Liquid-phase benzyl alcohol oxidation on gold-based catalysts: Effect of catalyst support and gold loading

Abstract

Selective synthesis of benzaldehyde from benzyl alcohol was investigated using Au-based catalysts supported on γ-Al2O3, TiO2, and ZnO. Commercial γ-Al2O3 was modified with gold added by deposition–precipitation method producing xAu/Al2O3 solids (x = 0.2–0.9 wt.% Au). Catalysts were thoroughly characterized. In general, transition metal (Cu, Ag, Pd) catalysts favored alcohol oxidation reactions due to their ability to activate O2 and facilitate electron transfer. However, the higher catalytic activity of gold has emerged as a noteworthy area of exploration. The catalytic performance of Au-based solids supported on different oxides (with ∼1.0 wt.% Au) depended on its acid-base properties. Alumina was the support that allow to obtain the most effective catalysts for benzaldehyde synthesis probably due to the highest acid site density with weak and moderate strength. Initial reaction rate values increase with increasing x while the turnover frequency reaches a maximum for 0.4Au/Al2O3.