Solvent-Free Catalytic Oxidation of Benzyl Alcohol over Au-Pd Bimetal Deposited on TiO2: Comparison of Rutile, Brookite, and Anatase

TiO 2 (P25)-supported Au-Pd bimetal nanoparticles displayed excellent performance in the solvent-free benzyl alcohol catalytic oxidation. However, little research attention has been paid to investigate the effects of TiO 2 form on the catalytic activity of Au-Pd/TiO 2 . In the present research, rutile, brookite, and anatase TiO 2 were successfully synthesized and subsequently applied as the carrier to load Au-Pd nanoparticles by the deposition-precipitation method. The experimental results indicated that the benzyl alcohol conversion employing the rutile TiO 2 -supported Au-Pd catalyst is higher than the conversion of anatase and brookite TiO 2 -loaded Au-Pd catalysts. However, the Au-Pd/TiO 2 -rutile displayed the lowest and highest selectivity toward benzaldehyde and toluene, respectively. ICP-AES, XRD, XPS, and TEM were conducted to characterize these catalysts. The corresponding experimental results revealed that the excellent performance of Au-Pd/TiO 2 -rutile catalyst was attributed to both the smaller Au-Pd nanoparticle size distribution and the higher concentrations of O α and Pd 2+ species on the catalyst surface. In the recycle experiments, the Au-Pd/TiO 2 -rutile catalyst displayed lower reaction stability compared with the Au-Pd/TiO 2 -anatase and Au-Pd/TiO 2 -brookite, which might be due to the coverage of larger amount of aldehyde products on the surface.