The conversion of HCN to NO and N2 in H2−O2−HCN−Ar flames at low pressure

We have investigated the kinetic mechanism for converting HCN to NO and N 2 in low pressure (30 Torr) H 2 −O 2 flames doped with HCN and diluted in argon. Major stable species concentrations were measured by mass spectrometric techniques and CN concentrations and temperature were measured by laser induced fluorescence. The three flames investigated had equivalence ratios of Φ=0.5, 1.0, and 1.5. The experimental results are compared to complete flame structure calculations based on a reaction mechanism developed almost solely from direct measurements of rate coefficients reported in the literature. The agreement is good. From the analysis we deduce that the nitrogen atom in HCN predominantly follows the following route to NO and N 2 , HCN→NCO→NH→N→NO→N 2 . The most important and rate controlling step for HCN removal is the reaction with oxygen atoms, HCN + O ⇄ products. Our results are not sensitive to the products formed: NCO+H or NH+CO. Most important and rate controlling for NO production and conversion of NO to N 2 is the extended Zel'dovich mechanism.

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