THERMAL DECOMPOSITONS OF 1,1,1-TRIFLUOROETHANE AND PENTAFLUOROETHANE IN A TURBULENT FLOW REACTOR

Abstract The thermal decompositions of 1,1,1-trifluoroethane (CH3CF3) and pentafluoroethane (CHF2CF3) were studied by using a turbulent flow reactor at atmospheric pressure over the temperature ranges of 1213–1333 K and 1273–1373 K. The rate coefficients for these thermal decompositions were determined from the first-order decays of the reactants to be k(CH3CF3) = 1012.9±1.2 exp[−(276 ± 29) kJ [sdot] mol−1/RT] and k(CHF2CF3) = 1013.9±1.4 exp [−(324 ± 36) kJ [sdot] mol−1/RT]s−1. To examine the reaction paths, we identified the decomposition products using gas chromatography-mass spectrometry (GC-MS) and performed ab initio MO calculations. These results showed that the sequential HF elimination reactions, CH3CF3 → CH2CF2 + HFand CH2CF2 → CHCF + HF, were favorable for the CH3CF3 pyrolysis. On the other hand, four initial steps: CHF2CF3 → CF3CF + HF, CHF2CF3 → CF2CF2 + HF, CHF2CF3 → CHF3 + CF2 and CHF2CF3 → CHF2 + CF3, were possible for the CHF2CF3 pyrolysis. Such a difference in the reaction paths between t...