Rate Coefficients of Hydroxyl Radical Reaction with Dimethyl Ether and Methyl tert-Butyl Ether over an Extended Temperature Range

Rate coefficients of the reaction of hydroxyl (OH) radicals with CH3OCH3 (k1) and CH3OC(CH3)3 (k2) over an extended temperature range are reported. Measurements were performed using a laser photolysis−laser-induced fluorescence technique under slow flow conditions at a total pressure of 740 ± 10 Torr. Arrhenius plots of the data exhibited significant curvature and were fitted in the form of k(T) = ATB exp(−C/T). The resulting modified Arrhenius expressions (error limits ±2σ) that best described these extended temperature measurements and prior low-temperature measurements were (in units of cm3 molecule-1 s-1) k1(295−650 K) = (1.05 ± 0.10) × 10-17T2.0 exp[(328 ± 32)/T] and k2(293−750 K) = (1.15 ± 0.11) × 10-17T2.04 exp[(266 ± 41)/T]. Comparison of our measurements for k1 with previous, overlapping low-temperature measurements indicated generally good agreement. Our measurements for k2, although consistent with previous room temperature measurements, exhibited a larger temperature dependence than previously reported. High-temperature oxidation mechanisms for these oxygenated fuel components are proposed. Support for the mechanisms is presented in the form of product analysis studies in high-temperature tubular flow reactors. For CH3OC(CH3)3, these studies suggest that H abstraction from the tert-butyl group is an important high-temperature oxidation pathway.