Hydrogenation of CO₂ to methanol over Cu/AlCeO catalyst

The hydrogenation of CO₂ to methanol is one of the most promising ways to reduce the CO₂ emission and mitigate the energy shortage, but it still confronts low CO₂ conversion and methanol selectivity. In this work, the Cu/Al₂O₃, Cu/AlCeO and Cu/CeO₂ catalysts with 60 wt.% Cu were prepared by co-precipitation method for the CO₂ hydrogenation to methanol, and the Cu particles were well dispersed on the supports. It was found that the composite of Al₂O₃ and CeO₂ can inhibit the growth of Cu crystallite, and the Cu/AlCeO had the smaller Cu particles, which was beneficial for catalytic activity improvement. Besides, CeO₂ introduced in the catalysts increased the surface basicity and the atom ratio of Cu⁺ species, which promoted the methanol selectivity. Kinetic experiments indicated that the Cu/AlCeO catalyst had the lowest apparent activation barriers for CO₂ activation and methanol synthesis. In the process of reaction, CeO₂ in the catalysts can inhibit the agglomerate of Cu, which improved the stability of catalysts. Hence, the Cu/AlCeO catalyst showed the highest space time yield (STY_methanol) for CO₂ hydrogenation into methanol. And the STY_methanol was 11.9 mmol h⁻¹ g⁻¹ at 533 K, V(H₂)/V(CO₂) = 3/1, gas hourly space velocity (GHSV) = 14,400 mL h⁻¹ g⁻¹ and P = 3 MPa.