Room temperature ionic liqulids (RTILs) are useful materials for generating supported ionic liquid membranes (SILM) due to their selectivity for acid gases e.g. CO2 and H2S, low vapor pressure as well as ‘green’ nature. RTILs are reported to have higher mass transport coefficients than traditional membranes generated from a variety of polymeric matrices, thus, leading to higher permeabilities and diffusivities. A number of studies have reported on SILM for separation of CO2/CH4, CO2/N2, olefin/ paraffin, etc. However, this prominent attribute suffers from IL clusters’ fragile nature within the polymeric membranes, thus, leading to their leaching from surface and reduction in performance. An alternative is to polymerize the RTILs either as homopolymers or copolymers. Poly (ionic liquids) (PRTIL) have been demonstrated to possess higher CO2 adsorption capacities than the respective monomers.
Separation ability was not reduced at the partial CO2 operating pressures of 207 kPa. Another work investigated the effect of polymerized and ‘free’ RTIL percentage on a composite gel membrane for CO2 separation . Polymerization percentage had different effects on CO2 permeability depending on the RTIL content of the composite membrane. Highest permeability was obtained with RTIL content of 75% (free). Other works have investigated polymerized RTIL/liquid RTIL composite membranes for CO2 separation. A maximum selectivity of 24.9 was reported for CO2 from a mixture with CH4. Such membranes had been extremely selective for CO2 in CO2/CH4 mixtures in previous works as well.
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