Effect of Water on Active Iron Sites for N2O Decomposition over Fe/ZSM-5 Catalyst

The effect of H2O on N2O decomposition in Fe/ZSM-5 catalyst was investigated by steady-state kinetics, transient response methods, in situ Raman, and IR spectroscopies. Fe/ZSM-5 catalysts show very high activity in N2O decomposition but are deactivated rapidly when trace amounts of water are present. In situ Raman spectra results indicate that the peroxide bridge on the binuclear Fe sites are converted to the hydroxylated binuclear Fe sites when exposed to water. It was found that the Raman band at 743 cm(-1) and the IR bands at 3628 and 3672 cm(-1) are associated with the deactivation of the catalyst during N2O decomposition. The catalyst was regenerated after calcination at a temperature over 773 K. The inhibiting effect of H2O on N2O decomposition indicates that the presence of water leads to the structural transformation from the dehydroxylated binuclear Fe sites to the hydroxylated binuclear Fe sites on Fe/ZSM-5.