Density, Viscosity, pH, Heat of Absorption, and CO2 Loading Capacity of Methyldiethanolamine and Potassium Lysinate Blend Solutions

In this work, a new solvent, an aqueous blend of methyldiethanolamine (MDEA) and potassium lysinate (K-Lys) has been selected as an alternative solvent for CO2 removal. The solubility of CO2 in aqueous MDEA + K-Lys solution was reported in the form of CO2 loading capacity (mols CO2/mols MDEA + K-Lys) using a stirred batch reactor (SBR) at temperatures from 298.15 K to 328.15 K for CO2 partial pressures between 1 kPa and 25 kPa, and the results are compared with those of single MDEA and monoethanolamine (MEA) solutions. The four equilibrium constants including equilibrium constants of amino acid deprotonation and carbamate hydrolysis were correlated as a function of temperature and K-Lys concentration. A thermodynamic model, based on a modified Kent-Eisenberg model, was developed to predict the CO2 loading capacity of single and blend solutions. In addition, the density, viscosity, and pH of MDEA + K-Lys solutions were measured before and after CO2 absorption tests at different temperatures and concentrations. The absorption heat of CO2 in the bend solution was also calculated using the Gibbs−Helmholtz equation. The results revealed that the MDEA + K-Lys solution is a promising absorbent for postcombustion CO2 capture.