Highly hydrophilic, rubbery membranes for CO2 capture and dehydration of flue gas

This paper reports the potential of highly hydrophilic, poly(ethylene oxide) based block copolymers for the simultaneous removal of CO2 and water vapor from a ternary gas simulating a flue gas in a post-combustion capture configuration. Water vapor sorption measurements show strong sorption of water vapor in these block copolymers especially above a water vapor activity of 0.6. Mixed water vapor/gas permeability measurements as a function of water vapor activity were performed using binary (H2O/CO2 and H2O/N2) and ternary (H2O/CO2/N2) feed mixtures. The water vapor permeability increased exponentially with the water vapor activity whereas the gas permeability in all cases slightly decreased. As the effect of the presence of water vapor was relatively stronger on the N2 permeability, the CO2/N2 selectivity increased slightly with increasing water vapor activity. No noticeable differences between the pure gas (from binary mixtures) and the mixed gas (from ternary mixtures) membrane performance have been observed. This indicates that plasticization effects, due to the sorption of CO2, are not significant at the low feed pressure (2.5 bar) used. Also, increasing water content did not cause plasticization. Overall, the block copolymers studied in this work combine a high CO2 permeability with a reasonable CO2/N2 gas selectivity. Due to their highly hydrophilic character, they also have the ability to simultaneously remove CO2 and water vapor from flue gases, which makes these PEO-ran-PPO based block copolymers an attractive membrane material for post-combustion CO2 capture applications.