Localisation of iron ions in NH4,Na-Y zeolite: A Mössbauer effect study

Localisation of Fe ions in deep-bed treated NH₄,Na-Y zeolite at 830K, 940K, and 1050K, as well as after reduction by hydrogen, and dealumination with subsequent calcination is studied by⁵⁷Fe Mössbauer spectroscopy. Most of the incorporated iron is present in the form of octahedrally coordinated ferric species with two distinct sets of hyperfine parameters assigned to atoms inside the zeolite structure and in extraframework positions. Fe²⁺ ions with high coordination are also detected and their amount increases with the temperature of deep-bed treatment. Low-temperature Mössbauer effect measurements at 77K and 4.2K were employed to facilitate the identification of iron sites.