Low-temperature oxidation of monobromobenzene: Bromine transformation and yields of phenolic species

Mohammednoor Altarawneh, Bogdan Z. Dlugogorski

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    12 Citations (Scopus)
    54 Downloads (Pure)

    Abstract

    Brominated benzenes and phenols constitute direct precursors in the formation of bromine-bearing pollutants; most notably PBDD/Fs and other dioxin-type compounds. Elucidating accurate mechanisms and constructing robust kinetic models for the oxidative transformation of bromobenzenes and bromophenols into notorious Br-toxicants entail a comprehensive understanding of their initial oxidation steps. However, pertinent mechanistic studies, based on quantum chemical calculations, have only focused on secondary condensation reactions into PBDD/Fs and PBDEs. Literature provide kinetic parameters for these significant reactions, nonetheless, without attempting to compile the acquired Arrhenius coefficients into kinetic models. To fill in this gap, this study sets out to illustrate primary chemical phenomena underpinning the low-temperature combustion of a monobromobenzene molecule (MBZ) based on a detail chemical kinetic model. The main aim is to map out temperature-dependent profiles for major intermediates and products. The constructed kinetic model encompasses several sub-mechanisms (i.e, HBr and benzene oxidation, bromination of phenoxy radicals, and initial reaction of oxygen molecules with MBZ). In light of germane experimental observations, the formulated kinetic model herein offers an insight into bromine speciation, conversion profile of MBZ, and formation of higher brominated congeners of benzene and phenol. For instance, the model satisfactorily accounts for the yields of dibromophenols from oxidation of a 2-bromophenol (2-MBP) molecule, in reference to analogous experimental measurements. From an environmental perspective, the model reflects the accumulation of appreciable loads of 2-bromophenoxy radicals at intermediate temperatures (i.e., a bromine-containing environmental persistent free radical, EPFR) from combustion of MBZ and 2-MBP molecules. Acquired mechanistic/kinetic parameters shall be useful in comprehending the complex bromine transformation chemistry in real scenarios, most notably those prevailing in thermal recycling of brominated flame retardants (BFRs).

    Original languageEnglish
    Article number130621
    Pages (from-to)1-12
    Number of pages12
    JournalChemosphere
    Volume280
    Early online date26 Apr 2021
    DOIs
    Publication statusPublished - Oct 2021

    Bibliographical note

    Funding Information:
    This study has been supported by the 2019 Abu Dhabi Award for Research Excellence (AARE) – ( Abu Dhabi Department of Education and Knowledge ), grant ID : 21N225-AARE2019–ADEK-103 . Computations were carried out at the high performance computing cluster at the United Arab Emirates Univerity (UAEU).

    Publisher Copyright:
    © 2021 Elsevier Ltd

    Copyright:
    Copyright 2021 Elsevier B.V., All rights reserved.

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