Shock wave studies of the pyrolysis of fluorocarbon oxygenates. I. The thermal dissociation of C3F6O and CF3COF. Issue 4 (13th January 2017)

• Record Type: Journal Article
• Authors: Cobos, C. J.; Hintzer, K.; Sölter, L.; Tellbach, E.; Thaler, A.; Troe, J.
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 4(2017)
• Page Start: 3151
• Page End: 3158
• Publication Date: 2017-01-13
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp06816b
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The thermal decomposition of hexafluoropropylene oxide, C3 F6 O, to perfluoroacetyl fluoride, CF3 COF, and CF2 has been studied in shock waves in Ar between 630 and 1000 K. The subsequent decomposition of CF3 COF has been followed between 1400 and 1900 K. Abstract : The thermal decomposition of hexafluoropropylene oxide, C3 F6 O, to perfluoroacetyl fluoride, CF3 COF, and CF2 has been studied in shock waves highly diluted in Ar between 630 and 1000 K. The measured rate constant k 1 = 1.1 × 10 14 exp(−162(±4) kJ mol −1 / RT ) s −1 agrees well with literature data and modelling results. Using the reaction as a precursor, equimolar mixtures of CF3 COF and CF2 were further heated. Combining experimental observations with theoretical modelling (on the CBS-QB3 and G4MP2 ab initio composite levels), CF3 COF is shown to dissociate on two channels, either leading to CF2 + COF2 or to CF3 + FCO. By monitoring the CF2 signals, the branching ratio was determined between 1400 and 1900 K. The high pressure rate constants for the two channels were obtained from theoretical modelling as k 5, ∞ (CF3 COF → CF2 + COF2 ) = 7.1 × 10 14 exp(−320 kJ mol −1 / RT ) s −1 and k 6, ∞ (CF3 COF → CF3 + FCO) = 3.9 × 10 15 exp(−355 kJ mol −1 / RT ) s −1 . The experimental results obtained at [Ar] ≈ 5 × 10 −6 mol cm −3 were consistent with modelling results, showing that the reaction is in the falloff range of the unimolecular dissociation. The mechanism of secondary reactions following CF3 COF dissociation has been analysed as well.