Reduction of iron oxide catalysts: The investigation of kinetic parametersusing rate perturbation and linear heating thermoanalytical techniques

The mechanisms and kinetics of the reduction of powdered Fe2O3 and Fe3O4 sa mples have been investigated under nonisothermal conditions to provide a de tailed insight into the processes occurring. Both conventional linear heati ng temperature-programmed reduction (TPR) and constant rate temperature-pro grammed reduction (CR-TPR) techniques were utilized. Fe2O3 was found to red uce to Fe in a two-step process via Fe3O4. The mechanism of the prereductio n 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 forma tion 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 t he activation energy measurements are compared with those obtained under co nventional linear heating conditions.