关键词: 加氢裂化, 催化剂, 费托合成蜡, 活性相, 选择性

Abstract: Hydrocracking catalyst for Fischer-Tropsch synthesis of wax was prepared by impregnation method with Ni/W metals on amorphous SiO2-Al2O3 support modified by USY sieve and characterized. The active phase and activity evaluation of sulfide catalyst were also studied. The results indicate that active metal components disperse on the support with high dispersion, and the catalyst with mesoporous structure has higher specific surface area and adsorption capacity. There exist three reduction peaks on the surface of catalyst at 340, 548 and 870℃, which represent NiO?Ni, W6+?W4+ and W4+?W2+ or W, respectively. Meanwhile, FT-IR spectra show that the species of NiWS, WS2 and NiSx exist on the surface of sulfide catalyst. The layer number of WS2 slabs is the important factor to determine the catalytic activity of catalyst. It is induced that alkene has higher hydrogenation activity. Alkane is cracked and isomerized to small molecule alkene, some of which may be in intermediate transition state for farther formation of the small molecule alkane during the hydrocracking and isomerization. At the reaction temperature of 370℃, pressure of 6.4 MPa, hydrogen/wax volume ratio of 800:1 and space velocity of 2.5 h-1, the wax conversion rate maintains almost 50%, and the diesel selectivity almost 90%. Ni/W metals supported on USY/SiO2-Al2O3 can obtain a relative balance of hydrogenation and cracking, thus the catalyst can assure higher wax conversion rate and diesel selectivity.

Key words: hydrocracking, catalyst, Fischer-Tropsch synthesis wax, active phase, selectivity