Interest of calorimetry to study carbon dioxide dissolution in aqueous solutions of amines
Résumé
The reduction of emissions of greenhouse gases is an option to fight against the global warning phenomenon. It concerns mainly the anthropogenic emissions of carbon dioxide CO2, resulting from fossil fuels combustion. This can be realized by CO2 capture in industrial effluents with a process, initially developed to remove acid gases from natural gas, consisting in CO2 separation by dissolution in aqueous solution of amine. The reaction of dissolution is reversible but the solvent regeneration represents actually an important economic cost in the treatment of post combustion effluents (1). The energy required for desorption of CO2 is related to the enthalpy of CO2 dissolution. The development of thermodynamic models to represent the gas-liquid equilibrium is then of interest in designing CO2 capture process. However the system {CO2 - H2O - Amine} is complex, because of the chemical reactions involved in gas dissolution. It has been particularly shown (2,3) that the development of rigorous model supposed to precisely know the equilibrium constant of the different chemical reactions. This work presents the interest of direct measurement of enthalpy of solution of carbon dioxide in aqueous solutions of amines. The enthalpy of solution can be derived from thermodynamic model. The enthalpy appears as a combination of different contribution terms related to the physical dissolution and the chemical reactions. Different amines(4-5) were investigated and experimental enthalpy data were used to test the ability of the model to predict enthalpy of solution. It appears that a good agreement between experimental and calculated enthalpies mainly depends on the precision on the contribution term attributed to the protonation of the amine. In case of primary and secondary amines, the results show difficulties to take into account the carbamate formation for which equilibrium constant is rarely available in literature. Then in addition to direct measurement of enthalpy of solution the calorimetric technique can also be used to study separately different contribution terms. References [1] Lecomte, F., Broutin, P., Lebas, E.: CO2 capture, Technologies to reduce greenhouse gas emissions. TECHNIP ed., Paris (2010) [2] Arcis, H., Rodier, L., Ballerat-Busserolles, K., Coxam, J.-Y. J. Chem. Thermodynamics. 41, 783-789 (2009) [3] Kim, I., Hoff, K.A., Hessen, E.T., Haug-Warberg, T., Svendsen, H.F. Chem. Eng. Sci. 64, 2027-2038 (2009) [4] H. Arcis, L. Rodier, K. Ballerat-Busserolles, J-Y Coxam, J. Chem. Thermodyn.,(2008) 40, 1022-1029. [5] Arcis, H., Rodier, L., Ballerat-Busserolles, K., Coxam, J.-Y. J. Chem. Thermodynamics. 41, 836-841 (2009)