Flow calorimetry: a technique for caracterisation of liquid-liquid and liquid-gas systems
Résumé
The laboratory develops projects on acid gas mitigation by capture and storage of carbon dioxide in post combustion industrial effluents. The systems investigated are complex and involve molecular and ionic species in solution and liquid-liquid or vapor-liquid phase equilibria. Then it is of interest to collect consistent experimental data to optimize parameters of theoretical models. In open literature, experimental data mainly concern phase equilibrium and solubility limits as function of temperature, pressure and phase compositions. The determination of energetic properties is more challenging and literature data become scarce. However, they are necessary for understanding chemical mechanisms (ARCIS). Our laboratory develops several calorimetric techniques for the determination of enthalpy of mixing. The description and principles of the techniques are illustrated by examples of applications in the domain of CO2 capture by dissolution in aqueous solutions of amines. The heat of gas dissolution is determined in dynamic mode (Mathonat Arcis MEA) using customized mixing flow unit adapted to Setaram heat conduction differential calorimeters (C80 or BT215). In order to represent the mechanism of chemical dissolution (Simond) the technique was adapted for the measurement of amine protonation constant. Recently it was used to investigate the gas dissolution in demixing amines of interest for breakthrough capture processes (Raynal). The particularity of such amines is a liquid-liquid phase separation in aqueous solution as function of temperature and CO2 gas loading. Such phase separation can be observed when determining excess enthalpies of binary {water + amine} mixtures. The presentation will report different examples in this field and will emphasis the limitations and difficulties associated to measurements at super ambient conditions. REFERENCES [1] Arcis, H.; Rodier, L.; Coxam, J.-Y. J. Chem. Thermodyn. 2007, 39, 878-887.