Nanocrystalline iron–boron catalysts for low-temperature CO hydrogenation: Selective liquid fuel production and structure–activity correlation

• Fe–B catalysts with different particle sizes and microstructures were prepared.
• They were carburized under Fischer–Tropsch synthesis (FTS) conditions at 423 K.
• In FTS at 423 K the catalysts displayed similar high selectivity to liquid fuels.
• The activities of the catalysts evolved positively with the ε-Fe2C contents.
• A linear relationship between the latter and the Fe–Fe coordination number was found.

Low-temperature Fischer–Tropsch synthesis (LTFTS) is one of the green routes for liquid fuel production. We prepared nanocrystalline Fe–B catalysts with different particle sizes and microstructures by adjusting the addition sequence of the precursors. In situ carburization of the Fe–B catalysts at 423 K revealed that the addition sequence influenced the rate and degree of carburization pronouncedly. In LTFTS at 423 K, the Fe–B catalysts displayed similar, markedly high selectivity to liquid fuels, with ∼48% for C5–C11 (gasoline fraction) and ∼31% for C12–C20 (diesel fraction) hydrocarbons, and low selectivities to CO2 and CH4, manifesting excellent carbon atom economy over the non-noble Fe–B catalysts. While the carburization degree did not affect the product distribution, the activities of the Fe–B catalysts evolved positively with the ε-Fe2C content. Moreover, a good linear relationship was established between the Fe–Fe coordination number and the ε-Fe2C content.

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