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The role of chlorine atoms and hydroxyl radicals in the formation of PCDDs from the oxidative pyrolysis of 2,4,6‐trichlorophenol
Author(s) -
Khachatryan Lavrent,
Burcat Alexander,
Dellinger Barry
Publication year - 2010
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20461
Subject(s) - chemistry , chlorine , radical , reactivity (psychology) , hexane , gas phase , pyrolysis , combustion , decomposition , phase (matter) , chlorine atom , chain reaction , kinetics , computational chemistry , organic chemistry , medicinal chemistry , photochemistry , medicine , physics , alternative medicine , pathology , quantum mechanics
A 132‐step gas‐phase reaction kinetic model has been combined with a four‐step surface model for the formation of 1,3,6,8‐tetrachlorodibenzo‐ p ‐dioxin (1,3,6,8‐TCDD) from the oxidation of 2,4,6‐trichlorophenol (2,4,6‐TCP) in the presence of hexane. The revised model is based on a simpler model previously published in the literature and modified by adding Cl‐releasing and the surface submodels, recalculating polynomial functions for thermodynamic parameters, and updating gas‐phase submodels for (i) 1,3,6,8‐TCDD formation, (ii) hydrogen oxidation, and (iii) hexane oxidation. The roles of the potential chain carriers, OH and Cl, in the formation of 1,3,6,8‐TCDD were specifically addressed. In spite of the reported high reactivity of Cl, it was found that OH:Cl ≫ 1, and OH is the dominant chain carrier from the apparent onset of purely gas‐phase reactions at 750 K to 99% conversion of 2,4,6‐TCP and hexane at 1075 K. This suggests that oxidation reactions are always dominant in realistic combustion systems, even where there are high concentrations of chlorine and relatively rich burning conditions. The update of the three gas‐phase submodels as well as incorporation of Cl‐releasing and the surface submodels resulted in improved agreement between calculated and experimental yields of 1,3,6,8‐TCDD yields at temperatures as low as 800 K. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 90–97, 2010