Atmospheric chemistry of CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) initiated by OH and Cl and their contribution to global warming

Abstract

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CF₃CHFCF₂OCH₃ (HFE-356mec3) and CHF₂CHFOCF₃ (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (k_OH(T) in cm³molecule^-1s^-1) between 263 and 353 K are well described by the following expressions: (1.21±0.28)×10^-12exp{-(1045±646)/T} for HFE-356mec3 and (4.39±0.70)×10^-13exp{-(1261±602)/T} for HFE-236ea1. The rate coefficients k_Cl was determined to be (2.30±1.08)×10^-13 cm³molecule^-1s^-1 for HFE-356mec3 and (1.19±0.10)×10^-15 cm³molecule^-1s^-1 for HFE-236ea1 at 298K and 760 Torr of air under free-NO_x conditions. The atmospheric lifetimes were estimated to be 1.4 and 8 years for HFE-356mec3 and HFE-236ea1 in urban inland and 8.7 and 49.7 years in coastal troposphere. IR absorption cross sections and global warming potentials at a time horizon of 100 years are presented and the atmospheric degradation of HFEs is discussed.