Preparation and characterization of nanosized silicalite-2 zeolites by steam-assisted dry gel conversion method

Abstract

Nanosized silicalite-2 zeolite was successfully synthesized by steam-assisted dry-gel conversion technique with TBAOH (tetrabutylammonium hydroxide) as structure directing agent and TEOS (tetraethoxysilane) as silica source. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption and desorption (BET) and Field emission scanning electron microscopy (FESEM). XRD pattern confirmed the crystallization of silicalite-2 obtained at 170°C for 48h, the diffraction lines of samples were broadened as a result of the decreased in particle size with the content of TBAOH increased. FESEM images showed that the silicalite-2 nanocrystals with a particle size of about 70–90nm. N2 adsorption and desorption provides manifest evidence that the porosity is fully accessible from the external surface of the zeolite crystal. The vibration bands at around 551.5 and 1229.2cm−1 indicated the presence of double 5-ring in the pentasil zeolite structure of MEL, values of the 550cm−1/460cm−1 band intensity ratios demonstrated that the crystallinity of zeolite closed to 100%.