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

Abstract

AbstractThe 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.