Highly Active SiO₂-supported Cu–ZnO Catalysts Prepared by Combustion Methods for Low-temperature Methanol Synthesis: Comparative Activity Test with or without SiO₂ Support

Abstract

Nanostructured (Cu–ZnO/SiO₂ and Cu/ZnO) catalysts are prepared by sol-gel and surface impregnation combustion methods with inexpensive raw materials and easily-operated conditions. The X-ray diffraction patterns and SEM analysis reveal that Cu crystallite and particle sizes prepared by surface impregnation combustion method are rather smaller. During the combustion process, the support SiO₂ can absorb heat and promote heat transfer, realizing a significantly mild and smooth catalyst-preparation process. As-prepared catalysts are tested in low-temperature methanol synthesis from syngas containing CO₂, with ethanol as a catalyst and solvent at 443 K and 5.0 MPa for 8 h. The activity and methanol selectivity of the supported Cu–ZnO/SiO₂ catalyst are much higher, which are closely related the metallic Cu surface area and Cu crystalline sizes. The different properties of as-prepared catalysts are investigated by XRD, TG-DTA, FT-IR, Raman spectrum, SEM, BET and N₂O chemisorption techniques in detail. Here, the support SiO₂ has a function of heat transfer to make catalysts preparation process much smoother, besides the dispersion effect.