Parametric investigation of chemical equilibrium in mixed aqueous amine systems for CO₂ capture processes: impact of amine protonation and reaction enthalpies on CO₂ absorption capacity, cyclic capacity, and absorption enthalpies

Formulated aqueous amine solvents incorporating two or more individual amines into a single blended solvent are often suggested as alternative options to mono-amine solvents employed for CO₂ capture processes. Using software developed in Matlab and existing knowledge of chemical equilibria, investigations into the fundamental properties of formulated amine solvents and their interaction with CO₂ have been carried out. A simple solvent formulation containing equimolar amounts of monoethanolamine (MEA), Amine 1, and a sterically hindered /tertiary amine, Amine 2, has been investigated here. Specifically, the role of Amine 2 in the overall equilibrium behaviour of amine blends is discussed. Systematic variations of the protonation constants and reaction enthalpies of Amine 2 over a range of typical values has revealed that significant improvement can be made in terms of absorption capacity, cyclic capacity, and overall absorption enthalpy in the blends when compared to the standard 5.0 M MEA solvent.