Experimental and Modeling Study of the Kinetics of Oxidation of Simple Biodiesel-Biobutanol Surrogates: Methyl Octanoate-Butanol Mixtures

There is growing interest for using butanol-biodiesel fuel blends in diesel engines, but neither kinetic data nor kinetic models were available for simulating their combustion. Therefore, the kinetics of oxidation of a biodiesel-biobutanol surrogate fuel (methyl octanoate-1-butanol) was studied experimentally in a jet-stirred reactor (JSR) at 10 atm, at a constant mean residence time of 0.7 s, over the temperature range 560-1190 K, and for several equivalence ratios ranging from 0.5 to 2. Concentration profiles of reactants, stable intermediates, and final products were determined as a function of temperature, by low-pressure sonic probe sampling followed by online Fourier transform infrared spectrometry (FTIR), and off-line gas chromatography (GC) analyses with thermal conductivity (TCD), flame ionization (FID), and mass spectrometry (MS) detection. The oxidation of this fuel in the aforementioned conditions was modeled using a detailed chemical kinetic reaction mechanism consisting of 4545 reactions and 1098 species. The proposed kinetic reaction mechanism generally yielded a good representation of the kinetics of oxidation of this biodiesel-biobutanol surrogate under the present conditions. The kinetic modeling was used to delineate the reactions enhancing the low-temperature oxidation of 1-butanol, important for diesel and HCCl engine applications. The present results also indicated that the methyl octanoate-1-butanol mixtures are less prone to emitting acetaldehyde than the corresponding methyl octanoate-ethanol mixtures oxidized in a JSR.