Highly Efficient Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over Gold Supported on Zinc Oxide Materials

Au/ZnO catalysts have been used for liquid-phase selective hydrogenation of cinnamaldehyde to cinnamyl alcohol and compared with Au/Fe₂O₃ catalysts. To investigate the influence of the support on the hydrogenation activity and selectivity, three different Au/ZnO catalysts were synthesized, including Au/rod-tetrapod ZnO, Au/porous ZnO, and Au/ZnO-CP prepared using a coprecipitation method. The influence of calcination temperature was also systematically investigated in this study. The characterization of Au/ZnO catalysts was performed using ICP, N₂ adsorption/desorption isotherms, X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy. Among all the supported Au catalysts prepared in this study, Au/ZnO-CP exhibits both the highest hydrogenation activity and selectivity. Using a 1.5% Au/ZnO-CP catalyst, 100% selectivity could be achieved with 94.9% conversion. We find that the Au particle (size and shape), the ZnO support (size and surface texture) and the interaction between Au and ZnO are three important parameters for achieving a highly efficient Au/ZnO catalyst.