Mixed water vapor/gas transport through the rubbery polymer PEBAX^® 1074

This work investigates the transport behavior of a hydrophilic, highly permeable type of poly ethylene oxide (PEO)-based block copolymer (PEBAX^® 1074) as membrane material for the removal of water vapor from light gases. Water vapor sorption isotherms in PEBAX^® 1074 represent Flory-Huggins type of sorption and the highly hydrophilic nature of the block copolymer results in high amounts of absorbed water (up to 0.4 g of water per gram of dry polymer at 20 °C). When taking into account the swelling of the polymer due to water vapor sorption, the Fickian diffusion coefficient increases over the full activity range and changes over two orders of magnitude. As determined from measurements with binary gas mixtures, the water vapor permeability increases exponentially with increasing water vapor activity whereas the nitrogen permeability slightly decreases with increasing water vapor activity. Consequently, the water over nitrogen selectivity increases with increasing water vapor activity. The results not only show the high potential of hydrophilic PEO-based block copolymers for dehydration purposes (e.g. the dehydration of flue gases, natural gas dew pointing or the humidification of air). Because of the high interaction of CO₂ with the polar ether linkages in PEO-based block copolymers, these polymers also offer attractive routes to the integration of dehydration and CO₂ capture using membrane technology.