Using Structure-Property Relationships to Develop Reversible Ionic Liquids for CO2 Capture

The capture and sequestration of CO₂ from flue gas streams is essential to mitigating the levels of CO₂ in the atmosphere that contribute to global warming. Non-aqueous silylamine solvents were designed at a molecular level to obtain specific physical properties in order to achieve effective CO₂ capture. These relatively non-polar solvents, upon selective reaction with CO₂, reversibly form ionic liquids. These reversible ionic liquids can capture additional CO₂ through physical absorption owing to high CO₂ solubility in the ionic liquid state. The reaction is equilibrium governed allowing for reversibility and control over the extent of reaction with CO₂. CO₂ is released upon moderate heating of the reversible ionic liquid or by sparging with an inert gas. The effects of changes in structure on (1) the CO₂ capture capacity, (2) the viscosity of the solvent systems at partial and total conversion to the ionic liquid state, (3) the temperature of solvent regeneration and (4) the temperature of solvent evaporation are reported.