XAFS STUDY OF TI-SILICALITE - STRUCTURE OF FRAMEWORK TI(IV) IN PRESENCE AND IN ABSENCE OF REACTIVE MOLECULES (H2O, NH3)

X-ray absorption at the Ti K edge (both XANES and EXAFS) of a very pure Ti-silicalite containing a small fraction of Ti(IV) substituting Si(IV), has been performed in order to study the effect of the presence or absence of ligands such as H2O and NH3 on the Ti(IV) coordination sphere. In particular, the effect of an outgassing treatment at 400 K and of the interaction With NH3 has been studied and described in detail. It has been found that the Ti(IV) is fourfold coordinated in the samples outgassed at 400 K and expands its coordination sphere number under the action of adsorbates.