Development of rate expressions for the catalytic decomposition of nitric oxide with ammonia on iron oxide

The reduction of nitric oxide with ammonia on iron oxide catalysts has been studied in a continuous-flow recycle reactor using simulated flue gas in the temperature range from 573 to 673 K. NO and HN₃ concentrations were varied between 0 and 1000 vpm, O₂ and H₂O concentrations between 0 and 9 vol.-%, the remainder being nitrogen. In the presence of oxygen, the formulated reaction rate equation describes the measured rates of the main reaction NO + 2/3 NH₃ ? 5/6 N₂ + H₂O. Its form corresponds to the Langmuir-Hinshelwood type. The rate equation well fits the data, which cover the whole industrial temperature and concentration range. In the absence of oxygen, the measured reaction rates can be best described by a power law.