XAFS, IR, RAMAN AND UV-VIS CHARACTERIZATION OF FRAMEWORK TI(IV) SPECIES IN TI-SILICALITES

The main results obtained by using IR, Raman and UV Vis techniques con cerning the structure of the Ti(IV) center in Ti-silicalite is briefly reviewed and discussed with recent XAFS results. The Ti(IV) is in tet rahedral coordination in vacuo and expands its coordination sphere upo n interaction with adsorbates. Present EXAFS results indicate, for the dehydrated sample, a first shell coordination number higher then four (4.45 +/- 0.3), suggesting, in a fraction of sites, the substitution of a bridged oxygen with two OH groups.