Novel Protic Ionic Liquid Composite Membranes with Fast and Selective Gas Transport Nanochannels for Ethylene/Ethane...

Protic ionic liquids (PILs) were utilized for the fabrication of composite membranes containing silver salt as the C₂H₄ transport carrier to perform C₂H₄/C₂H₆ separation for the first time. The intrinsic nanostructures of PILs were adopted to construct fast and selective C₂H₄ transport nanochannels. The investigation of structure-performance relationships of composite membranes suggested that transport nanochannels (polar domains of PILs) could be tuned by the sizes of cations, which greatly manipulated activity of the carrier and determined the separation performances of membranes. The role of different carriers in the facilitated transport was studied, which revealed that the PILs were good solvents for dissolution and activation of the carrier due to their hydrogen bond networks and waterlike properties. The operating conditions of separation process were investigated systemically and optimized, confirming C₂H₄/C₂H₆ selectivity was enhanced with the increase of silver salt concentration, the flow rate of sweep gas, and the feed ratio of C₂H₄ to C₂H₆, as well as the decrease of the transmembrane pressure and operating temperature. Furthermore, the composite membranes exhibited long-term stability and obtained very competitive separation performances compared with other results. In summary, PIL composite membranes, which possess good long-term stability, high C₂H₄/C₂H₆ selectivity, and excellent C₂H₄ permeability, may have a good perspective in industrial C₂H₄/C₂H₆ separation.