Volume 88, Issue 11 pp. 1684-1692
Research Article

Kinetics of Multi-Step Redox Processes by Time-Resolved In Situ X-ray Diffraction

Lukas C. Buelens

Lukas C. Buelens

Ghent University, Laboratory for Chemical Technology, Technologiepark 914, 9052 Ghent, Belgium

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Vladimir V. Galvita

Corresponding Author

Vladimir V. Galvita

Ghent University, Laboratory for Chemical Technology, Technologiepark 914, 9052 Ghent, Belgium

Ghent University, Laboratory for Chemical Technology, Technologiepark 914, 9052 Ghent, BelgiumSearch for more papers by this author
Hilde Poelman

Hilde Poelman

Ghent University, Laboratory for Chemical Technology, Technologiepark 914, 9052 Ghent, Belgium

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Christophe Detavernier

Christophe Detavernier

Ghent University, Department of Solid State Sciences, Krijgslaan 281, S1, 9000 Ghent, Belgium.

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Guy B. Marin

Guy B. Marin

Ghent University, Laboratory for Chemical Technology, Technologiepark 914, 9052 Ghent, Belgium

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First published: 10 August 2016
Citations: 11

Dedicated to Prof. Dr.-Ing. Andreas Seidel-Morgenstern on the occasion of his 60th birthday

Abstract

The kinetics of redox reactions of iron oxide in oxygen carrier 50Fe2O3/MgAl2O4 are examined using different time-resolved techniques. Reduction kinetics are studied by H2 temperature-programmed reduction (H2-TPR) monitored by time-resolved in situ XRD. In contrast to conventional TPR, in situ XRD distinguishes the three-stage reduction of Fe2O3 → Fe3O4 → FeO → Fe. It also shows that the oxidation of Fe → Fe3O4 by CO2 has no intermediate crystalline phases, explaining why its kinetics can easily be investigated by conventional CO2 temperature-programmed oxidation (CO2-TPO). A shrinking core model which takes into account solid state diffusion allows describing the experimental data.

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