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Keywords:

Science & Technology, Physical Sciences, Chemistry, Multidisciplinary, Chemistry, Physical, Chemistry

Abstract:

X-ray powder diffraction has been utilized to determine the location and coordination environment of iron cations in Y-type zeolites after a variety of pretreatment procedures. The iron is introduced by an anaerobic ion-exchange technique with the FeII cation. The exchange level in all samples is ca. 45%. After dehydration of FeIIY samples, the iron cations are found in six-fold coordination at site I and in three-fold coordination at site I′. Upon oxidation to FeIII, most of the iron migrates out of the hexagonal prism (site I) and can be localized at site I′. No evidence for oxide-bridged complexes was found in any of these samples. The zeolite lattice is unstable toward high-temperature oxidation of the FeII to FeIII as partial framework decomposition is observed. In all dehydrated samples, the precipitation of amorphous iron oxides is indicated.