Urea-derived Cu/ZnO catalyst being dried by supercritical CO₂ for low-temperature methanol synthesis

Methanol synthesis from syngas is a crucial process in the transformation of coal, natural gas and biomass into high-value added products. The high CO conversion and methanol yield are challenging in low-temperature methanol synthesis, thus improving catalyst activity is necessary. Cu/ZnO nanoparticles with a narrow size distribution were synthesized via homogeneous precipitation method using urea as the precipitant, being followed by supercritical CO₂ drying treatment (named as CZhp-S). The analysis results rendered that CZhp-S had a lower reduction temperature, higher Cu⁰ specific surface area and smaller crystal sizes compared with those of the catalyst prepared by co-precipitation method with conventional drying process (named as CZcp-H). Due to the large specific surface area and the enhanced amount of active sites, the CZhp-S with optimized supercritical CO₂ drying treatment condition demonstrated a maximum CO conversion of 52.7% and STY of methanol 87.6 g_MeOH/kg_catalyst.h⁻¹ for low-temperature methanol synthesis from syngas, which were much higher than those of CZcp-H (CO conversion 36.5%, STY of methanol 62.9 g_MeOH/kg_catalyst.h⁻¹).