6 Diesel and Burner Fuels from Hydrocracking in
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Situ Shale Oil PHILIP L. COTTINGHAM and L E O G. NICKERSON Laramie Energy Research Center, Energy Research and Development Administration, Laramie, Wyo. 82070
For several years, the Laramie Energy Research Center has conducted research in recovering shale o i l through in situ retorting by the underground combustion method. Crude shale o i l s produced by this method normally have lower specific gravities, viscosities, and pour points than do crude shale o i l s produced in the gas combustion or N-T-U retorts. They also contain somewhat less nitrogen, but the sulfur content is not greatly different from that of the crude o i l s from these aboveground retorts. Percentages of both elements are higher than desirable in liquid fuels or in feedstocks that are to be processed to high-quality liquid fuels by most catalytic refining processes. Catalytic hydrogenation at cracking conditions, referred to here as "hydrocracking," has been found by previous experiments to be a suitable method for producing low-sulfur, low-nitrogen "synthetic crude" o i l s from in situ crude shale o i l s (1,2,1). One of the primary objectives of these previous experiments has been to increase the quantity of gasoline contained in the hydrocracked synthetic crudes. A limited investigation of the s u i t a b i l i t y of fractions of the hydrocracked o i l s as catalytic reforming and catalytic cracking feedstocks for the production of gasoline has been made however, little attention has been given to the types of diesel fuels and fuel oils that can be prepared from the fractions. The purpose of the present work was to investigate the quant i t y and quality of diesel fuels and fuel o i l s that could be prepared from the liquid product obtained by hydrocracking of in situ combustion shale oil. A sample of the in situ crude o i l was hydrocracked at operating conditions that had been found by previous experiments to be effective in eliminating most of the nitrogen and sulfur from the o i l and in greatly reducing the average b o i l ing point of the oil. The hydrocracked o i l was d i s t i l l e d into a 350° F end-point reforming stock and small-volume heavier fractions. Diesel fuels, suitable for use also as fuel o i l s , were prepared by blending small-volume fractions.
99 In Hydrocracking and Hydrotreating; Ward, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
100
HYDROCRACKING A N D H Y D R O T R E A T I N G
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Apparatus and Operating Procedure A simplified flow diagram of the hydrocracking equipment is shown in Figure 1. The reactor was a type 316 stainless steel tube 40 inches long, with 9/16-inch inside diameter and 1-inch outside diameter. A stainless steel screen 10^ inches from the bottom of the reactor supported 50 ml of catalyst that extended approximately 12% inches above the screen. A second screen on top of the catalyst supported 50 ml of quartz chips in the upper, preheating section of the reactor. The reactor was surrounded by a c y l i n d r i c a l , 3-inch-outside-diameter aluminum block, contained in a 36-inch-long electric furnace that covered essentially a l l but the exposed high-pressure fittings at the ends of the reactor. Temperatures were measured by five thermocouples placed at uniformly spaced intervals along the catalyst-containing section of the reactor in a groove in the inner wall of the aluminum block. Other thermocouples were used to control the temperature of the surrounding furnace. Before the hydrocracking experiment, the catalyst was pretreated in the reactor for 16 hours at 700° F with a mixture of 1.1 standard cubic feet of a i r and 0.41 pound of steam per pound of catalyst per hour. After the pretreatment, the reactor was cooled to 500° F; then the steam was cut off. When the reactor cooled to 350° F, the a i r flow was cut off. The reactor was next purged with helium and pressurized to 250 psig with hydrogen. A stream of hydrogen containing 5 volume-percent hydrogen sulfide at a total pressure of 250 psig was then passed through the reactor at a rate of 1 scf per hour for 4 hours. During this time the reactor was heated from 350° to 600° F. The reactor was then heated to the planned hydrocracking temperature, and brought to the planned total reaction pressure with hydrogen, and a stream of hydrogen at the proposed experimental rate was passed through the reactor for 30 minutes. The o i l feed pump was then started. During the experiment, o i l pumped by positive displacement was mixed with hydrogen at the top of the reactor and passed downward through the catalyst. The resulting products passed through a backpressure regulator into a separator maintained at 200 psig and 75° F. Gas from the separator passed through a second backpressure regulator and was metered and sampled for gas chromatographic analysis. The liquid product was drained from the separator at the end of each 24-hour period and was washed with water to remove hydrogen sulfide and ammonia before i t was analyzed. Hydrogen flow was metered with a mass flowmeter, but total hydrogen feed was measured by the volume removed from calibrated storage vessels. Hydrogen consumption was calculated from the analyses of feed and product gases. After the experiment, the used catalyst was purged with steam and then regenerated with a mixture of steam and a i r ; the regeneration gas was dried and any carbon dioxide formed was absorbed by Ascarite for determination of the percent carbon deposit.
In Hydrocracking and Hydrotreating; Ward, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
coTTiNGHAM A N D NiCKERSON
Diesel and Burner Fuels
101
ROTAMETER
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BACK-PRESSURE REGULATOR METERING VALVE
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6.
PRODUCT OIL TO DISTILLATION
