Absorption of carbon dioxide in mixtures of N-methyl-2-pyrrolidone and 2-amino-2-methyl-1-propanol

It has been suggested that non-aqueous solvents containing amines may provide alternatives to aqueous alkanolamine solvents due to the potentially lower energy requirement for the regeneration of the amine. This paper presents experimental data on the solubility of CO₂ and heat of absorption in the organic solvent N-methyl-2-pyrrolidone (NMP) and mixtures of 2-amino-2-methyl-1-propanol (AMP) in NMP. The solubility of CO₂ was found to be very low at temperatures above 70 °C, the temperature at which the AMP/NMP solvent can be regenerated. The solubility of CO₂ was higher at lower temperatures, particularly when precipitation of the AMP carbamate occurred. The heat of absorption in the AMP/NMP solvent decreased with increasing temperature, from approximately 90 kJ/mol CO₂ at 40 °C and low loadings, to approximately 40 kJ/mol CO₂ and 65 kJ/mol CO₂, at 88 °C and low loadings, for the 15 wt% and 25 wt% AMP in NMP solvents, respectively. The results obtained complement our previous studies, together providing comprehensive data on the vapor–liquid equilibrium and the heat of absorption of CO₂, which can be used to model the system.