Oxidative desulfurization using ordered mesoporous silicas as catalysts

• Linear relationship between oxidative desulfurization activity and the amount of silanol groups on pure mesoporous silcas.
• Surface silanol groups act as the active sites of oxidative desulfurization.
• Mechanism of surface silanol-mediated oxidative desulfurization of dibenzothiophene.

Ordered mesoporous silicas with structures of MCM-41, MCM-48 and SBA-15 were synthesized. Oxidative desulfurization activities of dibenzothiophene and 4,6-dimethyl dibenzothiophene on the mesoporous silicas were investigated using tert-butyl hydroperoxide as an oxidant. Textures and surface properties of the synthesized mesoporous silicas were studied by X-ray diffraction, N2-sorption, FT-IR and NH3-temeprature programmed desorption. The results show that oxidative desulfurization catalytic activities increase with surface area and surface acidity of the mesoporous silicas. Oxidative desulfurization mechanism on MCM-41 was investigated by the addition of surface silanol inhibitor such as acetic acid, water and triethylolamine or silylation of surface silanol groups using trimethylchlorosilane. A hypothetical mechanism based on surface silanol-mediated oxidation desulfurization is proposed. Oxidative desulfurization activities for Mo catalysts supported on MCM-41 were also investigated to identify the difference in oxidative desulfurization mechanism between MoO3 catalysts and pure mesoporous silicas.

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