Ionic Liquid Confined in Mesoporous Polymer Membrane with Improved Stability for CO(2)/N(2) Separation

Supported ionic liquid membranes (SILMs) have a promising prospect of application in flue gas separation, owing to its high permeability and selectivity of CO(2). However, existing SILMs have the disadvantage of poor stability due to the loss of ionic liquid from the large pores of the macroporous support. In this study, a novel SILM with high stability was developed by confining ionic liquid in a mesoporous polymer membrane. First, a mesoporous polymer membrane derived from a soluble, low-molecular-weight phenolic resin precursor was deposited on a porous Al(2)O(3) support, and then 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF(4)]) was immobilized inside mesopores of phenolic resin, forming the SILM under vacuum. Effects of trans-membrane pressure difference on the SILM separation performance were investigated by measuring the permeances of CO(2) and N(2). The SILM exhibits a high ideal CO(2)/N(2) selectivity of 40, and an actual selectivity of approximately 25 in a mixed gas (50% CO(2) and 50% N(2)) at a trans-membrane pressure difference of 2.5 bar. Compared to [emim][BF(4)] supported by polyethersulfone membrane with a pore size of around 0.45 μm, the [emim][BF(4)] confined in a mesoporous polymer membrane exhibits an improved stability, and its separation performance remained stable for 40 h under a trans-membrane pressure difference of 1.5 bar in a mixed gas before the measurement was intentionally stopped.