Selective oxidation of benzaldehyde by molecular oxygen over molybdovanadophosphoric acid supported MCM-41

Abstract

A series of molybdovanadophosphoric acid (MVPA) supported on mesoporous silica was synthesized by an incipient wetness impregnation method. The catalysts were characterized by nitrogen adsorption-desorption, X-ray powder diffraction, Fourier-Transform Infra red spectroscopy (FT-IR), UV-Vis Diffused reflectance spectroscopy (UV-Vis DRS), Temperature programmed reduction (TPR) and P-31 MAS Nuclear magnetic resonance(NMR) study. The characterization data reveals the incorporation of vanadium in phosphomolybdic acid and retention of intact Keggin ion on the support. The catalytic activities were evaluated for oxidation of benzaldehyde using molecular oxygen as oxidant as the new green reaction system. Among all the promoted catalysts, 50wt% molybdovanadophosphoric acid supported on MCM-41 exhibits highest catalytic activity in oxidation of benzaldehyde, giving 95% conversion. Other oxidants like H2O2 and tert-butyl hydrogen peroxide (TBHP) were also tested for benzaldehyde oxidation reaction.