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Detailed experimental and kinetic modeling study of toluene/C2 pyrolysis in a single-pulse shock tube

Abstract : A combined experimental and kinetic modeling study is carried out to explore the influences of acetylene and ethylene addition on the species formation from toluene pyrolysis. Experiments are conducted separately with four different ar gon-diluted binary toluene/C 2 mixtures in a single pulse shock tube at a nominal pressure of 20 bar over a temperature range of 1150 −1650 K. All the experimental mixtures contain about 100 ppm toluene and different amounts of C 2 fuels (50, 216, 459 ppm acetylene and 516 ppm ethylene). Species concentrations as a function of the temperature are probed from the post-shock gas mixtures and analyzed through the gas chromatography/gas chromatography-mass spectrometry techniques. A kinetic model is developed, which successfully predicts the absolute species concentration measurements as well as the changes brought by the varied fuel compositions. With the neat fuel decomposition profiles as a reference, both fuel components exhibit increased reactivity in the pyrolysis of all studied binary mixtures, indicating the existence of obvious synergistic effects. In particular, such effects become more remarkable when increasing the initial acetylene concentration. This essentially results from the addition-elimination reaction of a toluene fuel radical and a C 2 fuel molecule leading to a C 9 molecule and a hydrogen atom. Indene is identified as the predominant C 9 product in all studied cases, and its peak concentrations sharply increase with the initial acetylene contents in toluene-acetylene pyrolysis. On the other hand, indane, produced from the addition-elimination reaction between benzyl and ethylene, is only detected at trace levels in toluene/ethylene pyrolysis. This indicates a relatively weaker interaction between benzyl and ethylene, compared to that of benzyl and acetylene. Apart from the increased concentrations of hydrogen atoms and C 9 aromatics, interactions between toluene and C 2 fuels also directly result in a reduced level of C 7 radicals in the reaction system. Overall, PAH species can be divided into two groups according to the way their peak concentrations varying with the initial fuel compositions. For those largely depending on benzyl reactions, such as bibenzyl, biphenylmethane, fluorene and phenanthrene, the peak concentrations decrease with the added C 2 fuels. In contrast, increasing trends are observed in the peak concentrations of the PAHs which rely on indenyl as a precursor, including naphthalene, methyl-indene, benzofulvene and acenaphthalene.
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https://hal.archives-ouvertes.fr/hal-03058325
Contributor : Andrea Comandini Connect in order to contact the contributor
Submitted on : Friday, December 11, 2020 - 5:00:19 PM
Last modification on : Tuesday, October 12, 2021 - 5:20:48 PM
Long-term archiving on: : Friday, March 12, 2021 - 8:11:41 PM

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Combustion and Flame 226 (2021...
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Wenyu Sun, Alaa Hamadi, Said Abid, Nabiha Chaumeix, Andrea Comandini. Detailed experimental and kinetic modeling study of toluene/C2 pyrolysis in a single-pulse shock tube. Combustion and Flame, Elsevier, 2021, 226, pp.129-142. ⟨10.1016/j.combustflame.2020.11.044⟩. ⟨hal-03058325⟩

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