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Iron-based catalysts often undergo dynamic carburization and oxidation phase transitions in a CO2/H2 atmosphere. The identification of the active phase and the control of stability remain key challenges affecting their industrial application. This study employed a gas-solid carburization method to prepare high-purity single-phase χ-Fe5C2 (Hägg carbide) and θ-Fe3C (cementite), with their structural purity systematically confirmed by XRD and Mössbauer spectroscopy (MES). Using techniques including fixed-bed reactor tests (H2/CO2=1, 0.1 MPa, 270–420 °C), pulse experiments (270 °C) and in situ XRD (10% CO2/He, 340 °C), the catalytic performance and structural evolution pathways of these carbides in the reverse water-gas shift (RWGS) reaction were thoroughly investigated. The results indicate that χ-Fe5C2 exhibits higher RWGS activity but is more susceptible to oxidation during the reaction. In contrast, θ-Fe3C demonstrates stronger anti-oxidation stability but lower RWGS activity. Under RWGS conditions with H2, θ-Fe3C can partially transform into χ-Fe5C2. However, in 10% CO2 atmosphere, both carbides are directly oxidized to Fe3O4, with no observed phase transformation between the iron carbides. These findings reveal the differences in the evolution mechanisms of χ-Fe5C2 and θ-Fe3C under different atmospheres, providing experimental basis for the regulation of phase structure and optimization of operational stability in iron-based Fischer-Tropsch and RWGS catalysts.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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