2020-019 – High-pressure Operable Supported Ionic Liquid Membrane Achieved by the Ionic Liquid Nanocapillary Effect in Surface Nanopore Structures

Background Supportedliquid membranes provide the possibility of both high selectivity and high fluxbecause liquids have lower viscosities (and higher gas diffusivities) thanpolymers and the liquids can be designed to have high solubility selectivity. Asubset of supported liquid membranes is supported ionic liquid membranes(SILMs). These are particularly interesting because many ionic liquids (ILs)have negligible vapor pressure, allowing extreme constancy; i.e., the liquidwill not evaporate into the gas phase. Many ILs also have high thermalstability, with operability at temperatures of 200-400° C; however, there areno commercially available liquid support membranes that can withstand thosetemperatures. Current supports allow the liquid to be blown out if there is anexcursion in the transmembrane pressure or if the membrane needs to be operatedat a high transmembrane pressure. Inaddition, one of the major limitations has been the absence of a support thatis extremely thin, which is necessary for high flux. Of course, the supportalso needs to be mechanically robust, which is inconsistent with an extremelythin support. For polymer membranes, this problem is solved by the synthesis ofasymmetric membranes, which have a thick, highly porous superstructure and athin dense layer on one side that provides the permeability selectivity. We arenot aware of any equivalent supports for SILMs. Technology Description Researchersat the University of New Mexico and the University of Texas at Austin havedeveloped the materials and method to permeate and separate gases with anextremely thin supported ionic liquid membrane (SILM). The SILM can withstandhigh transmembrane pressures and operate at high temperatures. By addingnanostructures to an inorganic support, the transmembrane operating pressurerange was extended to 18 bar without liquid blow-out. More importantly,depending on the applied transmembrane pressure, the effective SILM thicknesscan be controlled, resulting in mere micron thicknesses. This ultra-thin liquidat high operating pressure showed high gas flux through the membrane withoutseparation functionality loss. The SILM can be operated at temperatures up tothe decomposition temperature of the ionic liquid (in some cases up to 400 °C)without any degradation in performance. Gregg Banninger GBanninger@innovations.unm.edu 505-272-7908