Experimental and Modeling Study of the Oxidation of Two Branched Aldehydes in a Jet-Stirred Reactor: 2‑Methylbutanal and 3‑Methylbutanal

Aldehydes,
especially formaldehyde and acetaldehyde, are common
intermediates in the oxidation of many hydrocarbons and biofuels.
Alcohols are known to produce important quantities of aldehydes. This
work describes the oxidation of 2-methylbutanal and 3-methylbutanal
(isopentanal) at both low and high temperatures. The former aldehyde
is a main intermediate in 2-methylbutanol oxidation while the latter
in isopentanol oxidation. Experiments were conducted in a jet-stirred
reactor (JSR) at a pressure of 10 atm, for equivalence ratios of 0.35,
0.5, 1, 2, and 4 and over the temperature range 500–1200 K.
The mean residence time was kept constant (700 ms). Concentration
profiles of stable species were measured using gas chromatography
and Fourier transform infrared spectroscopy. A detailed chemical kinetic
mechanism including oxidation of various hydrocarbon and oxygenated
fuels was extended to include the oxidation chemistry of both aldehydes;
the resulting mechanism was used to simulate the present experiments.
Both aldehydes showed negative temperature coefficient behavior in
lean mixtures mainly due to the production of sec- and isobutyl radicals from 2- and 3-methylpentanal oxidation, respectively.