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

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, N-2 and CH4 permeabilities of the CA + IL composite membranes were measured, and the CO2/N-2 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/N-2 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/N-2 and CO2/CH4 permselectivities. Compared with membranes containing the nonfunctionalized analogues [CnPy][NTf2], the addition of [EnPy][NTf2] improves the ideal permselectivities of CA + IL composite membranes, whereas it decreases slightly the gas permeabilities.