Understanding kinetically interplaying reverse water-gas shift and Fischer-Tropsch synthesis during CO2 hydrogenation over Fe-based catalysts

Direct CO 2 hydrogenation into linear α-olefins presents a promising route in carbon-neutral chemical manufacture. This work systematically investigated the variable interplay between Reverse Water-Gas Shift (RWGS) and Fischer-Tropsch Synthesis (FTS) during CO 2 hydrogenation using model Na-Fe 5 C 2 catalysts, combining dynamic/steady-state CO/CO 2 hydrogenation performance, intrinsic kinetics and multiple characterization results. Na-Fe 5 C 2 proves to be surface-enriched with FeO x sites over which RWGS readily proceeds. Meanwhile, CO 2 conversion under integral reaction conditions is limited by the subsequent FTS step due to a lack of available FeC x sites. The catalyst performance is steered by the properties and relative quantities of the two different active sites. Na addition promotes the refresh of FeO x sites and β-elimination of alkyl intermediates over FeC x sites, but at the cost of inhibiting the surface fraction of FeC x sites and thus the single-pass CO 2 conversion. These fundamental understandings will enlighten further development of CO 2 hydrogenation catalysts with improved hydrocarbon yields.