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Downloaded by UNIV OF MISSOURI COLUMBIA on November 27, 2013 | http://pubs.acs.org Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch025
Hydropyrolysis: The Potential for Primary Upgrading of Tar Sand Bitumen J. W. BUNGER, D. E. COGSWELL, R. E. WOOD, and A. G. OBLAD Department of Mining and Fuels Engineering, 320 WBB, University of Utah, Salt Lake City, UT 84112 Upgrading of high molecular weight, residual materials is becoming increasingly important as a result of decreasing availability of lighter feedstocks. Conversion processes for residual materials must contend with high heteroatom content, high molecular weight (low volatility), high aromaticity and high metals content not encountered to the same degree in lighter feedstocks. These characteristics result in higher process costs and typically lower conversion and yield of desired products. But as production recovery and processing costs rise, yield and conversion efficiency become increasingly important. As a result, conventional techniques for primary conversion of residual materials such as tar sand bitumen, e.g. coking, may prove economically unacceptable. A possible alternative for the primary conversion of residual material is hydropyrolysis. Hydropyrolysis (HP) is a process for thermal cracking in the presence of hydrogen. This process has been shown to dramatically improve the yields of liquid and gaseous products compared to coking (1,2,3,4,5). Hydropyrolysis does not require the introduction of heterogeneous catalysts but requires elevated pressures. Through model compound work (5) and characterization (6) and processing (7) of high molecular weight tar sand bitumen, an understanding of the chemistry of this reaction is beginning to emerge. This paper reports our latest results and discusses the chemical changes effected by hydropyrolysis. The implication of the possible reactions to the suitability of various feedstocks for processing by hydropyrolysis is also discussed. Experimental Feedstock Source. Three feedstocks were used i n t h i s study. A l l were derived from U i n t a Basin, Utah Tar Sand d e p o s i t s . A Sunnyside bitumen was solvent extracted by procedures p r e v i o u s l y reported (6) from a f r e s h l y mined sample obtained from the o l d Asphalt Quarry northeast of Sunnyside, Utah. An Asphalt Ridge bitumen was extracted s i m i l a r l y from a sample f r e s h l y mined from
0097-6156/8l/0163-0369$05.00/0 © 1981 American Chemical Society
In Oil Shale, Tar Sands, and Related Materials; Stauffer, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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OIL
SHALE, TAR SANDS, AND RELATED MATERIALS
Downloaded by UNIV OF MISSOURI COLUMBIA on November 27, 2013 | http://pubs.acs.org Publication Date: September 3, 1981 | doi: 10.1021/bk-1981-0163.ch025
the U i n t a County Quarry southwest of V e r n a l , Utah. The TS-IIC o i l was used as r e c e i v e d from the U.S. Department of Energy, Laramie Energy Technology Center (LETC). The TS-IIC o i l i s r e p r e s e n t a t i v e of the o i l produced during an echoing i n - s i t u combustion o i l recovery p r o j e c t conducted at Northwest Asphalt Ridge by the LETC l a b o r a t o r i e s (8). Elemental A n a l y s i s and P h y s i c a l P r o p e r t i e s . Elemental a n a l y s i s was accomplished by conventional m i c r o a n a l y t i c a l techniques i n a commercial t e s t i n g l a b o r a t o r y . D e n s i t i e s were measured on a Mettler/Paar d i g i t a l d e n s i t y meter, model D.M. 40. Number average molecular weights were determined by VPO i n benzene. Simulated d i s t i l l a t i o n was accomplished using a 1/4" by 18" column of 3% d e x s i l 300 on chromosorb W, programmed from -30° to 350°C at 10°/minute with a 4 minute hold at 350°C. The detector was a flame i o n i z a t i o n detector maintained at 400°C. The percent n o n d i s t i l l a b l e m a t e r i a l was determined by using as an i n t e r n a l standard, an equal volume^mixture of C^ to C ^ n - a l k y l benzenes (See a l s o reference 9). C-NMR spectra data were obtained as reported i n reference (_3) . Hydropyrolysis Process. Two h y d r o p y r o l y s i s r e a c t o r s were used i n t h i s study. The Sunnyside and Asphalt Ridge bitumen were processed i n a r e a c t o r c o n s i s t i n g of a c o i l e d s t a i n l e s s s t e e l tube 3/16" i . d . x 236" long. T h i s r e a c t o r has been p r e v i o u s l y described by Ramakrishnan (1). The TS-IIC o i l was processed i n a r e a c t o r o r i g i n a l l y developed f o r short residence time c o a l l i q u e faction. T h i s r e a c t o r a l s o c o n s i s t s of c o i l e d s t a i n l e s s s t e e l tubes 3/16" i . d . The length of t h i s tube system can be v a r i e d from 20 to 120 f e e t , and has been p r e v i o u s l y described by Wood, et a l . (10). The length of the r e a c t o r f o r runs reported i n t h i s paper was 100 f e e t . Average residence times were c a l c u l a t e d from the volumetric flow r a t e s and the r e a c t o r volume at process c o n d i t i o n s . The r e a c t i o n mixture, which i s predominantly H^, was assumed f o r purposes of t h i s c a l c u l a t i o n to behave as an i d e a l gas. The r e a c t o r s were p r e - s u l f i d e d with H^S to i n h i b i t c a t a l y t i c r e a c t i o n s from w a l l s u r f a c e s . Results The elemental a n a l y s i s and p h y s i c a l p r o p e r t i e s f o r the U i n t a Basin d e r i v e d feedstocks are given i n Table I. The elemental analyses r e v e a l compositions t y p i c a l of U i n t a Basin bitumens (11) i n that H/C r a t i o s f a l l between 1.53 and 1.66, n i t r o g e n contents are a p p r e c i a b l e (~1%) and s u l f u r content i s low (
