Synthesis of nanometer-sized sodalite without adding organic additives

Aggregates (80 nm) of sodalite nanocrystals with crystallite sizes ranging from 20 to 40 nm have been synthesized from a sodium aluminosilicate solution at low temperature, without adding any organic additives, while paying attention to the key factors for the synthesis of nanosized zeolite crystals. The physical properties of nanosized sodalite crystals were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Si-29 solid-state magic-angle spinning (MAS) NMR, and N-2 adsorption. As expected, the external surface area of nanosized sodalite crystals is significantly increased compared with that of microsized socialite crystals. The size of synthesized sodalite crystals can be controlled from 20 mn to 10 mu m. It is found that the preparation of a homogeneous aluminosilicate solution followed by the formation of an aluminosilicate hard gel by adjusting the initial composition, for example, SiO2/Al2O3 and Na2O/H2O ratios, is critical for synthesis.