CO2 Capture by Water-Lean Amino Acid Salts: Absorption Performance and Mechanism

Water as a solvent remains the weakest point of CO2 capture systems using aqueous chemical absorbents due to large heat capacity and latent heat of water. Water-lean absorbents including low volatile solvent have been considered as potential use for CO2 capture in terms of reducing energy consumption. In this work, we have examined the capture performance of several water-lean amino acid salts. Ethylene glycol (EG) with high boiling point and low specific heat was used to replace water. The physical properties and the absorption and desorption rate of CO2 were determined and evaluated for potassium lysinate (LysK)/EG/water and potassium prolinate (ProK)/EG/water. Aqueous monoethanolamine (MEA), ProK, and LysK systems were used for comparison. The samples from the absorption test and continuous absorption desorption cycles were analyzed by NMR spectra to provide insight into the product species and the stability of absorbent. Absorption mechanisms and degradation species were also discussed as well as the main issues such as high viscosity of CO2-free/loaded absorbents and high desorption temperature related to these EG-based water-lean systems.