a s e r i e s of tetrahydroquinolines or oxygenated indoles, and again the range p a r a l l e l s the distribution of the c o r r e s p o n d i n g CnH2n_gN s e r i e s . P y r i d o n e s (CnH2n_5NO) - p a r t i c u l a r l y the lower m e m b e r s of this s e r i e s (C7 - C l l ) a r e apparent as a m i n o r s e r i e s (cf. C / H NO plot of Fig.3).

Shale specimen from the Colony Mine Again, the high-resolution m a s s spectral data of the total fractions and mass spectra from G.C.-M.S. runs indicate that the major mono-nitrogen constituents are compounds having the general compositions CnH2n_11N and CnH2n_7N. In minor amounts are found the series CnH2n-sN and CnH2~_9N. 134

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A s u m m a r y of the r a n g e d i s t r i b u t i o n s of t h e s e and v a r i o u s other h o m o l o g o u s s e r i e s is found in T a b l e I. Since t h e s e b a s e e x t r a c t s ( m i x t u r e s D and E) a r e virtually- i d e n t i c a l to the r e s p e c t i v e b a s e e x t r a c t s d i s c u s s e d e a r l i e r (see p. 126), only the n o t a b l e d i f f e r e n c e s a r e d i s c u s s e d in d e t a i l h e r e . An e x a m p l e of the h i g h - r e s o l u t i o n m a s s s p e c t r a l d a t a for m i x t u r e D is shown in F i g . 8 . Of p a r t i c u l a r i n t e r e s t a r e a g r o u p of i n t e n s e ions t h a t can be d i s c e r n e d in the C / H N2 plot of F i g . 8 . A homologous s e r i e s of m o l e c u l a r ions of c o m p o s i t i o n CnH2n-10N 2 for n = 1 4 - 1 8 , with n = 14 a s a m a x i m u m , is a p p a r e n t . The f r a g m e n t ions (due to CI-I3 l o s s ) of c o m p o s i t i o n C n H 2 n - l l N 2 for n --- 1 3 - 1 7 a r e a l s o p r e s e n t . This s e r i e s m a y be r e p r e s e n t e d by such s k e l e t a l t y p e s a s s t r u c t u r e I, t e t r a h y d r o c a r b o l i n e H, a z a q u i n o l i n e HI, and IV and V, which can be thought of a s b r e a k d o w n p r o d u c t s of p o r p h y r i n s . The s t r u c t u r a l t y p e s I I I - V s e e m to be the m o s t l i k e l y .

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DISCUSSION As noted earlier, the major nitrogenous constituents fall into the composition classes CnH2~-7N and CnH2~_II N, where the former could be represented by cycloalkylpyridines, tetrahydroquinolines or tetrahydroisoquinolines and dihydropyrindines, and the latter by quinoline or isoquinoline Chem. Geol., 7 (1971) 123-141

137

s t r u c t u r a l types. L e s s e r amounts of p y r i d i n e s (CnH2n--sN) and of the c l a s s CnH2~_9 N ( b i c y c l o a l k y l - p y r i d i n e s or - p y r i n d a n e s , indoles) a r e p r e s e n t , but r e l a t i v e l y s m a l l a m o u n t s of m a t e r i a l with a higher d e g r e e of u n s a t u r a t i o n . The b a s e m i x t u r e s r e s u l t i n g f r o m the two e x t r a c t i o n s t e p s ( m i x t u r e s A and B) exhibit e s s e n t i a l l y s i m i l a r distributions of component c l a s s e s ( s e e T a b l e I). The d e m i n e r a l i z e d shale e x t r a c t m i x t u r e , however, showed v e r y m a r k e d d i f f e r e n c e s . T h e total yield of b a s e s was much s m a l l e r and the only significant components a p p e a r to be quinolines (CnH2n-llN); p r e s u m a b l y , t h e s e m u s t be m o r e intimately i n c o r p o r a t e d into the m i n e r a l m a t r i x , but our r e s u l t s hardly w a r r a n t m o r e expansive speculations. The b a s e m i x t u r e D again exhibited the homologs of c o m p o s i t i o n s CnH2n_7 N and CnH2n_llN a s the m a j o r constituents, with an o v e r a l l d i s t r i bution analogous to m i x t u r e s A and B. B a s e m i x t u r e E f r o m the d e m i n e r a l i zation was of low yield and only the quinoline s e r i e s (CnH2n_llN) w a s p r e s e n t in significant concentration. O v e r a l l , the c l a s s or c l a s s e s of compounds c o r r e s p o n d i n g to the e m p i r i c a l composition CnH2n_7N(i.e., t e t r a h y d r o q u i n o l i n e s , d i h y d r o p y r i n dines, and r e l a t e d s u b s t a n c e s ) a p p e a r to be the m a j o r constituents of our e x t r a c t s . Among t h e s e the compounds of MW 189 (C13 H19N) a r e the m o s t p r o m i n e n t (see Fig.3, 8). A n u m b e r of compounds of this type a r e known f r o m p e t r o l e u m s o u r c e s , e.g., tetrahydroquinoline and the c y c l o h e x y l p y r i dine (VI) (Lochte and Littmann, 1955; B r a n d e n b u r g and L a t h a m , 1968), a s well a s s e v e r a l dihydropyrindines, e.g., (VII) (Lochte and P i t t m a n , 1960a and b).

VII

VIII

Our r e s u l t s do not allow a distinction between t h e s e p o s s i b l e r i n g s y s t e m s . F o r the group of c o m p o s i t i o n CnH2n_9N , indoles, as well as c y c l o a l k y l t e t r a h y d r o q u i n o l i n e s , c y c l o a l k y l d i h y d r o - p y r i n d i n e s or c y c l o a l k a n o d e r i v a t i v e s of t h e s e s t r u c t u r e s , m a y be c o n s i d e r e d . The p r e s e n c e of the weakly b a s i c indoles is p e r h a p s l e s s likely, since the isolation of the b a s e m i x t u r e involved an acid e x t r a c t i o n s t e p which should lead to the p r e f e r e n t i a l a c c u m u l a t i o n of the m o r e b a s i c nitrogen compound types. V e r y r e c e n t l y , the cyclopentanodi_hydropyrindine (VIII) was identified by B r a n d e n b u r g and L a t h a m (1968) in Wilmington p e t r o l e u m , the only compound of this s t r u c t u r a l c l a s s thus f a r c h a r a c t e r i z e d . A l k y l p y r i d i n e s (CnH2n_sN) and quinolines a r e known constituents of the shale oil derived f r o m the C o l o r a d o G r e e n R i v e r F o r m a t i o n . In a v e r y c o m p r e h e n s i v e study on the C o l o r a d o G r e e n R i v e r shale oil by Dinneen et al. (1961) sixteen a l k y l p y r i d i n e s a r e listed a m o n g the identified n i t r o g e n compounds. M a j o r constituents isolated w e r e 2 , 4 , 6 - t r i m e t h y l p y r i d i n e and 2 , 9 - d i m e t h y l - 6 - e t h y l p y r i d i n e , which would a g r e e with the m a s s s p e c t r o m e t r i c r e s u l t s (see Fig.3, 8) showing the C8 - and C 9 - p y r i d i n e s to be m a j o r components. Roughly two dozen individual alkylquinolines have been identified in p e t r o l e u m . In the Colorado G r e e n R i v e r shale oil naphtha~ 138

Chem. Geol., 7 (1971) 123-141

quinoline and 2 - m e t h y l q u i n o l i n e have been known to o c c u r (Ball et al., 1949). Our data suggest that a C3-alkylquinoline (C12 H 1 3 N ) i s the m a j o r constituent of the e x t r a c t a b l e b a s e s . T h e g e n e r a l distribution p a t t e r n of quinolines does not s e e m to v a r y a m o n g the f r a c t i o n s obtained (base m i x t u r e s A, B, C, D and E 9 cf. T a b l e I). Relatively m i n o r a m o u n t s of m o r e u n s a t u r a t e d polycyclic s y s t e m s a r e p r e s e n t . Such n o n - b a s i c s t r u c t u r a l types as c a r b a z o l e s (CnH2n_15 N) and aliphatic or a r o m a t i c n i t r i l e s would not be expected in our e x t r a c t s . T h i s is f u r t h e r s u b s t a n t i a t e d by the i n f r a r e d data (cf. Fig.2), w h e r e no band attributable to n i t r i l e s was found. Likewise, the r e l a t i v e absence of p y r r o l e s is not s u r p r i s i n g c o n s i d e r i n g the weakly b a s i c c h a r a c t e r of these c o m p o u n d s . P y r r o l e s (e.g., 2 - m e t h y l p y r r o l e ; 2 , 3 , 4 , 5 - t e t r a m e t h y l p y r r o l e ; 2~3,5-trim e t h y l - 3 - e t h y l p y r r o l e ) and n i t r i l e s (benzonitrile, alkyl substituted benzonitriles and aliphatic n i t r i l e s ) have been r e p o r t e d in Colorado G r e e n R i v e r shale oil ( J a n s s e n et al., 1951; Van M e t e r et al., 1952; Iida et al., 1966). No C / H N4 s p e c i e s w e r e detected, p r e s u m a b l y b e c a u s e the p o r p h y r i n s which fit into this c a t e g o r y a r e sufficiently n o n - b a s i c to be extracted by the method used in this study. Oxygen-containing nitrogen compounds a r e not abundant ( p e r h a p s again due to the e x t r a c t i o n method). The m a j o r r e p r e s e n t a t i v e s of t h e s e c l a s s e s fall into the c a t e g o r y CnH2n_TNO - i.e., o x y - t e t r a h y d r o q u i n o l i n e s or r e l a t e d s t r u c t u r e s . Finally~ the r e l a t i v e l y abundant dinitrogen compounds of c o m p o s i t i o n CnH2n_10N2 a r e of i n t e r e s t , since s t r u c t u r e s of this composition have not been d e s c r i b e d f r o m shale oil s o u r c e s although they a r e found in C a l i f o r n i a p e t r o l e u m d i s t i l l a t e s (Snyder et al., 1968; Snyder, 1969). In s u m m a r y , while a d i r e c t c o m p a r i s o n of the nitrogen compound s e r i e s found in the e x t r a c t s with those found in the shale oil is not p o s s i b l e , a general c o r r e l a t i o n can be made. The m a j o r constituents of shale oil (Dinneen et al., 1961) a r e of a m o r e dehydrogenated and n o n - b a s i c n a t u r e than the b a s i c e x t r a c t s of the shale. T h e s e d i r e c t e x t r a c t s contain h i g h e r p r o p o r t i o n s of m o r e s a t u r a t e d ring s y s t e m s and l o w e r amounts of the nonb a s i c and m o r e volatile constituents. Also, oxygenated nitrogen compounds a r e found in the e x t r a c t s . T h e y have not been r e p o r t e d significantly p r e s e n t in shale oil, probably b e c a u s e they would eliminate w a t e r during r e t o r t i n g . In California p e t r o l e u m d i s t i l l a t e s a whole suite of NO s p e c i e s has been found by Snyder et al. (1968) and Snyder (1969). F r o m these r e s u l t s , d i r e c t solvent extraction and subsequent isolation of nitrogenous m a t e r i a l a p p e a r s to be the m i l d e s t t r e a t m e n t to analyze the indigenous nitrogen compounds of the oil shale. T h u s , f u r t h e r w o r k in this a r e a is continuing at this l a b o r a t o r y . ACKNOWLEDGEMENTS We thank M r s . Ellen Scott for technical a s s i s t a n c e , Mr. E . F . M o r r i l l of the Colony D e v e l o p m e n t Company for the g e n e r o u s gift of Colorado G r e e n R i v e r oil shale, and the U.S. National A e r o n a u t i c s and Space A d m i n i s t r a t i o n for financial support (grants NGL 05-003-003, NAS 9-7889 and NAS 9-9593).

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