Shock tube study of the oxidation of C{sub 3}F{sub 6} by N{sub 2}O
- Univ. of Sydney, New South Wales (Australia)
The kinetics of the high-temperature oxidation of C{sub 3}F{sub 6} by O({sup 3}P) have been studied by experiment, using a single-pulse shock tube, and by kinetic modeling. The O atoms were generated by the thermal decomposition of N{sub 2}O. Three mixtures, each diluted in argon, were studied: 0.6 mol % of C{sub 3}F{sub 6} with 1.5 mol % N{sub 2}O; 6.2 mol % of C{sub 3}F{sub 6} with 0.6 mol % of N{sub 2}O; and 6.3 mol % of N{sub 2}O and 0.7 mol % of C{sub 3}F{sub 6}. The temperatures were in the range 1300--1600 K, the residence times behind the reflected shock were in the range 550--850 {micro}s, and the pressures were between 16 and 20 atm. Fluorinated products have been quantified with gas chromatography, oxidized products with Fourier transform infrared spectroscopy; identification of unknown fluorocarbons has been performed with gas chromatography-mass spectrometry. The most significant products detected were C{sub 2}F{sub 6}, C{sub 2}F{sub 4}, CF{sub 2}O, CO, CO{sub 2}, and CF{sub 4}. A detailed kinetic scheme is presented to model the experimental reactant and product yields as a function of temperature., Modeling showed that O-addition to either carbon of the double bond of C{sub 3}F{sub 6} occurs. The rate constant for O-addition to the terminal carbon of the double bond, C{sub 3}F{sub 6} + O({sup 3}P) {yields} {sup 3}CF{sub 3}CF + CF{sub 2}O, was deduced to be {kappa}{sub 71} = 10{sup 12.7}T{sup 0.05} exp({minus}0.4 kJ mol{sup {minus}1}/RT) cm{sup 3} mol{sup {minus}1} s{sup {minus}1}, and for addition to the central carbon, C{sub 3}F{sub 6} + O({sup 3}P) {yields} CF{sub 3} + CF{sub 2}CF{double_bond}O, {kappa}{sub 72} = 10{sup 12.5} cm{sup 3} mol{sup {minus}1} s{sup {minus}1}. Under oxidizer-rich conditions, ignition of the C{sub 3}F{sub 6} occurred. Rate of production analyses showed that ignition was propagated by an F atom chain involving the CF{sub 2} + O and unimolecular CFO decomposition reactions. Under C{sub 3}F{sub 6}-rich conditions, single- and double-bond pyrolysis were the important destruction routes.
- OSTI ID:
- 677960
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 30; Other Information: PBD: 29 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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