Atmospheric degradation and global warming potentials of three perfluoroalkenes

The vapour phase reactions of perfluoropropene, CF3---CF=CF2, and perfluorobuta-1,3-diene, CF2=CF---CF=CF2, with OH, NO3 and O3 were studied at 298±4 K and 740±5 Torr using long-path FT-IR detection. The reactions with ozone are very slow, kCF3CFCF2+O3=(6.2±1.5)×10−22 and kCF2CFCFCF2+O3=(6.5±0.2)×10−21 cm3 molecules−1 s−1, and upper limits of 3×10−15 cm3 molecules−1 s−1 are reported for the NO3 reaction rate coefficients. The OH reaction rate coefficients were determined as kCF3CFCF2+OH=(2.6±0.7)×10−12 and kCF2CFCFCF2+OH=(1.1±0.3)×10−11 cm3 molecules−1 s−1; perfluoropropene gave a nearly quantitative yield of CF3CFO and CF2O as organic products, while perfluorobuta-1,3-diene gave from 130% to 170% of CF2O. A chemistry transport model was applied to calculate the atmospheric distributions and lifetimes of the perfluoroalkenes; the global and yearly averaged lifetimes were calculated as 1.9 day for C2F4 and C4F6 and 6 days for C3F6. Quantitative infrared cross-sections of perfluoroethene, perfluoropropene, and perfluorobuta-1,3-diene have been obtained at 298 K in the region 100–2600 cm−1. Radiative forcing calculations have been performed for these gases assuming either constant vertical profiles or the distribution derived from the chemistry transport model. The results show that the Global Warming Potentials are totally negligible for these compounds.