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Ether-functionalized ionic liquid based composite membranes for carbon dioxide separation

Deng, Jing, Bai, Lu, Zeng, Shaojuan, Zhang, Xiangping, Nie, Yi, Deng, Liyuan, Zhang, Suojiang
RSC advances 2016 v.6 no.51 pp. 45184-45192
asymmetric membranes, carbon dioxide, cellulose acetate, gases, greenhouse gas emissions, ionic liquids, mechanical properties, methane, nitrogen, permeability, polymers
The efficient separation of CO₂ from other light gases has received growing attentions due to its importance in reducing greenhouse gas emissions and applications in gas purification. In this work, we developed a series of composite membranes composed of ether-functionalized pyridinium-based ionic liquids ([EₙPy][NTf₂]) and cellulose acetate (CA) polymer matrices to improve CO₂ separation performance. CA + [EₙPy][NTf₂] and CA + [CₙPy][NTf₂] composite membranes were fabricated by a casting method. The CO₂, N₂ and CH₄ permeabilities of the CA + IL composite membranes were measured, and the CO₂/N₂ and CO₂/CH₄ permselectivities were further calculated. The results showed that the CA + 40 wt% [E₁Py][NTf₂] composite membrane exhibits approximately a seven-fold increase in CO₂ permeability with CO₂/N₂ and CO₂/CH₄ permselectivities of 32 and 24, respectively. The characterization results showed that the mechanical properties and thermal stabilities of the CA + [E₁Py][NTf₂] composite membranes are affected by both plasticizing effect and affinity of the ILs for the gases, which also lead to the changes in the CO₂/N₂ and CO₂/CH₄ permselectivities. Compared with membranes containing the non-functionalized analogues [CₙPy][NTf₂], the addition of [EₙPy][NTf₂] improves the ideal permselectivities of CA + IL composite membranes, whereas it decreases slightly the gas permeabilities.