Modelling the fluid phase behaviour of aqueous mixtures of multifunctional alkanolamines and carbon dioxide using transferable parameters with the SAFT-VR approach

Among the many applications that alkanolamines find in industry, carbon dioxide (CO2) capture from large stationary sources is becoming the most relevant. Aqueous mixtures of amines and CO2 exhibit complex behaviour, characterized by extensive hydrogen bonding and other types of chemical reactions. An implicit treatment of the key reactions via appropriate association schemes has been shown to provide a promising physical basis for the modelling of these systems. Here, we introduce association models for use with SAFT-VR for some of the more promising multifunctional alkanolamines in the context of CO2 capture: monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), diethanolamine (DEA) and methyldiethanolamine (MDEA), and their mixtures with H2O and CO2. A revised model of the MEA+H2O+CO2 mixture is presented with an extension to high temperature. Excellent predictive capabilities are demonstrated for pure components and binary aqueous mixtures. A good overall description is also obtained for the ternary aqueous mixtures of alkanolamines and CO2, particulary for DEA and MDEA. Furthermore, the degree of speciation is successfully predicted for the MEA+H2O+CO2 mixture. Since only a limited number of parameters need to be estimated from vapour-liquid equilibrium data, the ternary SAFT-VR reaction-implicit models developed in this work offer a useful initial assessment of the different solvents and blends.