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

The elastic behavior of H-ZSM-5was investigated by in-situ synchrotron X-ray powder diffraction, using both silicone oil (s.o.) and (16:3:1) methanol:ethanol:water (m.e.w.) as ‘‘non-penetrating’’ and ‘‘penetrating’’ pressure transmitting media, respectively. From Pamb to 6.2GP the volumereductionobserved in s.o. is 16.6%. This testifies that H-ZSM-5 is one of the most flexible microporous materials up to now compressed in s.o. Volume reduction observed in m.e.w. up to 7.6GPa is 14.6%. Astrong increase in the total electron number of the extraframeworks ystem, 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 inzeolites undergoing this phenomenon without cell volume expansion. The higher compressibility ins.o.than in m.e.w.can be ascribed to the penetration of the extra-water/alcohol molecules, which stiffenthe structure and contrast the channel deformations.