Kinetic study of methyl tert-butyl ether (MTBE) oxidation in flames

Three premixed MTBE/H-2/O-2/Ar flat flames burning at low pressure (30 torr) have been investigated by molecular beam mass spectrometry for equivalence ratios ranging from 0.18 to 1.84. Profiles of stable, atomic, and radical species concentrations have been measured as well as the temperature ones. The structure of these flames has been established in order to deduce the rate coefficients of H-atom abstraction reactions (R1-R3) from MTBE by highly reactive species like H and O atoms and OH radicals. C5H12O + H --> Products (R1) C5H12O + O --> Products (R2) C5H12O + OH --> Products (R3) The rate coefficient of reaction R1 has been deduced in the rich flame k(1) = 3.92 x 10(13) exp(- 2830/T) cm(3) mole(-1) s(-1) between 700 and 1000 K. Rate coefficients of reactions R2 and R3 have been determined in the lean flame k(2) = 1.78 x 10(14) exp( -4000/T) cm(3) mole(-1) s(-1) between 1000 and 1300 K and in the the stoichiometric flame k(3) = 4.1 x 10(13) exp(-1450/T) cm(3) mole(-1) s(-1) between 650 and 900 K, respectively. Using the deduced rate coefficients k(1), k(2), and k(3), and the experimental mole fraction profiles of the involved species, the relative contribution of reactions (R1-R3) to the MTBE consumption has been determined in the investigated flames. The analysis of the flame structures has allowed also to evaluate the pathways leading to the formation of isobutene and acetone that are intermediate species arising from the first steps of the MTBE decay. It has been demonstrated that all MTBE conversion proceeds through isobutene formation whereas reactions leading to the formation of acetone have a weak contribution.