(542f) 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.