Selective Oxidation of Cyclopentene to Glutaraldehyde by H2O2 over the WO3/SiO2 Catalyst

A novel WO3/SiO2 was prepared by incipient wetness impregnation of the SiO2 support synthesized by the xerogel method with the W-containing salt solution. The as-prepared WO3/SiO2 catalyst exhibited a very high yield of glutaraldehyde in the liquid phase cyclopentene oxidation by aqueous H2O2 and the leach of WO3 species during the reaction could be neglected. As a heterogeneous catalyst, it seems more suitable for the industrial process than those homogeneous catalysts owing to its easy separation from reaction products, which makes it possible to use the catalyst repetitively. According to the XRD patterns, the WO3 was present in amorphous state due to its high dispersion on the SiO2 support. These amorphous WO3 species were proved to be the active sites since the crystallization at high temperature caused a considerable deactivation. The lifetime of the catalyst was measured and its regeneration method was proposed. Effects of various factors on the catalytic behaviors, such as the WO3 loading, the calcination temperature, and the reaction media, were also investigated and discussed based on the characterizations of BET, XRD, DSC, TEM, EXAFS, and Raman spectra.