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

Abstract

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.