Reactions of C<sub>12</sub>–C<sub>14</sub> <i>n</i>-Alkylcyclohexanes with Cl Atoms: Kinetics and Secondary Organic Aerosol Formation
Ke Wang, Weigang Wang, Cici Fan, Junling Li, Ting Lei, Wenyu Zhang, Bo Shi, Yan Chen, Mingyuan Liu, Chaofan Lian, Zhe Wang, Maofa Ge
Abstract
Long-chain alkanes are a type of intermediate volatility organic compound (IVOC) in the atmosphere and a potential source of secondary organic aerosols (SOAs). C12–C14 n-alkylcyclohexanes are important compositions of IVOCs, with considerable concentrations and emission rates. The reaction rate constants and SOA formation of the reactions of C12–C14 n-alkylcyclohexanes with Cl atoms were investigated in the present study. The reaction rate constants of the long-chain alkanes obtained via the relative-rate method at 298 ± 0.2 K (in units of ×10–10 cm3 molecule–1 s–1) were as follows: khexylcyclohexane = 5.11 ± 0.28, kheptylcyclohexane = 5.56 ± 0.30, and koctylcyclohexane = 5.74 ± 0.31. The gas-phase products of the reactions were identified as mainly small molecules of aldehydes, ketones, and acids. The particle-phase products were mostly monomers and oligomers, but there were still trimers even under high-NOx conditions. Moreover, under high-NOx conditions (urban atmosphere), the SOA yields of hexylcyclohexane are higher than that under low-NOx conditions (remote atmosphere), indicating that more attention should be given to the SOA formation of Cl-initiated n-alkylcyclohexane oxidations in polluted regions. This research can further clarify the oxidation processes and SOA formation of n-alkylcyclohexanes in the atmosphere.