CuPd bimetallic catalyst with high Cu/Pd ratio and its application in CO₂ hydrogenation

The surface and catalytic properties Cu-Pd bimetallic catalyst with a high Cu/Pd ratio of 33.5 was investigated for the hydrogenation of CO₂ and was compared with the corresponding monometallic catalysts. The catalysts were synthesized by the incipient-wetness impregnation method, characterized by N₂-physisorption, XRD, TPR, CO pulse titration, N₂O chemisorption, CO₂-TPD, and FT-IR of adsorbed CO, and were evaluated in a fixed-bed reactor. The interaction between Cu and Pd results in a better dispersion of both Cu and Pd atoms and facilitates the reduction properties. Phase separation of Pd₁Cu₃ alloy and Cu appears over the bimetallic catalyst, while at some part of the catalysts, isolated Pd sites exist over the Cu-rich particles. Both geometric and electronic effects are present over the bimetallic catalyst. The catalytic performances are found to be similar over Cu/SiO₂ and Cu-Pd/SiO₂ when normalized to the surface Cu sites. Specifically, CuPd/SiO₂ shows enhanced activity than Cu/SiO₂ mainly due to the geometric effect, whereas the electronic effect is weak for the catalytic performance.