θ-Fe3C dominated Fe@C core-shell catalysts for Fischer-Tropsch synthesis: Roles of θ-Fe3C and carbon shell

theta-Fe3C formation is usually considered as a deactivation factor in Fischer-Tropsch synthesis (FTS). Herein, theta-Fe3C dominated Fe@C core-shell catalysts were fabricated by pyrolysis of MIL-101(Fe) in ethyne for studying the roles of theta-Fe3C and carbon shell in FTS. In the evolution of MIL-101(Fe) into Fe@C catalysts, ethyne decomposition promotes the formation of theta-Fe3C and carbon shells around nanoparticles. By modulating the pyrolysis temperature, theta-Fe3C and/or alpha-Fe nanoparticles coated with different carbon shells (amorphous carbon, graphene or graphite shells) are acquired. By exploring the relationship between phase composition, structure of catalysts and FTS performance, it is found that O-Fe3C is confirmed to be FTS active, which exhibits superior CAC chain growth ability, i.e., higher C5+ selectivity and lower CH4 selectivity. Meanwhile, graphene shell inhibits iron nanoparticles aggregation and stabilizes the catalysts. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

By modulating pyrolysis temperature, catalysts with different carbon shells (amorphous carbon, graphene or graphite shells) coated theta-Fe3C and/or alpha-Fe nanoparticles are acquired. It is found that O-Fe3C is confirmed to be FTS active with superior CAC chain growth ability, showing higher C5+ selectivity and lower CH4 selectivity. Meanwhile, graphene shell inhibits iron nanoparticles aggregation and stabilizes the catalysts.