Effect of additive on CuO-ZnO/SBA-15 catalytic performance of CO2 hydrogenation to methanol

Three kinds of porous catalysts CuO-ZnO/SBA-15 (CZ/SBA-15), CuO-ZnO-MnO2/SBA-15 (CZM/SBA-15) and CuO-ZnO-ZrO2/SBA-15 (CZZ/SBA-15) were synthesized by impregnation method with a siliceous framework mesoporous molecular sieve SBA-15. The performance of all catalysts for catalytic hydrogenation of CO2 to methanol was evaluated on a fixed bed reactor, combined with N2 adsorption-desorption (BET), X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), temperature programmed desorption (H2-TPD, CO2-TPD), N2O titration, X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) . The results show that the introduction of metal oxide in the catalyst changes the pore size and specific surface area of the SBA-15 molecular sieve support. The CuO-ZnO-MnO2/SBA-15 and CuO-ZnO-ZrO2/SBA-15 have high copper dispersion (DCu), large specific surface area (ACu), small surface CuO particle size, and easy to be reduced. Compared with the Mn-O cluster, the Zr-O cluster enhances the basic site and improves the methanol selectivity. In addition, CuO-ZnO-ZrO2/SBA-15 has the highest oxygen vacancy concentration and better catalytic activity among three catalysts. The methanol selectivity of CuO-ZnO-ZrO2/SBA-15 is 25.02%, which is 28% and 136.9% higher than those of CuO-ZnO/SBA-15 and CuO-ZnO-MnO2/SBA-15, respectively.