Structural and kinetical studies on the supercritical CO2 dried Cu/ZnO catalyst for low-temperature methanol synthesis

Abstract

The Cu/ZnO catalyst prepared by supercritical phase CO2 drying (denoted as CZS catalyst) and the conventional Cu/ZnO catalyst prepared by heating dry process (denoted as CZO catalyst) were comparatively investigated. The low-temperature methanol synthesis reaction from CO+CO2+H2 using 2-butanol as solvent was conducted over the CZS and CZO catalysts at 443K and 5.0MPa for continuous 20h in a flow-type reactor. It was found that the total carbon conversion of the CZS catalyst was increased from 35.1% to 46.4% and the methanol yield of the CZS catalyst was enhanced from 33.8% to 44.8%, comparing with those of the CZO catalyst. The results of kinetic analysis by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) revealed that the reaction rate of the low-temperature methanol synthesis on CZS catalyst was faster than that on CZO catalyst at 443K, in good accordance to the catalytic reaction performances. It was indicated that the supercritical fluid CO2, which was used to dry the catalyst precursor, suppressed the sintering of the Cu and ZnO particles and increased both the BET surface area of the catalysts and metallic surface area of Cu0, which further improved the reaction activity of the catalyst for the low temperature methanol synthesis.