A comprehensive understanding of the combustion chemistry of methyl tert‑butyl ether (MTBE) is of key importance in its application as an additive in gasoline fuels. Ignition delay times (IDTs) of MTBE/air mixtures have been measured in both a high-pressure shock tube (HPST) and in a rapid compression machine (RCM) at equivalence ratios of 0.5, 1.0, and 2.0 in air, at pressures of 10 and 30 bar over the temperature range 600 – 1350 K. Species profiles for MTBE oxidation were obtained in a jet-stirred reactor (JSR) at 1 bar, at equivalence ratios of 0.5, 1.0, and 2.0 in the temperature range 700 – 1100 K.

A detailed reaction mechanism, comprising 813 species and 4319 reactions, has been developed and predicts well all of the experimental data obtained in this work and also texisitng literature data. Pressure- and temperature-dependent rate constants for the MTBE unimolecular elimination reaction producing isobutene and methanol were calculated using high-level ab-initio calculations. A sensitivity analysis reveals that this elimination reaction is important, and significantly inhibits fuel reactivity at temperatures above 1300 K. At intermediate temperatures (850 – 1300 K), the reaction MTBE + ȮH = TĊ₄H₈OCH₃ + H₂O plays a crucial role in promoting the reactivity of MTBE oxidation, whereas the reaction MTBE + ȮH = TC₄H₉OĊH₂ + H₂O is the most inhibiting reaction. At low temperatures (600 – 850 K), the isomerization reaction of TC₄OCȮ₂–1 ⇌ TĊ₄OCO₂H-2 significantly promotes the reactivity. Conversely, the reaction 2TC₄OCȮ₂–1 ↔ 2TC₄OCȮ-1 + O₂ inhibits reactivity the most. The NTC behavior in MTBE oxidation can be explained by the competition between the reactions involving the formation and consumption of cyclic ethers from TĊ₄H₈OCH₃ radicals and the reactions associated with the formation and consumption of carbonyl hydroperoxide species.