Characteristics of V-MCM-41 and Its Catalytic Properties in Oxidation of Benzene

Abstract

A series of mesoporous vanadosilicate V-MCM-41 molecular sieves with variable Si/V ratios have been hydrothermally synthesized at pH = 10. These materials were investigated by powder X-ray diffraction (XRD), framework FTIR, diffuse reflectance UV−visible spectroscopy, nitrogen sorption measurement, scanning electron microscopy, transmission electron microscopy (TEM), thermogravimetric analysis, and differential thermal analysis. XRD and FTIR showed that the solid products had the MCM-41 structure and contained only atomically dispersed vanadium consistent with framework vanadium in V-MCM-41. Nitrogen sorption results showed that all of the materials had a uniform pore size distribution with pore size of around 3.0 nm. The crystallinity of V-MCM-41 decreased with an increase of the vanadium content. The hexagonal array structure of uniform pore size was observed by TEM. It proved that the pores were highly aligned. The catalytic activities of V-MCM-41 were tested in the partial oxidation of benzene by diluted hydrogen peroxide in a batch reactor. Phenol was the only liquid product. The catalytic activities of V-MCM-41 were more active than those supported on Y and β zeolite. In addition, the V/MCM-41 prepared with hydrothermal synthesis was more active than that prepared with impregnation.