19 Pyrolysis of Shale Oil Crude and Vacuum Distillate Fractions ROBERT N. HAZLETT and ERNA J. BEAL
Downloaded by PURDUE UNIV on November 17, 2016 | http://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch019
Naval Research Laboratory, Washington, D C 20375
The vacuum d i s t i l l a t e from Paraho shale o i l crude was separated on s i l i c a gel into three f r a c t i o n s - saturate, aromatic, and p o l a r . The carbon-13 NMR spectra indicated that these f r a c t i o n s contained 58, 15 and 36 percent, respectively, of unbranched a l k y l groups. These fractions were subjected to pyrolysis at 450°C for various times. The y i e l d of JP-5 jet fuel was good for the saturate fraction, varying between 24 and 27 percent for pyrolysis times of 15 to 120 minutes. The JP-5 yield for the polar fraction was lower, 18 to 22%. The n-alkanes and 1-alkenes were determined by capillary gas chromatography. The sum of these two classes comprised over 30 percent of the JP-5 cut in the saturate pyrolysis product but less than 15 percent for the polar and aromatic pyrolysis products.
The f r e e z i n g p o i n t o f U.S. Navy j e t f u e l (JP-5) has been r e l a t e d to the amounts o f l a r g e n-alkanes present i n the f u e l (1,2). This behavior a p p l i e s t o j e t f u e l s d e r i v e d from a l t e r n a t e f o s s i l f u e l resources, such as shale o i l , c o a l , and t a r sands, as w e l l as those d e r i v e d from petroleum. In general, j e t f u e l s from shale o i l have the highest and those from c o a l the lowest n-alkane content. The o r i g i n o f these n-alkanes i n the amounts observed, e s p e c i a l l y i n shale-derived fuels, i s not readily explained on the b a s i s o f l i t e r a t u r e information. Studies of the processes, p a r t i c u l a r l y the ones i n v o l v i n g thermal s t r e s s , used t o produce these f u e l s are needed t o define how the n-alkanes form from l a r g e r molecules. The information developed w i l l s i g n i f i c a n t l y c o n t r i b u t e to the s e l e c t i o n o f processes and r e f i n i n g techniques f o r future f u e l production from shale o i l .
T h i s c h a p t e r n o t subject t o U . S . c o p y r i g h t . P u b l i s h e d 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.
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GEOCHEMISTRY A N D CHEMISTRY O F OIL SHALES
Carbon-13 nmr s t u d i e s i n d i c a t e that o i l shale from the Green River Formation contains much a l i p h a t i c m e t e r i a l ( 3 ) . F u r t h e r , the shale o i l derived from the rock a l s o gives i n d i c a t i o n of considerable s t r a i g h t c h a i n m a t e r i a l w i t h large peaks at 14, 23, 30 and 32 ppm i n the C-13 nmr spectrum. Previous p y r o l y s i s studies at NRL s t r e s s e d f r a c t i o n s of crude shale o i l r e s i d u a , measured the y i e l d s of JP-5, and determined the content of p o t e n t i a l n-alkanes i n the JP-5 d i s t i l l a t i o n range ( 4 ) . A d d i t i o n a l s t u d i e s have p y r o l y z e d model compounds w i t h long uhbranched a l k y l groups ( 5 ) . These types of compounds a r e thought t o be p r e s e n t i n s h a l e crude o i l . T h i s work presents the r e s u l t s o f two s t u d i e s : (a) the p y r o l y s i s of Paraho crude shale o i l and (b) the separation, a n a l y s i s and p y r o l y s i s of the shale o i l vacuum d i s t i l l a t e . In part ( b ) , a shale crude o i l vacuum d i s t i l l a t e (Paraho) was separated i n t o three chemical f r a c t i o n s . The f r a c t i o n s were then subjected to nmr a n a l y s i s to estimate the p o t e n t i a l f o r n-alkane production and to p y r o l y s i s studies to determine an experimental n-alkane y i e l d .
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Experimental D e t a i l s P y r o l y s i s Procedure. The shale o i l samples were stressed at c o n d i t i o n s s i m i l a r to the petroleum r e f i n i n g process known as delayed coking ( 6 ) . These c o n d i t i o n s are 450°C and about 90 p s i pressure. Each Thermal s t r e s s was conducted i n a 1/4 inch o.d. 316 s t a i n l e s s s t e e l tube f i t t e d w i t h a s t a i n l e s s s t e e l v a l v e v i a a Swagelok connection. The tube, with a weighed amount of sample (approximately 0.1 g ) , was attached to a vacuum system, cooled t o -78°C, and pumped to remove a i r . The tube was then thawed and the cooling/pumping process repeated. The tubes were heated by inserting them i n t o 9/32-inch holes i n a s i x - i n c h diameter aluminum block fitted with a temperature controller. Complete d e t a i l s of sample workup and a n a l y s i s can be found i n r e f e r e n c e ( 4 ) . One gas chromatographic (GC) technique d e t e r mined the JP-5 y i e l d from the p y r o l y s i s by summing the t o t a l FID area f o r carbon numbers 9 through 16. A second GC a n a l y s i s determined the i n d i v i d u a l n-alkanes and 1-alkenes w i t h a fused s i l i c a c a p i l l a r y column. Separation o f Vacuum D i s t i l l a t e . Paraho shale o i l was d i s t i l l e d at atmospheric pressure to an end p o i n t of 300°C. A second cut was obtained by continuing the d i s t i l l a t i o n at reduced pressure, 40 mm Hg. T h i s vacuum d i s t i l l a t e , with an end point of 300°C, was used i n the studies described below. The vacuum d i s t i l l a t e was separated on s i l i c a gel i n t o s a t u r a t e , a r o m a t i c , and p o l a r f r a c t i o n s by the p r o c e d u r e described e a r l i e r ( 4 ) . The vacuum d i s t i l l a t e comprised 33% of the crude shale o i l and contained 1.82% (W/W) of n i t r o g e n . The
Miknis and McKay; Geochemistry and Chemistry of Oil Shales ACS Symposium Series; American Chemical Society: Washington, DC, 1983.
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HAZLETT A N D BEAL
Shale Oil Crude & Vacuum Distillate
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three chemical c l a s s e s represented 36%-saturates, 22%-aromatics, and 42%-polars o f the vacuum d i s t i l l a t e and contained
