Construction of synergistic and efficient iron-based catalysts for hydrogenation of CO₂ to higher hydrocarbons

A series of fused iron (FI) catalysts promoted with biomass ash were prepared by physical mixing method and characterized by X-ray diffraction, transmission electron microscopy and Mossbauer spectroscopy. The catalytic performance of CO₂ hydrogenation to higher hydrocarbons was evaluated in a fixed bed reactor. The results show that compared with the catalyst without biomass ash (B-ash), the fused iron catalysts promoted with biomass ash have smaller particle size and narrower size distribution, and the four phases of Fe₃O₄, Fe₅C₂, Fe₃C as well as α-Fe coexist in synergy. Thus, the tandem reaction of reverse water gas shift (RWGS) and C-C coupling proceed efficiently, and the selectivity of higher hydrocarbons is significantly improved while methane formation is effectively suppressed. Among the products, C_4-18 hydrocarbons are dominant. The C_4-18 hydrocarbons' selectivity in all hydrocarbons reaches 73.9% at the conditions of 300℃, 1.0 MPa, 4800 h^-1, H₂/CO₂=3.0 as well as the additive amount of the promoter is 5% (mass ratio).