The non-isothermal oxidation of 2-methylpentane. II. The chemistry of cool flames

Abstract

The products of all the modes of non-isothermal oxidation of 2-methylpentane by molecu­lar oxygen and of the attendant slow combustion reactions have been analysed by gas-liquid chromatographic and chemical methods. Oxidation in the cool-flame temperature range produces more than forty molecular species, including O -heterocycles, peroxides, alkenes and saturated and unsaturated aldehydes and ketones. A good qualitative description of the mode of formation of this complex mixture and of its variation with temperature is afforded by the alkylperoxy radical isomerization theory. This theory is developed semi-quantitatively and is in reasonable agreement with the quantitative experimental results. It is concluded that chain propagation in the cool-flame region occurs predominantly by attack on the fuel by hydroxyl radicals; the resulting oxidation is rapid and unselective. In contrast, at temperatures too low for cool-flame formation alkylperoxy radicals are the likely chain-propagating species, whereas at temperatures above the upper cool-flame limit hydroperoxy radicals probably propagate the chain. The mechanism of chain branch­ing is not clear but it is established that, in the cool-flame region, peroxidic compounds are involved.

Chemical kinetics of cyclic ethers in combustion

“…This idea stated that alkenes react with HOȮ radicals to produce Q ̇OOH radicals, which further react to aldehydes or oxiranes together with one ȮH radical that is needed for chain propagation [441]. Since this mechanism did not predict the large amounts of 3,3-dimethyloxetane formed during neo-pentane low-temperature oxidation [442], this explanation was challenged by Fish and coworkers by proposing an alkylperoxy radical isomerization mechanism [443]. Numerous studies demonstrated that lowtemperature oxidation of any large alkanes yields CEs of various ring sizes belonging to the oxirane, oxetane, tetrahydrofuran and tetrahydropyran families.…”