Amine functionalized supported ionic liquid membranes (SILMs) for CO 2 / N 2 separation

Supported ionic liquid membranes (SILMs), containing aprotic N -heterocyclic anion ionic liquids (AHA ILs) in an inorganic inert support, exhibit CO 2 /N 2 permselectivity values as high as 640 at 35.0 degrees C and 0.03 bar CO 2 , which represents conditions similar to post -combustion carbon capture (PCCC) from a natural gas power plant. A Fickian model fit to the experimental data estimates CO 2 permeability at direct air capture (DAC) conditions of 10,400 barrer and a CO 2 /N 2 permselectivity of 4000 for the best performing IL, triethyl(octyl)phosphonium 4-bromopyrazolide ([P 2228 ][4-BrPyra]). The most important criterion for high selectivity is a large equilibrium constant for binding between the IL and CO 2 , which results in high CO 2 solubility. ILs with smaller molar volumes and with no fluoroalkyl chains enhance N 2 rejection. Low viscosity and high IL molar density also enhance CO 2 /N 2 permselectivity and CO 2 permeance.