An Investigation of the Behavior of Completely Siliceous Zeolite ZSM-5 under High External Pressures

The behavior of completely siliceous zeolite ZSM-5 (Si-ZSM-5) under high pressures up to 16 GPa were investigated by in situ Raman spectroscopy and X-ray diffraction with synchrotron radiation in a diamond anvil cell. Pressure-induced amorphization was observed in both as-made and calcined Si-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 as-made and calcined Si-ZSM-5. It was found that the existence of the template molecules occluded in the zeolite framework is mainly responsible for these differences.