Defect free silicalite-1 membranes were successfully prepared on the surface of tubular mullite supports in ultradilute solution containing fluoride by hydrothermal synthesis. The typical molar composition of synthesis solutions was 1SiO(2):0.2TPABr:0.2TPAOH:0.15NH(4)F:800H(2)O. The results of X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) of zeolite membranes were confirmed that the outer surface of support was fully covered with a randomly oriented and intergrown silicalite zeolite layer. The membrane prepared at 180 degrees C for 20 h showed high ethanol permselectivity for separation of ethanol/water mixtures. The flux and separation factor are achieved to 2.85 kg m(-2) h(-1) and 60 for 5 wt.% ethanol/water mixture at 60 degrees C, respectively. (C) 2011 Elsevier B.V. All rights reserved.