Equilibrium solubility of carbon dioxide in aqueous potassium l-asparaginate and potassium l-glutaminate solutions

• Due to their unique advantages, aqueous amino acid salts solutions are considered as the promising absorbents for CO2 capture.
• CO2 solubility in aqueous potassium salt solutions of l-asparaginate and l-glutaminate were measured.
• The CO2 partial pressures studied were up to 950 kPa.
• The temperatures studied were (313.2, 333.2, 353.2) K.
• The CO2 absorption capacity of aqueous amino acid salt systems was high and comparable with monoethanolamine.

Aqueous amino acid salt solutions are promising alternatives to aqueous alkanolamine absorbents for CO2 capture. In this study, the absorption of CO2 in two amino acid salt systems: aqueous potassium l-asparaginate (KAsn) and aqueous potassium l-glutaminate (KGln) were investigated. Using a vapor–liquid equilibrium apparatus, the solubility of CO2 in aqueous KAsn and KGln solutions were determined at temperatures 313.2, 333.2, and 353.2 K and pressures up to 950 kPa. The amino acid salt concentration in the solutions was varied from 8.5 to 34.0 wt% for KAsn and 9.2 to 36.8 wt% for KGln. The studied amino acid salt systems were found to have appreciable CO2 absorption capacities, which were comparable with those of commonly used alkanolamines. A modified Kent–Eisenberg model was applied to correlate CO2 solubility (expressed as mole CO2 per mole amine) in the solution with CO2 partial pressure, temperature, and amino acid salt concentration. The model satisfactorily predicted the equilibrium data. The obtained average absolute deviations between the experimental and the calculated values of equilibrium CO2 partial pressures were 12.8% and 10.3%, for aqueous KAsn and KGln systems, respectively.