Direct Transformation of Carbon Dioxide to Value-Added Hydrocarbons by Physical Mixtures of Fe₅C₂ and K-Modified Al₂O₃

Conversion of CO₂ by hydrogenation into higher hydrocarbons has attracted much attention due to the continuous increasing concentration of CO₂ in the atmosphere. Fe₅C₂ was used as the active site and mixed with K-modified supports for CO₂ hydrogenation to synthesize value-added hydrocarbons. A series of supports were tested, and the alkaline Al₂O₃ was the best choice for light olefins and C₅₊ hydrocarbons. The transformation of product selectivity at time on stream demonstrated that potassium migrated into Fe₅C₂ during reaction. The selectivity of C₂₊ is 69.2% containing 35.8% C₂-C₄ ⁼ and 29.1% C₅₊ value-added hydrocarbons with the 31.5% CO₂ conversion (H₂/CO₂ = 3). When the ratio of H₂ and CO₂ was switched to 4, CO₂ conversion improved to 40.9%, and the C₂₊ selectivity to 73.5%, containing 37.3% C₂-C₄ ⁼ and 31.1% C₅₊ value-added hydrocarbons. The mixture catalysts can be directly used without any reduction before reaction, reducing the consumption H₂ and simplifying the operation.