270616 Reversible Ionic Liquids for CO2 Capture: A Thermodynamic Study
We have developed reversible ionic liquids (RevILs) for CO2 capture that are capable of dual mode absorption: chemical and physical. Chemical absorption takes place when the silylamine-based solvents chemically react with CO2 forming an ammonium-carbamate ion pair (RevIL). Physical absorption is then observed due to the solubility of CO2 in the RevIL. The chemically and physically absorbed CO2 may be released by heating the CO2-swollen RevIL to temperatures below 100°C.
CO2 capture with reversible ionic liquids is governed by the thermodynamics of the process. The reaction equilibrium constant, K, of the silylamine and CO2 dictates the extent of reaction at capture conditions and reversal temperatures. The additional CO2 that is captured through physical absorption is determined by the solubility of the CO2 in the RevIL (Henry’s constant). During regeneration (release of CO2) the RevIL is heated to the reversal temperature. The energy required to complete the reversal is structure-specific and depends on the heat capacity of the RevIL, the regeneration temperature and the enthalpy of reaction.
We have identified structural changes that may be made to the RevIL to increase CO2 capture capacity and reduce the energy required for reversal.