A shock tube study of reactions of CN with HCN, OH, and H2 using CN and OH laser absorption

Abstract

Quantitative, narrow-line laser absorption measurements of CN time-histories at 388.444 nm were acquired in high-temperature pyrolysis and laser photolysis shock tube experiments. The data were analyzed using a detailed kinetics mechanism to determine the rate coefficients of the reactions for temperatures between 940 and 1860 K. Two independent experimental approaches were utilized: laser photolysis (at 193 nm) of dilute C2N2/HCN/argon and C2N2/H2/argon mixtures in reflected shock wave experiments, and shock heating of HNO3/HCN/argon mixtures in incident and reflected shock wave experiments. Laser absorption measurements of OH at 306.687 nm were also taken in the HNO3/HCN/argon experiments The results are in good agreement with rate coefficient determinations from previous studies at different temperatures. The expression derived by Yang et al (1992) from their k2 measurements in combination with those of Szekely et al (1983), is recommended for the broad temperature range 300–3000 K. The uncertainty factors f and F give the limiting values of the rate coefficient kmin = f kbest fit, kmax = Fkbest fit. The recommended expression for the rate coefficient of reaction (3) also valid for temperatures 300–3000 K, is taken from the transition state theory analysis of the CN + H2 reaction by Wagner and Bair (1986). The rate coefficient for reaction (1) was measured to be 4.0 × 1013cm3mol−1 s−1(f = 0.61, F = 1.40) for the temperature range 1250–1860 K. © 1996 John Wiley & Sons, Inc.