Large-area ZSM-5 zeolite membranes were successfully prepared on porous alpha-Al2O3 supports with optimized synthesis solution composition and synthesis conditions. The membranes were achieved by repeated hydrothermal synthesis with cheap NBA (n-butylamine) as template and from clear synthesis solution. Not only the membranes were prepared on tubular supports, but also the membrane area is up to 260 cm(2). All the membranes were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and single-gas permeation. As a result of these measures, the yield of high-quality membranes with a minimum permselectivity of H-2 to n-C4H10 of 27 (which is five times the Knudsen factor) as a quality criterion was increased to 50% of all preparations. (C) 2003 Elsevier Science B.V. All rights reserved.