Synthesis and characterization of molybdena and phosphate doped silica-titania oxidative catalyst for epoxidation of styrene

Abstract

New oxidative catalysts of molybdena and phosphate doped silica-titania (xMo/PO4 3-/ SiO2-TiO2, x = 0, 1, 2, 4 and 5 wt%) have been prepared in this study. Silica-titania was prepared via sol-gel method by using titanium isopropoxide and tetraethyl orthosilicate as precursors of titania and silica, respectively. Sufficient amount of ammonium molybdate tetrahydrate and 0.2 M phosphoric acid were loaded on silica-titania through impregnation method. The XRD results confirmed the amorphous phase of all the samples Mo/PO4 3-/ SiO2-TiO2, indicating well dispersion of Mo, phosphate and Ti on the silica support. DRUV-Vis analysis revealed the existence of both tetrahedral and octahedral Ti species in the samples. The N2 adsorption surface area analysis showed the surface area decreased with the increasing amount of doped molybdenum. The oxidation catalytic behavior of xMo/PO4 3-/SiO2-TiO2 was evaluated through epoxidation of styrene using H2O2 as oxidant. Amongst, 5Mo/PO4 3-/ SiO2- TiO2was the best oxidative catalyst which gave the highest conversion of styrene and the highest yield of styrene oxide.