Diffusion rates of water, methanol, ethanol, 2-propanol and acetone through a Ge-ZSM-5 zeolite membrane were measured (table 58) in the steady state and for high coverages by using isotopic labeling. Labeled molecules were added to the feed during pervaporation, and their transient responses in the permeate were measured. At 313K, 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.

Measurements of Diffusion through a Zeolite Membrane using Isotopic-Transient Pervaporation. T.C.Bowen, J.C.Wyss, R.D.Noble, J.L.Falconer: Microporous and Mesoporous Materials, 2004, 71[1–3], 199–210

Table 58

Diffusion in Ge-ZSM-5 Zeolite at 313K