Correlation and Prediction of Solubility of CO2 in Amine Aqueous Solutions

The solubility of CO2 in the primary, secondary, tertiary and sterically hindered amine aqueous solutions at various conditions was studied. In the present work, the Modified Kent-Eisenberg (M-KE), the Extended Debye-Huckel (E-DH) and the Pitzer models were employed to study the solubility of CO2 in amine aqueous solutions. Two explicit equations are presented to evaluate the concentration of H+ as well as the equilibrium constants of protonation reactions for the tertiary and sterically hindered amine aqueous solutions. Using the M-KE model, the equilibrium constants of protonation reactions of amines were correlated in terms of temperature, CO2 partial pressure and amine concentration. Also the E-DH and Pitzer models were used to correlate the solubility of CO2 in MDEA aqueous solution. The binary interaction parameters for the models studied in this work as well as the parameters for the equilibrium constants of protonation reactions were obtained using the Davidon-Fletcher-Powell (DFP) minimization method. The results show that the M-KE, E-DH and the Pitzer models can accurately predict the corresponding experimental data. Although the solubility data for CO2 in amine aqueous solutions have been reported in the literature to a large extent, accurate data are required to model the CO2 absorption process. Therefore, two criteria for the tertiary and sterically hindered amines were presented using the M-KE model to screen the experimental data.