Exploring the oxidation chemistry of diisopropyl ether: Jet-stirred reactor experiments and kinetic modeling

Diisopropyl ether (DIPE) is considered as a promising gasoline additive due to the favorable blending Reid vapor pressure and the low water solubility. To get a good understanding of the DIPE oxidation chemistry, oxidation experiments of a stoichiometric mixture of DIPE/O₂/Ar/Kr were performed in a jet-stirred reactor (JSR) at atmospheric pressure over the temperature range of 525-900 K in this work. About 30 intermediates and products were identified and quantified using a photoionization molecular-beam mass spectrometer (PI-MBMS). Furthermore, a detailed kinetic model was proposed for DIPE oxidation, which showed satisfactory performances in predicting the species concentration profiles in this work as well as those in literature. For DIPE oxidation, the fuel consumption was observed only above 750 K, even though DIPE has two tertiary hydrogen atoms that are easy to be abstracted so that low-temperature oxidation reactivity is expected. The low oxidation reactivity at low temperature is because the formed OOQOOH radical mostly dissociates back to QOOH+O₂, instead of undergoing intramolecular isomerization which leads to the low-temperature chain-branching. At higher temperature, DIPE is mainly consumed by hydrogen abstraction reactions from the carbon atoms adjacent to the oxygen atom, producing dominantly the IC₃H₇OC(CH₃)₂ fuel radical, which then decomposes rapidly via CO bond β-scission instead of combining with O₂. In contrast, the minor fuel radical IC₃H₇OCH(CH₃)CH₂ tends to go through the O₂ addition reaction and the subsequent chain branching reactions, as confirmed by the detection of cyclic ether intermediates. Propylene and acetone are the most abundant intermediates in DIPE oxidation, both of which predominantly come from the initial fuel decomposition steps. Other intermediates are mainly formed via the consumption of these two species.