Modeling study of the low-temperature oxidation of large methyl esters from C11 to C19

Abstract

The modeling of the low temperature oxidation of large saturated methyl esters really representative of those found in biodiesel fuels has been investigated. Models have been developed for these species and then detailed kinetic mechanisms have been automatically generated using a new extended version of software EXGAS, which includes reactions specific to the chemistry of esters. A model generated for a binary mixture of n-decane and methyl palmitate was used to simulate experimental results obtained in a jet-stirred reactor for this fuel. This model predicts very well the reactivity of the fuel and the mole fraction profiles of most reaction products. This work also shows that a model for a middle size methyl ester such as methyl decanoate predicts fairly well the reactivity and the mole fractions of most species with a substantial decrease in computational time. Large n-alkanes such as n-hexadecane are also good surrogates for reproducing the reactivity of methyl esters, with an important gain in computational time, but they cannot account for the formation of specific products such as unsaturated esters or cyclic ethers with an ester function.

Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels

“…23 Overall, the present mechanism produces agreement with experimental results of Hakka et al [47] that is very similar to the agreement provided by Herbinet et al [36]. The paper of Herbinet et al provides an excellent and extensive analysis of these experiments of Hakka et al The present mechanism shows a slightly greater low temperature selectivity for unsaturated methyl esters than the model of Herbinet et al, but these minor differences are due to small differences in reaction rate rules for the low temperature reaction classes.…”

“…The two distinct reaction regimes are shown very strongly in both the experimental and computational results, and the agreement between the experimental and computational results is excellent. The slightly greater amount of low temperature conversion of methyl palmitate than that of n-decane can be attributed primarily to the weakly bound H atoms at the '2' site adjacent to the methyl ester group in methyl palmitate [28][29][30]36,37], so the total rate of methyl palmitate consumption is slightly greater than that of n-decane. It is interesting to note that the 1-olefin concentrations are significantly higher than their corresponding 1-olefin methyl esters.…”

“…These studies have examined ignition and combustion of alkyl esters from methyl and ethyl hexanoate and methyl and ethyl heptanoate to methyl decanoate [24][25][26][27][28][29][30][31][32][33], followed closely by extensions to methyl stearate and rapeseed methyl ester [34][35][36][37].…”

Detailed chemical kinetic reaction mechanism for biodiesel components methyl stearate and methyl oleate

“…The detailed kinetic mechanism for methyl stearate and methyl oleate is based on the reaction pathways and rate rules developed originally for alkane fuels by Curran et al [14,15], with modifications for alkyl esters by Herbinet et al [21,26] . The presence of the methyl ester group modifies C -H bond strengths adjacent to the ester group, which modifies the rate of their H atom abstraction reactions.…”

“…Based on their previous works on alkanes [19] and the success of the methyl decanoate mechanism [16], the Nancy combustion group updated the reaction pathway and rate rules used by the software EXGAS, for the automatic generation of detailed kinetic models, for methyl and ethyl esters, leading to their application to mechanisms for methyl and ethyl butanoates [13] and larger methyl esters up to methyl decanoate [20] and methyl palmitate [21].…”