Effect Of Ni-modified α-al_2o_3 Prepared By Sol-gel And Solvothermal Methods On The Characteristics And Catalytic Properties Of Pd/α-al_2o_3 Catalysts

摘要

In the present study, Ni-modified α-Al_2O_3 with Ni/Al ratios of 0.3 and 0.5 were prepared by sol-gel and solvothermal method and then were impregnated with 0.3 wt.% Pd. Due to different crystallization mechanism of the two preparation methods used, addition of nickel during preparation of α-Al_2O_3 resulted in various species such as NiAl_2O4, mixed phases between NiAl_2O_4 and α-Al_2O_3, and mixed phases between NiAl_2O_4 and NiO. As revealed by NH_3-temperature programmed desorption, formation of NiAl_2O_4 drastically reduced acidity of alumina, hence lower amounts of coke deposited during acetylene hydrogenation was found for the Ni-modified α-Al_2 O_3 supported catalysts. For any given method, ethylene selectivity was improved in the order of Pd/Ni-Al_2O_3-0.5 > Pd/Ni-Al_2O_3-0.3 > Pd/Ni-Al_2O_3-0 ? Pd/α-Al_2O_3-commercial. When comparing the samples prepared by different techniques, the sol-gel-made samples showed better performances than the solvothermal-derived ones.