Origin of the redox deactivation phenomena in modified alumina-supported Ce/Pr mixed oxide. Aboussaid, K. b, Bernal, S., Blanco, G., Cifrado, G., Galtayries, A., Pintado, J., & El Begrani, M. Surface and Interface Analysis, 40(3-4):250-253, 2008. cited By 6
Origin of the redox deactivation phenomena in modified alumina-supported Ce/Pr mixed oxide [link]Paper  doi  abstract   bibtex   1 download  
In this study, we have investigated the redox deactivation of a Ce/Pr mixed oxide supported on modified alumina. Two samples have been prepared by using silica- or lanthana-modified alumina as supports: 25% Ce0.8Pr 0.2O2-x/Al2O3-SiO2 and 25% Ce0.8Pr0.2O2-x/Al2O 3-La2O3. The redox behavior was studied by reduction of the samples at selected temperatures, from 200 to 900°C. Oxygen Storage Capacity (OSC) of reduced samples was measured by their reoxidation at 200°C. The reduction degree attained by the supported mixed oxide, after reduction at temperatures up to 800°C, increases in parallel for both samples. However, at 900°C, there is a decrease of OSC, which is moderate for silica-modified sample, while for lanthana-modified catalyst, the OSC is almost negligible. XPS analysis of the fresh samples shows that the redox state of cerium cations close to the surface is mainly +4, while praseodymium appears always as Pr3+. Samples reduced at different temperatures were also investigated by XPS. In the case of silica-modified alumina reduced at 900°C, significant amounts of Ce4+ can still be detected, which is in good agreement with the OSC value observed at that temperature. However, lanthana-modified sample reduced at 800°C shows an important amount of Ce3+, being the only oxidation state observed for cerium after reduction at 900°C. This is in good agreement with the strong drop in OSC observed for this latter sample, which can be thus attributable to the trapping of trivalent cations by the alumina, forming a stable perovskite-like aluminate, LnAlO3, as confirmed by X-Ray Diffraction (XRD). Copyright © 2008 John Wiley & Sons, Ltd.
@ARTICLE{Aboussaid2008250,
author={Aboussaid, K.a  b  and Bernal, S.a  and Blanco, G.a  and Cifrado, G.A.a  and Galtayries, A.c  and Pintado, J.M.a  and El Begrani, M.S.b },
title={Origin of the redox deactivation phenomena in modified alumina-supported Ce/Pr mixed oxide},
journal={Surface and Interface Analysis},
year={2008},
volume={40},
number={3-4},
pages={250-253},
doi={10.1002/sia.2768},
note={cited By 6},
url={https://www.scopus.com/inward/record.url?eid=2-s2.0-42449145502&partnerID=40&md5=adc1a221cdbbd8dbe101b514bd5dbd1a},
affiliation={Departamento de Ciencia de los Materiales e Ingenieria Metalürgica y Quimica Inorganica, University of Cádiz, Apdo. 40. Puerto, Real (Cádiz). 11510, Spain; Faculté des Sciences, Université Abdelmalek Essaadi, B.P. 2121 Mhannech II, 93002-Tétouan, Maroc, Morocco; Laboratoire de Physico-Chimie des Surfaces, ENSCP, 11 Pierre et Marie Curie, 75005 Paris, France},
abstract={In this study, we have investigated the redox deactivation of a Ce/Pr mixed oxide supported on modified alumina. Two samples have been prepared by using silica- or lanthana-modified alumina as supports: 25% Ce0.8Pr 0.2O2-x/Al2O3-SiO2 and 25% Ce0.8Pr0.2O2-x/Al2O 3-La2O3. The redox behavior was studied by reduction of the samples at selected temperatures, from 200 to 900°C. Oxygen Storage Capacity (OSC) of reduced samples was measured by their reoxidation at 200°C. The reduction degree attained by the supported mixed oxide, after reduction at temperatures up to 800°C, increases in parallel for both samples. However, at 900°C, there is a decrease of OSC, which is moderate for silica-modified sample, while for lanthana-modified catalyst, the OSC is almost negligible. XPS analysis of the fresh samples shows that the redox state of cerium cations close to the surface is mainly +4, while praseodymium appears always as Pr3+. Samples reduced at different temperatures were also investigated by XPS. In the case of silica-modified alumina reduced at 900°C, significant amounts of Ce4+ can still be detected, which is in good agreement with the OSC value observed at that temperature. However, lanthana-modified sample reduced at 800°C shows an important amount of Ce3+, being the only oxidation state observed for cerium after reduction at 900°C. This is in good agreement with the strong drop in OSC observed for this latter sample, which can be thus attributable to the trapping of trivalent cations by the alumina, forming a stable perovskite-like aluminate, LnAlO3, as confirmed by X-Ray Diffraction (XRD). Copyright © 2008 John Wiley & Sons, Ltd.},
author_keywords={Alumina-supported catalyst;  Ce/Pr mixed oxide;  Lanthanide aluminate;  Oxygen storage capacity;  Redox deactivation;  XPS},
document_type={Conference Paper},
source={Scopus},
}

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