Bimetallic PdCu Nanoparticle Catalyst Supported on Hydrotalcite for Selective Aerobic Oxidation of Benzyl Alcohol

ABSTRACTTo decrease the amount of precious metal usage for Pd-catalyzed aerobic alcohol oxidation, various amount of Cu-contained Pd bimetallic nanoparticle-supported solid base hydrotalcite catalyst (PdxCuy-PVP/HTs) were prepared and applied for aerobic benzyl alcohol oxidation. It was found that the addition of Cu atoms into Pd in the range of 0-40% provided a similar or a little superior activity to that of Pd100-PVP catalyst, whereas a large quantity of co-existence Cu (>40%) gradually decreased their activity of the catalyst. The aerobic benzyl alcohol oxidation over Pd80Cu20-PVP/HT served 77% yield and 95% selectivity towards benzaldehyde at 313 K for 5 h in toluene under O2 flow. X-ray adsorption spectroscopy (XAS) studies and scanning transmission electron microscopy-high angle annuar dark field (STEM-HAADF) with energy dispersive X-ray spectroscopy (EDS) analyses suggested that Cu atoms doping into Pd(0) NP influenced not only localized nanostructure but also oxidation state around Pd atoms. We suggested that substitution of precious metal with small amount of transition metals such as Cu lead to geometric/electronic changes in active sites would be one of nice strategies for reducing the cost for the catalyst in the oxidation process.