Synthesis and characterization of nano-sized zeolites

Synthesis of zeolite ZSM-5 and silicalite-1 by hydrothermal crystallization of clear supersaturated homogeneous synthesis mixture has been achieved. The influence of the templates, synthesis temperature, synthesis time and SiO₂/Al₂O₃ ratio on the properties of the nano-sized zeolite has been investigated. The properties of the samples were characterized by X-ray powder diffraction, N₂ adsorption/desorption, scanning electron microscopy, and transmission electron microscopy. The results show that the temperature at 170°C was favorable to synthesize the nano-size zeolites. The use of tetrapropylammonium hydroxide as the template in the hydrothermal synthesis conditions employed was favorable to form nanozeolite than tetramethylammonium hydroxide. The synthesis time also plan an important role. 1 day was required to obtain a fully crystallized product. The longer crystallization time would produce bigger particles. A decrease in Al₂O₃ content would decrease the crystallite size. The nanosize ZSM-5 and silicalite with crystallite size of 150 nm have been successfully synthesized.