INTERPRETING THE OXIDATIVE CATALYTIC ACTIVITY IN IRON-SUBSTITUTED FERRIERITES USING IN-SITU MOSSBAUER-SPECTROSCOPY

Iron- and iron + aluminum-substituted ferrierites (Fe-FER and Fe+Al-FE R) have been characterized and their properties compared. Fe-FER exhib its excellent catalytic performance in mild oxidation processes, where as Fe+Al-FER is hardly active. To specify the source of catalytic acti vity, in situ Mossbauer studies were performed to distinguish the vari ous iron-containing species. Upon treatment in hydrogen performed on F e-FER, the temporary presence of the Fe2+ state was evidenced in tetra hedral framework sites, and removal of iron did not occur in significa nt amounts from these lattice positions. In contrast, similar treatmen t on Al+Fe-FER results in permanent Fe3+ to Fe2+ reduction and in remo val of iron in considerable amounts from the framework sites. From com parison of the behavior of samples and additional analysis of data, it is suggested that dinuclear Fe-lattice-O-Fe-extralattice centers are present in Fe-FER and that they have a primary role in mild oxidations .