Comparison of preparation methods of iron-based catalysts for enhancing Fischer-Tropsch synthesis performance

Carbon supported iron catalysts for Fischer-Tropsch synthesis, with the same iron loading of ca. 35 wt.%, were prepared by pyrolysis process and incipient wetness impregnation methods. The effect of the preparation methods on the catalyst structure, catalytic properties, and the direct conversion of syngas via Fischer-Tropsch synthesis was investigated. The iron species, iron particle size and iron reducibility depended on the preparation method. The pyrolysis of homogeneous fusion yielded a unique core-shell structure with dispersed iron species embedded in a matrix of porous carbon. The FeOx/AC catalyst obtained by incipient wetness impregnation contained Fe2O3 species after calcination, while the core-shell structured catalyst obtained by pyrolysis process contained Fe3C species after calcination. The results show that the core-shell structure iron-based catalyst had higher extent of carburization and dispersion, which led to higher activity for Fischer-Tropsch reaction than that of other two catalysts obtained by different synthesis methods. Furthermore, the Fe3[email protected] catalyst promoted by alkali metals (Na, Mg, K, Ca) resulted in the increase of O/P ratio and low carbon olefin selectivity, and the decrease of methane selectivity.