276862 Designing Reversible Ionic Liquids for CO2 Capture
Reversible ionic liquids (RevILs) have been developed as alternatives to traditionally cited CO2 capture solvents such as monoethanolamine (MEA). RevILs capture CO2 through chemical reaction of CO2 with an amine functionality to form an ionic liquid. The resulting ionic liquid is then capable of absorbing additional CO2 through physical absorption. Physical absorption is attractive because it has a relatively low energy penalty for reversal. RevILs also present additional energy advantages over MEA. Whereas MEA is used as a dilute aqueous solution, reversible ionic liquids are designed to be non-aqueous solvents, utilizing only the residual water present in the emission source. This strategy allows for significant energy savings by eliminating the need to heat large amounts of unused water during regeneration, improving the overall efficiency of the CO2 capture process.
The design of reversible ionic liquids has been an important focal point in our research group. Using structure-property relationships we have shown an ability to tune the relevant CO2 capture properties by altering the structure of the starting RevIL. Properties targeted include CO2 capture capacity, ionic liquid viscosity, temperature of CO2 release, temperature of RevIL evaporation, and the enthalpy of CO2 absorption. In example, we have observed that by varying the degree and length of alkyl chain branching in the RevIL, we can favorably affect CO2 capacity, ionic liquid viscosity, as well as the temperatures of CO2 release and RevIL evaporation. We have also examined several additional modifications to the structure of our RevILs and investigated their effects on CO2 capture properties. Our progress on developing these structure-property relationships to further the design of optimized solvents for CO2 capture will be discussed.