Polycrystalline ferrierite/alumina composite membranes were prepared by a vapor-phase transport method. Pervaporation of m-xylene and 1,3,5-triisopropylbenzene was then used to evaluate the compactness of the membranes. Permeation measurements were carried out for hydrogen, helium, methane, n-butane, i-butane and sulfur hexafluoride at 300-375 K. Ideal selectivities and the mixed gas separation factors were compared. The separation factor of butane isomers depended on the compactness of the membrane. The separation factor of n-butane/i-butane was as high as 40-70 at 375 K, and no detectable permeation flux of m-xylene was observed at 303 K. Separation of a 25/75 p-xylene/m-xylene mixture was also performed at 303 K using pervaporation. The permeation of p-xylene was detectable, whereas that of m-xylene was below the detection limit of the experiment. The separation factor of p-xylene to m-xylene was greater than 16, which is much higher than the value of 1.0 expected from the vapor-liquid equilibrium. (C) 2000 Elsevier Science B.V. All rights reserved.
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