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Keywords:

  • selective hydrogenation;
  • cinnamaldehyde;
  • α,β-unsaturated aldehyde;
  • Au-Cu alloys;
  • synergistic effect

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/SiO2 bimetallic catalysts were superior to monometallic Cu/SiO2 and Au/SiO2 catalysts under identical conditions. Adding a small amount of gold (6Cu-1.4Au/SiO2 catalyst) afforded eightfold higher catalytic reaction rate compared to Cu/SiO2 along with the high selectivity (53%, at 55% of conversion) toward cinnamyl alcohol. Characterization techniques such as x-ray diffraction, H2 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/SiO2 catalyst was ascribed to the synergistic effect of Cu and Au species: the Au sites were responsible for the dissociative activation of H2 molecules, and Cu0 and Cu+ sites contributed to the adsorption-activation of C[DOUBLE BOND]C and C[DOUBLE BOND]O 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