Formation of a Y-Type Zeolite Membrane on a Porous α-Alumina Tube for Gas Separation

Abstract

A porous α-alumina support tube, polished with a finely powdered X-type zeolite for use as seeds, was placed vertically in an autoclave containing an aqueous mixture of water glass and sodium aluminate. Hydrothermal synthesis was carried out at 90 °C for 24 h. A polycrystalline layer of Y-type zeolite was thus formed on the outer surface of the support tube. After washing and drying in air, permeances of single components and mixtures of CO 2 and N 2, as well as CH 4, C 2 H 6, and SF 6, were determined. The CO 2 permeance was higher than that of N 2 at temperatures of 30−130 °C. When an equimolar mixture of CO 2 and N 2 was fed into the feed side, the CO 2 permeance was nearly equal to that for the single-component system and the N 2 permeance for the mixture was greatly decreased, especially at lower permeation temperatures. This was due to selective adsorption of CO 2 in subnanometer micropores of the membrane. At 30 °C, the permeance of CO 2 was higher than 10 -7 mol·m -2 ·s -1 ·Pa -1, and the permselectivity of CO 2 to N 2 was 20−100.