Products from the Oxidation of Linear Isomers of Hexene

Abstract

The experimental study of the oxidation of the three linear isomers of hexene was performed in a quartz isothermal jet-stirred reactor (JSR) at temperatures ranging from 500 to 1100 K including the negative temperature coefficient (NTC) zone, at quasi-atmospheric pressure (1.07 bar), at a residence time of 2 s and with dilute stoichiometric mixtures. The fuel and reaction product mole fractions were measured using online gas chromatography. In the case of 1-hexene, the JSR has also been coupled through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization.A difference of reactivity between the three fuels which varies with the temperature range has been observed and is discussed according to the changes in the possible reaction pathways when the double bond is displaced. An enhanced importance of the reactions via the Waddington mechanism and of those of allylic radicals with HO 2 radicals can be noted for 2-and 3-hexenes compared to 1-hexene.

Experimental and Kinetic Modeling Study of 2-Methyl-2-Butene: Allylic Hydrocarbon Kinetics

“…An important result of Battin-Leclerc et al 26 describes oxidation of the linear hexenes over a rather wide temperature range, from about 500 to 1100K. In the lowest temperature range of that study, between 500 and 700K, experiments showed the familiar behavior of the 1-hexene isomer reacting fastest among these isomers, followed in turn by 2-hexene and then 3-hexene.…”

“…, where RCM reaction pressures were always greater than 6.5 bar, the experimental ignition delays for 1-hexene were much faster than those for 2-hexene and 3-hexene at the lowest temperatures studied (700 The reaction path reversal first observed by Battin-Leclerc et al 26 that occurs at about 700 -725K in their atmospheric pressure experimental conditions is moved to about 850K by the higher pressure (~8-10 bar) conditions Subsequent studies have steadily refined these kinetic mechanisms. Vanhove et al 27 provided a complex analysis of the hexene isomers in terms of 4 distinct reaction pathways, two of them involving addition of OH and HO 2 to the double bond in each hexene isomer, and two more involving abstraction of H atoms from the hexene, followed by abstraction of another H atom from the allylic hexenyl radical to produce hexadiene.…”

“…Experimental studies have been carried out behind reflected shock waves, stirred reactors, and rapid compression machines for 1-hexene [23][24][25] , and for all three linear isomers of hexene [26][27][28] . Most of these experimental studies also included either detailed kinetic modeling or kinetics-based interpretation of their results, while others 18,28,29 are primarily kinetic modeling studies that provide analyses of these olefin experiments.…”

“…These studies address relative rates of combustion of isomers in a particular family of linear alkenes, most often hexenes [26][27][28][29] , but also including families of linear heptanes 28 , decenes 32 , and methyl nonenoates 31 as well. All of these studies address reaction at low temperatures in RCM, JSR, plug flow reactors, shock tubes, and motored engines.…”

“…Battin-Leclerc et al 26 summarized the current state-of-the-art with respect to kinetic modeling of the linear alkene fuels. The present study examines how the same kinetic modeling capabilities can be applied to a branched olefin.…”