High Si zeolite H-ZSM-5 and hydrophobic zeolite silicalite-I were characterized by powder XRD, FT-IR and 29Si MAS nmr. Hydrophobic zeolite silicalite-I possesses a monoclinic symmetry at room temperature The facts that high resoln. of IR spectra for framework vibration and 29Si MAS NMR spectra, and the loss of Si-OH IR vibration at 3450 and 3730 cm-1 prove a perfect arrangement of [SiO4] tetrahedra in the cell of silicalite-I.

Key words: INFRARED SPECTROPHOTOMETRY, X-RAY DIFFRACTION ANALYSIS, SILICON COMPOUNDS, HYDROPHOBILITY, FOURIER TRANSFORM, SILICALITE