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Decomposition of Selected Chlorinated Volatile Organic Compounds on CeO2

Abstract

Chlorinated volatile organic compounds (CVOCs) are toxic chemical entities emitted invariably from stationary thermal operations when a trace of chlorine content is present. Replacing the high-temperature destruction operations of these compounds with catalytic oxidation has led to formulating various potent metal oxides catalysts; among them ceria-based materials. Guided by recent experimental measurements, this study theoretically investigates initial steps operating in the interactions of ceria surface CeO2(111) with three CVOCs model compounds; namely chloroethene (CE), chloroethane (CA) and chlorobenzene (CB). We find that, CeO2(111) surface mediates fission of the carbon-chlorine bonds in the CE, CA and CB molecules via modest reaction barriers. As a result of localization of excess electrons left behind after a creation of an oxygen vacancy; analogous fission over an oxygen vacant surface systematically necessitates lower energy barriers. Dehydrochlorination of CE and CA molecules preferentially proceed via a dissociative addition channel; however, subsequent desorption of vinyl and ethyl moieties require less energy than the surface assisted β C-H bond breakage. The profound stability of hydrocarbons species on the surface contributes to the observed deactivation of ceria at temperature as low as 580 K under pyrolytic conditions. Adsorption of an oxygen molecule at an oxygen vacant site initiates decomposition of adsorbed phenyl moiety. Likewise, adsorbed surface hydroxyl group serves as the hydrogen source in the observed conversion of CB into benzene. A plausible mechanism for the formation of 1,4-dichlorobenzene incorporates abstraction of a para hydrogen in the CB molecule by an O-1 surface anion followed by a chlorine transfer from the surface. Plotted conversion – temperature profiles via a simplified kinetic model against corresponding experimental profiles exhibit a reasonable agreement. Results from this study could be useful in the ongoing efforts to improve the ceria’s catalytic capacity in destroying CVOCs.

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Publication details

The article was received on 02 Jun 2017, accepted on 01 Aug 2017 and first published on 01 Aug 2017


Article type: Paper
DOI: 10.1039/C7CY01096F
Citation: Catal. Sci. Technol., 2017, Accepted Manuscript
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    Decomposition of Selected Chlorinated Volatile Organic Compounds on CeO2

    H. Miran, M. Altarawneh, Z. Jiang, H. Oskierski, M. H. Almatarneh and B. Z. Dlugogorski, Catal. Sci. Technol., 2017, Accepted Manuscript , DOI: 10.1039/C7CY01096F

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