Experimental study and modeling of the oxidation reactions of neopentane and isopentane

The different behaviour of hydrocarbons with respect to autoignition phenom ena is, at present, not yet fully explained. We have therefore investigated the oxidation of two alkanes that have different octane numbers: neopentan e (85.5) and isopentane (92.3), to obtain a better understanding of their r eaction mechanisms, in particular, those reactions that are responsible for the onset of knock in spark ignition engines. The experimental study was p erformed at 873 K in a jet-stirred flow reaction vessel. The oxidation mech anisms were simplified by using the CHEMKIN programme of simulation of reac tion mechanisms. These mechanisms were compared to those accounting for the oxidation of n-pentane, cyclopentane, n-heptane, and isooctane that we hav e previously studied. This comparison shows that the different behaviour of these hydrocarbons can be explained, at least in part, by the presence, in the reaction medium, of resonance-stabilized radicals.