Regulatory effect of Zr on formation of Cu/ZnO interface in CuZnAl−xZr catalysts during CO₂ hydrogenation to methanol reaction

The catalytic conversion of CO₂ to methanol presents an effective approach to mitigate its adverse climatic and environmental impacts. The composition and structure of catalysts significantly influence the efficiency and selectivity of catalytic reactions. To enhance the activity of CuZnAl industrial catalysts in CO₂ hydrogenation to methanol, Zr⁴⁺ was introduced into the CuZnAl catalyst system via impregnation, successfully preparing CZA−xZr （CuZnAl with different Zr contents） catalysts. The role of Zr in regulating the formation of Cu/ZnO interfaces was systematically investigated. The catalyst structure and surface electronic states were characterized using XRD, HRTEM, XPS, N₂O titration, ICP-OES, H₂-TPR, and CO₂-TPD. Results indicate that under reaction conditions of 3 MPa, 230 ℃, 40000 mL/（g·h）, φ（H₂）∶φ（CO₂） = 4, the CZA−2Zr catalyst exhibits the highest methanol production rate of 25.4 mmol/（g·h）, representing a 23.9% increase compared to the unmodified CZA catalyst. The apparent activation energy of the catalysts remains unchanged, and the methanol synthesis activity is determined by the number of active sites on the catalyst surface. As the Zr content increases, no electronic interaction occurs between Cu and Zr. However, due to the interaction between Zn and Zr, electrons gradually transfer from Zr to Zn, promoting an increase in methanol selectivity. Zn and Zr species initiated mutual interactions during the calcination process. HRTEM results clearly reveal the metal-oxide interfaces in the catalysts and show that the ZnO particle size initially decreases and then increases. The dispersion of Cu⁰ is negatively correlated with ZnO dispersion. With increasing Zr content, the number of Cu/ZnO interfaces in the catalyst follows a volcanic trend, and the effective CO₂ adsorption capacity exhibits the same variation pattern. the CZA−2Zr catalyst exhibits the highest reactant conversion rate due to the highest number of Cu/ZnO interfaces.