How the Content of Protons and Vanadium Affects the Activity of H3+nPMo12-nVnO40 (n=0, 1, 2, or 3) Catalysts on the Oxidative Esterification of Benzaldehyde with Hydrogen Peroxide

In this work, the activity of various Bronsted acid catalysts (i.e., Vanadium-doped phosphomolybdic acids, sulfuric and phosphoric acids) was assessed in one-pot reactions of oxidative esterification of benzaldehyde with hydrogen peroxide and alkyl alcohols. A series of Keggin heteropolyacids with general formulae H3+nPMo12-nVnO40 (n = 0, 1, 2, or 3) was synthesized aiming to evaluate the impacts of protons and Vanadium loading in the conversion and selectivity of benzaldehyde oxidation. Among the catalysts assessed, the H5PMo10V2O40 was the most active and selective. The highest activity was assigned to the suitable proportion between Lewis (V+5+) and Bronsted (H+) active sites present in the disubstituted catalyst. A Vanadium doping at an adequate level increases its potential redox and accelerate the redox step where the catalyst participates. The effects of main reaction parameters, such as alcohol, concentration and type of catalyst, temperature and oxidant load were investigated.

Automated summary

This study assessed the activity of various Bronsted acid catalysts in the oxidative esterification reaction of benzaldehyde. It was found that the Vanadium-doped phosphomolybdic acid H5PMo10V2O40 showed the highest activity and selectivity. The doping of Vanadium increased the redox potential of the catalyst and accelerated the reaction step.