Tailoring of Fe/MnK-CNTs Composite Catalysts for the Fischer–Tropsch Synthesis of Lower Olefins from Syngas

Iron-catalyzed conversion of coal/biomass-derived syngas directly to lower olefins through Fischer–Tropsch synthesis (i.e., FTO) is a sustainable and short-flow process. Herein, effects of Mn and K promoter loadings on FTO performance over the Fe-based catalyst supported on the promoter-adjustable carbon nanotubes (Fe/Mn x K y -CNTs) are systematically studied. Several Mn x K y -CNTs are prepared by the treatment of CNTs using aqueous KMnO 4 solution via a redox reaction, where promoter loadings are tailored by changing the aqueous KMnO 4 solution concentration and water amount for sample washing. FTO performance of these catalysts suggests that the increase in Mn and K loadings shows the enhanced lower olefins selectivity but suppressed activity. The resultant Fe/Mn 16.5 K 1.2 -CNTs exhibit the highest lower olefins yield. Further increasing K promoter content leads to slightly enhanced activity to lower olefins but dramatically suppressed CH 4 formation and enhanced chain growth. Moreover, appropriate precarburization temperature can facilitate the activity and selectivity toward lower olefins formation.