A study of the low temperature autoignition of methyl esters

The autoignition of a series of C-4 to C-8 fatty acid methyl esters has been studied in a rapid compression machine in the low and intermediate temperature region (650-850 K) and at increasing pressures (420 bar). Methyl hexanoate was selected for a full investigation of the autoignition phenomenology, including the identification and determination of the intermediate products of low temperature oxidation. The oxidation scheme and overall reactivity of methyl hexanoate has been examined and compared to the reactivity of C-4 to C-7 n-alkanes in the same experimental conditions to evaluate the impact of the ester function on the reactivity of the n-alkyl chain. The low temperature reactivity leading to the first stage of autoignition is similar to n-heptane. However, the negative temperature coefficient region is located at lower temperature than in the case of the n-alkanes of corresponding reactivity. An evaluation of the distribution of esteralkyl radicals R-center dot and esteralkylperoxy radicals ROO center dot gives an insight into. the main reaction pathways. (C) 2009 The Combustion Institute. Published by Elsevier Inc. All tights reserved.