Atmospheric Chemistry of (CF_3))2CF-C≡N: A Replacement Compound for the Most Potent Industrial Greenhouse Gas, SF_6

摘要

FTIR/smog chamber experiments and ab initio quantum calculations were performed to investigate the atmospheric chemistry of (CF_3)_2CFCN, a proposed replacement compound for the industrially important sulfur hexafluoride, SF_6. The present study determined k(CI + (CF_3)_2CFCN) = (2.33 ± 0.87) X 10~(-17), k(OH + (CF_3_)2CFCN) = (1.45 ± 0.25) × 10~(-15), and k(O_3 + (CF_3)_2CFCN) ≤ 6 X 10~(-24) cm~3 molecule~(-1) s~(_1), respectively, in 700 Torr of N_2 or air diluent at 296 ± 2 K. The main atmospheric sink for (CF_3)_2CFCN was determined to be reaction with OH radicals. Quantum chemistry calculations, supported by experimental evidence, shows that the (CF_3)_2CFCN + OH reaction proceeds via OH addition to -C(≡N), followed by O_2 addition to -C(OH)=N-, internal H-shift, and OH regeneration. The sole atmospheric degradation products of (CF_3)_2CFCN appear to be NO, COF_2, and CF_3C(O)F. The atmospheric lifetime of (CF_3)_2CFCN is approximately 22 years. The integrated cross section (650-1500 cm~(-1)) for (CF_3)_2CFCN is (2.22 ± 0.11) × 10~(-16) cm~2 molecule~(-1) cm~(-1) which results in a radiative efficiency of 0.217 Wm~(-2) ppb~(-1). The 100-year Global Warming Potential (GWP) for (CF_3)_2CFCN was calculated as 1490, a factor of 15 less than that of SF_6.