Solvent-Free Catalytic Oxidation of Benzyl Alcohol over Au-Pd Bimetal Deposited on TiO(2): 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.