Structure–property relationships in sorption of vapours with different polarities in zeolites and zeolite-filled poly(dimethylsiloxane)

Abstract

Three faujasite (FAU) zeolite samples with different Si:Al ratios and OH contents were prepared from a NaY-type zeolite and their structure was studied by XRD, ²⁹Si NMR, ²⁷Al NMR and IR. These studies showed that the SiCl₄ treatment mainly dealuminated the starting NaY zeolite, while the additional hydrothermal treatment reduced the OH groups on the zeolite surface, and the final acid treatment removed further the residual Al traces in the framework. The sorption measurement shows that the zeolite affinity to a non-polar organic solvent increases with increasing Si:Al ratio and decreasing surface OH groups. When zeolites were used to fill a poly(dimethylsiloxane) membrane, the affinity of the sorption sites and their capacity decreased, leading to a low contribution of the zeolites to the sorption capacity of the composite membranes. The sorption selectivity of zeolite-filled membranes was consistent with that of pure zeolites at low solvent activities, but at high activities, the sorption property of the PDMS matrix prevailed.