Synthesis, modification, and characterization of NH4 zeolites and their relationships to their hydrogen forms

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Zeolites belong to the most important classes of materials with main applications as catalysts, adsorbants, and ion exchangers. Ammonium exchanged zeolites play an important role as precursor materials in the production of H-zeolites representing the main group of zeolite catalysts. We have compiled more than 5,000 entries of crystal-structure descriptions of zeolites in standardized settings which enables us to easily compare their crystal structures. It is our aim to characterize ammonium exchanged zeolites by single-crystal structure analyses and to correlate the crystal-chemical environment of NH4 with other NH4 zeolites contained in our database. A special focus will be on the role of ammonium upon calcination to make the H-zeolite catalysts. In this context additional experiments will be performed on the deammoniation process of selected zeolites. The results will be correlated with the structural data in our database, leading to a complete analysis of hydrogen bonding schemes in NH4 zeolites, to a comparative analysis of framework flexibilities of H-zeolites, and to a redetermination of the ionic radius of the NH4 ion in zeolites. Characterization will be done by X-ray powder and single-crystal diffraction, transmission electron microscopy, scanning electron microscopy with EDX attachment, IR spectroscopy, and solid state NMR spectroscopy. Deuterium exchanged forms of zeolites will be studied by neutron diffraction methods.