The role of MgO in the formation of surface active phases of CoMo/Al2O3–MgO catalysts for hydrodesulfurization of dibenzothiophene

A series of CoMo/Al2O3–MgO–x (x = [MgO/(Al2O3 + MgO)], weight ratio) catalysts were prepared by incipient wetness impregnation method with urea as chelating agent. The characterization results of UV–vis diffuse reflectance spectroscopy and Raman spectroscopy showed that Mo and Co species were highly dispersed in small clusters. Introduction of a proper amount of MgO into Al2O3 support not only induced new active forms of Mo species formed on the surface of the catalysts but also successfully inhibited the formation of inactive CoAl2O4 or Co3O4 phases, thus significantly improving the hydrodesulfurization activity.