Tunable Reversible Ionic Liquids for CO2 Capture

Regulation of CO₂ emissions is likely in the near future.  The technology for CO₂ capture from large point-source CO₂ generators, such as coal-fired power plants, needs to be developed before CO₂ emission regulation is mandated.  Effective CO₂ capture systems must produce pure CO₂ streams without becoming an overly parasitic burden to the energy production process.  Monoethanol amine (MEA) and other aqueous-based systems have a record of high CO₂ capture capacities but also high regenerative energies resulting in an increased parasitic load to the plant.  Our research uses tunable reversible ionic liquids (RevILs) as the CO₂ capture system.  Here, we maintain the benefit of high CO₂ capture capacities through chemisorptions of CO₂ without the water excesses resulting in the possibility of a less parasitic regeneration of the absorption system.

The RevILs that will be discussed here are one-component silylamines.  Before CO₂ capture they are silylamine molecular liquids.  Upon reaction with CO₂, the ionic form of the silylamine is produced reversibly. The silyl group was incorporated with a reactive primary amine to form the RevILs with reduced viscosities. The structure of these silylamines can be tuned to examine and ultimately enhance the desired properties of the absorption system.  The impact of these structure modifications on the properties of the silylamines have been studied with two objectives in mind.  The first objective is to establish an understanding of what the structural modifications do to the overall behavior of the RevILs, including CO₂ capture capacity, energy of regeneration and viscosity.  Once these structure-property relationships are developed, the second objective is to use these structure-property relationships to design a commercially viable RevIL system.  Additional factors that are considered in this second objective include ease of synthesis of the silylamine and stability of the silylamine during CO₂ capture and release cycling.  Promising RevILs identified will be compared to conventional CO₂ capture systems.