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

The reduction-oxidation characteristics and proper kinetic models of three different iron ores having respective main phases of FeOOH, Fe 3 O 4 , and Fe 2 O 3 were investigated using an isothermal method. A proposed kinetic model was well satisfied to explain the experimental data for CO 2 activation to CO with a high accuracy. The kinetic data of the different phases of iron ores for its reduction by H 2 and for the oxidation by CO 2 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, Fe 2 O 3 , and Fe 3 O 4 for the oxidation by CO 2 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 CO 2 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 Fe 3 O 4 phase on the outer surfaces even under the reduction-oxidation reaction cycle. [ABSTRACT FROM AUTHOR]