DEHYDRATION AND ADSORBATE INTERACTIONS OF FE-Y ZEOLITE BY MOSSBAUER SPECTROSCOPY

The local environment of ferrous ions exchanged into Y zeolite has been studied by Mössbauer spectroscopy. A model consistent with the results is presented. It is proposed that while Fe2+ ions go preferentially into hexagonal prism sites in the zeolite, dehydration leads to ferrous ions in fourfold coordination near the hexagonal windows. In this configuration there are three FeOAl bonds and one FeOH or FeOFe bond. The effects of dehydration and of adsorption of O2, N2, CO, NO, C2H4, pyridine, piperidine, ethanol, t-butyl alcohol, CS2, and NH3 at room temperature are discussed in terms of the proposed model. The use of the adsorption of gas molecules of varying size and chemical behavior as an aid in characterizing surface sites by Mössbauer spectroscopy is demonstrated.