On the metal-support synergy for selective gas-phase ethanol oxidation over MgCuCr₂O₄ supported metal nanoparticle catalysts

Achieving high yields in the production of bulk chemicals is an important goal for the chemical industry. We investigated the influence of the metal on the catalytic performance of M/MgCuCr₂O₄ (M = Cu, Ag, Pd, Pt, Au) catalysts to better understand the metal-support synergy for the aerobic oxidation of ethanol. Pt/MgCuCr₂O₄ and Pd/MgCuCr₂O₄ are more active and less selective for ethanol oxidation than the other catalysts, mainly because they can dehydrogenate and then cleave the carbon-carbon bonds in ethanol at relatively low temperature. Because of the facile oxidation of Cu⁰ and Ag⁰ under aerobic oxidation conditions, Cu/MgCuCr₂O₄ and Ag/MgCuCr₂O₄ are less active for ethanol oxidation. On contrary, Au/MgCuCr₂O₄ is a very active, selective and stable catalyst for sustainable production of acetaldehyde, achieving 96% selectivity at full ethanol conversion (space-time-yield up to 583 g_aldehyde g_Au^-1 h^-1) at 250 °C. Low gold loading and high gold dispersion are important to enhance the Au⁰-Cu⁺ synergy and the catalytic efficiency of Au/MgCuCr₂O₄.