New Pyridinium Type Poly(Ionic Liquids) as Membranes for CO(2) Separation

New pyridinium based PILs have been prepared by modification of their precursors based on high molecular weight aromatic polyethers bearing main chain pyridine units. The proposed methodology involves the conversion of the precursors to their ionic analogues via N-methylation reaction, followed by anion exchange methathesis reaction to result in PILs with the desirable anions (tetrafluoroborate and bis(trifluoromethylsulfonyl)imide). These PILs show excellent thermal stability, excellent mechanical properties, and most importantly can form very thin, free standing films with minimum thickness of 3 μm. As expected, the PIL containing the TFSI(−) anion showed improved CO(2) and CH(4) permeabilities compared to its analogue containing the BF(4)(−). PIL-IL composites membranes have also been prepared using the same PIL and different percentages of pyridinium based IL where it was shown that the membrane with the highest IL weight percentage (45 wt %) showed the highest CO(2) permeability (11.8 Barrer) and a high CO(2)/CH(4) ideal selectivity of 35 at room temperature.