Preparation of Faujasite membranes and their permeation properties

NaX and NaY zeolite membranes were grown hydrothermally on the surface of a porous cylindrical support. The molar compositions of the starting gel of NaX and NaY zeolite membranes were SiO2/Al2O3 = 3.6-5.3 (X), 25 (Y), Na2O/S iO2 = 1.2-1.4 (X), 0.88 (Y), H2O/Na2O = 30-50. X-ray diffraction (XRD) patt erns of membranes consist of peaks corresponding to the support and NaX or NaY zeolite. The Si/Al ratio of these NaX and NaY zeolites determined by at omic absorption spectrophotometry was 1.3 and 2.1, respectively. The outer- surface of the porous support was completely covered with randomly oriented , intergrown NaX or NaY zeolite crystals and the thickness of the membrane was about 20-30 mum, judging from the scanning electron microscopy (SEM) ob servation. Pervaporation and vapor permeation of organic mixtures through N aY and NaX zeolite membranes was investigated. The zeolite membranes showed high alcohol selectivity for several feed mixtures with methanol or ethano l. Furthermore, high benzene selectivity was observed for benzene/cyclohexa ne and benzene/n-hexane separation. High perm-selectivity of the zeolite me mbrane can be attributed to the selective sorption into the membrane. (C) 2 001 Elsevier Science B.V. All rights reserved.