For 5.0, 20.5, 50.0, and 75.0 mass % methyldiethanolamine (MDEA) aqueous solutions, solubilities of CO2 were measured at 323.15, 348.15, and 373.15 K, respectively. Isothermal absorption capacities of CO2 as a function of MDEA concentration are presented. Lastly, the absorption enthalpy of CO2 in 50.0 mass % MDEA solution was calculated to be 54 kJ·mol-1 CO2.

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Reaction rate constants of aqueous 2-amino-2-methyl-1-propanol (AMP)/ammonia (NH3) solutions with carbon dioxide (CO2) were determined by measuring their absorption rates. The CO2 absorption characteristics of an NH3 solution added to AMP were investigated using a stirred-cell reactor. The CO2 absorption rates into aqueous blended amine solutions were measured at different pressures (p A = 5, 10, and 15 kPa) and temperatures (293, 303, 313, and 323 K). Additive concentrations of 1, 3, and 5 wt % NH3 were added for each 30 wt % AMP solution. The results showed that the addition of NH3 to AMP significantly increased the CO2 absorption rates of AMP by 144%. In addition, the reaction rate constant for a blend of AMP and NH3 with CO2 as a function of temperature was 1.6- to 2.4-fold higher than that of AMP without NH3. The reaction rate constants were k 2,AMP = 1.543 × 107 exp(−3019.92/T) and k 2,NH3 = 1.847 × 1010 exp(−4954.25/T).

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