Modified CNT-Supported Fe Catalysts for Enhanced CO2 Hydrogenation in Fischer–Tropsch Synthesis

Fischer–Tropsch synthesis (FTS) is a promising route for the sustainable production of synthetic fuels and light olefins from CO2-derived syngas. Iron-based catalysts are widely studied due to their high CO2 conversion ability and low cost; however, improving light-olefin selectivity while maintaining high CO2 conversion remains challenging. In this study, Fe-based catalysts supported on carbon nanotubes (CNTs) were synthesized and optimized using a statistical design of experiments (DOE) approach in Design-Expert software. Catalysts with different Fe/K ratios were evaluated for CO2 hydrogenation under industrial conditions (280 °C, 2 MPa, H2/CO2 = 3, GHSV = 2000 h–1). The optimum catalyst was further promoted with Cu, Co, and Zn to examine synergistic effects. Characterization by XRD, BET, TGA, ICP, XPS, and FTIR revealed important structure–performance relationships. The addition of 3 wt % Co significantly enhanced catalytic activity and increased light-olefin selectivity to nearly 50 mol % by modifying the active-site structure and electronic environment.