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 Brønsted 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 H 3+n PMo 12-n V n O 40 (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 H 5 PMo 10 V 2 O 40 was the most active and selective. The highest activity was assigned to the suitable proportion between Lewis (V +5+ ) and Brønsted (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. Graphical Abstract