XAFS, IR, Raman and UV-Vis Characterization of Framework Ti(IV) Species in Ti-Silicalites

摘要

The main results obtained by using IR, Raman and UV-Vis techniques concerning the structure of the Ti(IV) center in Ti-silicalite is briefly reviewed and discussed with recent XAFS results. The Ti(IV) is in tetrahedral coordination in vacuo and expands its coordination sphere upon 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.