Reduction of CO2 to methane, paraffins (C2–C4) and light olefins (C =2–C =4) over a bimetallic Fe–Co–MgO catalyst

Abstract

A bimetallic Fe–Co catalyst supported on MgO was synthesized by the co-precipitation method for selective CO₂ hydrogenation to C₂–C₄ hydrocarbons. The effect of temperature (280–430 °C), pressure (15–25 bar), and the H₂/CO₂ ratio was evaluated in a packed bed reactor. The catalysts were characterized by various techniques, and the physicochemical characteristics were correlated with the catalytic activity data of the fresh and spent catalysts, respectively. The experimental results suggested that the 15Fe5CoMgO catalyst was very active and selective to hydrocarbons (methane and paraffins). The higher activity of this catalyst was due to high metal dispersion, moderate basicity, and the formation of iron carbide. The maximum CO₂ conversion of ∼38% was achieved with a total hydrocarbon selectivity of ∼84% at 400 °C and 25 bar pressure. The interaction between Fe and Co significantly affected the CO₂ methanation, CO formation via reverse water gas-shift reaction (RWGS), and C–C coupling. The formation of an Fe–Co bimetallic alloy facilitated the C–C coupling and the formation of paraffin hydrocarbons. The times-on-stream study suggested that the catalyst was stable and selective for more than 100 h without any significant coke deposition. The spent catalyst characterization results showed that the formation of a new Fe₂O₃ phase provided the required stability of the catalyst.