THERMAL DECOMPOSITONS OF 1,1,1-TRIFLUOROETHANE AND PENTAFLUOROETHANE IN A TURBULENT FLOW REACTOR
Title:
THERMAL DECOMPOSITONS OF 1,1,1-TRIFLUOROETHANE AND PENTAFLUOROETHANE IN A TURBULENT FLOW REACTOR
Author:
Takahashi, K. Harada, A. Horigome, S. Cho, R. Inomata, T.
Appeared in:
Combustion science and technology
Paging:
Volume 179 (2007) nr. 7 pages 1417-1432
Year:
2007-07
Contents:
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 ⋅ mol-1/RT] and k(CHF2CF3) = 1013.9±1.4 exp [-(324 ± 36) kJ ⋅ 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 the CH3CF3, and CHF2CF3 pyrolyses can be explained by fluorine hyperconjugation and by repulsion between the fluorine atoms on the 1- and 2-carbons of each hydrofluoroethane.