Insights into active iron phosphide as Fischer-Tropsch synthesis catalyst for sustainable light olefins production

• Iron phosphide-based catalysts showed higher stability and resistance to reoxidation during Fischer-Tropsch synthesis compared to Fe/SA. • Superior selectivity for light olefins (C 2 ⁻–C 4 ⁻) was achieved over iron phosphide-based catalysts. • Lower CO 2 formation in iron phosphide-based catalysts suggests minimized water-gas shift reaction compared to Fe/SA. • Iron phosphide-based catalysts catalyst significantly reduced methane and heavy hydrocarbon formation compared to the Fe/SA catalyst. • Iron phosphide-based catalysts has higher resistance to iron species reoxidation during Fischer-Tropsch synthesis. Here reports preliminary results on the performance of iron phosphide-based catalysts supported on SiO 2 -Al 2 O 3 (denoted as SA) for sustainable light olefin production via Fischer-Tropsch synthesis, compared to conventional iron-based catalysts. Characterization results confirmed the presence of a well-defined FeP phase in the iron phosphide-based catalysts (FeP/SA), whereas the iron-based catalysts (Fe/SA) displayed a mixture of metallic iron (Fe 0 ), oxidized iron (Fe +2 /Fe +3 ), and Hägg iron carbide phase (χ-Fe 5 C 2 ). The FeP/SA catalyst exhibited significantly higher CO conversion and stability over long reaction times, attributed to its resistance to surface iron species reoxidation, lower loss of exposed surface Fe species, and lower coke formation during the FTS reaction. The FeP/SA catalyst exhibited higher selectivity toward light olefins formation (C 2 ⁻- C 4 ⁻), while reducing selectivity for methane (CH 4 ) and heavier hydrocarbon formation compared to the Fe/SA catalyst. Furthermore, FeP/SA exhibited lower selectivity to CO 2 formation, which may indicate reduced water-gas shift (WGS) activity or the oxidation of adsorbed CO by surface-bound oxygen, resulting from the direct dissociation of CO on the surface, compared to Fe/SA catalyst. These results suggest that iron phosphide-based catalysts provide an efficient alternative for hydrocarbon production in FTS, particularly in the selective formation of light olefins.