Reaction of HY Zeolite with Molecular Fluorine

At room temperature, gaseous F2 extracts tetrahedrally coordinated aluminum from the lattice of an acid, near-faujasite HY zeolite (Si/Al≈13) and forms fluoro-hydroxy-aluminum complexes of the type Al2F(OH)(5−n)+n in which Al is octahedrally coordinated. Moreover, the crystallinity of the zeolite is almost unchanged by the fluorination process. The HY dehydrated at 200°C under vacuum and treated under a F2 pressure of 300 mbar at room temperature is practically totally dealuminated. At lower pressure the transformation is partial. The coordination shell of the complex becomes unstable at about 500°C. Upon losing ligands, octahedral Al reverts partially to the tetrahedral coordination and is partially reinserted into the lattice. At a higher temperature an amorphous alumina phase is formed. 27Al and 19F high-resolution solid-state NMR, FT-IR, X-ray diffraction, and temperature-programmed desorption (TPD) are the main tools used in this work.