Innovative methods for preparation and testing of Al2O3 supported silicalite-1 membranes

The aim of the present study is to develop a novel type of zeolite membrane and exploit some of the inherent and unique advantages of this membrane in gas separations. The development of inorganic membranes formed from a cohe rently grown layer of zeolite crystals is a particularly promising approach , since such membranes offer substantially higher permeabilities and select ivities compared with polymeric materials and can perform under extreme con ditions, e.g. at elevated temperatures and in aggressive chemical environme nt. Such zeolite membranes are prepared by in-situ hydrothermal synthesis o f zeolite layer within the macropores of alumina ceramic supports (tubes/di scs). In this way more stable zeolite membranes are produced, avoiding oute r separating layers which are prone to mechanical damage. These membranes h ave also been shown to have good thermal stability up to 500 degreesC, with no evidence of crack formation. The synthesized materials have been charac terized by several techniques such as Hg and Nz porosimetry, scanning elect ron microscopy (SEM), and X-ray diffraction (XRD). From these measurements it appears that the structure of the zeolite membrane is influenced by seve ral factors, such as structure and size of the pores of the support, chemic al composition of the precursor solution from which the crystals will be ha rvested, reaction conditions, etc. Finally, gas permeabilities and/or selec tivities have been measured fur several important gas systems. The results of this study indicate the important role of influencing the outcome of the crystal formation by controlling the conditions of the hydrothermal treatm ent in obtaining optimum gas permeabilities and/or selectivities of these s ystems. (C) 2001 Elsevier Science Ltd. All rights reserved.