Preparation of inner-side tubular zeolite NaA membranes in a continuous flow system

Zeolite NaA membranes were synthesized on the inner side of porous titania (rutile) asymmetric tubular supports in a flow system where the synthesis gel was circulated through the support with flow rates in the range 1.5–4 mL min−1 by the action of gravity. The syntheses were carried out hydrothermally at 358 K for 6–7 h either with or without previous brush-seeding of the supports. The membranes (10–20 μm in thickness) showed great ability to dehydrate ethanol/water mixtures (92:8, w/w) by pervaporation with selectivities and fluxes, respectively, up to 8500 and 1.2 kg m−2 h−1 at 323 K. The role of intercrystalline defects in the pervaporation performance of the synthesized membranes was also investigated.