Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters

Niveen W. Assaf, Mohammednoor Altarawneh, Marian W. Radny, Jomana Al-Nu'Airat, Bogdan Z. Dlugogorski

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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 Al 2 O 3 and hydrated Al 2 O 3 ·nH 2 O 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.

Original languageEnglish
Pages (from-to)52672-52683
Number of pages12
JournalRSC Advances
Volume7
Issue number83
Early online date15 Nov 2017
DOIs
Publication statusPublished - 2017
Externally publishedYes

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Aluminum Oxide
Free radicals
Free Radicals
Alumina
Phenols
Phenol
Hydroxyl Radical
Catalyst activity
Desorption
Aluminum Hydroxide
Hydrated alumina
Dioxins
Energy barriers
Acidity
Oxides
Condensation
Adsorption
Molecules
Water

Cite this

Assaf, N. W., Altarawneh, M., Radny, M. W., Al-Nu'Airat, J., & Dlugogorski, B. Z. (2017). Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters. RSC Advances, 7(83), 52672-52683. https://doi.org/10.1039/c7ra09527a
Assaf, Niveen W. ; Altarawneh, Mohammednoor ; Radny, Marian W. ; Al-Nu'Airat, Jomana ; Dlugogorski, Bogdan Z. / Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters. In: RSC Advances. 2017 ; Vol. 7, No. 83. pp. 52672-52683.
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Assaf, NW, Altarawneh, M, Radny, MW, Al-Nu'Airat, J & Dlugogorski, BZ 2017, 'Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters', RSC Advances, vol. 7, no. 83, pp. 52672-52683. https://doi.org/10.1039/c7ra09527a

Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters. / Assaf, Niveen W.; Altarawneh, Mohammednoor; Radny, Marian W.; Al-Nu'Airat, Jomana; Dlugogorski, Bogdan Z.

In: RSC Advances, Vol. 7, No. 83, 2017, p. 52672-52683.

Research output: Contribution to journalArticleResearchpeer-review

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Assaf NW, Altarawneh M, Radny MW, Al-Nu'Airat J, Dlugogorski BZ. Formation of environmentally-persistent free radicals (EPFR) on α-Al 2 O 3 clusters. RSC Advances. 2017;7(83):52672-52683. https://doi.org/10.1039/c7ra09527a