• Nucleation and growth history of zeolite LTA synthesized from kaolinite by two different methods.

      Rios, Carlos A.; Williams, Craig D.; Fullen, Michael A. (Amsterdam: Elsevier, 2009)
      The synthesis of zeolite Linde Type A (LTA) from kaolinite by two different routes: (1) conventional hydrothermal alkaline activation and (2) alkaline fusion prior to hydrothermal reaction, as well as its nucleation and growth history, were investigated. Using the first method, co-crystallization of sodalite and cancrinite, probably via an unstable zeolite LTA intermediate, was observed during treatment of kaolinite in NaOH solutions. The addition of a SiO2 source promoted the co-precipitation of several zeolite phases, including zeolites LTA, X and P, with traces of sodalite and cancrinite. By fusion with NaOH followed by hydrothermal reaction, kaolinite was converted into zeolite LTA. Synthesized materials appeared stable thermodynamically under the experimental conditions. The synthesis products have been characterized by X-ray diffraction, scanning electron microscopy and Fourier Transform Infrared Spectroscopy.
    • Synthesis of Zeolites and Zeotypes by Hydrothermal transformation of Kaolinite and Metakaolinite.

      Rios, Carlos A.; Williams, Craig D.; Maple, Martin J. (Bucaramanga, Colombia: Universidad de Pamplona, 2007)
      The synthesis of zeolitic materials by hydrothermal transformation of kaolinite and metakaolinite in NaOH solutions of various concentrations was investigated between 100 and 200 degrees C, over different reaction times, using in some cases precipitated SiO2 or organic templates. Materials were obtained, including clathrasils: cancrinite (CAN), sodalite (SOD), and Linde Type A (LTA), faujasite (FAU), NaP1 (GIS), analcime (ANA) and nepheline hydrate I (JBW) zeolites. In general, co-crystallization of CAN and SOD, likely via an unstable LTA zeolite intermediate, was observed after dissolution of kaolinite at low temperature; although the feldspathoids tend to be unstable at high temperature. LTA zeolite was synthesized after metakaolinite reaction, with minor amount of FAU zeolite, ANA and SOD. Solids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA).