High temperature measurements of the rate of the reaction of OH with NH3

Abstract

AbstractLow pressure (4.67 kPa) CH4/O2/Ar flames were seeded with approximately 5300 ppm NH3. The concentration profiles of stable and radical species in lean (ϕ = 0.92) and rich (ϕ = 1.13) flames were determined by molecular beam sampling mass spectrometry. Temperature profiles in these flames were measured with thermocouples whose readings were corrected for radiative losses by the Na‐line reversal method. Regions of the flames were selected where the principal reaction leading to the destruction of NH3 was equation image By correcting the measured concentrations for diffusion, the net rate of NH3 loss rate was determined in the temperature range 2080–2360 K. The rate constant k1 was determined from the net loss rate with correction for the reaction equation image using measured values of (O) and k2 values given by Salimian, Hanson, and Kruger [1]. The best‐fit Arrhenius expression for k1 in the temperature range 2080–2360 K is 1013.88 exp(−4539/T) cm3/mol‐s. The results of this study combined with previous lower temperature data confirm the non‐Arrhenius behavior of k1 suggested by Salimian, Hanson, and Kruger [1]. The best‐fit modified three parameter expression for the range 300–2360 K is 106.33±0.2 T2 exp(−169/T) cm3/mol‐s.