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 carrie d out on the samples in presence of template and after template removal at increasing temperatures in order to follow the evolution of the local envir onment of the metal heteroatoms. Ti(IV) atoms in (TS-I) show a great stabil ity, while Ga(III) and particularly Fet(III) atoms have propensity to migra te from framework into extraframework positions, forming small oxide partic les trapped inside the MFI channels upon increasing the template burning te mperature. The established stability scale is Ti(IV) > Ga(III) > Fe(III). T hese conclusions are qualitatively supported by W-Vis, LR and Raman data.