Thermodynamic analysis of carbamate formation and carbon dioxide absorption in N-methylaminoethanol solution

Protonation and carbamate formation are critical reactions for CO₂ capture using amine-based absorbents which impact both CO₂ absorption and amine regeneration. In this regard, thermodynamic analysis towards CO₂ absorption in N-methylaminoethanol solution is carried out with specific attention to the corresponding protonation and carbamate formation reactions. The CO₂ absorption mechanism is investigated with the acquisition of reaction equilibrium constant and heat of reaction. CO₂ absorption performance of N-methylaminoethanol solution was evaluated in terms of CO₂ loading and solution pH. A thermodynamic model was then developed to mathematically describe the investigated system and make prediction on equilibrium CO₂ solubility, species profiles, and absorption/regeneration heat. Results show that the average relative deviation of equilibrium CO₂ solubility calculated from the is 4.2%. The predictive species profile and CO₂ absorption heat of N-methylaminoethanol solution indicates less energy cost to desorb CO₂. This is in line with the relative unstable N-methylaminoethanol carbamate formation and consequential conversion to (bi)carbonate. The position of N-methylaminoethanol as a potential absorbent in amine based carbon capture is shown in terms of chemical reaction constants, equilibrium CO₂ solubility, second order rate constant (k₂), and pKa.