Direct synthesis of ethanol via CO2 hydrogenation over the Co/La-Ga-O composite oxide catalyst

A new Co/La2O3-La4Ga2O9 catalyst was prepared by reducing LaCo1−xGaxO3 perovskite and used in the direct synthesis of ethanol from CO2 hydrogenation. The composite catalyst was characterized by XRD, XPS, TPD and TEM and its catalytic performance in CO2 hydrogenation was investigated in a micro fixed-bed reactor operated at 230−290°C, 3 MPa, gas hourly space velocity (GHSV) of 3000 mL/(gcat·h) and H2/CO2 molar ratio of 3.0. The results indicate that the Co/La-Ga-O composite oxide catalyst exhibits high selectivity to ethanol in CO2 hydrogenation. In comparison with the LaCoO3 catalyst, the incorporation of Ga dopant can inhibit the formation of CH4 and then promote the production of alcohols, especially ethanol. With a Co/Ga atomic ratio of 7:3, the Co/La-Ga-O composite oxide catalyst displays the best performance in CO2 hydrogenation, with a CO2 conversion of 9.8%, a selectivity of 74.7% to total alcohols and ethanol content of 88.1% in the alcohols mixture. On the basis of the experimental results, it is speculated that the synergistic effect of surface Co0 and Coδ+ may contribute to the excellent performance of the Co/La2O3-La4Ga2O9 catalyst in CO2 hydrogenation to ethanol.