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 (C5-12 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 C5-12 hydrocarbons with a higher CO conversion of about 95% was obtained for the FeNa2.0@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 C5-12 hydrocarbon selectivity.