Synergistic Na–Mn Promotion on High-PurityFe5C2 Nanocatalysts for Enhanced Light OlefinSelectivity in Fischer–Tropsch Synthesis

Abstract Light olefins are essential chemical feedstocks, typically produced from syngas through Fischer–Tropsch synthesis. While iron-based catalysts are favored for their high activity, the reaction often suffers from secondary hydrogenation of olefins, resulting in low selectivity for light olefins. To address these constraints, we introduce a synergistic modification strategy employing Na as an electronic promoter and Mn as a structural overlayer on high-purity Fe5C2 nanoparticles. As a result, the Na/Fe5C2@Mn catalyst exhibited markedly enhanced catalytic performance, demonstrating a CO conversion of 68.9% and a space-time yield for C2–4 olefins of 99.7 mmol gcat–1 h–1. Specifically, Na acts as an electron donor to promote CO activation, while Mn concurrently optimizes surface adsorption of hydrogen, improves the dispersion of Fe5C2, and stabilizes the Fe5C2 phase. Furthermore, this study introduces the hydrogenation capability coefficient as a novel descriptor to quantify the hydrogenation capacity.