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/SiO2 = 1.2-1.4 (X), 0.88 (Y), H2O/Na2O = 30-50. X-ray diffraction (XRD) patterns 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 atomic 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) observation. Pervaporation and vapor permeation of organic mixtures through NaY and NaX zeolite membranes was investigated. The zeolite membranes showed high alcohol selectivity for several feed mixtures with methanol or ethanol. Furthermore, high benzene selectivity was observed for benzene/cyclohexane and benzene/n-hexane separation. High perm-selectivity of the zeolite membrane can be attributed to the selective sorption into the membrane. (C) 2001 Elsevier Science B.V. All rights reserved.