Saturation of the Siliceous Zeolite TON with Neon at High Pressure

Abstract

The insertion of neon and argon in the 1-D pore system of the zeolite TON was studied at high pressure by X-ray diffraction and by Monte Carlo (MC) molecular modeling. Rietveld refinements of the crystal structure of TON and the MC results indicate that 12 Ne atoms enter the unit cell of TON, completely filling the pores. This is much greater than the degree of filling observed for argon, which due to size considerations lies in a vertical plane in the pores. A phase transition from the Cmc21 to a Pbn21 structure occurs at 0.6 GPa with cell doubling. The compressibility and structural distortions, such as pore ellipticity, are considerably reduced as compared to the argon-filled or the empty-pore material. In addition, the crystalline form persists to pressures of the order of 20 GPa, and the Pbn21 phase is recovered after decompression. The results show the very strong and different effects of pore filling by noble gases on the structural stability and mechanical properties of this prototypical 1-D zeolite-type material.