The partial pressures of carbon dioxide (CO2) over a 30 mass % aqueous solution of monoethanolamine (MEA) and a 50 mass % aqueous solution of methyldiethanolamine (MDEA) were measured. The range of partial pressures of CO2 measured at 120 °C over 30 mass % MEA was from (7 to 192) kPa with loadings from (0.16 to 0.42). The partial pressures of CO2 ranging from (66 to 813) kPa with loadings from (0.17 to 0.81) over 50 mass % MDEA were also measured at the temperatures (55, 70, and 85) °C. An approximate value of the enthalpy of solution of CO2 in the aqueous MDEA solution was estimated using the solubility data.

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This work focuses on the experimental determination and thermodynamic modeling of the solubility of carbon dioxide (CO2) in an aqueous solution of 30 mass % 2-((2-aminoethyl)amino)ethanol (AEEA), with AEEA being a potentially new solvent for postcombustion CO2 capture by absorption. The vapor−liquid equilibrium (VLE) experiments were performed over a range of temperatures from 40 to 120 °C and for partial pressures of CO2 ranging from 0.01 to 220 kPa. The results obtained were then modeled by use of a modified Deshmukh−Mather thermodynamic model. The model provides a very good representation of the experimental data over the whole temperature range. In addition, 1H and 13C 1D NMR spectra were acquired for species identification and quantitative analysis of the major species distribution. The predicted speciation obtained from the model was also found to be in agreement with the speciation from the NMR data. Protonation constants (pK a) for AEEA were obtained by titration.

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In view of increased requirements on absorption rates and loading capacity for carbon dioxide (CO 2 ) absorption solvents, more research is directed toward alkanolamines having more than one amino group. In the present work, AEEA {2-((2-aminoethyl)amino)ethanol}, a diamine containing primary and secondary amino groups, is used to study the CO 2 absorption kinetics. The reaction kinetics between CO 2 and aqueous solutions of AEEA were measured over a range of temperatures from 32 to 49 °C with the concentrations of AEEA ranging between 1.19 and 3.46 kmol m -3 using a string of discs contactor. All kinetic experiments were interpreted using the single-step-termolecular mechanism approach as proposed by Crooks and Donnellan (J. Chem. Soc., Perkin Trans. 2 1989, 331) and reviewed by da Silva and Svendsen (Ind. Eng. Chem. Res. 2004, 43, 3413).