Atmospheric chemistry of HFE-7300 and HFE-7500: Temperature dependent kinetics, atmospheric lifetimes, infrared spectra and global warming potentials

Abstract

The atmospheric degradation of two hydrofluoroethers, HFE-7300 [n-C2F5CF(OCH3)CF(CF3)2] and HFE-7500 [n-C3F7CF(OC2H5)CF(CF3)2] used in industrial applications has been studied. The kinetics and reaction products were determined at atmospheric pressure as a function of temperature in a reaction chamber using GC/FID and GC/MS techniques for the analysis. The following Arrhenius expressions were obtained (in units of cm3 molecule−1 s−1): kHFE-7300 + OH = (5.6 ± 2.0) × 10−13 exp(−(1186 ± 111)/T); kHFE-7300 + Cl = (3.8 ± 1.3) × 10−12 exp(−(968 ± 101)/T); and kHFE-7500 + OH = (7.6 ± 6.0) × 10−12 exp(−(1163 ± 385)/T) (temperature range 271–333 K). The atmospheric lifetimes calculated from kinetic data for HFE-7300 and HFE-7500 were 5.24 and 0.30 years, respectively. In the oxidation of HFE-7300 with OH and Cl radicals, the only detected product was CF3CF2CF(OCHO)CF(CF3)2, whereas in the oxidation of HFE-7500 by OH radicals the detected products were: C3F7CF(OC(O)CH3)CF(CF3)2 and C3F7CF(OC(O)H)CF(CF3)2. Infrared spectra of the studied HFEs have also been measured and radiative forcing efficiencies were determined. Combining these results with the kinetic data, we estimated 100-year time horizon global warming potentials of 440 and 12 for HFE-7300 and HFE-7500, respectively.