Reverse Water-Gas Shift Iron Catalyst Derived from Magnetite

• Main Authors: Chen-Yu Chou, Jason A. Loiland, Raul F. Lobo
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Catalysts
• Subjects: RWGS; iron oxides; CO₂ conversion; gas-switching
• Online Access: https://www.mdpi.com/2073-4344/9/9/773

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 h^−1 g_cat.^−1), high turnover frequency (0.180 s^−1), high CO selectivity (>99%), and high stability (753 K, 45000 cm³h^−1g_cat.^−1) under a 1:1 H₂ to CO₂ ratio. Reaction rates over the Fe₃O₄ catalyst displayed a strong dependence on H₂ partial pressure (reaction order of ~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 H₂) indicated that a redox mechanism is the predominant reaction pathway.