Highly active SiO2-supported Cu-ZnO catalysts prepared by combustion methods for low-temperature methanol synthesis: Comparative activity test with or without SiO2support

Abstract

Nanostructured (Cu-ZnO/SiO2and 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 SiO2can absorb heat and promote heat transfer, realizing a significantly mild and smooth catalyst-preparation process. As-prepared catalysts are tested in lowtemperature 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/SiO2catalyst 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 SiO2has a function of heat transfer to make catalysts preparation process much smoother, besides the dispersion effect.