The reaction of cyclohexane with H‐atoms: A shock tube and modeling study

Abstract

AbstractThe present work deals with experimental investigations on the bimolecular reaction of H‐atoms with cyclohexane (cC6H12). Iodoethane (C2H5I) was used as an in situ source for H‐atoms to investigate the bimolecular reaction. As the reaction of cC6H12 with H‐atoms yields H2 and cyclohexyl radicals (cC6H11), the mechanism of the thermal decomposition of cC6H11 is of fundamental importance for the interpretation of the experiments. Therefore, also the thermal decomposition of 1‐hexene‐6‐yl (16‐C6H11) was analyzed due to the assumption that cC6H11 almost exclusively isomerizes to 16‐C6H11. 6‐Iodo‐1‐hexene (16‐C6H11I) was used as a precursor molecule for the generation of 16‐C6H11 radicals. The experiments were carried out in a stainless steel shock tube. For the reaction of cC6H12 molecules with H‐atoms, the measurements were performed over a temperature range of 1050–1190 K, at pressures ranging from 1.8 to 2.5 bar; the 16‐C6H11I experiments were carried out at temperatures between 1060 and 1160 K and pressures around 2.0 bar. Behind reflected shock waves, the H‐atom absorption was monitored by atomic resonance absorption spectrometry at the Lyman‐α line (121.6 nm). The experiments reveal important aspects about the thermal dissociation of cyclohexyl radicals (cC6H11). Concerning the reaction cC6H12 + H → cC6H11 + H2 (R1), a rate coefficient expression was derived: kR1(T) = 6.3 × 1013 exp(−2505 K/T) cm3 mol−1 s−1. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: 130–146, 2012