CO2 absorption into aqueous potassium salts of lysine and proline: Density, viscosity and solubility of CO2

Amino acid salts have potential use as alternative absorbents to alkanolamines for post combustion CO 2 capture, because of their negligible volatility, resistance to oxidative degradation and fast absorption rates. In this work, the density and viscosity of CO 2 -free and CO 2 -loaded aqueous solutions of potassium lysinate (LysK) and potassium prolinate (ProK) were measured at temperatures from (298.15 to 348.15)   K and for their concentrations from (0.2 to 3.0)   mol   L −1 . The data were correlated accurately ( R 2   ≥   0.99) as a function of temperature, concentration and CO 2 loading by nonlinear regression analysis. The solubility of CO 2 in 2.5   mol   L −1 amino acid salt solutions was also determined in vapor–liquid equilibrium vessels at temperatures (313 and 333)   K and CO 2 partial pressures relevant to flue gas conditions. It was found that, the CO 2 absorption capacity of LysK is higher than that of industrially used monoethanolamine (MEA) and the CO 2 loadings vary as LysK   >   ProK   >   MEA at given CO 2 partial pressures. Moreover, LysK may offer higher cyclic loading than MEA for CO 2 capture.