Reverse Water-Gas Shift Iron Catalyst Derived from Magnetite

The catalytic properties of unsupported iron oxides, specifically magnetite (Fe 3O 4), 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 h ？1 g cat. ？1), high turnover frequency (0.180 s ？1), high CO selectivity (>99%), and high stability (753 K, 45000 cm 3h ？1g cat. ？1) under a 1:1 H 2 to CO 2 ratio. Reaction rates over the Fe 3O 4 catalyst displayed a strong dependence on H 2 partial pressure (reaction order of ~0.8) and a weaker dependence on CO 2 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 Fe 3C, while the surface contained Fe 2+, Fe 3+, metallic Fe and Fe 3C. Catalyst tests on pure Fe 3C (iron carbide) suggest that Fe 3C is not an effective catalyst for this reaction at the conditions investigated. Gas-switching experiments (CO 2 or H 2) indicated that a redox mechanism is the predominant reaction pathway. View Full-Tex