Binary and ternary VLE of the 2-(diethylamino)-ethanol (DEEA)/3-(methylamino)-propylamine (MAPA) water system

Abstract

A mixed 2-(diethylamino)-ethanol (DEEA) and 3-(methylamino)-propylamine (MAPA) system could be an attractive alternative solvent to improve the performance of CO2 capture for low partial pressure cases. This solvent has the advantages of forming two liquid phases upon CO2 loading, one rich in CO2 and the other very low in CO2. Having a highly concentrated rich solvent improvements could be reached by reducing the sensible heat and improving the equilibrium sensitivity hence reducing the need for stripping steam. Also it is possible that the heat of absorption may change to the better.

To better understand this system in designing the separation unit requires substantial work on characterization of the solvent. One important aspect is to provide equilibrium data. In this work new ebulliometric VLE data for the binary DEEA/H2O and DEEA/MAPA systems and the ternary DEEA/MAPA/H2O system are reported at different temperatures and concentrations. Results show that pure MAPA is more volatile than DEEA, but in aqueous solution MAPA was found to be less volatile. A mix of DEEA and MAPA in aqueous solution tends to lower the volatility thus makes the system more advantageous by reducing volatility. The activity coefficients for the species in the ternary aqueous system are found to be lower than the activity coefficients obtained from the corresponding binary aqueous mixtures.

The UNIQUAC framework was implemented to represent the experimental data. The six UNIQUAC parameters were determined and were able to predict P-T-x-y, activity coefficient, excess enthalpy and freezing point depression for both the binary and ternary systems. However, a small inconsistency was observed between water activity coefficients determined from ebulliometer and freezing point depression measurements.