Characterization of zeolite membranes by temperature programmed permeation and step desorption

A temperature programmed permeation (TPP) system was employed to measure the single gas permeances of H2, N2, CO2, methane, ethane, propane and n-butane through MFI membranes prepared on tubular alumina and stainless steel supports. The same system was used to measure the CO2/N2 separation selectivity using mixed feeds. The results obtained by TPP were in good agreement with permeation data gathered by on-line gas chromatography at fixed temperatures. However, the amount of information that could be obtained from TPP experiments in a comparable experimental time was much larger. Step desorption (SD) experiments were also carried out in which the response of the membrane to a step change in the feed side concentration was continuously analyzed. The permeation-temperature and permeation-time data gathered in the TPP and SD experiments with model compounds and mixtures provided valuable information on the permeation regimes, the adsorption processes taking place and the overall quality of the membranes.