Preparation and properties of ZSM-5 zeolite membrane obtained by low-temperature chemical vapor deposition

A zeolite membrane was obtained by in situ crystallization of silicalite-1 from a layer of silica species prepared by the novel method of low-temperature chemical vapor deposition (LTCVD) on a porous cordierite support. The XRD and SEM analyses showed a three-layer membrane: a 3-5 mum-thick compact layer, a 45 mum-thick zeolite-inpore layer and the support. The pure gas permeation data indicate that the synthesized zeolite layer is dense and pinhole-free. In, water-alcohol mixture pervaporation, the membrane exhibited a behavior of hydrophilic materials, with a high selectivity to water and a fair flux. This behavior can be explained by the presence of Al in the framework due to Al migration from the support. The membrane flux and selectivity decreased fairly slowly with time in the transient regime of water-ethanol pervaporation with the dry membrane, suggesting slow sorption equilibria of water and ethanol with the dry zeolite.