Abstract: MoO₃-CeO₂-SiO₂ mixed oxides were prepared by the sol-gel method. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The catalyst activity for the oxidative desulfurization of dibenzothiophene (DBT) with cumene hydroperoxide as the oxidant in toluene was investigated at 40 ^oC and atmospheric pressure. The optimum Mo/Si and Ce/Si molar ratios were 0.1 and 0.02, respectively. Crystalline MoO₃ was observed in the MoO₃-CeO₂-SiO₂ catalysts. The introduction of CeO₂ promoted the high dispersion of MoO₃ over SiO₂. Mo⁶⁺ was the predominant species in MoO₃/SiO₂, and Mo⁵⁺ species appeared after the introduction of CeO₂. The presence of Mo⁵⁺ may be responsible for the good performance of MoO₃-CeO₂-SiO₂ in the oxidative desulfurization of DBT.

Key words: molybdenum oxide, cerium oxide, silica, sol-gel method, dibenzothiophene, oxidative desulfurization