Fischer-Tropsch to olefin reaction over Fe-based catalysts: Effect of preparation method and synergistic effect of Mn and Zr promoters.

• The effects of preparation methods on Fe-based catalysts were investigated. • Hydrothermal prepared catalysts exhibited better FTO performance than microemulsion. • The synergistic effects of Mn and Zr influenced the structure of catalysts. • Synergistic effect of Mn and Zr benefited for the production of heavy hydrocarbons. Direct production of light olefins (basic chemical raw materials in the industrials) from syngas using promoted catalysts demonstrates great potential, because of their upgraded performances. In this study, a series of Fe-based catalysts promoted by Mn and Zr were prepared by hydrothermal and microemulsion methods and applied to the Fischer-Tropsch reaction. To optimize the catalysts, response surface methodology combined with the central composite design was applied to three independent parameters of the synthesis method, weight percent of Zr promoter (2th promoter) and reaction temperature. To clarify the relationship between the synthesis methods, the synergistic effect of Zr and Mn promoters, and catalyst performance, in detail, different characterization analyses were studied, including XRD, BET, SEM-EDS, FESEM, TEM, H 2 -TPR, and CO-TPR. According to developed statistical equations, it was revealed that the synthesis method is the most influential parameter on CO% and O/P ratio. The experimental results indicated that Zr and Mn promoters had a negative synergistic effect on the CO% and O/P, but a positive one on the heavy hydrocarbons selectivities. The characterization results demonstrated that hydrothermal prepared FeMn catalyst, due to having uniform particle size distribution, cubic morphology, and better reduction at low temperature had highest CO%. [Display omitted] [ABSTRACT FROM AUTHOR]