XAFS Studies of Fe−SiO2 Fischer‐Tropsch Catalyst During Activation in CO, H2, and Synthesis Gas

Abstract Highly dispersed catalysts are widely used in industry and academia because of their large surface active sites. However, the predominant short‐range ordered structures in catalysts cannot be revealed by bulk characterization tools. The present study chooses a highly dispersed Fe−SiO 2 FTS catalyst as a research object and shows how X‐ray absorption fine structure (XAFS) helps to analyze the chemical information (iron composition, reduction degree, and iron valence) and structural information (coordinating atom and coordination number) of catalyst. The activation process of catalysts are detailedly studied under different atmospheres (CO, H 2 , or 2H 2 /CO) by using both ex‐situ and in‐situ XAFS. CO activation behaves most effective during the whole process and finally produces the highest content of active iron species compared with H 2 and 2H 2 /CO activation. The coordination number evolution of nearest Fe−O and Fe−C shells around Fe are put forward to understand the activation process. The present study demonstrates how XAFS elaborately reveals the phase transformations of the highly dispersed Fe−SiO 2 FTS catalyst.