Sodium modified Fe-Mn microsphere catalyst for Fischer-Tropsch synthesis of light olefins

Both one-pot solvothermal method and impregnation were adopted to synthesize sodium modified Fe-Mn microsphere catalysts for Fischer-Tropsch synthesis (FTS) of light olefins. The effects of Mn and Na promoters on the microsphere morphology, electronic state and catalytic performance of Fe3O4 catalysts were evaluated by Ar adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy mapping (EDS-mapping), H2 temperature-programmed reduction (H2-TPR), CO temperature-programmed desorption (CO-TPD), X-ray photoelectron spectroscopy (XPS) and Mo center dot ssbauer spectra. SEM, TEM and Ar adsorption-desorption showed that catalysts were in a uniform spherical shape with the size of 300-400 nm, while FeMn microsphere owned a smaller size and a larger surface area. Mn promoter could enhance the chemisorption of CO, and suppressed the hydrogenation of olefins, then lead to higher selectivity of light olefins. Na promoter strengthened the FTS reaction activity due to its basicity and electronic donation. Mn15Na32im showed the highest CO conversion of 97.21 % with the light olefin selectivity of 33.02 %.