Highly active and selective Cu-ZnO based catalyst for methanol and dimethyl ether synthesis via CO2 hydrogenation

Abstract

Highly active and selective Cu-ZnO based catalysts with high BET surface areas and Cu surface areas were prepared using the co-precipitation method. The Cu-ZnO based catalysts were systematically characterized and studied for methanol synthesis. Bifunctional catalysts, composed of Cu-ZnO based catalysts and HZSM-5 were studied for one-step dimethyl ether (DME) synthesis via CO2 hydrogenation. The effects of catalyst preparation conditions, reaction temperature, and pressure on methanol and DME synthesis were investigated and the optimum reaction conditions were determined. The optimized catalyst showed a BET surface area of 128 m2/g and a Cu surface area of over 59.3 m2/g, and demonstrated a high catalytic activity for CO2 hydrogenation. A bifunctional catalyst, prepared by a synthesized Cu-ZnO catalyst and HZSM-5, showed a high DME selectivity in one-step CO2 hydrogenation and methanol dehydration. The high activity and selectivity of the catalysts were attributed to the microstructure of the catalysts, which can be greatly affected by the catalyst preparation process. A long-term stability test showed a considerable decrease in activity within the first 20 h; however, the CO2 conversion (21.4%) and DME selectivity (55.5%) were still very high after 100 h.