Enthalpy of absorption of CO2 with alkanolamine solutions predicted from reaction equilibrium constants

Differential enthalpies of absorption of CO2 in aqueous solutions of 2-aminoethanol (MEA) and N-methyldiethanolamine were predicted from reaction equilibrium constants using the Gibbs–Helmholtz equation. Correlations for the reaction equilibrium constants and enthalpies of reaction found in the literature for each of the individual reactions taking place at CO2 absorption were compared to experimental data, and from this, a set of equations was selected for the Deshmukh–Mather model in this work. The carbamate dissociation constant for MEA was fitted to experimental PCO2PCO2 and ΔHabs data. Heat contributions from each of the individual reactions taking place in the systems MEA+H2O+CO2 and MDEA+H2O+CO2 were calculated and presented as functions of loading and temperature. Predicted enthalpies of absorption agree well with the data from literature and with experimental data from this work. The calculation procedure described in this work may be used for the adjustment of reaction equilibrium constants by fitting the equilibrium model also to experimentally measured heats of absorption data in addition to PCO2PCO2 data.