Ammonium nitrate formation in low concentration mixtures of oxides of nitrogen and ammonia

Abstract The formation of ammonium nitrate in a reaction system containing oxides of nitrogen, ammonia, water vapour and oxygen present in ppm quantities in nitrogen was investigated. The measured amounts of nitrate produced were compared with those predicted by use of a kinetic model for the reacting system. For any temperature there was an initial pressure of ammonia below which nitrate was not found. This pressure was determined solely by thermodynamic considerations. At higher pressures of nitrogen dioxide, equilibrium was quickly attained, but at low pressures nitrate was not always formed in the time of contact of reactants. Water vapour enhanced the rate of formation of nitrate. The work has relevance to the possibility of formation of ammonium nitrate in nitric acid plants and to its formation in the atmosphere.