CO2/H2 separation through poly(ionic liquid)-ionic liquid membranes: The effect of multicomponent gas mixtures, temperature and gas feed pressure

This work presents mixed gas separation performance through PIL-IL membranes bearing pyrrolidinium-based PILs with [NTf2](-) and [C(CN)(3)](-) anions and different weight percentages of the corresponding ILs using a ternary mixture of H-2, CO2 and N-2 and different feed pressures ranging from 1 to 4 bar and temperatures from 20 to 80 degrees C. COSMO-RS was successfully used to understand the separation behavior of the PIL-IL composites for the H-2 + CO2 + N-2 mixture. The effect of temperature between 20 degrees C and 80 degrees C and feed pressure between 1 bar and 4 bar was also studied and is here discussed. The increased of the mixed H-2, CO2 and N-2 permeabilities with increasing temperature was shown to be due to dominant role of gas solubility at low temperature, and diffusivity at high temperature. The small pronounced differences between mixed and ideal CO2/H-2 permselectivities through the prepared PIL-IL composites indicated that membrane separation efficiency can be maintained, despite the competition effect between gases in mixed gas experiments. Depending on the operating conditions, the best mixed separation performance was obtained for PIL C(CN)(3)-60 [C(2)mim] [C(CN)(3)], with a CO2 permeability of 324.7 Barrer and a CO2/H-2 permselectivity of 11.4. The great potential of the studied PIL-IL membranes for biohydrogen separation is here clearly evidenced, since they revealed mixed CO2/H-2 separation performances above the Robeson upper bound even at the highest temperature and feed pressure tested.

Automated summary

This study demonstrates the mixed gas separation performance of PIL-IL membranes using different weight percentages of ILs, showing increased permeabilities with temperature and minimal differences in permselectivities between mixed and ideal gas mixtures. The PIL-IL membranes exhibit great potential for biohydrogen separation, surpassing the Robeson upper bound for CO2/H-2 separation even under high temperature and pressure conditions.