Kang, Running, Ma, Pandong, He, Junyao, Li, Huixin, Bin, Feng, Wei, Xiaolin, Dou, Baojuan, Hui, Kwun Nam and Hui, Kwan San (2021) Transient behavior and reaction mechanism of CO catalytic ignition over a CuO–CeO2 mixed oxide. Proceedings of the Combustion Institute, 38 (4). pp. 6493-6501. ISSN 1540-7489

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Abstract

As a key heterogeneous process, the catalytic oxidation of CO is essential not only for practical applications such as automotive exhaust purification and fuel cells but also as a model reaction to study the reaction mechanism and structure-reactivity correlation of catalysts. In this study, the variation in activity-controlling factors during CO catalytic ignition over a CuO-CeO 2 catalyst was investigated. The activity for CO combustion follows the decreasing order of CuO-CeO 2 > CuO > CeO 2. Except for inactive CeO 2, increasing temperature induces CO ignition to achieve self-sustained combustion over CuO and CuO-CeO 2. However, CuO provides enough copper sites to adsorb CO, and abundant active lattice oxygen, thus obtaining a higher hot zone temperature (208.3 °C) than that of CuO-CeO 2 (197.3 °C). Catalytic ignition triggers a kinetic transition from the low-rate steady-state regime to a high-rate steady-state regime. During the induction process, Raman, X-ray photoelectron spectroscopy, CO temperature-programmed desorption and IR spectroscopy results indicated that CO is preferentially adsorbed on oxygen vacancies (Cu +-[Ov]-Ce 3+) to yield Cu +-[C≡O]-Ce 3+ complexes. Because of the self-poisoning of CO, the adsorbed CO and traces of adsorbed oxygen react at a relative rate, which is entirely governed by the kinetics on the CO-covered surface and the heat transport until the pre-ignition regime. The Cu +-[C≡O]-Ce 3+ complex is a major contributor to CO ignition. The step-response runs and kinetic models showed that after ignition, a kinetic phase transition occurs from a CO-covered surface to an active lattice oxygen-covered surface. During CO self-sustained combustion, the rapid gas diffusivity and mass transfer is beneficial for handling the low coverage of CO. The active lattice oxygen of CuO takes part in CO oxidation.

Item Type:	Article
Uncontrolled Keywords:	carbon monoxide,catalytic ignition,copper-cerium oxide,reaction mechanism,transient behavior,chemical engineering(all),mechanical engineering,physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/1500
Faculty \ School:
Related URLs:	http://www.scopus.com/inward/record.url?... https://linkinghub.elsevier.com/retrieve...
Depositing User:	LivePure Connector
Date Deposited:	15 Sep 2020 23:55
Last Modified:	13 Jan 2022 13:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/76883
DOI:	10.1016/j.proci.2020.06.186

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