Abstract
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•Preparation of highly selective Betaine based Deep Eutectic Solvent.•Simultaneous CO2 permeability and selectivity exhibited by DES based liquid membrane.•Membranes showed excellent thermal stability relevant to desired applications.
This study demonstrates a new strategy in which deep eutectic solvents (DES), a new class of sustainable organic solvents, were impregnated into micro porous polymer support for separation of CO2 from CH4. Three different types of DESs were prepared by mixing and subsequent heating of betaine as hydrogen bond acceptor (HBA) in combination with either glycerol (G), ethylene glycol (EG) or urea (U) as hydrogen bond donors (HBD) in 1:3 stoichiometric mole ratio. The Fourier transform infrared (FTIR) spectroscopy was performed to confirm the formation of DESs. The gas permeation results showed that permeability of CO2 increased from 31.23 to 35.67 Barrer on substitution of HBD from glycerol to urea. The selectivity of CO2/CH4 increased from 43.32 to 57.53 for the substitution of HBD from ethylene glycol to urea. These intriguing results are ascribed by the high interaction of CO2 with DES in which solubility of CO2 is directly influenced by the HBDs. The membranes were also tested under conditions relevant to industrial feed gas and the results were compared with the competing state of the art membranes. The impregnation of DESs into the porous polymer supports provides a pathway for future material design for the efficient separation of CO2 from gases mixtures.