Oxidation of ethyl methyl ether: Jet-stirred reactor experiments and kinetic modeling

Larger ethers such as diethyl ether (DEE) and di-n-propyl ether (DPE) have different oxidation behavior (double-NTC behavior) compared to the simplest dimethyl ether (DME). Such phenomena are interpreted with different reactions and processes in different ether kinetic models, which also predict different formation pathways of oxidation intermediates such as acids. To gain further insights into the oxidation kinetics of linear ethers, ethyl methyl ether (EME), which has a nonsymmetrical structure, was studied in this work. Oxidation experiments of 1% of EME were performed in a jet-stirred reactor at 1 atm, a residence time of 2 s, an equivalence ratio of 1, and over a temperature range of 375–850 K. The intermediates were analyzed with photoionization molecular-beam mass spectrometry. To explain the oxidation behavior of EME, a detailed kinetic model was also constructed. The oxidation of EME spans a wider temperature range than DME, but no obvious double-NTC behavior was observed as DEE. Based on the model analysis and profiles of critical intermediates such as ketohydroperoxides (KHPs) and CH 3 O 2 H, the low-temperature oxidation behavior of EME was explained by the chain-branching reactions of the fuel itself and the oxidation intermediates. Abundant species such as aldehydes, acids, esters, and fuel-specific dione species were detected and could be well reproduced by the current model. In particular, acids are produced by the decomposition of KHPs and subsequent reactions of the intermediate CH 3 CHO. Esters and dione species are mainly formed via fuel-related pathways.