Transient behavior and reaction mechanism of CO catalytic ignition over a CuO–CeO2 mixed oxide

Kang, Running, Ma, Pandong, He, Junyao, Li, Huixin, Bin, Feng, Wei, Xiaolin, Dou, Baojuan, Hui, Kwun Nam and Hui, Kwan San (2020) Transient behavior and reaction mechanism of CO catalytic ignition over a CuO–CeO2 mixed oxide. Proceedings of the Combustion Institute. ISSN 1540-7489

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Abstract

This study focuses on the variation in activity-controlling factors during CO catalytic ignition over a CuO-CeO 2 catalyst. 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 (XPS), CO temperature-programmed desorption (CO-TPD) and infrared (IR) spectroscopy results suggested that CO is preferentially adsorbed on oxygen vacancies (Cu + -[O v ]-Ce 3 + ) to yield Cu + -[C =O]-Ce 3 + complexes. Because of the selfpoisoning 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. Nonetheless, the Cu + -[C =O]-Ce 3 + complex is a major contributor to CO ignition. The step-response runs and kinetic models testified 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
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Depositing User: LivePure Connector
Date Deposited: 15 Sep 2020 23:55
Last Modified: 18 Sep 2020 00:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/76883
DOI: 10.1016/j.proci.2020.06.186

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