Lawrence Berkeley National Laboratory

The low-temperature oxidation of a stoichiometric 2-methylhexane/O2/Ar mixture was examined in a jet-stirred reactor coupled with synchrotron vacuum UV photoionization molecular-beam MS. Low-temperature oxidation intermediates with two to five oxygen atoms were observed. The detection of C7H14O5 and C7H14O4 species implies that a third O2 addition process occurred in 2-methylhexane low-temperature oxidation. A detailed kinetic model was developed to describes the third O2 addition and subsequent reactions leading to C7H14O5 (keto-dihydroperoxide and dihydroperoxy cyclic ether) and C7H14O4 (diketo-hydroperoxide and keto-hydroperoxy cyclic ether) species. The kinetics of the third O2 addition reactions revealed that the addition reactions promoted 2-methylhexane auto-ignition at low temperatures.