Measurement of the rate constant for H + O₂ + M → HO ₂ + M (M = N₂, Ar) using kinetic modeling of the high-pressure H₂/O₂/NO_x reaction

The reaction of dilute H₂/O₂/N₂ and H ₂/O₂/Ar mixtures perturbed with small quantities of NO has been studied in a variable-pressure flow reactor between 800 and 900 K. At high pressures (10-14 atm), the consumption of H₂ and the conversion of NO to NO₂ were highly sensitive to the pressure-dependent reaction (Equation presented) Rate coefficient data for the low-pressure limit (Equation presented) were inferred by comparison of the experimental data with a reaction mechanism that uses the high-pressure limit k_2,∞ = 4.52 × 10¹³ (T/300)⁰.⁶ with F_c ^N₂ = 0.5 and F_c^Ar = 0.45. The data obtained with M = Ar are consistent with previous shock-tube data at comparable temperatures and are in good agreement with recent recommendations for k _2,0^Ar. However, the data obtained for M = N₂ are 40% lower than recent recommendations and are combined with previously published data to yield (Equation presented) over the temperature range 300-1600 K. The rate coefficient data obtained in this study are insensitive to the competing reaction (Equation presented) and, when used with the k₁ recommendation from Pirraglia et al. [27], are in good agreement with H ₂/O₂ explosion limit data in the intermediate temperature range of 700-900 K.