Nucleation and growth process of sodalite and cancrinite from kaolinite-rich clay under low-temperature hydrothermal conditions

the synthesis of low-silica zeotypes by hydrothermal transformation of kaolinite-rich clay and the nucleation and growth processes of sodalite and cancrinite in the system na2o-al2o3-sio2-h2o at 100 a°c were investigated. the synthesis products were characterized by x-ray powder diffraction (xrpd), scanning electron microscopy (sem), fourier transform infrared spectroscopy (ft-ir), 29si and 27al magic angle spinning nuclear magnetic resonance (mas-nmr) and thermogravimetric analysis (tga). our data show that the sequence of the transformation of phases is: poorly crystalline aluminosilicate a？’ zeolite lta a？’ sodalite a？’ sodalite + cancrinite a？’ cancrinite. synthesized materials appeared stable thermodynamically under the experimental conditions, with zeolite lta (a metastable phase) occurring as a minor phase, compared with the presence of sodalite and cancrinite.