Activity of Catalysts Derived from Au101 Immobilized on Activated Carbon

Abstract

The performance of catalysts made using Au101(PPh3)21Cl5 nanoparticles immobilized on Norit® activated carbon powder was investigated in the aerobic oxidation of benzyl alcohol in basic methanolic solution. The catalyst was activated by washing with hot toluene, followed by heat treatment in static air at 100 °C for 3 h. Effects of key parameters, such as the amounts of benzyl alcohol and base (K2CO3), reaction temperature, reaction time and solvent were explored, as was the longer-term stability of the catalyst during storage. The product mixtures were analysed by high-performance liquid chromatography. Under relatively mild conditions [p(O2) = 5 bar and T = 80 °C], catalysts with a loading of 1.0 wt% give up to 100 % conversion of benzyl alcohol in the presence of equimolar K2CO3 over 24 h. The main products are methyl benzoate and benzoic acid, with selectivities that vary with reaction conditions. Comparison with results obtained with ethanol solvent support a reaction mechanism involving benzaldehyde as an intermediate.