Modeling the thermal De-NOx process: Closing in on a final solution

We have extended our previous kinetic model for the Thermal De-NOx Process to include recent information about the branching fraction α1(T) of the NH2 + NO reaction, NH2 + NO ⟷ N2 + H2O (R1a) NH2 + NO ⟷ NNH + OH, (R1b)where α1(T) = k1b/(k1a + k1b). The values of the rate coefficients k1a(T) and k1b(T) used in the model are k1a = 2.77 × 1020 T−2.65 exp(−1258/RT) cm3/mole-sec. and k1b = 2.29 × 1010 T0.425 exp(814/RT) cm3/mole-sec. These two rate coefficients combine to give values of the total rate coefficient and branching fraction that are in excellent agreement with experiments over a wide range of temperatures, 300 K < T < 1400 K for k1 = k1a + k1a and 300 K < T < 2000 K for α1(T). The smaller values of α1(T) in the Thermal De-NOx temperature window, 1100 K < T < 1400 K, used in the model allow us to reduce the value of the NNH lifetime to 1.5 × 10−8 sec, which is consistent both with the upper limit set by experiment and with the best theoretical predictions. We compare the model predictions with the experiments of Kasuya et al. and discuss the results in some detail.