An effective heterogeneous WO3/TiO2-SiO2 catalyst for selective oxidation of cyclopentene to glutaraldehyde by H2O2

TiO2-SiO2 mixed oxide with large pore size was synthesized by the xerogel method and it was then used to prepare the WO3/TiO2-SiO2 catalyst by an incipient wetness method. The as-prepared WO3/TiO2-SiO2 sample was employed as the first heterogeneous catalyst in the liquid-phase cyclopentene oxidation by aqueous H2O2, which exhibited higher selectivity (about 75%) to glutaraldehyde (GA) and, in turn, higher GA yield than the WO3/SiO2 heterogeneous catalyst and even the tungstic acid homogeneous catalyst under the same reaction conditions. The amorphous WO3 phase was identified as the active sites and the loss of the active sites was proved to be not important. The lifetime of the catalyst was determined and its regeneration method was proposed. The effects of various factors on the catalytic behaviors, such as the WO3 loading, the calcination temperature, the surface acidity and the reaction media, were investigated and discussed based on various characterizations including BET, XRD, XPS, FTIR, EXAFS and Raman spectra etc.