Rate and mechanism of the atmospheric degradation of 2H-heptafluoropropane (HFC-227)

The atmospheric chemical behaviour of 2H-Heptafluoropropane (CF3CHFCF3, HFC-227) with respect to its rate and mechanism of degradation in the troposphere has been investigated. The rate coefficient for the reaction of HFC-227 with OH radicals has been determined in direct time resolved experiments using a combination of laser-pulse initiation and LIF. In the temperature range T=298-463 K the Arrhenius expression k(T) = (3.8±0.8) 10−13 exp(-1596±77K/T) cm3/s, which corresponds to k (298 K) = (1.8±0.3) 10−15cm3/s, was found. The mechanism of the atmospheric degradation of HFC-227 has been investigated using both, laser-pulse initiated/time resolved and UV photolysis/FTIR product studies. It is concluded that the major carbonyl products are CF3COF and CF2O which result from the decomposition of the oxy radical CF3CF(O)CF3 by C-C bond fission. The rate coefficient for this decomposition process has been determined to be k = (2±1) 103s−1 at 298K. Based on the reactivity of HFC-227 with respect to the reaction with OH radicals, the atmospheric lifetime and the GWP value for HFC-227 are estimated to be ∼40 years and 0.6±0.2, respectively.