title: Experimental investigation of the low temperature oxidation of the five isomers of hexane.
abstract: The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which are known to be soot precursors.
authors.affiliation: Laboratoire Réactions et Génie des Procédés, CNRS - Université de Lorraine, BP 20451, 1 rue Grandville, 54000 Nancy, France.
authors.forename: Zhandong
authors.initials: Z
authors.lastname: Wang
authors.forename: Olivier
authors.initials: O
authors.lastname: Herbinet
authors.forename: Zhanjun
authors.initials: Z
authors.lastname: Cheng
authors.forename: Benoit
authors.initials: B
authors.lastname: Husson
authors.forename: René
authors.initials: R
authors.lastname: Fournet
authors.forename: Fei
authors.initials: F
authors.lastname: Qi
authors.forename: Frédérique
authors.initials: F
authors.lastname: Battin-Leclerc