High-temperature rate constant measurements for OH + xylenes

The overall rate constants for the reactions of hydroxyl (OH) radicals with o-xylene (k1), m-xylene (k2), and p-xylene (k3) were measured behind reflected shock waves over 890–1406 K at pressures of 1.3–1.8 atm using OH laser absorption near 306.7 nm. Measurements were performed under pseudo-first-order conditions. The measured rate constants, inferred using a mechanism-fitting approach, can be expressed in Arrhenius form as:k1=2.93×1013exp(-1350.3/T)cm3mol-1s-1(890–1406K)k2=3.49×1013exp(-1449.3/T)cm3mol-1s-1(906–1391K)k3=3.5×1013exp(-1407.5/T)cm3mol-1s-1(908–1383K)This paper presents, to our knowledge, first high-temperature measurements of the rate constants of the reactions of xylene isomers with OH radicals. Low-temperature rate-constant measurements by Nicovich et al. (1981) were combined with the measurements in this study to obtain the following Arrhenius expressions, which are applicable over a wider temperature range:k1=2.64×1013exp(-1181.5/T)cm3mol-1s-1(508–1406K)k2=3.05×109exp(-400/T)cm3mol-1s-1(508–1391K)k3=3.0×109exp(-440/T)cm3mol-1s-1(526–1383K)