Liquid‐phase hydrogenation of cinnamaldehyde over Cu‐Au/SiO 2 catalysts

The synthesis, characterization, and application of silica‐supported Cu‐Au bimetallic catalysts in selective hydrogenation of cinnamaldehyde are described. The results showed that Cu‐Au/SiO 2 bimetallic catalysts were superior to monometallic Cu/SiO 2 and Au/SiO 2 catalysts under identical conditions. Adding a small amount of gold (6Cu‐1.4Au/SiO 2 catalyst) afforded eightfold higher catalytic reaction rate compared to Cu/SiO 2 along with the high selectivity (53%, at 55% of conversion) toward cinnamyl alcohol. Characterization techniques such as x‐ray diffraction, H 2 temperature‐programmed reduction, ultraviolet‐visible spectroscopy, transmission electron microscopy, Fourier‐transform infrared spectra of chemisorbed CO, and x‐ray photoelectron spectroscopy were employed to understand the origin of the catalytic activity. A key genesis of the high activity of the Cu‐Au/SiO 2 catalyst was ascribed to the synergistic effect of Cu and Au species: the Au sites were responsible for the dissociative activation of H 2 molecules, and Cu 0 and Cu + sites contributed to the adsorption‐activation of CC and CO bond, respectively. A combined tuning of particle dispersion and its surface electronic structure was shown as a consequence of the formation of Au‐Cu alloy nanoparticles, which led to the significantly enhanced synergy. A plausible reaction pathway was proposed based on our results and the literature. © 2014 American Institute of Chemical Engineers AIChE J , 60: 3300–3311, 2014