Synthesis of Bimodal Mesoporous TiO2 -PTA/BMMS and Its Enhanced Performance in the Photocatalytic Oxidative Desulfurization

With the bimodal mesoporous silica (BMMS) acting as the support and the composite of TiO2 with phosphotungstic acid (PTA) functioning as the active constituent, TiO2-PTA/BMMS was synthesized by the two-step impregnation route. This catalyst was applied in the photocatalytic oxidative desulfurization (PODS) process, with dibenzothiophene serving as the model sulfur compound. PODS proceeds in one pot, in which H2O2 acts as the oxidant and methanol plays the role of the solvent. TiO2-PTA/BMMS was characterized by XRD, N-2 adsorption and desorption, XRF, FTIR, UV-vis, SEM, EDS and TEM techniques. It showed that the introduction of PTA contributes higher order, higher surface area and pore volume to the bimodal mesoporous support. With TiO2-PTA/BMMS used as the catalyst under the UV irradiation, the desulfurization rate can reach 99.6%. This result is obviously higher than that achieved by TiO2/BMMS. The catalyst also has no significant drop in catalytic activity after eight runs of reusing. In such catalytic system, the synergistic effects of this photocatalytic oxidation and the extraction with the methanol serving as the solvent played an indispensable role.