Kinetics of the gas‐phase reaction between nitric oxide, ammonia and oxygen

For the purpose of developing a simple and quantitative description of the rate of reactions occurring in the Thermal DeNO_x process, the kinetics of the homogeneous reaction between NO and NH₃ with excess of O₂ has been studied in an isothermal plug flow reactor. Temperature windows of NO reduction were observed with the optimum temperature decreasing with increasing residence time. The degree of reduction of NO increases with residence time at lower temperatures but is sensitive to residence time only at very short residence times at higher temperatures. The degree of conversion of NH₃ increases with both temperature and residence time. A simple model has been proposed to describe the reaction rates: r_NO = k_ax [NH₃] ‐ k_r [NH₃] [NO] r NH 3 =‐k_ax [NH₃]‐ k_r [NH₃] [NO] The two rate constants in the model were estimated based on the experimental data obtained in the present plug flow reactor at about 4% (vol.) oxygen: k_ax = (2.21 ± 0.33) × 10¹⁴ exp [‐(38160 ± 170)/T], I/s k_r = (2.45 ± 0.49) × 10¹⁴ exp [‐(29400 ± 250)/T], m³mol. s It is verified that the kinetic model can give a satisfactory prediction of the experimental results under different conditions.