Enhancing the light olefin selectivity of an iron-based Fischer–Tropsch synthesis catalyst by modification with CTAB

Abstract

The effects of the surfactant hexadecyltrimethylammonium bromide (CTAB) on the catalytic performance of a manganese-promoted iron (FeMn) catalyst for the Fischer–Tropsch to olefin (FTO) reaction were investigated. The use of the CTAB-assisted FeMn catalyst resulted in the production of light olefin (C_2–4) selectivity of up to 55.45% with a ratio of olefin to paraffin among the C₂–C₄ hydrocarbons as high as 7.75 under industrially relevant conditions (320 °C, 1.0 MPa, H₂/CO ratio of 1.5 (v/v), GHSV = 4200 h⁻¹). The characterization results indicate that CTAB has a great influence on the structure, composition, chemical state, and catalytic performance of the iron-based catalyst. Most interestingly, a greater amount of Mn promoter was found to be dispersed on the surface of α-Fe₂O₃, rather than being dissolved into the α-Fe₂O₃ lattice when CTAB was employed, which contributed towards enhancing the promotional effects of the Mn promoter, leading to the formation of certain surface-specific activity sites.