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 catalyzed by Fe/ZSM-5 prepared by sublimation. Under certain conditions stable oscillations occur which have been monitored by mass spectrometry. The phenomenology differs characteristically from that of the oscillating N2O decomposition observed over other catalysts. Excess O-2 has only a small effect on the reaction rate and oscillation frequency but water, besides lowering the reaction rate, is found to be crucial for isothermal oscillations on this catalyst. The occurrence of such oscillations indicates that two different states of catalytic activity exist. FTIR shows that the same chemisorbed nitro/nitrate groups are formed as found previously upon exposing the same catalyst 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 rights reserve