Formation of NO in High-Temperature N₂/O₂/H₂O Mixtures: Re-evaluation of Rate Coefficients

A re-evaluation of the flow reactor experiments of Abián et al. ( Abián, M.; Alzueta, M. U.; Glarborg, P. Formation of NO from N 2 /O 2 Mixtures in a Flow Reactor: Toward an Accurate Prediction of Thermal NO. Int. J. Chem. Kinet. 2015, 47, 518−532, DOI: 10.1002/kin.20929) is presented. In these experiments, nitrogen oxide formation was measured at atmospheric pressure in the temperature range of 1700–1810 K using several mixtures containing different ratios of oxygen, nitrogen, and water vapor. On the basis of the mechanism of Abián et al., the two most important reaction steps for NO formation (reaction R1, NO + N = N 2 + O; reaction R2, N 2 O + O = 2 NO) were identified by local sensitivity analysis. For the optimization of the Arrhenius parameters of these reaction steps, 25 data points measured by Abián et al., two direct rate coefficient measurements (73 data points), and one theoretical calculation were used. The obtained mechanism with the optimized Arrhenius parameters (reaction R1, A = 1.176 × 10 10 cm 3 mol –1 s –1, n = 0.935, and E / R = −693.68 K; reaction R2, A = 1.748 × 10 16 cm 3 mol –1 s –1, n = −0.557, and E / R = 14 447 K) described the results of the flow reactor experiments, direct measurements, and theoretical calculations much better compared to the Abián et al. mechanism and also several recent NO x mechanisms. The rate coefficients of these elementary reactions were obtained with low uncertainty in the temperature range of 1600–2200 K.