Enhancement of ZnO-ZrO2 Solid Solution Catalyst via Cu Addition for CO2 Hydrogenation to Methanol
The introduction of an appropriate amount of Cu effectively enhances the catalytic performance of ZnO-ZrO2 solid solution catalysts in CO2 hydrogenation to methanol. However, systematic studies on the effect of Cu content in ZnO-ZrO2 solid solution catalysts remain limited. In this work, a ZnO-ZrO2 solid solution and a series of Cu/ZnO/ZrO2-x catalysts (x = 0.3, 0.7 and 0.9, denoting the molar ratio of Cu/(Cu+Zn+Zr)) were prepared by co-precipitation method. Among these catalysts, the Cu/ZnO/ZrO2-0.7 catalyst exhibited the optimal catalytic performance, with a space-time yield of methanol (162.7 g/(kg·h)) that was 6.6 times higher than that of the ZnO-ZrO2 solid solution catalyst (24.8 g/(kg·h)) at 250 °C. Structural characterizations reveal that the introduction of an appropriate amount of Cu led to the coexistence of a solid solution and individual metal oxides, and promoted the formation of medium-strength basic sites. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results further confirm that Cu introduction facilitated the conversion of key reaction intermediates. This work provides a systematic investigation of the influence of Cu content on the methanol synthesis performance of ZnO-ZrO2 solid solution catalysts and elucidates the promotional mechanism induced by Cu incorporation.