Synthesis of hierarchical mesoporous vanadium silicate-1 zeolite catalysts for styrene epoxidation with organic hydroperoxide

Abstract

Hierarchical mesoporous vanadium silicate-1 zeolites were successfully synthesized via a hydrothermal route using amphiphilic organosilanes as pore-directing templates. Also, to investigate the effect of the amount of vanadium metal on the physicochemical properties and catalytic activity, different hierarchical mesoporous vanadium silicate-1 zeolites have been successfully synthesized with varying vanadium contents. The physicochemical properties of these materials were characterized by various techniques, e.g. nitrogen sorption (for surface area, pore volume and pore size distribution), FTIR, TEM, SEM and UV-visible spectroscopy. UV-visible and X-ray photoelectron spectroscopy analysis showed that the vanadium atom was effectively incorporated into the framework of vanadosilicate. The samples have high BET and external surface areas. The catalytic performance of the hierarchical mesoporous vanadium silicate-1 zeolites was investigated in the oxidation of styrene with tert-butyl hydroperoxide as the oxidant. The amount of vanadium content plays a very important role not only in the physicochemical properties of the samples but also in the catalytic conversion of styrene and the selectivity of the products. The sample with the lowest vanadium content shows a 49% styrene conversion, the highest (54%) styrene oxide selectivity and the highest (189) turn-over frequency. Meanwhile, the sample with the highest vanadium content shows the highest (85%) styrene conversion and the highest (49.5%) benzaldehyde selectivity with respect to the other products.