<figure><img src="image_1.png" /></figure>

HAL
open science

# On the characterization of highly oxidized products from cool flames in a continuously-stirred tank reactor

Philippe Dagaut, Roland Benoit

<figure><img src="image_2.png" /></figure>

## To cite this version:

Philippe Dagaut, Roland Benoit. On the characterization of highly oxidized products from cool flames in a continuously-stirred tank reactor. ICME 2025: International Conference on Measurements of Energy, international measurement confederation, Jun 2025, Orléans, France. hal-05122770

HAL Id: hal-05122770

https://hal.science/hal-05122770v1

Submitted on 20 Jun 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

Public Domain
# On the characterization of highly oxidized products from cool flames in a continuously-stirred tank reactor

Philippe Dagaut¹*, Roland Benoit¹

¹CNRS, ICARE, Orléans, France

**Introduction:** Terpenes could be used as renewable fuel in the future. However, these chemicals are relatively complex. Therefore, model-fuels could be used to better understand their oxidation pathways. Methylcyclohexenes were selected for that purpose in this work.

**Methodology:** In the present study, the oxidation of methylcyclohexene isomers (1-methyl-, 3-methyl-, and 4-methyl-1-cyclohexene) was conducted in a continuously stirred tank reactor at an initial pressure of 10 bar, with excess oxygen (equivalence ratio of 0.5) across a temperature range of 500 to 1150 K. Reaction mixtures were collected using a sonic probe and subsequently analysed offline. The experimental phase of the study involved the utilisation of gas chromatography (GC) and ultra-high pressure liquid chromatography (UHPLC)-Orbitrap mass spectrometry. Gas samples were analysed by gas chromatography (GC). The samples were dissolved in acetonitrile by means of bubbling the gas emanating from the probe. Subsequent analysis was conducted either through direct injection or after UHPLC separation. The incorporation of D₂O into acetonitrile solutions was employed for the purpose of conducting H/D exchange, a process which was utilised to investigate the presence of hydroxyl (OH) or hydroperoxy (OOH) groups within the products of oxidation. The 2,4-dinitrophenylhydrazine reaction was utilised in conjunction with sample solutions in acetonitrile, with the objective of characterising the C=O function in the products of oxidation.

**Experimental Evaluation:** An extensive data set comprising chemical formulae was analysed. The presence of highly oxygenated compounds, polyunsaturated products, and aromatic products was detected under cool flame conditions. In order to elucidate the outcomes, Van Krevelen plots were employed, and the aromaticity index and aromaticity equivalence index were calculated. As previously documented, the production of benzene has been reported in the context of the oxidation of cyclohexane, cyclohexene, and 1,3-cyclohexadiene. However, the present study has identified the presence of aromatic, polyunsaturated, and polyaromatic hydrocarbons under cool flame conditions. The characterisation of the chemical classes present in the oxidation products was achieved by means of chemometric tools. The present results demonstrate the high complexity of the chemical oxidation pathways and chemical by-products associated with them.

**Keywords:** methylcyclohexene, oxidation, high-resolution mass spectrometry

*Corresponding author email: philippe.dagaut@cnrs-orleans.fr

**Acknowledgements:** Support from the CAPRYSSES project (ANR-11-LABX-006-01) funded by ANR through the PIA (Programme d'Investissement d'Avenir) is gratefully acknowledged.

<figure><img src="image_3.png" /></figure>