CO2 hydrogenation to methanol over CuO-ZnO-ZrO2-SiO2 catalysts: Effects of SiO2 contents

Catalytic CO2 hydrogenation to methanol is a powerful alternative for renewable energy, which can tackle both global warming through CO2 utilization and depletion of fossil fuels. However, the lack of efficient catalysts in terms of delivering sufficient activity and stability remains the major obstacles for practical application of such reaction. Herein, the introduction of silica as a promoter in a CuO-ZnO-ZrO2 catalytic system is reported. A series of CuO-ZnO-ZrO2-SiO2 catalysts were prepared by a reverse co-precipitation of Cu, Zn and Zr precursors with dispersed colloidal silica nanoparticles. The effect of silica content (0-5 wt%) on the physicochemical properties of the resulting catalysts as well as their catalytic activity in CO2 hydrogenation were investigated. The catalysts were characterized by thermal gravimetric analysis (TG), X-ray diffraction (XRD), N-2-sorption, N2O chemisorption, temperature programmed H-2 reduction (H-2-TPR), transmission electron microscope (TEM), time -resolved X-ray absorption spectroscopy (TRXAS), temperature programmed CO2 and H-2 desorption (CO2 and H-2-TPD). The promotional effect was characterized by a geometric modification which was most effective for low amounts of SiO2 wt%). With the addition of 1 wt% SiO2, an increase in methanol synthesis activity of 26% compared to the ternary SiO2-free system was observed. In addition to methanol synthesis activity, the stability in terms of CO2 conversion-to-CO-was improved by the catalyst prepared with the presence of silica. Moreover, reaction mechanisms for CO2 hydrogenation to methanol and CO were discussed on the basis of correlations between microstructure and activity of the studied catalysts. (C) 2017 Elsevier B.V. All rights reserved.