Catalytic performance and hydrogen spillover in Cu/ZnO/Al2O3: Insights from DFT calculations on alkali and alkaline earth oxides promoters for CO2 hydrogenation

Abstract

This study evaluates Cu/ZnO/Al2O3 catalysts promoted with K2O, BaO, Cs2O, and SrO for CO2 hydrogenation to methanol, focusing on the effect of synthesis methods. Catalysts prepared via co-precipitation and impregnation were evaluated for activity, selectivity, and stability under industrial conditions. Analyses (H2-TPR, H2/CO2-TPD, XRD) showed potassium and barium improve copper reducibility, enhance H2/CO2 adsorption, and reduce sintering through strong promoter-support interactions. Co-precipitated potassium demonstrated superior performance, achieving higher methanol production rates, improved stability, and minimal deactivation, with methanol selectivity exceeding 86 % and CO2 conversion surpassing 42 %. In contrast, impregnated Potassium increased CO formation, highlighting the significance of the synthesis strategy. DFT calculations revealed that K2O and BaO promote strong H2/CO2 adsorption and favorable reaction pathways. These findings offer valuable insights into optimizing promoter selection and synthesis techniques for advanced catalysts, enabling efficient CO2 conversion and sustainable methanol production.