MODELING THE DYNAMICS OF THE N2O REDUCTION ON IRON-OXIDE

The reduction of N2O to N-2 on iron oxide under transient conditions w as studied in the temperature range of 270-340 degrees C. Six differen t models were used to simulate the experimental data. The conventional second-order reaction between gas phase N2O and surface oxygen vacanc ies failed to describe the dynamic experiments. Upon introducing linea r or exponential distributions of the second-order surface reaction ra te constant in function of the degree of reduction of the surface, sat isfactory fittings to the experiment could not be achieved either. It was necessary to take into account subsurface oxygen diffusion to desc ribe the low rates of reaction measured at low degrees of reduction of the catalyst. The combination of subsurface oxygen diffusion with a l inear activity distribution for the surface reaction provided a good d escription of the transient N2O reduction. Finally, the surface reacti on rate constant as well as the diffusion coefficient of oxygen in iro n oxide could be fitted with the Arrhenius law.