POLARIZED SINGLE-CRYSTAL MICRO-RAMAN SPECTROSCOPY OF AS-SYNTHESIZED SILICALITE-1, AL MFI-TYPE AND FE MFI-TYPE ZEOLITES

Polarized single-crystal Raman spectra were collected from as-synthesi zed silicalite-1, Al MFI-type zeolites with different Si/Al ratios and Fe MFI-type zeolite using microspectrometry. These spectra are discus sed in relation to the crystal structure of the as-synthesized materia ls. The assignment of the Raman bands to the zeolite framework and to the occluded tetrapropylammonium (TPA) ion templating the MFI structur e was examined through the contribution of the different elements of t he Raman tensors as functions of the Al or Fe content, respectively. T he spectroscopic results are in good agreement with the conformation a nd location of the TPA ion in the as-synthetized MFI materials, and al so with theoretical predictions of preferential substitution sites des pite the low Al or Fe content of the zeolite framework.