The behaviour of completely siliceous zeolite ZSM-5 under high pressure up to 16 GPa were investigated by in situ Raman spectroscopy, Infrared spectroscopy and X-ray diffraction with synchrotron radiation using diamond anvil cell. Pressure-induced amorphization was observed in both as-made and calcined siliceous ZSM-5 which transform to a low-density amorphous silica first and then to a high-density amorphous silica. However, transition pressures and reversibility were different for the as-made and calcined siliceous ZSM-5. It was found that the occluded template molecules are the major factor for these differences.
The crystallization mechanism of AIPO4-I6 molecular sieve was preliminarily investigated under dry gel conversion method by X-ray diffraction and Solid-State NMR spectroscopy. The AIPO4-I6 and a crystalline by-product which has similar structure were formed via a semi-crystalline layered A1PO intermediate. The by-product could be transformed to amorphous materials with different structures by calcination and washing with distilled water
