Elastic behavior of MFI-type zeolites: Compressibility of H-ZSM-5 in penetrating and non-penetrating media

The elastic behavior of H-ZSM-5 was investigated by in-situ synchrotron X-ray powder diffraction, using both silicone oil (so.) and (16:3:1) methanol:ethanol:water (mew.) as non-penetrating and penetrating pressure transmitting media, respectively. From P-amb to 6.2 GPa the volume reduction observed in so. is 16.6%. This testifies that H-ZSM-5 is one of the most flexible microporous materials up to now compressed in so. Volume reduction observed in m.e.w, up to 7.6 GPa is 14.6%. A strong increase in the total electron number of the extraframework system, due to the penetration of water/alcohol molecules in the pores, is observed in m.e.w. This effect is the largest up to now observed in zeolites undergoing this phenomenon without cell volume expansion. The higher compressibility in so. than in m.e.w, can be ascribed to the penetration of the extra-water/alcohol molecules, which stiffen the structure and contrast the channel deformations. (C) 2011 Elsevier Inc. All rights reserved.