The oxidation of methyl formate and methanol: An updated kinetic model

In an attempt toward the development of a biodiesel kinetic model, the present study presents an updated kinetic model for the smallest methyl ester, methyl formate, as well as for methanol, one of its main intermediate species. The model is assembled by performing a careful and critical review of elementary rate constants that have been previously measured and/or calculated from first principles. Most sensitive reactions during methanol oxidation and pyrolysis are discussed, and the kinetic parameters used in the present model are validated by comparison against experimental observations. Methanol oxidation was found to be extremely sensitive to HO₂ chemistry (H abstraction reactions on methanol) between 800 and 1300 K in flow reactor and shock tube conditions, while laminar flame speeds are highly sensitive to the hydroxymethyl (CH₂OH) radical decomposition at fuel rich conditions. Methyl formate decomposition reactions, either through concerted elimination reactions or hemolytic bond scission, are discussed. The proposed rate constants were tested against time speciation profiles but could not capture methanol pyrolysis over the entire temperature range. The present study suggests that despite the recent efforts, additional efforts on methyl formate and methanol oxidation kinetics are required.