Abstract:

Cu-based catalysts are widely employed for CO₂ hydrogenation to methanol. However， their catalytic performance highly depends on supports. Herein， the nano-spherical SiO₂ support was synthesized by the Stöber method and used as a component in Cu-ZnO@SiO₂ catalyst. The catalyst was tested in hydrogenation of CO₂ to methanol and compared with the Cu-ZnO catalyst（6.9% yield of methanol and 36.5% selectivity of methanol） prepared via conventional coprecipitation process. It was found that Cu-ZnO@SiO₂ catalyst exhibits the best catalytic performance， the yield of methanol reached 11.1% with 88.2% selectivity of methanol at n（H₂）/n（CO₂）=3，230 ℃， 2.0 MPa and gaseous hourly space velocity（GHSV）=3600 mL·g{}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^-1. The catalysts were thoroughly characterized by X-ray diffraction（XRD）， scanning electron microscope（SEM）， X-ray photoelectron spectroscopy（XPS）， tempera-ture-programmed reduction（H₂-TPR） and CO₂ temperature-programmed desorption（CO₂-TPD）. The results show that Cu-ZnO@SiO₂ catalyst has higher Cu dispersion and CO₂ adsorption capacity， and the addition of SiO₂ increases the Cu⁺/Cu⁰ molar ratio on the catalyst surface， which affects the catalytic performance. The characterization analysis of Diffuse reflectance fourier transform infrared spectroscopy（DRIFT） showed that CO₂ generated methanol on Cu-ZnO@SiO₂ catalyst mainly through reverse water gas reaction（RWGS）+CO hydrogenation path.

Key words: Catalyst, CO₂ hydrogenation, Methanol