Reduction-oxidation kinetics of three different iron oxide phases for CO2 activation to CO

- Kinetic model of three different iron phases were investigated for CO2 activation to CO.
- Three-dimensional diffusion Jander equation was well fitted with experimental data.
- Iron ores having a phase of FeOOH showed a superior activity and stability.
- Large surface area with a stable Fe3O4 phase was formed on the porous FeOOH surfaces.

The reduction-oxidation characteristics and proper kinetic models of three different iron ores having respective main phases of FeOOH, Fe3O4, and Fe2O3 were investigated using an isothermal method. A proposed kinetic model was well satisfied to explain the experimental data for CO2 activation to CO with a high accuracy. The kinetic data of the different phases of iron ores for its reduction by H2 and for the oxidation by CO2 were relatively well described by a simple three-dimensional diffusion model of Jander equation. Activation energies of three different iron ores with the phase of FeOOH, Fe2O3, and Fe3O4 for the oxidation by CO2 were found to be 42, 25, and 12 kJ/mol, respectively. Iron ore having a FeOOH phase exhibited a higher redox property by showing a large amount of CO generation through CO2 activation with an activation energy of 42 kJ/mol and a rate constant of 0.0065 min-1. The superior activities on the FeOOH were mainly attributed to a large surface area with medium grain size of FeOOH crystallites by forming a thermodynamically stable Fe3O4 phase on the outer surfaces even under the reduction-oxidation reaction cycle.

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