New insights into the low-temperature oxidation of 2-methylhexane

​New insights into the low-temperature oxidation of 2-methylhexane

Z. Wang, S. Y. Mohamed, L. Zhang, K. Moshammer, D. M. Popolan-Vaida, V. S. B. Shankar, A. Lucassen, L. Ruwe, N. Hansen, P. Dagaut, S. M. Sarathy

Proceedings of the Combustion Institute 36 (1),  373-382 (2017)
Z. Wanga, S. Mohameda, L. Zhangb, K. Moshammerc, D. Vaidad, V. Shankara, A. Lucassenf, L. Ruweg, N. Hansenc, P. Dagauth, M. Sarathy
Auto-oxidation; Highly oxidized multifunctional molecules; Peroxides; Alternative isomerization; Synchrotron VUV photoionization mass spectrometry

In this work, we studied the low-temperature oxidation of a stoichiometric 2-methylhexane/O2/Ar mixture in a jet-stirred reactor coupled with synchrotron vacuum ultraviolet photoionization molecular-beam mass spectrometry. The initial gas mixture was composed of 2% 2-methyhexane, 22% O2 and 76% Ar and the pressure of the reactor was kept at 780 Torr. Low-temperature oxidation intermediates with two to five oxygen atoms were observed. The detection of C7H14O5 and C7H12O4 species suggests that a third O2 addition process occurs in 2-methylhexane low-temperature oxidation. A detailed kinetic model was developed that describes the third O2 addition and subsequent reactions leading to C7H14O5 (keto-dihydroperoxide and dihydroperoxy cyclic ether) and C7H12O4 (diketo-hydroperoxide and keto-hydroperoxy cyclic ether) species. The kinetics of the third O2 addition reactions are discussed and model calculations were performed that reveal that third O2 addition reactions promote 2-methylhexane auto-ignition at low temperatures.