Amphiphobic surface fabrication of iron catalyst and effect on product distribution of Fischer–Tropsch synthesis

Abstract

The core-shell Fe3O4@SiO2–PFTS with amphiphobic property was prepared through successive hydrothermal process, stöber method, and silylation reaction, where perfluorodecyltrlethoxysilane (PFTS) was employed as silylation agent to form amphiphobic surface. As-synthesized Fe3O4@SiO2–PFTS catalyst was exposed to the industrially relevant Fischer-Tropsch synthesis (FTS) conditions in a fixed-bed reactor and showed altered activity and product distribution different from traditional iron catalysts. Modified Fe3O4@SiO2–PFTS reduced evidently the production of CO2 from 44% of selectivity to 12% ascribed to suppression against the water gas shift (WGS) reaction, although CO conversion on Fe3O4@SiO2–PFTS as well as on Fe3O4@SiO2 declined compared with that on Fe3O4. Surface modification also caused the disappearance of mesopores and increase in steric hindrance, which inhibited diffusion of hydrocarbons. Secondary reactions of primary olefins were thus intensified, resulting in fall in olefin selectivity but rise in production of light hydrocarbons. The catalyst exhibited good stability within 120 h of time-on-stream.