Detailed chemical kinetic reaction mechanism for biodiesel components

New chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet‐stirred reactor experiments for rapeseed oil methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions. 1. Introduction Biofuels have the potential to supplement conventional petroleum‐based transportation fuels. Such fuels can reduce dependence on imported petroleum fuels and, since they are derived from renewable sources, can reduce net emissions of greenhouse gases. An important class of biodiesel fuels is long‐chain monoalkyl esters of fatty acids from vegetable oils and animal fats, and currently soy oil and rapeseed oil represent major sources of these oils. Use of biodiesel in diesel engines can decrease emissions of CO, unburned hydrocarbons, and soot [1‐4]. The principal components of both soy and rapeseed oil methyl ester fuels are the same five saturated and unsaturated methyl esters, specifically methyl palmitate (C 17 H 34 O 2), methyl stearate (C 19 H 38 O 2), methyl oleate (C 19 H 36 O 2), methyl linoleate (C 19 H 34 O 2) and methyl linolenate (C 19 H 32 O 2), with structures summarized in Figure 1. Their average compositions in soybean and rapeseed biodiesel fuels are given in Table 1 [5]. It is important to note that the most common components of both of these fuels are the molecules with one or two double bonds within the long carbon chain.