Enhanced CO₂ hydrogenation to higher alcohols over K-Co promoted In₂O₃ catalysts

The use of CO₂ to produce higher alcohols is a promising route to reduce emissions and make a profit. However, low activity of existing catalysts is a barrier for such processes to reach the industrial level. Here we report a novel K-Co promoted In₂O₃ catalyst for CO₂ hydrogenation to higher alcohols. The K-Co promoted In₂O₃ with an optimum K and Co of 2.5 and 5.0 wt% achieves a high C₂₊OH space time yield of 169.6 g kg_cat⁻¹h⁻¹ with the excellent C₂₊OH distribution of 87.4% in the total alcohols, while a very low space time yield of C₂₊OH (0.4 g kg_cat⁻¹h⁻¹) is obtained over In₂O₃ promoted with 5 wt% Co. Characterization results reveal that, after reduction with H₂ at 380 °C for 2 h, K-O-Co species is created for K-Co promoted In₂O₃ (2.5 wt% K and 5 wt% Co) sample which significantly reduces a number of weak H₂ adsorption and strengthens the interaction of adsorbed H compared to 5 wt% Co promoted In₂O₃ sample containing a mixture of Co⁰ and CoO. The reduction of weak H₂ adsorption and the improved interaction of adsorbed H with the catalyst surface retard the hydrogenation ability, allowing the CO insertion into adsorbed C_xH_y species prior to its hydrogenation to form hydrocarbon, resulting in a remarkable reduction of CH₄ and higher hydrocarbon, and significant improvement of higher alcohols.