Thermal Decomposition of Hydrogen Cyanide in Shock Waves

Abstract

The thermal decomposition of hydrogen cyanide diluted to 0.2, 0.5, and 1.0 mol% in argon was studied behind incident shock waves over the temperature range 2600–3600 K. The decomposition process was followed by monitoring the CN X2Σ+-B2Σ+ (0-0) absorption centered at 3883 Å. The bimolecular rate constants for the reaction HCN+Ar→H+CN+Ar were obtained from the initial slopes of absorption; k1=(1.26±0.28)×1016exp[–(99.69±1.39)kcal mol−1/RT] cm3 mol−1 s−1. The kinetic results are well fitted by the classical collision-theory expression, k1=λ(Z⁄n!)(E⁄RT)nexp(–E⁄RT), with λ=0.22, n=3.5, and E=D0(H–CN)= 118.7 kcal/mol. The overall absorption profiles were found to be explicable on the basis of the reaction scheme involving the homorecombinations of H and CN as well as the chain reaction with H and CN as carrier species.

Dynamics Study of the Reaction Ar + HCN → Ar + H + CN

“…Note that the calculated k 1 from the present work (which is shown by the long-dashed line), is nearly indistinguishable from the total rate constant (solid line). Experimental data: (□) Tabayashi et al; (▵) Roth and Just; (○) Szekely et al; (◊) Szekely et al (as cited in refs and ); (---) recommended, ref . …”

Uncertainty quantification and robust predictive system analysis for high temperature kinetics of HCN/O2/Ar mixture

“…It is interesting to note that the values of A 1 and m 1 obtained by Szekely et al [53,54] and Tabayashi et al [30] lie inside the high probability region and are similarly probable for these cases. The relatively flat shape of the marginal PDFs of A 1 and m 1 indicates that this experiment is not very informative to identify a smaller set of the more probable values of A 1 and m 1 .…”

“…Here, R1 is the thermal decomposition of HCN, and the model coefficients in the Arrhenius form for a certain temperature range have been obtained by several researchers [29][30][31]. It can be seen that the model coefficients obtained by these researchers show large variation (See Table 1 which includes the result from [1]).…”

On the Rate Constant for the Association Reaction H + CN + Ar → HCN + Ar

“…However, we should qualify at this stage what we mean by experimental data. Indeed, although there are some experimental − and evaluated data for the inverse dissociation reaction HCN + Ar → H + CN + Ar, the reaction of interest here has, to our knowledge, not been studied experimentally. For the association reaction, Tsang only published estimates of the kinetics coefficients constants for cases where the third-body was N 2 and CO 2 but not Ar.…”