Abstract: Ionic liquid have shown preferential solubility for CO₂, more and more attentions have been paid to CO₂ separation with supported ionic liquid membranes (SILMs). In this paper, three conventional imidazolium-based ionic liquids containing different anions, [bmim][BF₄], [bmim][PF₆] and [bmim][Tf₂N], were used as membrane liquids for CO₂/CH₄ separation. The performances of these SILMs were studied and discussed. The supported liquid membrane with [bmim][Tf₂N] showed the highest permeability of CO₂ for this ionic liquid has the best solubility to CO₂ and rather low viscosity. And the effect of the alkyl chain length of imidazole ring on the performance of SILMs was also investigated. With the increase of alkyl chain length, the CO₂ permeability and ideal selectivity of CO₂/CH₄ decrease. A new task-specific ionic liquids (TSIL) which has two CO₂-philic groups, amino and carboxyl group ([bmim][β-Ala]) was synthesized and the corresponding ionic liquid supported membrane was made. FT-IR spectra of [bmim][β-Ala]-PVDF before and after CO₂ permeation test showed that the chemical reaction occurred between NH₂ and CO₂, generating a new carboxyl groups, which made CO₂ difficult to desorb on the downstream side of SILMs. Therefore the SILMs with [bmim][β-Ala] showed very low CO₂ permeability.

Key words: ionic liquid, supported liquid membrane, CO₂

摘要： 由于离子液体对CO₂具有较好的溶解选择性，离子液体支撑液膜分离CO₂越来越受到关注。比较了含3种不同阴离子的常规离子液体([bmim][BF₄]、[bmim][PF₆]、[bmim][Tf₂N])作为支撑液膜的液膜相分离CO₂/CH₄的性能，考察了咪唑环上烷基链长对离子液体支撑液膜性能的影响。考虑向离子液体中引入胺基和羧基等亲CO₂基团，制备了1-丁基-3-甲基咪唑丙氨酸离子液体([bmim][β-Ala])，考察了 [bmim][β-Ala]支撑液膜分离CO₂/CH₄的性能，并对在CO₂渗透测试前后的支撑液膜进行了FT-IR分析，发现氨基酸离子液体中的—NH₂和CO₂的较强作用以及该离子液体的高黏性影响了CO₂的透过性，使[Bmim][β-Ala]支撑液膜的CO₂透过率低。

关键词: 离子液体, 支撑液膜, CO₂