Iron exchanged ZSM-5 and Y zeolites calcined at different temperatures: activity in N2O decomposition

ZSM-5 and Y zeolites were modified with iron by an ion-exchange method and then calcined at 773, 873, 973 and 1,073 K. The obtained materials were characterized with respect to textural parameters (low-temperature N-2 sorption), structure (X-ray diffraction, UV-vis-DRS), redox properties (H-2-temperature programmed desorption, TPD) and surface acidity (NH3-TPD). The obtained results have shown that the structure of zeolites influenced form, aggregation and content of the introduced iron species. In case of the FAU type structure characterized by wide pores (max. ring size, T-atoms-12) mainly iron in form of mononuclear Fe3+ cations and Fe (x) (3+) O-y oligonuclear clustered species was found. On the other hand for the MFI type structure characterized by smaller pores (max. ring size, T-atoms-10) significant contribution of iron in the form of bulky Fe2O3 clusters located possibly on the outer surface of ZSM-5 was detected. Such significant differences in distribution of iron species is probably related to various mobility of iron species in the pore systems of both zeolites. The obtained materials were tested as catalysts in the process of N2O decomposition. Calcination of zeolites at different temperatures influenced neither the properties nor the activity of the obtained catalysts.