Pd-modified CuO–ZnO–ZrO₂ catalysts for CH₃OH synthesis from CO₂ hydrogenation

The Pd-modified Cu–ZnO–ZrO₂ quaternary catalysts for CO₂ hydrogenation to CH₃OH was investigated. The effect of Pd on CZZ were characterized systematically to illustrate the interaction between Pd and CZZ. The addition of Pd results in an increase in the crystalline sizes of Cu and a higher reduction temperature of bulk CuO. A suitable amount of Pd addition is crucial for the modification of surface Cu sites. 1.0Pd-CZZ shows the highest selectivity for CH₃OH and 0.5Pd-CZZ exhibits the highest intrinsic CH₃OH STY. Excess amount of Pd loadings (1.0% and 1.4%) would result in surface Cu aggregation, and exhibit decreased intrinsic CH₃OH STY. By correlating the characterization and the catalytic performance results, it is inferred that both the independent Cu site and the Cu site with strong interactions are responsible for CH₃OH production. This work would provide molecular insight into the modification of intrinsic surface sites for CH₃OH synthesis from CO₂.