CHARACTERIZATION OF IRON SPECIES IN Y-TYPE ZEOLITE AND MODIFIED FORM OF THE ZEOLITE

Iron zeolites with SiO2 Al2O3 ratios in the range 5.8-10.7 were prepared for impregnating LZY-82 zeolite in an aqueous solution of iron(III) nitrate or iron(II) sulfate, and calcined at 500°C. Some of the samples were treated in an atmosphere of hydrogen at 400 or 450°C. Chemical forms and reduction behaviour of iron species in these modified iron(III) zeolites were examined by 57Fe Mössbauer and e.s.r. spectroscopies and by electron microscopy. Iron(III)-oxide clusters bonding with the zeolite framework and fine iron oxide with diameters less than 1.2 nm produced in the zeolite cavities were detected except for iron(III) located in the cationic sites of zeolites. The strength of bonding between the fine iron oxide and/or iron-oxide cluster and the zeolite lattice was influenced by the preparative conditions of the iron(III) impregnation. It was possible to make distinctions between irons(III) of the cationic sites for the iron zeolites reflexed in toluene by a Mössbauer spectroscopy. © 1990.