Hydrothermal stability of Fe-ZSM-5 and Fe-BEA prepared by wet ion-exchange for N2O decomposition

摘要

The hydrothermal stability of WIE based Fe-ZSM-5 and Fe-BEA for N2O decomposition in the presence of NO, H2O and O2 was studied at 723 K. Catalysts were characterized with UV-Vis, IR and Al-XANES. The N2O conversion remains at a constant level with Fe-H-BEA even in the presence of large amounts of H2O. Deactivation was, however, observed with Fe-H-ZSM-5 already in the presence of 0.5 vol% water. The analysis of deactivated samples indicated that steam-dealumination and clustering of iron occurred during the reaction with Fe-ZSM-5. Replacement of protons for sodium in Fe-ZSM-5 slowed down the rate of catalyst deactivation significantly. Steam-dealumination is likely to precede the clustering of iron in Fe-H-ZSM-5. The excellent hydrothermal stability of WIE based Fe-H-BEA relates to the high initial degree of dealumination in the as-received BEA.