Experimental dissociation constants of amines at temperature up to 343 K
Résumé
This work is part of a general study on the dissolution of carbon dioxide in aqueous solutions of amines. In order to reduce the cost of CO2 capture in industrial post combustion effluents, researches are carried out on new amines that could be used instead of classical alkanolamines, such as the monoethanolamine (MEA), in amine washing process. The chemical dissolution of carbon dioxide in aqueous solutions of amines can be represented as a combination of elementary reactions including water dissociation, carbon dioxide dissociation, amine protonation and carbamate formation. All this reactions have to be characterized separately in order to develop rigorous models representative of the CO2 dissolution. Among these elementary reactions, it has been shown that the amine protonation represents the major contribution to the enthalpy of solution Hs. This enthalpy can be derived from theoretical models (1,2) describing gas-liquid equilibria. This work was carried out on the determination of enthalpy of amine protonation from dissociation constant Ka of protonated amine. For this purpose it is necessary to have accurate data of dissociation constants Ka as function of temperature. The literature data is still scarce and experimental determinations of Ka are necessary. Potentiometric and calorimetric techniques used in our laboratory to measure dissociation constants of protonated amine will be presented, together with examples of experimental data. The measurements reported were obtained at temperature up to 343 K. References [1] Arcis, H., Rodier, L., Ballerat-Busserolles, K., Coxam, J.-Y. J. Chem. Thermodynamics. 41, 783-789 (2009) [2] Kim, I., Hoff, K.A., Hessen, E.T., Haug-Warberg, T., Svendsen, H.F. Chem. Eng. Sci. 64, 2027-2038 (2009)