Investigation of CO2-to-methanol hydrogenation performance over Cu-ZnO/ZrO2 catalysts by tuning ZrO2 crystalline phases

Cu-ZnO/ZrO 2 catalysts are promising for CO 2 hydrogenation to methanol, yet the role of ZrO 2 phase composition remains unclear. Here, monoclinic and tetragonal ZrO 2 were separately prepared and combined to construct catalysts with systematically varied m/t-ZrO 2 compositions. The actual t-ZrO 2 fractions of the mixed-phase catalysts were 26.6, 51.5, and 84.0 wt%. Increasing t-ZrO 2 generally enlarged CuO/ZnO crystallites and shifted CuO x reduction to higher temperatures, while Cu 0 /Cu + varied non-monotonically. The mixed-phase catalyst containing 84.0 wt% t-ZrO 2 showed the highest H 2 -TPR consumption (5.559 mmol g −1 ) and CO 2 desorption amount (0.482 mmol g −1 ), and achieved a maximum methanol space-time yield of 71.78 g methanol ·kg cat −1 ·h −1 at 220 °C. At 250 °C, CO 2 conversion correlated with H 2 -TPR consumption (R 2 = 0.929) and CO 2 adsorption (R 2 = 0.916). These results indicate that catalytic performance is governed by the combined balance of Cu reducibility, CO 2 adsorption, hydrogen-binding characteristics, and defect-related surface oxygen species.