Single-Phase θ-Fe₃C Derived from Prussian Blue and Its Catalytic Application in Fischer-Tropsch Synthesis

Elucidation of the intrinsic catalytic principle of iron carbides remains a substantial challenge in iron-catalyzed Fischer-Tropsch synthesis (FTS), due to possible interference from other Fe-containing species. Here, we propose a facile approach to synthesize single-phase θ-Fe₃C via the pyrolysis of a molecularly defined Fe-C complex (Fe₄[Fe(CN)₆]₃), thus affording close examination of its catalytic behavior during FTS. The crystal structure of prepared θ-Fe₃C is unambiguously verified by combined XRD and MES measurement, demonstrating its single-phase nature. Strikingly, single-phase θ-Fe₃C exhibited excellent selectivity to light olefins (77.8%) in the C₂-C₄ hydrocarbons with less than 10% CO₂ formation in typical FTS conditions. This strategy further succeeds with promotion of Mn, evident for its wide-ranging compatibility for the promising industrial development of catalysts. This work offers a facile approach for oriented preparation of single-phase θ-Fe₃C and provides an in-depth understanding of its intrinsic catalytic performance in FTS.