Preparation and characterization of Mesopoous VOx/SBA-16 and their application for the direct catalytic hydroxylation of benzene to phenol

Vanadium oxide supported on mesoporous SBA-16 (VOx/SBA-16) catalysts have been prepared by the impregnation method and characterized by small-angle XRD, wide-angle XRD, TEM, N2-physisorption, DRUV–vis, Raman spectrum and H2-TPR. The VOx/SBA-16 catalysts retained the cubic cage-like pore structure of SBA-16. The dispersion and the nature of the vanadium species depend strongly on the V amount. At V loading of less than 3.6 wt%, isolated tetrahedral VO4 is the main existence species that is highly dispersed in the pores of the support SBA-16. With the increase in V loading, the aggregation of isolated tetrahedral VO4 species occurred to form polymerized VO4 units. When the V loading was above 5.5 wt%, nanostructured V2O5 crystallites were formed besides aggregation of polymerized VO4 units. VOx/SBA-16 with 7.3 wt% V showed excellent activity for the hydroxylation of benzene. The effect of reaction time, temperature and the amount of catalyst was investigated over VOx/SBA-16 (7.3 wt%) catalyst. The highest phenol yield and turnover number were 13.8% and 32.4, respectively, which were attributed to the formation of highly dispersed VO4 species and polymerized VO4 units. The TON and yield of phenol also increase in the presence of the V2O5 crystallites but its selectivity decreases.

VOx/SBA-16 catalyst with 7.3 wt% V loading showed excellent activity for the hydroxylation of benzene, which was attributed to the formation of highly dispersed VO4 species and nanostructured V2O5 crystallite. The highest phenol yield and turnover number were 13.8% and 32.4 with a selectivity of 97.5%, respectively.Figure optionsDownload as PowerPoint slide