Thin Ionic Liquid Film Deposition within Porous Substrates

Technology development has widened in scope to focus beyond creating better products to also considering sustainability. As this shift has occurred, ionic liquids (ILs) have received greater interest for a wide variety of applications, as ILs have the ability to replace hazardous materials that emit volatile organic compounds. Ionic liquids are essentially liquid nonvolatile salts with unique chemical and physical properties such as tunable solubility, negligible vapor pressure, thermal stability, and variability. In fact, it has been estimated that there are 1018 possible ionic liquids, and a tremendous amount of highly successful research has gone into developing ILs for a huge number of separations. 

For commercially practical separation technologies, ILs typically function as solvents. Although this approach is viable, the high cost of ILs and their unique characteristics lend themselves better to application as transport media in membranes. Membranes, the next generation of gas separation devices, have the advantages of relatively simple process control and favorable energetics, but these advantages come at the cost of increased demands on materials. However, using ILs in membrane functions is challenging, as supported ionic liquid membranes (SILMs) are difficult to produce in thin, stable membrane layers. 

NETL inventors have solved this problem by creating a method for depositing thin liquid layers within the pores of a thick porous substrate. The method creates the equivalent for a commercially viable asymmetric membrane, but with a liquid, rather than a solid, active layer. In doing so, the new technique makes many classes of supported liquid membranes, including SILMs, practical for gas separations, lowering the cost of gas separation while maintaining effectiveness.