An Na-modified Fe@C core–shell catalyst for the enhanced production of gasoline-range hydrocarbons via Fischer–Tropsch synthesis

Abstract

Although numerous studies have been conducted in the field of converting syngas to value-added fuels, selectively converting syngas to gasoline-range hydrocarbons (C_5–12 hydrocarbons) remains a big challenge. Alkali metal (namely, K, Na and Li)-modified Fe@C core–shell catalysts were synthesized by a one-step hydrothermal method for Fischer–Tropsch synthesis. An optimized selectivity of 56% for the C_5–12 hydrocarbons with a higher CO conversion of about 95% was obtained for the FeNa_2.0@C catalyst compared to that for other alkali metal-modified Fe@C catalysts. According to the characterization results, the incorporation of alkali metals into Fe@C enhanced the conversion of FeCO₃ to Fe₃O₄, which promoted the formation of the FTS active phase iron carbides. In particular, the strongest interaction of Fe–alkali metal and the highest amount of surface carbon layers were observed after adding an Na promoter into Fe@C in contrast to that observed for K and Li promoters, which strengthened the synergistic effect of Fe–Na metals and the spatial confinement of the core–shell structure, further improving the C_5–12 hydrocarbon selectivity.