In the present study, Ni-modified alpha-Al2O3 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 alpha-Al2O3 resulted in various species such as NiAl2O4, mixed phases between NiAl2O4 and alpha-Al2O3, and mixed phases between NiAl2O4 and NiO. As revealed by NH3-temperature programmed desorption, formation of NiAl2O4 drastically reduced acidity of alumina, hence lower amounts of coke deposited during acetylene hydrogenation was found for the Ni-modified alpha-Al2O3 supported catalysts. For any given method, ethylene selectivity was improved in the order of Pd/Ni-Al2O3-0.5 > Pd/Ni-Al2O3-0.3 > Pd/Ni-Al2O3-0 >> Pd/alpha-Al2O3-commercial. When comparing the samples prepared by different techniques, the sol-gel-made samples showed better performances than the solvothermal-derived ones. (C) 2008 Elsevier B.V. All rights reserved.