Selective Aerobic Oxidation of Alcohols over Gold-Palladium Alloy Catalysts Using Air at Atmospheric Pressure in Water

摘要

A series of bimetallic Au-Pd alloy nanoparticles (NPs) with varied Au/Pd molar ratios was supported on Gamma-alumina (gamma-Al2O3) surface through the co-impregnation-reduction method using HAuCl4 and PdCl2 as metal precursors. Characterization results suggested the high dispersion of Au-Pd alloy NPs, as well as the interplay between the two compositions. Benefitting from the synergistic effects of Au-Pd alloying, the bimetallic Au-Pd-x@gamma-Al2O3 catalysts were highly efficient for selective aerobic oxidation of various alcohols either aromatic or aliphatic in water using air at atmospheric pressure as a sole oxidant without the need for any cocatalyst. Quantitative yields of corresponding aldehydes or ketones were achieved over Au-Pd-1.2@gamma-Al2O3 within 2 h, whereas pure Au@gamma-Al2O3 or Pd@gamma-Al2O3 was far less efficient. More importantly, the "alloying effect" appeared to stabilize the bimetallic NPs against aggregation and poisoning, which made the Au-Pd-x@gamma-Al2O3 more stable and reusable in the aerobic oxidation of alcohols.