| Summary: | Understanding the effects of water vapour on gas permeation and separation properties of zeolite membranes especially at lower temperatures is important for the applications of these zeolite membranes for gas separations involving water vapour. Zeolite membranes have high potential for the purification of natural gas, biogas and syn-gas to produce the pipe-line gas and often those gases contain moisture. The separation of gases via zeolite is quite complex, particularly in the presence of water vapour in the feed stream. The increase of the fluxes of other gaseous components has been reported in some articles while the decrease is reported in the others. As well, both increase and decrease of selectivity are reported. Despite many works conducted during the past 15 years the details on the effect of the water vapour remain unknown. In this paper attempts are made to summarize the results of the experimental investigations with an emphasis on five types of zeolites, e.g. ZSM (MFI), DDR (deca-dodecasil 3R), SAPO-34 (silicoaluminophosphate), FAU (fauzasite) and 4A zeolite. As well, interpretation of the experimental observations is attempted based on a simple transport mechanism
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