Mesoporous titania–silica–polyoxometalate nanocomposite materials for catalytic oxidation desulfurization of fuel oil

Abstract

A series of mesoporous titania–silica–polyoxometalate (HPW–TiO₂–SiO₂) nanocomposite materials with different silica–titania ratios were prepared in the presence of non-ionic surfactant by evaporation induced self-assembly method. XRD, TEM, nitrogen adsorption–desorption isotherm and FTIR measurements indicated these materials possess mesoporous structure with relatively uniform channel-like pores and large internal BET surface areas. The incorporated polyoxometalate clusters preserve intact their Keggin structure into the mesoporous frameworks. The nanocomposites were used as catalysts for oxidative desulfurization of model fuel, which was composed of dibenzothiophene (DBT) and hydrocarbon, while H₂O₂ is used as oxidant. The catalytic oxidation results show that the catalysts are very active in refractory bulky molecule organosulfur compounds in fuel oil. The mesoporous HPW–TiO₂–SiO₂ also shows high selectivity for DBT oxidation in the presence of benzene and achieved the goal of desulfurization. The surface acid strength and acidic sites were characterized by NH₃–TPD and Py-FT-IR. It revealed that Lewis acidic sites play an important role in the removal of organic sulfur compounds from the DBT–petroleum ether–benzene system. After regeneration of used catalysts three times, the activity of catalysts has not obviously decreased.