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# Search for simple surrogates to represent terpenes biofuels in combustion models

Philippe Dagaut

► To cite this version:

Philippe Dagaut. Search for simple surrogates to represent terpenes biofuels in combustion models. 5th International Conference on Biofuels and Bioenergy, Coalesce Research Group, Oct 2024, Tokyo (Japan), Japan. http://hal-04756391

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https://hal.science/hal-04756391v1

Submitted on 28 Oct 2024

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Title: Search for simple surrogates to represent terpenes biofuels in combustion models.

Name: Dagaut, P.

Affiliation: CNRS, ICARE, Orleans, France

Abstract:

Terpenes such as limonene, α-pinene, and β-pinene pertain to a class of hydrocarbons naturally released by plants. These high-energy density chemicals can be blended with liquid fuels. For the development of clean combustion of such biofuels, chemical kinetic reaction mechanisms need to be proposed. However, due to the relative complexity of such fuels, search for appropriate surrogates is highly desirable. Methylcyclohexenes isomers have been selected among possible available cyclic unsaturated hydrocarbons. The oxidation of terpenes has been performed under well control conditions. Limonene, α-pinene, and β-pinene, were oxidized in a jet-stirred reactor. Similarly, 1,1-methyl cyclohexene, 1,3- methyl cyclohexene, and 1,4- methyl cyclohexene were oxidized in the same reactor. FTIR and gas chromatography were used to characterize simple products of oxidation. In addition, samples of the reacting mixtures containing more complex products were collected, dissolved in acetonitrile, and analyzed by high-resolution mass spectrometry. Direct flow injection or chromatographic separation by ultra-high-performance liquid chromatography. Heated electrospray ionization and atmospheric pressure chemical ionization were used to characterize the products of oxidation. H/D exchange using D₂O was performed for probing the presence of hydroxyl and hydroperoxyl groups in the products. Reaction with 2,4-dinitrophenylhydrazine was used to assess the presence of carbonyl functional groups in the products of oxidation. A large set of oxidation products, including highly oxygenated organic products with up to 9 oxygen atoms, was observed. Aromatic and/or polyunsaturated products were also detected. Van Krevelen plots, computed oxidation state of carbon, aromaticity index, maximum carbonyl ratio, and degree of unsaturation in products were used to analyze the results. A comparison of the products of oxidation of the three terpenes and the three methyl cyclohexene indicated that none of the surrogates studied could fully represent the selected terpenes under cool-flame conditions.

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.