title: Role of LiBF4 in Ionic Liquid Membranes for Facilitated CO2 Transport.
abstract: The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4)/LiBF4 electrolyte was prepared for highly selective facilitated CO2 transport membranes. When LiBF4 was incorporated into BMIM BF4, synergy effects by free Li+ ion and imidazolium cations is expected to enhance the separation performance for CO2/N2 and CO2/CH4. The free state of BF4- ions in BMIM BF4/LiBF4 solutions was investigated by FT-Raman spectroscopy. For the coordination of LiBF4 with BMIMBF4, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) was utilized. Electrolyte membranes consisting of BMIM BF4 and LiBF4 showed selectivities of 8.40 and 8.25 for CO2/N2 and CO2/CH4, respectively. Neat BMIM BF4 membrane showed selectivities of 5.0 and 4.8, respectively. Enhanced separation performance was attributed to increased free Li+ and abundant free imidazolium cations.
authors.forename: Yeji
authors.initials: Y
authors.lastname: Choi
authors.forename: Gil Hwan
authors.initials: GH
authors.lastname: Hong
authors.forename: Sang Wook
authors.initials: SW
authors.lastname: Kang
mesh_terms: D001881:Borates / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D052578:Ionic Liquids; D018020:Lithium Compounds / Q000737:chemistry*
chemical_list: D001881:Borates; D052578:Ionic Liquids; D018020:Lithium Compounds; D002245:Carbon Dioxide; C021051:lithium borate; D005459:Fluorides