Water vapour separation from permanent gases by a zeolite-4A membrane

The permeation of H2O vapour, CO, H2, and CH4 and their binary mixtures through a thin zeolite-4A membrane has been investigated. The zeolite-4A membrane synthesized with pre-treatment of the supporting TiO2 with UV-photons exhibits a high permeance property and maintains a high selectivity for water. The permeance of the water vapour in the binary mixtures is almost the same as its unary permeance and only weakly temperature-dependent. The permeances of the gaseous components are strongly suppressed by water, resulting in high selectivities for water removal in the presence of these gases. This is ascribed to the high adsorption affinity and capacity of water inside the zeolite-4A cages, preventing the bypassing of the second component through the membrane. The temperature dependence of the unary permeation is interpreted in terms of the activation energy for diffusion and the heat of adsorption in zeolite-4A. Pre-treatment of the zeolite-4A membrane at a high temperature in the absence of water vapour may lead to membrane cracks.