Modeling CO2 absorption in aqueous monoethanolamine with ePC-SAFT

We examine whether one explicit-ion electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) formulation with carbamate chemistry can represent the equilibrium, caloric and density properties of loaded aqueous monoethanolamine (MEA). After separate water, CO2–water and dielectric fits, sixteen parameters are fitted jointly to pressure, species, integral absorption heat, density, heat capacity and binary equilibrium data. For nominal 30 wt% MEA, one parameter set thus represents CO2 pressure, the amine and carbamate fractions, integral heat at 313.15K and loaded density through 353.15K. Pressure average absolute relative deviations are 11.86 % over 47 fitted observations at 313.00–333.15K and 20.55 % over 159 observations at 313.00–393.15K, including 112 not fitted but examined during model development. The shared subset of 94 fitted species fractions gives 7.10 % at 293.15–333.15K. The fitted integral-heat root-mean-square error is 1.84 kJmol−1 CO2; the average absolute relative density deviation is 0.18 % over 47 fitted loaded densities, calculated without volume translation, with 44 within twice the assigned scale and three accepted misses at 353.15K. The 159-pressure deviation lies within the range of pressure deviations reported for related MEA models, which use different data sets and fitting roles. A fit with wider bounds on the protonated-amine diameter and its water interaction matches the properties similarly but predicts a second liquid phase at some states; narrowing these bounds removes the detected instabilities in a finite search at 162 states between 313.15 and 393.15K, with a 0.45 % higher fitting cost. Carbonate shares, titration bicarbonate, the 0.51MPaArcis integral heats, loaded densities above 353.15K and the unloaded heat capacity at 318.15K remain discrepant, and pressure deviations reach 29.5 and 56.0 % at 15 and 45 wt% MEA. The available comparisons do not yet establish suitability across absorber and stripper temperatures.