A shock tube study of reactions of CN with HCN, OH, and H 2 using CN and OH laser absorption

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 $$\rm CN + OH\ \longrightarrow Products \eqno{(1)}$$ $$\rm CN + HCN \longrightarrow C_2N_2+H \eqno{(2)}$$ $$\rm CN + H_2\ \longrightarrow HCN+H \eqno{(3)}$$ for temperatures between 940 and 1860 K. Two independent experimental approaches were utilized: laser photolysis (at 193 nm) of dilute C 2 N 2 /HCN/argon and C 2 N 2 /H 2 /argon mixtures in reflected shock wave experiments, and shock heating of HNO 3 /HCN/argon mixtures in incident and reflected shock wave experiments. Laser absorption measurements of OH at 306.687 nm were also taken in the HNO 3 /HCN/argon experiments The results are in good agreement with rate coefficient determinations from previous studies at different temperatures. The expression $$k_2=1.51\times 10^{7}\times T^{1.71}\exp(-770/T){\rm cm}^3\ {\rm mol}^{-1}\ s^{-1}\ \ \ (f=0.85, F=1.15),$$ derived by Yang et al (1992) from their k 2 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 k min = f k best fit , k max = F k best fit . The recommended expression for the rate coefficient of reaction (3) $$k_3=2.95\times 10^{5}\times T^{2.45}\exp(-1126/T){\rm cm}^3\ {\rm mol}^{-1}\ s^{-1}\ \ \ (f=0.83, F=1.22),$$ also valid for temperatures 300–3000 K, is taken from the transition state theory analysis of the CN + H 2 reaction by Wagner and Bair (1986). The rate coefficient for reaction (1) was measured to be 4.0 × 10 13 cm 3 mol −1 s −1 (f = 0.61, F = 1.40) for the temperature range 1250–1860 K. © 1996 John Wiley & Sons, Inc.