The Utilization of Rice Husk as Both the Silicon Source and Mesoporous Template for the Green Preparation of Mesoporous TiO2/SiO2 and Its Excellent Catalytic Performance in Oxidative Desulfurization

In recent years, TiO2-based catalysts have received extensive attention from researchers for their excellent oxidative desulfurization (ODS) performances. In this paper, a series of mesoporous TiO2/SiO2catalysts with different TiO2loadings are prepared, using an incipient wetness impregnation method with agricultural waste rice husk as both the silicon source and mesoporous template and tetrabutyl titanate as the titanium source. The effect of different TiO2loadings on the ODS performance of the samples is investigated, and the appropriate TiO2loading is 2.5%. Compared with pure TiO2, the 2.5%TiO2/SiO2sample exhibits high catalytic activity for oxidative desulfurization. This is, on the one hand, due to the high specific surface area and mesopore volume of the 2.5%TiO2/SiO2sample. On the other hand, it is due to the uniform dispersion of TiO2grains with an average diameter of 6.1 nm on the surface of the mesoporous SiO2carrier, which greatly increases the active sites of the 2.5%TiO2/SiO2sample, thus improving the catalytic activity of the sample. The recycling performances of the 2.5%TiO2/SiO2sample are further investigated. The results show that, after fifteen cycles, the 2.5%TiO2/SiO2sample still maintains high conversions of dibenzothiophene (99.8%) and 4,6-dimethyldibenzothiophene (99.7%) without deactivation. In addition, the 2.5%TiO2/SiO2sample treated with TBHP aqueous solution is characterized by the technique of UV-Vis, and the Ti-peroxo (Ti-OOtBu) species, the active intermediate for the ODS of bulky organic sulfides, is successfully captured. Finally, a possible reaction mechanism for the ODS process over the 2.5%TiO2/SiO2sample is proposed.