Highly Selective CO2/CH4 Membranes Based on Ethanolamine Ionic Liquids

In the pursuit of advanced carbon capture methods, ionic liquid (IL)-based membranes have emerged as promising materials for CO2 separation due to their high permeation and selectivity. This research focuses on the development of composite membranes with highly CO2 selective ethanolamine-based ionic liquids and poly(vinyl alcohol) (PVA). ILs and membranes were characterized by water content, FT-IR, H-1, and C-13 NMR. The addition of ethanolamine-based ILs and stream humidification promoted an outstanding increase of PVA membranes' CO2 permeability and CO2/CH4 selectivity of 53x and 36x, respectively. Effects of transmembrane pressure (1.0 to 3.0 barg), temperature (313.15 to 343.15 K), and CO2:CH4 ratio (10 to 40%) were studied. Effects of IL's cations and alkyl chain length (anion) on CO2 separation performance were studied via the production of PVA membranes with seven ethanolamine-based ILs. CO2 permeabilities up to 209 barrer and selectivities up to 241 were obtained. The comparison of these membranes with some of the most promising materials in the literature indicates that the ethanolamine-based ILs + PVA membranes have moderate CO2 permeabilities, associated with outstanding CO2/CH4 selectivities.