Experimental and Updated Kinetic Modeling Study of Neopentane Low Temperature Oxidation

Neopentane
is an ideal fuel model to study low-temperature oxidation
chemistry. The significant discrepancies between experimental data
and simulations using the existing neopentane models indicate that
an updated study of neopentane oxidation is needed. In this work,
neopentane oxidation experiments are carried out using two jet-stirred
reactors (JSRs) at 1 atm, at a residence time of 3 s, and at three
different equivalence ratios of 0.5, 0.9, and 1.62. Two different
analytical methods (synchrotron vacuum ultraviolet photoionization
mass spectrometry and gas chromatography) were used to investigate
the species distributions. Numerous oxidation intermediates were detected
and quantified, including acetone, 3,3-dimethyloxetane, methacrolein,
isobutene, 2-methylpropanal, isobutyric acid, and peroxides, which
are valuable for validating the kinetic model describing neopentane
oxidation. In the model development, the pressure dependencies of
the rate constants for the reaction classes Q̇OOH + O2 and Q̇OOH decompositions are considered. This addition improves
the prediction of the low-temperature oxidation reactivity of neopentane.
Another focus of model development is to improve the prediction of
carboxylic acids formed during the low-temperature oxidation of neopentane.
The detection and identification of isobutyric acid indicates the
existence of the Korcek mechanism during neopentane oxidation. Regarding
the formation of acetic acid, the reaction channels are considered
to be initiated from the reactions of ȮH radical addition to
acetaldehyde/acetone. This updated kinetic model is validated extensively
against the experimental data in this work and various experimental
data available in the literature, including ignition delay times (IDTs)
from both shock tubes (STs) and rapid compression machines (RCMs)
and JSR speciation data at high temperatures.