Study on the Mechanism of Rapid Synthesis of Small Grain NaX Type Molecular Sieve with Calcined Kaolin

Abstract

Small grain X zeolite molecular sieve was synthesized using calcined kaolin and sodium hydroxide directly and crystallization for 3.5h without template agents，directing agents and seed. The products were characterized using the transmission electron microscopy (TEM) and x-ray diffraction (XRD) analysis. TEM observed that the small grains in 70-80 nm size were well distributed. The hydrothermal crystallization products was X zeolite with complete crystal analysised by XRD. Fourier transform infrared spectroscopy (FTIR) characterization showed that the basic structural unit of component in the solid phase of calcined kaolin and X zeolite had no significant change. After an induction phase of calcined kaolin in the hydrothermal system, large numbers of Nanocrystalline of X zeolite molecular sieve were formed and became the growth unit. And then it has turned into the main structure growth mechanism of the X zeolite. Therefore, rearrangement of crystal phase rotating is believed to be the mechanism of calcined kaolin synthetizing X zeolite.