Solubility measurements of carbon dioxide and nitrous oxide in an aqueous mixture of 2-dimethylaminoethanol and N-methyl-1,3-propanediamine

Abstract

Aqueous monoethanolamine (MEA) is a mature post-combustion CO2 capture technology, but it faces significant drawbacks including corrosivity, high regeneration energy (∼4 GJ/t-CO2), and reactivity with contaminants. This study investigates an aqueous blend of 2-Dimethylaminoethanol (DMAE, 30% wt.) and N-Methyl-1,3-propanediamine (MAPA, 10% wt.) as an alternative solvent to capture CO2. Given the scarcity of Vapour-Liquid Equilibrium (VLE) data for such amine blends, this research aims to expand the thermodynamic understanding of this specific aqueous DMAE + MAPA system. We thoroughly investigate its VLE with CO2 and N2O across temperatures between (313.15–393.15) K. The physical solubility of CO2 was determined using the N2O/CO2 analogy. N2O solubility measurements were conducted in a monobloc equilibrium cell from 1 to 5 MPa. The expanded relative uncertainty of the N2O solubility, expressed in molality, was estimated to be 0.8% (k = 2). Henry's constants were derived using Krichevsky-Ilinskaya analysis and CO2 solubility was determined using a static-isochoric Van Ness-type apparatus over 313.15–363.15 K and up to 7 MPa with a relative uncertainty of ur(αexp) = (0.3–5) %. Finally, speciation profiles and the heat of CO2 absorption were predicted using established thermodynamic models optimized for this system.