Detailed chemical kinetic mechanisms of ethyl methyl, methyl tert-butyl and ethyl tert-butyl ethers: The importance of uni-molecular elimination reactions

A reaction mechanism of ethyl methyl ether (EME), methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) for pyrolysis and oxidation have been constructed using the same method applied to di-ethyl ether (DEE) in our recent work [1]. The mechanism, comprising of 1051 reactions involving 215 species, was tested against the experimental data obtained using shock tubes with good agreement. It was found that the uni-molecular elimination reaction has a larger influence on the pyrolysis and oxidation of MTBE and ETBE compared to EME and DEE at high temperatures. The energy barrier height between reactants and transition states of molecular elimination reactions calculated by high level ab initio MO methods has revealed the difference in reactivity among the four ethers. It is also shown that ETBE or MTBE inhibit the reactivity of an equi-molar 2% mixture of hydrogen and oxygen, whereas EME and DEE do not inhibit reactivity.