Letters to the Editor Changes in coal particles during simultaneous coal hydrogenation and bitu- men hydrocracking Marten Ternan and Basil I. Parsons Energy Research Laboratories, Department of Energy, Mines and Resources, Ottawa, Ontario KlA OG 1, Canada (Received 11 July 19751 When Athabasca bitumen is hydrocracked, coke and met- als formed from compounds in the bitumen are deposited on the catalyst surface. This fouling and deactivation ne- cessitate frequent catalyst replacement, which causes con- siderable operating expense. In an attempt to reduce the cost of catalyst replacement, studies in our laboratories have been directed at hydrocracking bitumen in the pre- sence of coal particles, rather than conventional catalyst. It has been shown *? that the coal pa rt’ le are able to accu- rc s mulate metals and coke deposited from the bitumen. The objectionable material is thereby removed from the reaction system with the coal particles. The reaction conditions used for hydrocracking the bitumen also cause some hydro- genation of the coal. The purpose of this Letter is to des- cribe the changes in the coal particles while they were in the reactor. The hydrocracking experiments were performed using a bench-scale fixed-bed reactor3 having a volume of 15.5 ml and a length-to-diameter ratio of 12. Semi-anthracite coal (M = O-8, V’Rf = 13-4, ash= 7.8, FC= 78.0 wt %) from Can- more, Alberta, or lignite (M = 18.3, I’M = 35.6, ash = 10.2, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGF FC = 35.9%) from Estevan, Saskatchewan in the form of 2.38 to 4.76 mm diameter particles (-4 +8 mesh U.S. stan- dard sieve size) were placed in the reactor. Bitumen from the Alberta oil sands, described previously’, and electroly- tic hydrogen (purity, = 99-9 wt %) flowed continuously into the bottom of the reactor and up through it. The product leaving the top of the reactor flowed to receiver vessels where the liquid and vapour were separated. Each experi- ment was performed at the following steady-state condi- tions for a period of 10.8 ks (3 h): pressure 13.9 MPa (2000 psig), temperature 723 K, bitumen volumetric space velocity O-278 ks-1 (1.0 h-l) based on an empty reactor, and a hydrogen flow rate of 35.9 cm3/s at STP (5000 ft3/ bbl). After the hydrocracking experiment, the solids were taken from the reactor, and the adhering oil was removed with toluene in a Soxhlet apparatus. Subsequently, the to- luene was evaporated from the solids at room temperature. F&w-e I shows the change in weight of coal solids with time, where time has been measured in terms of the num- ber of experimental cycles. Each experimental cycle con- sisted of bringing the reactor and its contents up to the ex- perimental conditions, maintaining the reaction conditions for 3 h, and bringing the system back to ambient condi- tions. The weight of solids is simultaneously decreased ow- ing to hydrogenation of coal and increased through deposi- tion of coke formed from compounds in the bitumen. It is apparent, from the data shown in Figure I, that coal hydro- genation was the predominant process at the conditions used in these experiments. It is also clear that the weight reduction of lignite was much more rapid than that of semi- anthracite coal. The higher moisture and volatile matter in the lignite may contribute to this phenomenon. In any event, this result is consistent with data obtained by hydro- genating coal in the absence of bitumen. For example, a I I Number of cycles Figure 1 Weight % solids remaining in reactor versus number of cycles (reaction time). Each experimental cycle consisted of bring- ing the reactor and its contents up to the experimental conditions, maintaining the experimental conditions for 10.8 ks (3 h), and bringing the system back to ambient conditions 0 semi-anthracite, 0 lignite summary prepared by Wu and Storch4 shows that higher yields of gasoline and middle oil are obtained from low- rank coals than from high-rank coals. Figure 2 shows that the size of the solid particles decrea- ses with increasing reaction time. The largest change in size was observed after the first cycle. A much smaller change in particle size occurred between the first and later cycles. At similar reaction times, the size of the lignite particles was generally smaller than that of the less reactive semi-anthra- cite coal particles. By combining the information in Figures 1 and 2, it is apparent that the total weight of solid-phase material decreased, and that the material which did remain as solid-phase particles became smaller in size as the reaction time increased. Hawever, the reduction in particle size was not directly proportional to the decrease in solids weight as may be seen by comparing lignite particles after 4 cycles and semi-anthracite particles after 5 cycles. The extent of coal hydrogenation and coke deposition reactions is indicated in Figure 3 as a function of the final FUEL, 1975, Vol 54, October 297