Solubility of CO2 in aqueous potassium l-prolinate solutions—absorber conditions

The solubility of CO2 in aqueous potassium salt of l-proline solutions has been measured in the temperature range of 285 and 323 K, for amino acid salt concentrations of 0.5, 1, 2 and 3 mol dm−3 and CO2 partial pressures relevant to flue gas conditions, and up to 70 kPa. Precipitation was encountered in the system when absorbing CO2 in 3 mol dm−3 potassium l-prolinate solution at 285 K. A beneficial effect of the solid formation on the overall CO2 solubility was observed. The vapor–liquid equilibrium data from the present work (for the non-precipitating regime) were interpreted by a concentration-based chemical equilibrium model. In spite of numerical simplicity of the model, a reasonable good description of the CO2–AAS–H2O systems could be observed. In the absence of literature data on equilibrium constant of the carbamate hydrolysis for l-prolinate, this parameter was calculated from the equilibrium CO2 solubility data. In addition, the enthalpy of absorption of CO2 in l-prolinate solutions was estimated using the solubility data, compared to that of monoethanolamine (MEA) and other common CO2 absorbents. Potassium salt of l-proline was found to be a promising candidate for CO2 capture.

► Solubility of CO2 in potassium l-prolinate solutions was measured at absorber conditions. ► Precipitation was encountered when absorbing CO2 in concentrated solutions at 285 K. ► The VLE data were interpreted by a concentration-based chemical equilibrium model. ► Potassium salt of l-proline was found to be a promising solvent for CO2 capture.