Unravelling the formation of Fe2SiO4 on Fischer-Tropsch Fe/SiO2 catalyst.

Fe-SiO 2 interaction is a critical issue in the study of Fischer-Tropsch Fe/SiO 2 catalyst. It has been advanced that the formation of Fe-O-Si bond is related to Fe-SiO 2 interaction and responsible for dispersing iron particles and stabilizing active phases. This work formulates studying the relationship and interconversion between Fe-O-Si bond and Fe 2 SiO 4 phase, and further concludes that Fe 2 SiO 4 is another form of Fe-SiO 2 interaction. A well mixing of Fe-O and Si-O domains in the catalyst precursor benefits the distribution of extensive Fe-O-Si bond, which in turn facilitates the formation of Fe 2 SiO 4 during the catalyst reduction process. High ramp rate and diluted H 2 favor the transition of discrete Fe-O-Si to Fe 2 SiO 4 kinetically and thermodynamically, respectively. During the transition, amorphous Fe 2 SiO 4 initially forms before undergoing a rapid crystallization process, at ca. 560 ± 10 °C, to transform to large crystals detectable by XRD. In addition, the amorphous nature of Fe 2 SiO 4 requires the combination of characterization techniques capable of detecting short-range ordered structures, e.g., XAFS, MES, and magnetometer. [Display omitted] • Fe 2 SiO 4 is another form of Fe-SiO 2 interaction for Fischer-Tropsch Fe/SiO 2 catalyst. • Well distributed Fe-O-Si bond can transform to amorphous Fe 2 SiO 4. • High ramp rate and diluted H 2 kinetically favor the transition of Fe-O-Si to Fe 2 SiO 4. • Amorphous Fe 2 SiO 4 undergoes rapid crystallization process to form large particles at 560 ± 10 °C. • The dehydration of Si-OH facilitates the crystallization of Fe 2 SiO 4. [ABSTRACT FROM AUTHOR]