Reverse Water-Gas Shift Iron Catalyst Derived from Magnetite

The catalytic properties of unsupported iron oxides, specifically magnetite (Fe3O4), were investigated for the reverse water-gas shift (RWGS) reaction at temperatures between 723 K and 773 K and atmospheric pressure. This catalyst exhibited a fast catalytic CO formation rate (35.1 mmol g(cat.)(-1)), high turnover frequency (0.180 s(-1)), high CO selectivity (>99%), and high stability (753 K, 45000 cm(3) h(-1) g(cat.)(-1)) under a 1:1 H-2 to CO2 ratio. Reaction rates over the Fe3O4 catalyst displayed a strong dependence on H-2 partial pressure (reaction order of similar to 0.8) and a weaker dependence on CO2 partial pressure (reaction order of 0.33) under an equimolar flow of both reactants. X-ray powder diffraction patterns and XPS spectra reveal that the bulk composition and structure of the post-reaction catalyst was formed mostly of metallic Fe and Fe3C, while the surface contained Fe2+, Fe3+, metallic Fe and Fe3C. Catalyst tests on pure Fe3C (iron carbide) suggest that Fe3C is not an effective catalyst for this reaction at the conditions investigated. Gas-switching experiments (CO2 or H-2) indicated that a redox mechanism is the predominant reaction pathway.