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

• Density and viscosity of CO2-free and CO2-loaded aqueous LysK and ProK were measured.
• Empirical correlations as a function of T, C and α were developed.
• LysK has higher CO2 absorption capacity and cyclic loading than MEA.
• VLE data for 2.5 M LysK and ProK were determined at 313 K and 333 K.
• LysK was proposed as a novel candidate absorbent for CO2 absorption.

Amino acid salts have potential use as alternative absorbents to alkanolamines for post combustion CO2 capture, because of their negligible volatility, resistance to oxidative degradation and fast absorption rates. In this work, the density and viscosity of CO2-free and CO2-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 (R2 ≥ 0.99) as a function of temperature, concentration and CO2 loading by nonlinear regression analysis. The solubility of CO2 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 CO2 partial pressures relevant to flue gas conditions. It was found that, the CO2 absorption capacity of LysK is higher than that of industrially used monoethanolamine (MEA) and the CO2 loadings vary as LysK > ProK > MEA at given CO2 partial pressures. Moreover, LysK may offer higher cyclic loading than MEA for CO2 capture.