Performance of Cu-Mn-Zn/ZrO₂ catalysts for methanol synthesis from CO₂ hydrogenation: The effect of Zn content

A series of Cu-Mn-Zn/ZrO₂ catalysts with different Zn contents were prepared by sol-gel method and characterized by XRD, BET, TPR, N₂O-adsorption, XPS, TPD and in-situ DRIFTS. It was found that by increasing a certain amount of Zn, the catalytic activity for CO₂ hydrogenation increased. Among all samples, Cu₃MnZn_0.5Zr_0.5 (CMZZ-0.5) possessed the best CO₂ conversion (6.5%) and methanol selectivity (73.7%) at 250 °C and 5 MPa. Characterization results showed that Zn entered the Cu_1.5Mn_1.5O₄ spinel structure, forming ZnO_x and thus more surface OH groups. This increased the content of Cu⁰ and Cu^α+, which improved the activation of H₂ and CO₂. The pathway of CO₂ to methanol was also clarified through in-situ DRIFTS.