High-pressure adsorption phenomena in natural and synthetic zeolites with EAB topology

Abstract

The high-pressure behaviour and the crystal-fluid interaction of zeolites with EAB topology were investigated by in-situ single-crystal and powder synchrotron X-ray diffraction, both on synthetic and natural samples. The experiments were conducted using a diamond anvil cell and different pressure transmitting fluids, including: the non-penetrating silicone oil and the potentially penetrating methanol:ethanol:H2O = 16:3:1 mixture, methanol and distilled H2O. The zeolites intrinsic compressional behaviour investigated with a non-penetrating fluid showed the significant role of the extra framework population on the bulk compressibility. Notably, within the first ∼0.5 GPa of the silicone oil ramp, the bulk modulus (KV0 = βV0−1) resulted to be KV0 = 62(1) GPa for the natural bellbergite and KV0 = 16(4) GPa for the synthetic K-analogue. The synthetic EAB zeolites demonstrated a high host capacity for methanol molecules, which were not able to penetrate the natural bellbergite cavities. A comparative analysis between the behaviour of zeolites with EAB topology and structurally similar zeolites, such as erionite (ERI topology) and offretite (OFF), is provided.