Synergy of high permeability, selectivity and good stability properties of silver-decorated deep eutectic solvent based facilitated transport membranes for efficient ethylene/ethane separation

For ethylene/ethane separation, fabrication of facilitated transport membranes (FTMs) with properties of high ethylene permeability, selectivity, long-term stability and economic feasibility remains a great challenge. In this study, a series of deep eutectic solvents (DESs) containing NO3- as anion were designed, synthesized and characterized for the first time. Then, novel DES-FTMs were fabricated successfully through the incorporation of the transport carrier (AgNO3) into as-synthesized DESs. The investigation of structure-performance relationships of FTMs suggested that the hydrogen bond acceptors (HBAs), hydrogen bond donors (HBDs) and their molar ratios greatly manipulated separation performance of FTM, which was also greatly affected by the carrier concentration. The right combinations of HBAs, HBDs and carrier concentration could significantly enhance the ethylene/ethane selectivity up to 125. The operating conditions of the separation process were optimized, confirming ethylene/ethane selectivity increased with the decrease of the transmembrane pressure and operating temperature. The synergetic regulation of hydrogen bond and coordination interactions between DES and carrier could tune the interactions between the silver cation and its counter anion, which efficiently promoted the disassociation of carrier and increased carrier activity, leading to high ethylene permeability and ethylene/ethane selectivity. The Bronsted acidic property of HBAs endowed the FTMs with good stability. The low cost and facile availability of the DESs and carrier rendered FTMs with good economic feasibility. This study may reveal the definite potentiality of DES-FTMs in ethylene/ethane separation.