Reduction of Iron Oxide Catalysts: The Investigation of Kinetic Parameters Using Rate Perturbation and Linear Heating Thermoanalytical Techniques

• Published in: The journal of physical chemistry. B 2001-01, Vol.105 (1), p.220-228
• Main Authors: Tiernan, Michael. J, Barnes, Philip. A, Parkes, Gareth. M. B
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp003189+

The mechanisms and kinetics of the reduction of powdered Fe2O3 and Fe3O4 samples have been investigated under nonisothermal conditions to provide a detailed insight into the processes occurring. Both conventional linear heating temperature-programmed reduction (TPR) and constant rate temperature-programmed reduction (CR-TPR) techniques were utilized. Fe2O3 was found to reduce to Fe in a two-step process via Fe3O4. The mechanism of the prereduction step of Fe2O3 to Fe3O4 was found to follow an nth order expression where nucleation or diffusion was not the rate-controlling factor while the main reduction step to metal was described by a model involving the random formation and growth of nuclei. A CR-TPR rate perturbation method, “rate-jump”, was applied to the measurement of variations in apparent activation energy throughout the reduction processes, under near-equilibrium conditions and the activation energy measurements are compared with those obtained under conventional linear heating conditions.