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Issue 83, 2017, Issue in Progress
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Formation of environmentally-persistent free radicals (EPFR) on α-Al2O3 clusters

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Abstract

Alumina oxides assume prominent catalytic applications in a wide range of industrial processes. However, alumina surfaces also serve as potent promoters in the heterogeneous formation of the notorious environmentally-persistent free radicals (EPFR). Herein, we theoretically examine dissociative adsorption mechanisms of phenol molecules over Al2O3 and hydrated Al2O3·nH2O clusters that mimic dehydrated and hydrated alumina structures, respectively. We show that fission of the phenol's hydroxyl bond over dehydrated alumina systematically incurs lower energy barriers in reference to the hydrated structures. A 1,2-water elimination step marks the most feasible channel in the interaction of phenol with hydrated clusters. The relevance of the acidity sites to the catalytic activity of alumina is clearly supported by the finding that the catalytic activity of the alumina surface in producing the phenoxy/phenolate species reversibly correlates with the degree of hydroxyl coverage. Desorption of adsorbed phenolates requires sizable desorption energies, and thus is expected to facilitate surface-mediated condensation into dioxin-like moieties.

Graphical abstract: Formation of environmentally-persistent free radicals (EPFR) on α-Al2O3 clusters

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Publication details

The article was received on 28 Aug 2017, accepted on 25 Oct 2017 and first published on 15 Nov 2017


Article type: Paper
DOI: 10.1039/C7RA09527A
Citation: RSC Adv., 2017,7, 52672-52683
  • Open access: Creative Commons BY license
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    Formation of environmentally-persistent free radicals (EPFR) on α-Al2O3 clusters

    N. W. Assaf, M. Altarawneh, M. W. Radny, J. Al-Nu'airat and B. Z. Dlugogorski, RSC Adv., 2017, 7, 52672
    DOI: 10.1039/C7RA09527A

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