Nickel phosphide catalysts supported on the TiO 2 ÀAl 2 O 3 composite oxide were successfully prepared by impregnation of nickel phosphate precursors followed by temperature-programmed reduction. The catalysts were characterized by X-ray diffraction, thermogravimetric analysis, IR spectroscopy, N 2 adsorption, and X-ray photoelectron spectroscopy. The catalytic activity was characterized in a fixed-bed reactor for hydrodesulfurization using a model liquid-feed dibenzothiophene, which contained 2000 mg/kg sulfur. Experimental results indicate that the TiO 2 ÀAl 2 O 3 composite support effectively prevents the formation of aluminum phosphates due to the strong interaction between phosphorus and γ-Al 2 O 3 , and it also shows strong interactions with Ni and P species on the surface, which is the main reason for the enhancement in hydrodesulfurization activity and stability. Among the Ni 2 P/TiO 2 ÀAl 2 O 3 samples tested, the catalyst at a Ni loading of 15 wt % showed the highest activity with a steady-state dibenzothiophene conversion of 99.9% at 613 K, 2.5 MPa, WHSV 3 h À1 , and volume ratio of hydrogen/oil of 450.

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