Selective catalytic oxidation over Au-Pd/titanate nanotubes and the influence of the catalyst preparation method on the activity

Abstract

The dependence of the selective oxidation catalytic activity of Au-Pd supported on titanate nanotubes on the catalyst preparation method has been investigated. The most active Au-Pd/Ti-NT catalyst for the selective oxidation of benzyl alcohol is shown to be that prepared using colloidal synthesis and immobilization with PVA as a stabilizer, which has markedly superior catalytic activity compared to catalysts prepared by deposition-precipitation, adsorption, and dry impregnation methods. Au-Pd NPs stabilized by graphene oxide sheets and immobilized on Ti-NT has also been studied and while not optimum shows promising catalytic activity. The superior catalytic activity of the catalysts prepared by colloidal synthesis is attributed to the high metal dispersion on the external surfaces of Ti-NT, the narrow particle size distribution, and the high degree of Au-Pd alloying. This work also demonstrates that in the adsorption method of preparation using HAuCl4.3H2O and PdCl2 precursors, the uptake of Pd ions in solution by Ti-NT is proportional to the sodium content in Ti-NT, which implies that Na is involved in an ion-exchange reaction with Pd ions.