Improving CO2 separation performance of thin film composite hollow fiber with Pebax®1657/ionic liquid gel membranes

Blending CO2-selective ionic liquid with block copolymers have been shown to improve the gas separation performance. In this work, defect-free Pebax (R) 1657/[emim][BF4] gel membranes were fabricated in the form of thin film composite hollow-fiber membranes to meet the mechanical stability and high packing density requirement for industrial application. Environmentally benign solvent comprising ethanol/water mixture (70/30 w/w) was selected to allow up to 80 wt% IL loading with 300% improvement in CO2 permeability and CO2/N-2 and CO2/CH4 selectivities of 36 and 15, respectively. Characterizations of membrane morphological change responding to the IL loading indicated that the preferential interaction between IL and PEO segments was by hydrogen bonding that resulted in decrease in polymer crystallinity, but this interaction inhibited potential interaction with CO2, which lowered the gas permeability below the estimated value. Examinations on the effects of various operating conditions on the TFC gel membranes showed excellent mechanical durability and chemical stability of the membranes and good CO2 separation performance with mixed-gas feed containing traces of water vapor and NOx, suggesting the potential application for CO2 capture with real gas feed. The stability of the high IL-loaded gel membranes with up to 8 bar feed pressure also opens up possibility for other industrial gas applications.