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

摘要

The atmospheric degradation of two hydrofluoroethers, HFE-7300 [n-C_2F_5CF(OCH_3)CF(CF_3)_2] and HFE-7500 [n-C_3F_7CF(OC_2H_5)CF(CF_3)_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 cm~3 molecule~(-1) s~(-1)): k_(HFE-7300 + OH) = (5.6 ± 2.0) × 10~(-13) exp(-(1186 ± 111)/T); k_(HFE-7300+Cl) = (3.8 ± 1.3) × 10~(-12) exp(-(968 ± 101)/T); and k_(HFE-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 CF_3CF_2CF(OCHO)CF(CF_3)_2, whereas in the oxidation of HFE-7500 by OH radicals the detected products were: C_3F_7CF(OC(O)CH_3)CF(CF_3)_2 and C_3F_7CF(OC(O)H)CF(CF_3)_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.