Silica-Supported Au–CuOx Hybrid Nanocrystals as Active and Selective Catalysts for the Formation of Acetaldehyde from the Oxidation of Ethanol

The selective oxidation of ethanol with molecular O 2 is increasingly becoming an important process to develop fine chemicals because it can be obtained from renewable biomass feedstock while reducing the demand on fossil fuels. We have synthesized silica-supported Au–Cu alloy nanoparticles, and through an oxidative dealloying process, we have developed Au–CuO x hybrid catalysts for the selective oxidation of ethanol into acetaldehyde. Using a combination of XRD, XPS, and HR-STEM experiments, we have confirmed that the active catalyst is a Au core with a thin CuO x shell. Oxidation of the AuCu/SiO 2 alloy catalyst at 300 °C was found to produce the most active and stable catalyst for ethanol conversion (∼90%) with the highest selectivity (∼80–90%) at a reaction temperature of 200 °C for 50 h on-stream. TEM and XRD results show that Au–CuO x /SiO 2 catalysts calcined at 300 and 500 °C are also more resistant to sintering during pretreatment and catalytic conditions than pure gold supported on silica. Furthermore, the silica-supported Au–CuO x catalysts (calcined at 300 and 500 °C) were also found to be more active and selective in the dehydrogenation of ethanol to form acetaldehyde. It is likely that the increased interfacial contact between the Au and CuO x forms the most active site on the catalyst and is responsible for the enhanced catalytic properties when compared with pure Au/SiO 2 .