Determination of the rate coefficient for the C_3H_3 + C_3H_3 reaction at high temperatures by shock-tube investigations

摘要

The kinetics of the C_3H_3 + C3H3 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.