Formation of NO from N₂/O₂ mixtures in a flow reactor: Toward an accurate prediction of thermal NO

We have conducted flow reactor experiments for NO formation from N2/O2 mixtures at high temperatures and atmospheric pressure, controlling accurately temperature and reaction time. Under these conditions, atomic oxygen equilibrates rapidly with O₂. The experimental results were interpreted by a detailed chemical model to determine the rate constant for the reaction N₂ + O ⇌ NO + N (R1). We obtain k₁ = 1.4 × 10¹⁴ exp(-38,300/T) cm³ mol^-1 s^-1 at 1700-1800 K, with an error limit of ±30%. This value is 25% below the recommendation of Baulch et al. for k₁, while it corresponds to a value k_1b of the reverse reaction 25% above the Baulch et al. evaluation. Combination of our results with literature values leads to a recommended rate constant for k_1b of 9.4 × 10¹² T^0.14 cm³ mol^-1 s^-1 over 250-3000 K. This value, which reconciles the differences between the forward and reverse rate constant, is recommended for use in kinetic modeling.