Tubular-type pervaporation module with zeolite NaA membrane☆

Zeolite NaA membranes were prepared on the surfaces of porous tubular supports composed of mullite, α-alumina and/or cristobalite using the hydrothermal synthesis. The zeolite NaA crystals and the surface morphologies of the membranes were characterized by X-ray diffraction and SEM. EPMA analysis revealed that the zeolite composite membranes consisted of three layers — the zeolite layer, the intermediate layer and the mullite support. According to pervaporation measurements using H2OEtOH mixture, the permselectivity increased in the alumina content of the substrate and reached a constant at >70 wt% Al2O3. Zeolite NaA membrane showed very high water-selective permeation through all the ethanol concentrations. The tubular-type module with ca. 0.5 m2 membrane area was composed of 17 pieces of zeolite membrane using 65 wt% alumina content substrate, which has high pervaporation performance and can be purchased at a low price. The efficiency of the module on permeation rate increased in proportion to the feed flow rate and exhibited 100% at Reynolds number >80. Pervaporation flux and separation factor of the module for 5 wt% water/95 wt% ethanol mixture at 95°C was ca. 2.35 kg m−2 h−1 and was greater than 5 000, respectively.