Detailed product analysis during low- and intermediate-temperature oxidation of ethylcyclohexane

An experimental study of the oxidation of ethylcyclohexane has been performed in a jet-stirred reactor with online gas chromatography, under quasi-atmospheric pressure (800 Torr), at temperatures ranging from 500 to 1100 K (low- and intermediate-temperature zone including the negative temperature coefficient area), at a residence time of 2 s, and for three equivalence ratios (0.25, 1, and 2). Ethylcyclohexane displays important low-temperature reactivity with a well-marked negative temperature coefficient behavior. In addition to 47 products with a mass lower than ethylcyclohexane which have been quantified, many species with a C(8)H(14)O formula (molecular weight of 126) were detected by GC-MS and 7 of them were quantified. These molecules are cyclic ethers, ketones, and aldehydes with the same carbon skeleton as the reactant. Experiments were also carried on under the same conditions for two other C(8) hydrocarbons, n-octane and 1-octene, showing that the reactivity of ethylcyclohexane is close to that of the alkene and lower than that of the alkane. Simulations using a detailed kinetic model of the literature allow a good prediction of the global reactivity and of the main hydrocarbon products for temperatures above 800 K. The main reaction channels leading to the observed reaction products at both low (below 800 K) and intermediate temperature (above 800 K) are discussed.