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.