Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts

Authors: Atsushi Satsuma, Kaoru Osaki, Masatoshi Yanagihara, Junya Ohyama, Kenichi Shimizu

Abstract:
The effect of supports (CeO₂, TiO₂, Al₂O₃, ZrO₂, and SiO₂) on CO oxidation over Pd catalysts atlow temperatures was investigated, and activity-controlling factors were discussed. The light-off temperature was in the order of Pd/CeO₂ < Pd/TiO₂ < Pd/Al₂O₃ < Pd/ZrO₂ ≤ Pd/SiO₂ which was fairly in agreement with the reduction temperature of supported Pd to metallic species in CO-Temperature programmed reduction (CO-TPR) profile. The result indicates that higher reducibility of supported Pd to metallic species is one of the activity-controlling factors for the oxidation activity. The activation of oxygen on metal oxide supportis suggested to be another factor for the low temperature oxidation. Actually, in situ IR measurement revealed that the oxidation of CO proceeds on Pd/CeO₂ and Pd/TiO₂ even under nearly 100% coverage of CO over Pd, though Pd/Al₂O₃ showed CO oxidation activity below 50% coverage of CO. The supports having oxygen storage property, CeO₂ and TiO₂, contribute to the oxygen activation to proceed CO oxidation irrespective of self-poisoning of metallic Pd surface by adsorbed CO. It was concluded that both of the following two factors are essential for CO oxidation at low temperature: (1) formation of metallic Pd and (2) oxygen storage property of metal oxide support.

Keywords:
Pd
Support effect
CO oxidation
Oxygen storage capacity
Activity-controlling factor

Published in: Applied Catalysis B: Environmental (Volumes 132–133, Pages 1-552, 27 March 2013)

Publisher: Elsevier  

ISSN Information: 0926-3373

Activity controlling factors for low-temperature oxidation of CO over supported Pd catalysts

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