Oxidation and Reduction of Nitrogen Oxides in Air (8)

—The behaviors of NO and NH₃ in NO-NH₃-N₂ mixture under the UV irradiation—

Abstract

The behaviors of N₂O, NO and NH₃ in N₂O-NH₃-N₂ and NO-NH₃-N₂ mixture under the UV irradiation were studied at room temprature. The decomposition rate of NH₃ in NH₃-N₂ mixture under the UV irradiation was proportional to the concentration of NH₃, and the rate under a low pressure mercury lamp irradiation was three times larger than that under a high pressure mercury lamp irradiation. No effect of NH₃ and N₂O was observed on the decomposition rate of N₂O and NH₃ under the irradiation with a low pressure mercury lamp. While N₂O did not change and NH₃ decomposed slowly by the irradiation with a high pressure mercury lamp, and the rate was not affected by N₂O.
NO and NH₃ in NO-NH₃-N₂ mixture decomposed rapidly with the formation of small amount of N₂O as a by-product under a low pressure mercury lamp irradiation. The amount of NO decomposed was nearly equal to that of NH₃, the rate of decomposition of NH₃ increased with the increase of the concentration of NO, and was expressed by the following equation:
d [NH₃] /dθ=k₁ [NH₃] +k₂ [NH₃] [NO] ^1/2 [θ; W/F (watt⋅min⋅l^-1) ]
The decomposition rate of NO in NO-NH₃-N₂ mixture under a low pressure mercury lamp irradiation was nearly equal to the decomposition rate of NH₃, and was ten times larger than that under a high pressure mercury lamp irradiation. The yield of N₂O (less than 10% of the amount of NO decomposed) increased proportionally to the amount of NH₃ decomposed and the concentration of NO.