Boosting the Production of Higher Alcohols from CO₂and H₂over Mn- and K-Modified Iron Carbide

Abstract

The catalytic conversion of CO2 to higher alcohols (HAs, representing ethanol and alcohols with more than two carbon atoms) has been of great interest to mitigating the greenhouse effect and effectively utilizing CO2. However, most present catalysts have disadvantages of poor activity (conversion less than 30%) and selectivity (less than 10%) and high price. Herein, we report a Mn- and K-modified iron carbide catalyst that offers a CO2 conversion higher than 40% and a selectivity of higher alcohols exceeding 10%, and the proportion of propanol and butanol in alcohol products is more than 30%. Unpromoted iron carbide has a strong ability of hydrocarbon chain growth, leading to the fast formation of hydrocarbon products rather than HAs. However, on the Mn- and K-modified iron carbide catalyst, K is used to increase the surface C/H ratio of the catalyst by enhancing the adsorption of CO2 on the catalytic surface. The increased C/H ratio is indispensable to the formation of HAs, and the addition of Mn promoter dramatically improves the production of HAs, especially the formation of propanol and butanol. The synergistic effect between Mn and K on iron carbide is the key to produce HAs. In addition, the Mn- and K-modified iron carbide is of low cost, which can potentially provide an alternative for the hydrogenation of CO2 to produce valuable chemicals.