Crosslinked PEG and PEBAX Membranes for Concurrent Permeation of Water and Carbon Dioxide.

Membrane technology can be used for both post combustion carbon dioxide capture and acidic gas sweetening and dehydration of natural gas. These processes are especially suited for polymeric membranes with polyether functionality, because of the high affinity of this species for both H₂O and CO₂. Here, both crosslinked polyethylene glycol diacrylate and a polyether-polyamide block copolymer (PEBAX 2533(©)) are studied for their ability to separate CO₂ from CH₄ and N₂ under single and mixed gas conditions, for both dry and wet feeds, as well as when 500 ppm H₂S is present. The solubility of gases within these polymers is shown to be better correlated with the Lennard Jones well depth than with critical temperature. Under dry mixed gas conditions, CO₂ permeability is reduced compared to the single gas measurement because of competitive sorption from CH₄ or N₂. However, selectivity for CO₂ is retained in both polymers. The presence of water in the feed is observed to swell the PEG membrane resulting in a significant increase in CO₂ permeability relative to the dry gas scenario. Importantly, the selectivity is again retained under wet feed gas conditions. The presence of H₂S is observed to only slightly reduce CO₂ permeability through both membranes.