Silver-Based Deep Eutectic Solvents as Separation Media: Supported Liquid Membranes for Facilitated Olefin Transport

Supported liquid membranes (SLMs) nave exhibited great potential as interesting materials for the separation of olefin/paraffin mixtures. To further improve the performance of SLMs, novel and sustainable silver-based deep eutectic solvents (DESs) constructed from trifluoromethanesulfonate (AgCF3SO3) and acetamide (CH3CONH2) were synthesized as membrane liquids for the first time. Their formation mechanism and structure were investigated intensively, confirming that multiple coordination and hydrogen-bonding interactions yielded homogeneous and stable liquids that contained free silver ions and silver-containing cationic complexes as carriers for the facilitated transport of C2H4. The as prepared DES-SLMs were characterized by SEM and ATR-FTIR and their separation performances were investigated by C2H4/C2H6 separation experiments. The effects of the composition of the silver-based DESs, the operating temperature, and the transmembrane pressure were also investigated systemically. The permeability selectivity, solubility selectivity, and diffusivity selectivity were also quantitatively analyzed. Compared with previously reported results, the as-prepared DES-SLMs exhibited excellent permeabilities of C2H4 and comparable selectivities of C2H4/C2H6, thus exceeding the upper bound. This investigation might provide alternatives for the development of high-performance SLMs for olefin/paraffin separations and insights into the formation mechanism of silver-based DESs for further design and strengthening.