Excess Molar Enthalpies for Various {Amine + Water} Systems as Function of Temperature and Pressure - Experimental Measurements and Correlations Using Redlich-Kister and Dortmund Modified UNIFAC Models
Résumé
Carbon dioxide, released in the atmosphere is considerate as responsible of the so-called greenhouse effect, leading to global warming. Our research programs are concerned with CO2 capture by dissolution in absorbent solutions. This project is part of a French research program ACACIA on minimization of the economical cost of CO2 treatment. In order to design future process units, it is of interest to develop thermodynamic models representative of gas-absorbent systems. The work is the continuation and the extension of studies carried on the enthalpies of solution of CO2 in aqueous amines solutions [1,2,3]. The main purpose of this work is a characterization of the binary systems amine + water. Excess enthalpies for various amines are presented as function of temperature and pressure. The measurements are performed using a flow mixing unit developed in the laboratory and adapted to a BT2.15 Setaram calorimeter. Excess enthalpies are correlated as a function of mole fractions using the Redlich-Kister equation. The performance of Dortmund modified UNIversal Functional groups Activity Coefficient model is also tested. The first amines presented are classical alkanol-amines, namely monoethanol amine (MEA) and methyldiethanolamine (MDEA), used to validate our experimental technique. Then, more specific amines, leading to phase separation in aqueous solution when increasing temperature, are studied : N-methyl piperidine and 2-methyl piperidine that exhibit in water lower critical solution temperatures about 320 K.