Methodological and operational aspects of permeation measurements on silicalite-1 membranes

Permeation measurements with zeolite membranes are evaluated by comparing data obtained from different experimental methods: a batch method and the Wicke-Kallenbach method. The permeation of methane, ethane, propane and n-butane was studied between 270 and 625 K at pressures between 10 and 425 kPa. The experiments were performed in a continuous and discontinuous way, with and without the use of a sweep gas. From the comparison of the different techniques it was found that the sweep gas significantly influences the permeation of the feed component. This effect was found to be dependent on the nature of the sweep gas and on the magnitude of the counter permeation. The experimental configuration, such as the orientation of the composite membrane with respect to the feed side, affects the local conditions at both sides of the zeolite layer, resulting in quite different permeances. Only if these effects are taken into account properly, intrinsic data on permeation through the zeolite layer can be obtained. (C) 1998 Elsevier Science B.V.