Isothermal oscillations during N2O decomposition over Fe/ZSM-5: effect of H2O vapor

The decomposition of N2O to N-2 and O-2 in diluted feed streams is catalyze d by Fe/ZSM-5 prepared by sublimation. Under certain conditions stable osci llations occur which have been monitored by mass spectrometry. The phenomen ology differs characteristically from that of the oscillating N2O decomposi tion observed over other catalysts. Excess O-2 has only a small effect on t he reaction rate and oscillation frequency but water, besides lowering the reaction rate, is found to be crucial for isothermal oscillations on this c atalyst. The occurrence of such oscillations indicates that two different s tates of catalytic activity exist. FTIR shows that the same chemisorbed nit ro/nitrate groups are formed as found previously upon exposing the same cat alyst to NO+O-2. This suggests that binuclear oxygen bridged complexes play an important role in this chemistry. (C) 2000 Elsevier Science B.V. All ri ghts reserved.