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

• Total carbon conversion and methanol yield on CZS were higher than that on CZO.
• The supercritical fluid CO2 suppressed the sintering of Cu and ZnO particles.
• The supercritical fluid CO2 improved the specific metallic Cu surface area.
• The kinetic analysis revealed the reaction rate on CZS was faster than that on CZO.

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 443 K and 5.0 MPa for continuous 20 h 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 443 K, 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.