Synthesis, characterization and catalytic evaluation of SBA-15 supported 12-tungstophosphoric acid mesoporous materials in the oxidation of benzaldehyde to benzoic acid

A series of 12-tungstophosphoric acid catalysts supported on mesoporous molecular sieves SBA-15 were synthesized via wet impregnation method and characterized by various techniques. It has been found that all the catalysts retained the mesopore structure of SBA-15. The surface areas and pore volumes decreased with the increase of HPW loadings, whereas the mean pore diameter exhibited the opposite behavior. In addition, HPW units were highly dispersed on the SBA-15 supports when the 12-tungstophosphoric acid loading was less than 20 wt.%. The results of the catalytic oxidation of benzaldehyde to benzoic acid with aqueous hydrogen peroxide, in the absence of any organic solvent and co-catalysts, indicated that SBA-15 supported 12-tungstophosphoric acid was an efficient catalyst. The sample with 20 wt.% loading of 12-tungstophosphoric acid was found to be more active than other catalysts under the reaction conditions.