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Formation of Polycyclic Aromatic Hydrocarbons (PAHs) and Oxygenated PAHs in the Oxidation of Ethylene Using a Flow Reactor

ABSTRACT Interest in polycyclic aromatic hydrocarbons (PAHs) including a functional group in its chemical structure, particularly oxygenated PAHs (OPAHs), has been growing due to the toxicity and wide presence of the compound. Understanding the formation mechanism of OPAHs is very important for reducing their emission during combustion. However, studies on the quantitative evaluation of OPAHs have been very limited. In this study, the formation of OPAHs was quantitatively evaluated in addition to that of PAHs using a flow reactor system in which a mixture of ethylene, O2, and N2 reacted at atmospheric pressure. 5 types of OPAHs were targeted in this study: phenol, benzofuran, dibenzofuran, 9-fluorenone, and benzanthrone. 3 types of monocyclic aromatic hydrocarbons (MAHs) and 17 types of PAHs were also analyzed by gas chromatography mass spectrometry. Measurements were performed at different reaction gas temperatures (1050 to 1350 K), residence times (0.40 to 1.5 second), and equivalence ratios (3.0 to 12.0). Some measured data, mainly MAHs and PAHs, were compared with the concentrations predicted using existing kinetic models. Finally, we evaluated the reaction pathways that contributed to the formation of the OPAHs such as benzofuran, dibenzofuran, 9-fluorenone, and benzanthrone quantified in this study.