| The difficulty in the research of HDM catalysts is to improve the stability of such catalysts, which is closely related to the pore structure of catalysts. In order to prepare alumina supports with desired pore size distribution, several pore-enlarging methods have been researched in this paper. Firstly, the influence of several factors during the preparation process on the pore structure of alumina supports were investigated in details, such as calcination temperature, peptizing agent, extrusion fore and so on. Secondly, the pore-enlarging effect of hydrothermal treatment, which was affected greatly by processing mode, hydrothermal environment, duration and temperature, had also been researched. Thirdly, the influence of different kinds of pore-expanding agents had been studied. By combining the hydrothermal process and adding pore-expanding agents, four kinds of HDM catalysts with different pore structure were prepared. The activity and stability of these catalysts have been investigated by using 100mL High-pressure fixed bed reaction unit.The pore structure with diameter greater than 10nm in aluminum hydroxide would collapse totally after extrusion, drying and calcination. The extrusion force is the main factor which caused the collapse of pore structure above 10nm. These pore structure originate from the loosing pack of fibrous particles of the aluminum hydroxide. The extrusion force is strong enough to force these fibrous particles to form compact packing, which is responsible for the diminishing of large pore structure. The influence of the extrusion force on large pore structure can be greatly decreased by adding the water/powder ratio used in the extrusion process. When the water/powder ratio equals to 1.52, the alumina support as-prepared would have a bimodal pore size distribution.Under the same condition, the pore-enlarging effect by hydrothermal treating alumina is better than the effect by treating aluminum hydroxide. Hydrothermal environment has a great effect both on pore structure and micro-morphology. The average diameter of alumina supports as-prepared under different hydrothermal environment decreased follow this order: ammonia>deionized water>acetate solution. The concentration degree of the Pore size distribution of alumina supports is associated with the homogeneity of the micro-morphology of the boehmite as-prepared. The pore structure of alumina supports can be adjusted and controlled selectively by adjusting the duration and temperature of the hydrothermal treatment.The pore-enlarging effect of different pore-expanding agents varies greatly. Pore structure with the diameter greater than 100nm can be generated by using PAM with the molecular weight 3,000,000, CMC or micron-sized activated carbon. But pore volume of alumina support can't be improved efficiently by using PAM or CMC as pore-expanding agent. Pore volume of the alumina support increased greatly as the amount of the activated carbon added, so did the ratio of the pore volume of the macro-pores generated to the total volume.The stability of the catalyst with bigger average diameter was better than others. The existence of some macro-pores with diameter greater than 100nm in the calyst was also benefit for improving the stability of the catalyst in HDV reaction. The catalyst with a dispersed distribution between 10-30nm had high activity, and the stability of which is also good. Pore structure of the catalysts has less effect on the HDNi activity than the HDV activity. The amount of coke deposited on the spent catalysts was massive, with the highest amount could reach 12.7%. The V removed would also deposit on the surface of catalysts. HDM-3 catalyst had the highest activity in HDV reaction after the duration of 96h, which can reach 56.0% and was much higher than reference catalyst RDM by 8.5%. The activity of HDM-3 catalyst in HDNi reaction can reach 33.0%, as well as RDM catalyst.
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