Cinnamyl alcohol oxidation using supported bimetallic Au–Pd nanoparticles: an investigation of autoxidation and catalysis

Abstract

In this study, we examine autoxidation and its role on the catalytic aerobic oxidation of cinnamyl alcohol using supported AuPd nanoparticles. We further report the crucial role of reaction conditions in the reaction pathway. Close attention is paid to the mechanism of the formation of benzaldehyde, a by-product formed in large quantities from the process of autoxidation. The activity of the catalysts depends on the preparation method with different sizes of nanoparticles obtained by the two methods of preparation. The catalysts can inhibit the autoxidation process or the two processes, namely catalytic oxidation and autoxidation, can coexist. In the case of oxidation of cinnamyl alcohol, 0.5%(wt) Au–0.5%(wt) Pd/TiO₂ catalysts prepared by various methods allow different product distributions to be obtained. The catalyst prepared by the sol-immobilisation method seems to prevent autoxidation, leaving the catalytic process dominant. Catalysts prepared by the impregnation method seem to enable both the catalytic process and autoxidation to occur at the same time. We show that using the optimum catalyst for this reaction, the autoxidation process can be mitigated.