Determination of the rate coefficient for the C 3H 3 + C 3H 3 reaction at high temperatures by shock-tube investigations

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The kinetics of the C 3H 3 + C 3H 3 reaction was investigated behind incident shock waves at temperatures ranging from 995 to 1440 K and at pressures between 600 and 1000 mbar with argon as bath gas. The C 3H 3 radicals were generated by thermal decomposition of propargyl iodide with initial concentrations between 3 × 10 15 and 6 × 10 15 cm −3 corresponding to initial mole fractions between 750 and 800 ppm. Measurement of the UV absorption at 332.5 nm was used to monitor the C 3H 3 concentration, and the rate coefficients for the C 3H 3 + C 3H 3 reaction were determined by fitting a second-order rate law to the absorption–time profiles. Values between 2 × 10 −11 cm 3 s −1 near 1000 K and 7.5 × 10 −12 cm 3 s −1 near 1400 K were obtained with no significant pressure dependence. The negative temperature dependence can be expressed in the form k 1 = 5.8 × 10 −13 exp (3534 K/ T) cm 3 s −1 with an estimated maximum error of ±30% in k 1. The reaction channel leading to C 6H 5 + H is estimated to contribute with less than 10% to the overall reaction at temperatures between 1000 and 1300 K and, pressures ranging from 80 to 500 mbar.