WAXS study of the formation and evolution of phase-pure iron carbide catalysts for Fischer-Tropsch reaction

Fe-carbides have been identified as the active phase in Fe-based Fischer-Tropsch (FT) catalysts. The presence of other phases than Fe-carbide, such as metallic Fe or Fe-oxide, lowers the FT activity and, especially Fe-oxides are problematic as they also catalyze the formation of CO2 from CO, implying loss of valuable C atoms. Moreover, the presence of other phases complicates the study of fundamental structure-performance relationships. Therefore, it is highly desirable to synthesize phase-pure Fe-carbide catalysts [2,3]. Here,we prepared phase-pure χ-Fe5C2 by a dedicated carburization procedure of a high-purity Fe-oxide precursor obtained by flame spray pyrolysis (FSP). The resulting phase-pure χ-Fe5C2 catalyst outperforms reference catalysts with a high CTY and a very low selectivity to undesired CO2 and CH4 [2–11]. our goal is to determine in detail the evolution of the catalyst during carburization and the FT reaction employing operando WAXS combined with MS.

铁碳化物（Fe-carbides）已被确认为铁基费托（Fischer-Tropsch, FT）催化剂的活性物相。除铁碳化物外的其他物相（如金属铁或铁氧化物）会降低费托反应活性，其中铁氧化物尤为棘手：其不仅会催化CO转化为CO₂，还会造成宝贵碳原子的流失。此外，其他物相的存在会使基础结构-性能构效关系的研究复杂化。因此，合成纯相铁碳化物催化剂具有极高的研究价值[2,3]。本研究通过火焰喷雾热解（flame spray pyrolysis, FSP）制备高纯度铁氧化物前驱体，再经专用渗碳工艺合成纯相χ-Fe₅C₂催化剂。所得纯相χ-Fe₅C₂催化剂的性能优于参比催化剂，其CTY较高，且对副产物CO₂和CH₄的选择性极低[2–11]。本研究的目标是结合原位广角X射线散射（operando WAXS）与质谱（Mass Spectrometry, MS），详细解析催化剂在渗碳过程及费托反应中的演化行为。