The combustion kinetics of 4-butoxyheptane, a novel oxygenated bioblendstock for diesel fuel obtained from the catalytic upgrading of acetic and butyric acid, was investigated using a plug flow reactor. The flow reactor experiments employed oxygen as the oxidizer and helium as the diluent with oxidation carried out at atmospheric conditions at temperatures from 400 – 1000 K at 20 K intervals. The fuel, oxidizer, and diluent flow rates were varied at different temperatures to maintain a constant initial fuel mole fraction of 1000 ppm, stoichiometric condition, and a residence time of 2.0 s. The reacted gas was fed to two separate GC systems that could detect qualitatively and quantitatively the product species. The first GC system, GC1, contains a flame ionization detector (FID) equipped with a methanizer for quantitation and a mass spectrometer (MS) for identification and was used to detect higher carbon number compounds (&gt; C5). The second GC system, GC2, utilizes three detectors and is set to detect lighter compounds (C1 – C5). GC2 contains an FID for quantitation of hydrocarbon species and two thermal conductivity detectors (TCDs) to quantitate carbon monoxide and carbon dioxide. The fuel species profile at the outlet indicated a double negative temperature coefficient (NTC) behavior for the conditions investigated. The product distribution from the plug flow reactor was then compared to the 0-D simulation from the existing detailed kinetics mechanism for 4-butoxyheptane (unpublished mechanism developed by Lawrence Livermore National Laboratory). Most of the product concentrations showed quantitative agreement with experimental data, but the pathway to a few species was not reproduced from the simulation. The reaction pathway to the missing product was then further analyzed theoretically using the G4 composite method to calculate species energies. We identified new pathways to the missing products with plausible energy barriers, showing a good agreement with our flow reactor experiments.

Elucidating the low temperature reaction pathways of 4-butoxhyheptane — a novel bioblendstock for diesel fuel

ACS Fall 2021

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