Oxidation of benzyl alcohol catalyzed by ligand-stabilized Au nanoparticles in the presence of weak bases

Ligand-stabilized gold nanoparticles (tetrakis(hydroxymethyl)phosphonium chloride-Au, citrate-Au, cetrimonium bromide-Au) were synthesized and mixed with several weak-base solids (barium carbonate, Amberlite IRA-900) and acidic solid  (Dowex 50WX2 resin). Those catalysts were applied for the oxidation of benzyl alcohol in water at 80 oC. Almost ligand-stabilized Au nanoparticles/weak-base solids showed good conversion of benzyl alcohol and high selectivity of benzoic acid, whereas ligand-stabilized Au nanoparticles/acidic solid were catalytically inactive. Nanoparticles were characterized by transmission electron microscopy, zetapotential measurement, and dynamic light scattering. The catalytic activity and product selectivity were determined by using a gas chromatography coupled with a mass selective detector. Our study suggests that the oxidation reaction in water could be catalyzed by gold with the presence of weak-base solids.