Influence of reduction treatment on the structural and redox behaviour of ceria, La/Ce and Y/Ce mixed oxides

A methodology based on reoxidation at 298 K with O2(5%)/He pulses followed by quantitative TPO runs allowed us to study the redox state reached by CeO2 and Ln3+ -containing ceria‐based mixed oxide samples Ln3+:La3+ or Y3+) after their reduction in a flow of hydrogen. The temperature range covered in...

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Bibliographic Details
Published in:Catalysis letters 1998-07, Vol.53 (1-2), p.51-57
Main Authors: BERNAL, S, BLANCO, G, CAUQUI, M. A, CIFREDO, G. A, PINTADO, J. M, RODRIGUEZ-IZQUIERDO, J. M
Format: Article
Language:English
Subjects:
Catalysis
Catalysts: preparations and properties
Cerium oxides
Chemistry
Exact sciences and technology
General and physical chemistry
Mixed oxides
Reduction
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
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Summary:A methodology based on reoxidation at 298 K with O2(5%)/He pulses followed by quantitative TPO runs allowed us to study the redox state reached by CeO2 and Ln3+ -containing ceria‐based mixed oxide samples Ln3+:La3+ or Y3+) after their reduction in a flow of hydrogen. The temperature range covered in the reduction treatments was from 623 up to 1223 K. During the severe reduction treatments hexagonal sesquioxide phases segregate from all the samples. The reduction temperature at which segregation occurs follows the trend La/Ce < Y/Ce < CeO2. The TPO and H2-TPD traces of reduced samples which showed evidence of segregation in XRD exhibit characteristic features which can also be used as an indication of this effect. The discussion is focussed on the overall and detailed understanding of the reoxidation process and on the analysis of the H2-TPD profiles.
ISSN:1011-372X
1572-879X
DOI:10.1023/A:1019005922456