SEPARATION OF ETHANOL-WATER MIXTURE BY SILICALITE MEMBRANE ON PERVAPORATION

Pure silicalite membranes were prepared on porous supports of sintered stainless steel or alumina discs. The silicalite layer was characterized by X-ray diffraction, SEM and mercury porosimetry. Individual crystals were intergrown in three dimensions into the polycrystalline phase. The membranes were not disintegrated by thermal treatment in vacuo or calcination for removing the organic amine occluded in the channels of silicalite, indicating high thermomechanical stability of the membrane. The liquid separation potential of the membrane was investigated by pervaporation of an aqueous ethanol solution. The high ethanol permselectivity with a separation factor cr (EtOH/H2O) of more than 60 was achieved for a 5 vol% aqueous ethanol solution at 30 degrees C, indicating no cracks and pores between the silicalite grains within the membrane. From adsorption experiments of ethanol and water on silicalite, it was found that the high permselectivity is attributable to the selective sorption of ethanol into the silicalite membrane.