Ozone-assisted low-temperature oxidation of methane and ethane

Ozone addition is a promising way to control and monitor the combustion process, e.g., enhancing the low-temperature oxidation reaction. This paper studied the ozone-initiated low-temperature oxidation of methane and ethane in a jet-stirred reactor (JSR) at atmospheric pressure. For the first time, we observed that the low-temperature oxidation of methane and ethane started ca. 450 K. Dozens of low-temperature oxidation products, which are dominantly oxygenated species, were identified and quantified by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). These data are valuable for evaluating the C₁–C₂ chemistry of base models. NUIGMech1.1 was used to simulate the experimental data in this work. The results reveal that the model can predict methane conversion, but a large deviation is observed for the intermediate species. In the case of ethane, NUIGMech1.1 overpredicts the low-temperature reactivity of ethane. We found that the reaction mechanism of the alkylperoxy radicals (CH₃Ȯ₂ and C₂H₅Ȯ₂) is crucial in accurately predicting the low-temperature oxidation chemistry of methane and ethane. The bimolecular reactions of the alkylperoxy radicals with Ö atoms and ȮH and HȮ₂ radicals, as well as the self and cross reactions of the alkylperoxy radicals, determine the balance of the radical pool of Ö, ȮH, and HȮ₂, and subsequently the fuel reactivity and the formation of the oxidation intermediates. This work provides new insights into the reaction mechanism of the key intermediates in the base model for chemically sensitized low-temperature fuel oxidation that need to be thoroughly studied in the future.