Stabilization of \u03b5-iron carbide as high-temperature catalyst under realistic Fischer\u2013Tropsch synthesis conditions

Shuai Lyu,Jie Chen,Ye Wang,Zhe Li,Yuhua Zhang,Jinlin Li,Li Wang,Shukun Yin

doi:10.1038/s41467-020-20068-5

Abstract

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe2C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). Here, we succeed in stabilizing pure-phase ε-Fe2C nanocrystals by confining them into graphene layers and obtain an iron-time yield of 1258 μmolCO gFe−1s−1 under realistic FT synthesis conditions, one order of magnitude higher than that of the conventional carbon-supported Fe catalyst. The ε-Fe2C@graphene catalyst is stable at least for 400 h under high-temperature conditions. Density functional theory (DFT) calculations reveal the feasible formation of ε-Fe2C by carburization of α-Fe precursor through interfacial interactions of ε-Fe2C@graphene. This work provides a promising strategy to design highly active and stable Fe-based FT catalysts.

Highlights

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe2C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K)
Unlike Ru- or Co-based FT catalysts, where metallic Ru0 or Co0 functions as the active phase, metallic Fe0 is unstable and the evolution of a conventional Febased catalyst typically results in a mixture of different iron phases including Fe3O4 and iron carbides under FT reaction conditions[15,16,17,18,19,20,21]
Iron carbides are believed to be responsible for the activation of CO and the chain growth in FT synthesis, but the nature of the true active iron-carbide phase is still under debate and this hinders the rational design of highly active and stable Fe-based FT catalysts

Summary

Introduction

The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. ε-Iron carbide (ε-Fe2C) was proposed as the most active iron phase for FT synthesis, but this phase is generally unstable under realistic FT reaction conditions (> 523 K). The development of efficient catalysts for Fischer–Tropsch (FT) synthesis, a core reaction in the utilization of non-petroleum carbon resources to supply energy and chemicals, has attracted much recent attention. Because FT synthesis is a core reaction in the utilization of various non-petroleum carbon sources (such as coal, natural or shale gas, biomass, and CO2) to supply energy and chemicals, the development of efficient FT catalysts has received much-renewed interest in recent years[1,2,3,4,5,6]. Fe2C, which contains carbon atoms in octahedral interstices of hexagonal closed-packed iron lattice, was more active than a χFe5C2-dominant catalyst in the low-temperature (≤473 K) FT reaction[29]. It is highly challenging to synthesize stable catalysts that are dominated by the highly active ε-Fe2C phase for FT synthesis

Methods

Results

Conclusion