Non-dispersive solvent absorption of post-combustion CO2 in membrane contactors using ionic liquids

Abstract

Post-combustion carbon-capturing (PCC) is one of the technologies that has been expanded in recent years, to control greenhouse gas emissions. This work aims to explore the potential applications of polymeric hydrophobic membranes and green ionic liquids (ILs). Experiments were conducted on lab-scale flat sheet (FS) membrane contactors (MCs) where CO2 was captured from a continuous feed mixture (CO2 + N2) with a recirculated-based aqueous solution of IL at a constant temperature of 298 K and with no pressure driving force. The effects of contact angle, liquid entry pressure (LEP), initial CO2 concentration, and type of solvents and membrane material on the CO2 capture efficiency and membrane wetting in the PCC process have been experimentally investigated and evaluated. Polytetrafluoroethylene (PTFE) has shown the most hydrophobic property with 6–17O loss in the contact angle. Furthermore, 1-Methyl-3-octyl-imidazolium-tetrafluoroborate ([OMIM][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF6]) have exhibited only 5–8 % loss in LEP using PTFE membrane support. The CO2 capture efficiency has been achieved as 80.8–99.8 % in different combinations of ILs and membrane support keeping all other variables constant. While increasing CO2 concentration from 15 to 45 % vol., an increase of nearly three folds in the CO2 mass transfer flux was observed. Combination of [OMIM][BF4] and PTFE membrane witnessed good long-term stability with only 20 % loss in CO2 capture efficiency in 480 min of continuous operation.