Kinetics of C2 Reactions during High-Temperature Pyrolysis of Acetylene

The kinetics of C2 radical reactions during the first stage of acetylene high-temperature pyrolysis was studied by monitoring C, C2 and C3 radicals. Quantitative C2 detection was performed by ring dye laser absorption spectroscopy, C atoms were measured by applying atomic resonance absorption spectroscopy, and C3 radicals were monitored by their emission using a combination of a spectrograph and an intensified CCD camera system. The experiments were performed behind reflected shock waves and cover the temperature range of 2580−4650 K at pressures around 2 bar. In the first part of the study initial mixtures containing Ar with 5−50 ppm C2H2 were used. In this very low concentration range, rate coefficients for the following four reactions were determined:  C2H2 + M C2H + H + M (R1); C2H + M C2 + H + M (R2); C2 + C2 C + C3 (R3); C2 + M C + C + M (R4); where k1 = 6.96 × 1039 T-6.06 exp(−67 130/T) cm3 mol-1 s-1, k2 = 1.74 × 1035 T-5.16 exp(−57 367/T) cm3 mol-1 s-1, k3 = 3.2 × 1014 cm3 mol-1 s-1, and k4 = 1.5 ...