EXAFS study of Ti, Fe and Ga substituted silicalites

The local environment of isomprphous substituted Ti, Fe and Ga metal atoms in silicalite thereafter indicated as TS-1, Fe-S and Ga-S respectively) has been studied by means of EXAFS spectroscopy. Measurements have been carried out on the samples in presence of template and after template removal at increasing temperatures in order to follow the evolution of the local environment of the metal heteroatoms. Ti(IV) atoms in (TS-I) show a great stability, while Ga(III) and particularly Fet(III) atoms have propensity to migrate from framework into extraframework positions, forming small oxide particles trapped inside the MFI channels upon increasing the template burning temperature. The established stability scale is Ti(IV) > Ga(III) > Fe(III). These conclusions are qualitatively supported by W-Vis, LR and Raman data.