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Abstract: 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 723K. 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 0.5vol.% 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. [Copyright &y& Elsevier]

Abstract: The N2O decomposition activity of the Fe-ZSM-5 catalysts, prepared by chemical vapor deposition (CVD) and aqueous ion exchange (IE), was studied after steaming and high temperature treatment at 1218K (HT) and compared with the activity of the corresponding non-steamed catalysts after pretreatment at 873K. FTIR spectra showed that dehydroxylation and/or dealumination took place during steaming and high temperature treatment of the catalysts, which leads to the formation of oxygen vacancies (i.e. lattice defect). These lattice defects leads to a change in electronic properties of the iron sites, which are associated with electron withdrawing Al Lewis centers. The iron sites in close proximity of defects are responsible for the initial higher N2O decomposition (transient activity) of the steamed and HT catalysts. The increase in steady-state activity over steamed and HT catalysts can be mainly attributed to an increase in the number of active sites created by autoreduction of the iron centers during steaming and high temperature treatment. The above-mentioned trends are valid for both CVD and IE samples. [Copyright &y& Elsevier]