Insight into CO2 capture by aqueous solutions of N,N-diethylethanolamine promoted with potassium salts of amino acids

Abstract

N,N-Diethylethanolamine (DEEA) is a potential high-capacity CO₂-capturing solvent. The CO₂ reactivity of DEEA can be improved by the addition of rate promoters. Both equilibrium CO₂ solubility and desorption rate are also influenced by promoters. In this work, the effect of promotion of DEEA with three amino acid salts, potassium arginate (PA), potassium prolinate (PP), and potassium glycinate (PG), was investigated. In a stirred cell reactor, CO₂ reactivity of the promoted solutions was studied at 303 K. Rate promotion with PA was most effective; this was then followed by PP and PG. The value of the liquid-side mass transfer coefficient (0.005 cm/s) for CO₂ absorption in water inside the stirred cell was found. Equilibrium CO₂ solubility in the promoted mixtures was measured. Empirical equations that predicted solubility data (accuracy 99%) were proposed. Desorption trials were performed at 363 K. PA, PP, and PG lowered sensible energy constraint by 59%, 32%, and 30%. PA was most-suited for faster desorption of aqueous solutions of DEEA. Overall, potassium salts of arginine, proline, and glycine were promising candidates for improving the performance of the tertiary amine DEEA. Finally, catalytic desorption of loaded solutions of DEEA was studied and it was found that alumina was a promising catalyst for faster desorption.