Na-Manipulated Reaction Pathways Boosting Long-Chain Olefin Production via Fischer-Tropsch Synthesis over NaRu/TiO2 Catalysts

Non-classical Fischer–Tropsch to olefins (FTO) is a crucial yet highly complex industrial reaction that enables the direct conversion of syngas, derived from renewable feedstocks such as biomass, municipal solid waste, or captured CO 2 , into long-chain olefins (C 5+ = ) via a carbide mechanism. Here, we systemically investigate mechanisms and performance of Na-modified Ru/TiO 2 catalysts in non-classical FTO, and experimentally discover a new CO insertion pathway. Our findings show that Na modification alters the adsorption and activation behaviors of CO, H 2 and intermediates, eventually manipulating reaction mechanisms. The Ru/TiO 2 catalyst with less Na exhibits high CO dissociation and C-C coupling abilities but a poor dehydrogenation ability, which mainly obeys the carbide mechanism, benefiting to produce C 5+ alkanes, rather than olefins. However, excessive addition of Na would primarily make the Ru/TiO 2 catalyst alternately follow the CO insertion mechanism, preferring to produce short olefines (C 2-4 = ) because of the poor C-C coupling ability. After rational coordination of the two pathways through regulating the Na loadings, the 0.5NaRu/TiO 2 catalyst robustly exhibits ultra-high C 5+ = selectivity (80.9%) and impressive C 5+ = space time yield (1.68 × 10 -2 mol CO g cat -1 h -1 ) at 260 °C, without deactivation for over 100   h. These findings not only provide fundamental insights into the underlying mechanisms for long-chain olefin synthesis, but also offer theoretical guidance for developing advanced catalysts for industrial applications.