LAUSR

Abstract The effect of adding Ag to CuO-ZrO 2 catalysts for the hydrogenation of CO 2 to methanol was investigated using CuO-ZrO 2 , Ag/CuO-ZrO 2 , and Ag/ZrO 2 . The addition of Ag to CuO-ZrO 2 catalysts decreased the specific surface area and also broke its mesostructure. Thus, Ag played a significant role as a sintering aid in the preparation of Ag/CuO-ZrO 2 catalysts. We note that the as-prepared Ag/CuO-ZrO 2 catalysts contained Ag + and Zr q + ( q q + content increased with increasing Ag + content. Furthermore, the presence of CuO in the Ag/CuO-ZrO 2 catalyst appeared to stabilize Ag + and Zr q + species under air. Based on H 2 chemisorption and powder X-ray diffraction patterns, formation of a Ag-Cu alloy was observed on completely reduced and spent Ag/CuO-ZrO 2 catalysts. Completely reduced Ag/CuO-ZrO 2 catalysts exhibited a higher methanol production rate (7.5 mL h −1  g cat −1 ) compared to completely reduced CuO-ZrO 2 (6.9 mL h −1  g cat −1 ) and Ag/ZrO 2 catalysts (2.2 mL h −1  g cat −1 ) under the following reaction conditions: CO 2 /H 2 /N 2  = 1/3/1, catalyst loading = 500 mg, W/F total  = 1000 mg cat  s mL −1 , reaction temperature = 230 °C, pressure = 10 bar.