Preparation of hydrophilic and acid-proof silicalite-1 zeolite membrane and its application to selective separation of water from water solutions of concentrated acetic acid by pervaporation

Hydrophilic and acid-proof silicalite-1 zeolite membrane was successfully prepared by repeating hydrothermal synthesis of silicalite-1 layer on an alumina ceramic filter (repeated batch synthesis) followed by a liquid phase oxidation method with H2O2 to remove template molecules. This prepared membrane has marked amount of silanol group both in the micro pores of silicalite-1 crystals and in the apertures among the crystals. Networks of water molecules are formed via hydrogen bond in silanol groups. These networks allow only water molecules to diffuse through the networks. Therefore, when this membrane was applied to the pervaporation of concentrated acetic acid (30-98 wt.%), only water molecules passed through the membrane. To examine the usefulness of the membrane, the pervaporation of two kinds of water solutions, acetone and ethanol, were conducted by this membrane. In both systems, only water was permeated, as well as the case of the water solution of acetic acid. The permeation rate at the pervaporation temperature was found to lie on a single line for acetone-water, ethanol-water and acetic acid-water systems. Thermogravimetric analysis of hydrophilic silicalite-1 powders indicated that dominant channels for the permeation of water molecules were apertures among fine silicalite-1 crystals of the membrane. (C) 2003 Elsevier Science B.V. All rights reserved.