Atmospheric oxidation of C10~14 n-alkanes initiated by Cl atoms: Kinetics and mechanism

Abstract

The Cl-initiated photo-oxidation reactions of n-alkanes: C10~C14, were investigated by using Proton-Transfer-Reaction Mass Spectrometry in the smog chamber, and the present work provided the kinetic parameters of the reactions of Cl atoms with C11~14 n-alkanes for the first time. The rate constants (in units of cm3molecule−1s−1) were obtained using relative rate method with trans-2-butene, m-xylene and ethylbenzene as references at (298 ± 1)K and 760 Torr were k(n-decane)=(4.82 ± 0.32) × 10−10, k(n-undecane)=(5.02 ± 0.33) × 10−10, k(n-dodecane)=(5.12 ± 0.29) × 10−10, k(n-tridecane)=(5.30 ± 0.30) × 10−10, k(n-tetradecane)=(5.68 ± 0.34) × 10−10, respectively. The measured rate constants have also been used to calculate tropospheric lifetimes of these compounds (C10, C11, C12, C13, C14), which were 11.5, 11.1, 10.9 10.5 and 9.8 h for each n-alkane. In addition, the gas-phase photooxidation products of the reactions were also measured. Based on the obtained results, the reaction mechanisms of Cl atoms with these five alkanes were proposed.