Reaction mechanism for the free-edge oxidation of soot by O 2

Abhijeet Raj, Gabriel da Silva, Suk Ho Chung

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


The reaction pathways for the oxidation by O 2 of polycyclic aromatic hydrocarbons present in soot particles are investigated using density functional theory at B3LYP/6-311++G(d,p) level of theory. For this, pyrene radical (4-pyrenyl) is chosen as the model molecule, as most soot models present in the literature employ the reactions involving the conversion of 4-pyrenyl to 4-phenanthryl by O 2 and OH to account for soot oxidation. Several routes for the formation of CO and CO 2 are proposed. The addition of O 2 on a radical site to form a peroxyl radical is found to be barrierless and exothermic with reaction energy of 188kJ/mol. For the oxidation reaction to proceed further, three pathways are suggested, each of which involve the activation energies of 104, 167 and 115kJ/mol relative to the peroxyl radical. The effect of the presence of H atom on a carbon atom neighboring the radical site on the energetics of carbon oxidation is assessed. Those intermediate species formed during oxidation with seven-membered rings or with a phenolic group are found to be highly stable. The rate constants evaluated using transition state theory in the temperature range of 300-3000K for the reactions involved in the mechanism are provided. © 2012 The Combustion Institute.
Original languageEnglish (US)
Pages (from-to)3423-3436
Number of pages14
JournalCombustion and Flame
Issue number11
StatePublished - Nov 2012

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work has been supported by Saudi Aramco, KSA through KAUST CCRC.

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • General Physics and Astronomy
  • General Chemical Engineering
  • General Chemistry
  • Fuel Technology


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