Abstract: To study the effect of alumina surface properties on hydrodesulfurization selectivity of CoMo/Al₂O₃ catalysts, three alumina supports, Al₂O₃-1, Al₂O₃-2 and Al₂O₃-3, were used to prepare corresponding catalysts, respectively. The catalyst samples were characterized by Mo equilibrium adsorption test, XRD, SEM, N₂ adsorption-desorption, IR, XPS and TEM techniques. The characterization results indicated the large difference in surface area, pore volume and pore size distribution of the supports, which coule be attributed to the difference in crystallite size, crystallite shape and crystallite stacking mode of alumina. The difference of alumina surface properties could be evaluated by Mo equilibrium adsorption capacity. The CoMo/Al₂O₃ catalyst prepared by using alumina support with lower Mo equilibrium adsorption capacity exhibited better HDS selectivity than others due to its weaker metal-support interaction, which promoted higher degree of Mo sulfidation and formed more Co-Mo-S active phase with longer slab length.

Key words: alumina, surface properties, Mo equilibrium adsorption, Co-Mo-S active phase, slab size, hydrodesulfurization selectivity