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.