A series of CoMo catalysts were prepared by various methods with three different supports (Al2O3-1 of gamma phase, Al2O3-2 containing gamma and delta mixed phases. SiO2). And the effect of morphology of(Co)MoS2 phases oil selective hydrodesulfurization was studied systematically The TEM images showed, in general, the average slab length, the stacking number and the ratio of edge/corner of the sulfided catalysts increase remarkably in the order: SiO2 > Al2O3-2 > Al2O3-1, with the extent of metal-support interaction decreasing in the order: SiO2 < Al2O3-2 < Al2O3-1. And the hydrodesulfurization selectivity correlates linearly with the slab length (or the ratio of edge/corner) Of (CO)MoS2 phases, the longer average slab length, the higher ratio of edge/corner. and then the better hydrodesulfurization selectivity. Among all the catalysts, sulfided CoMo/SiO2 Of the longest average slab length and the highest edge/corner ratio exhibits the best hydrodesulfurization selectivity. (C) 2009 Elsevier B V All rights reserved.