LIQUID-LIQUID EQUILIBRIUMS IN AQUEOUS SOLUTIONS OF DEMIXING AMINES : from visual techniques to calorimetric determinations

International audienceThe chemical absorption of carbon dioxide (CO2) in alkaline solvents (typically aqueous solution of amines) is considered as a promising avenue for CO2 capture from post-combustion industrial effluents. The DACOOTA project, supported simultaneously by the French National Agency of Research (ANR) and the Natural Sciences and Engineering Research Council of Canada (NSERC), concerns the understanding of a new class of amines for CCS, namely the demixing amines. These amines show a liquid-liquid phase separation at moderately elevated temperatures. Such a phase separation will concentrate carbon in the water rich phase. Then only this part of the solvent will be heated in the regeneration step of the separation process. The presentation will focus on the phase separations occurring in {water + substituted piperidine} systems. The phase diagrams (T,x) are usually obtained from classical visual methods. This work will show how calorimetric techniques can be interestingly used to determine phase diagrams. The first technique for LLE determination presented will be differential scanning calorimetry. This method allows to determine simultaneously the specific heat capacity of the solution, and the temperature of phase separation. For this purpose we used microcalorimeters (Setaram microDSC III and SC) based on Calvet principle, from 253 K to 393 K. The second technique presented here allows measurements of excess molar enthalpies at constant temperature and pressure. C80 calorimeters from SETARAM, equipped with customized flow mixing cells are used to detect heat of mixing. Compositions at LLE are obtained by analysis of the shape of the hE curves.The influence of the position of the substituted group on the temperatures of liquid-liquid phase separation will be analyzed