SOLUBILITY OF CARBON-DIOXIDE IN AQUEOUS MIXTURES OF ALKANOLAMINES

The solubility Of CO2 in water + N-methyldiethanolamine + monoethanolamine (MDEA + MEA) and water + N-methyldiethanolamine + diethanolamine (MDEA + DEA) are reported at two compositions of 3.4 M MDEA + 0.8 M MEA or DEA and 2.1 M MDEA + 2.1 M MFA or DEA at temperatures from 70 to 180-degrees-C and CO2 Partial pressures from 100 to 3850 kPa. The solubility of CO2 in the blends decreased with an increase in temperature but increased with an increase in CO2 Partial pressure. At low partial pressures of CO2 and the same total amine concentration, the equilibrium CO2 loadings were in the order MDEA + MEA > MDEA + DEA > MDEA. However, at high CO2 Partial pressures, the equilibrium CO2 loading in the MDEA solutions were higher than those of the MDEA + MEA and MDEA + DEA blends of equal molar strengths due to the stoichiometric loading limitations of MEA and DEA. The nonadditivity of the equilibrium loadings for single amine systems highlights the need for independent measurements on amine blends.