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

Abstract

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.