Shock tube study of the oxidation of C3F6 by N2O

The kinetics of the high-temperature oxidation of C3F6 by O(P-3) have been studied by experiment, using a single-pulse shock tube, and by kinetic mode ling. The O atoms were generated by the thermal decomposition of N2O. Three mixtures, each diluted in argon, were studied: 0.6 mol % of C3F6 With 1.5 mol % N2O; 6.2 mol % of C3F6 With 0.6 mol % of N2O; and 6.3 mol % of N2O an d 0.7 mol % of C3F6 The temperatures were in the range 1300-1600 K, the res idence times behind the reflected shock were in the range 550-850 Cls, and the pressures were between 16 and 20 atm. Fluorinated products have been qu antified with gas chromatography, oxidized products with Fourier transform infrared spectroscopy; identification of unknown fluorocarbons has been per formed with gas chromatography-mass spectrometry. The most significant prod ucts detected were C2F6, C2F4, CF2O, CO, CO2, and CF4. A detailed kinetic s cheme is presented to model the experimental reactant and product yields as a function of temperature. Modeling showed that O-addition to either carbo n of the double bond of C3F6 occurs. The rate constant for O-addition to th e terminal carbon of the double bond, C3F6 + O((3)p),--> (CF3CF)-C-3 + CF2O ,was deduced to be k(71) = 10(12.7)T(0.05), exp(-0.4 kJ mol(-1)/RT) cm(3) m ol(-1) s(-1), and for addition to the central carbon, C3F6 + O(P-3) -C CF3 + CF2CF=O, k(72) = 10(12.5) cm3 mol(-1) s(-1). Under oxidizer-rich conditio ns, ignition of the C3F6 occurred. Rate of production analyses showed that ignition was propagated by an F atom chain involving the CF2 + O and unimol ecular CFO decomposition reactions. Under C3F6-rich conditions, single- and double-bond pyrolysis were the important destruction routes.