Study On Nano Iron-Based Catalyst For Fischer-Tropsch Synthesis Of Light Olefins

Fischer Tropsch synthesis(FTS)provides a way to produce fuels and chemicals from coal,natural gas and renewable biomass resources.Nano Fe3O4 particles own the adjustable morphology and size.Thus Fe3O4 microspheres are expected to be used as nano iron-based catalysts for Fischer Tropsch synthesis of olefins efficiently.In this paper,the effect of promoters and preparation methods on the performance of Fe3O4 microsphere catalysts was investigated.And Ar-physisorption,XRD,SEM,HRTEM,H2-TPR,CO-TPD,XPS and MES were used to characterize the catalysts.Both one-pot solvothermal method and impregnation method were adopted to prepare the FeMn and FeMnNa microsphere catalysts with different content of Mn.The addition of Mn interacted with Fe3O4.CO chemisorption was enhanced with a proper content of Mn.Mn could donate electrons to Fe3O4,and the formation of ?-Fe5C2 was promoted by Mn in FTS reaction.Mn was able to inhibit the secondary hydrogenation of olefins and improve the selectivity of light olefins.Under the reaction conditions of 320?,1.5MPa,11000ml/g/h,CO conversion was 97.21%,olefins selectivity of C2-C4 was 33.02%and the value of O/P was 5.33 as the atomic ratio of Mn/Fe and Na/Fe was 0.15 and 0.032.FeMnNa microsphere catalysts with different content of Na were prepared by impregnation.The interaction between Na and Fe enhanced the crystallinity and stability of catalysts.Na could provide electrons and increase the basicity of catalysts,then improved the H2 adsorption and promoted the reduction property.Na improved the CO chemisorption of catalysts,and promoted the formation of ?-Fe5C2.Both CO conversion and olefins selectivity of C2-C4 increased with the proper content of Na.FeMn catalysts with different preparation conditions were obtained by one-pot solvothermal method.With the concentration of iron source decreased in solvent and with the amount of surfactant(PVP)increased,the diameter of microsphere catalyst became smaller.Microsphere catalysts with smaller and uniform diameters exhibited higher FTS activity and olefins selectivity of C2-C4.When the atomic ratio of Mn/Fe was 0.15,the reaction performance was the best with 0.2mol/L iron in solvent and 0.0003mol PVP.