Measurements of diffusion through a zeolite membrane using isotopic-transient pervaporation

Diffusion rates of water, methanol, ethanol, 2-propanol, and acetone through a Ge-ZSM-5 zeolite membrane were measured at steady state and high coverages using isotopic labeling. Labeled molecules were added to the feed during pervaporation, and their transient responses in the permeate were measured. At 313 K, methanol diffused at approximately the same rate as water, but 3.3, 4.8, and 20 times faster than acetone, ethanol, and 2-propanol, respectively. For ethanol/methanol mixtures, ethanol slowed the rate of methanol diffusion and methanol increased the rate of ethanol diffusion. (C) 2004 Elsevier Inc. All rights reserved.