Thermodynamic study of systems {CO2-AMINE-WATER} for CO2 capture processes

OraleThe carbon dioxide released in the atmosphere is the principal cause of the so-called greenhouse effect, leading to global warming. According to the Kyoto protocol the emission of greenhouse and acid gases, resulting from the combustion of fossil fuels, or present as constituents of natural gas, must be reduced. Different national and international research projects have emerged and the present work is a thermodynamic study carried out in the frame work of the ANR CapCO2 (French National Research Agency) on the capture of CO2 in post-combustion processes. Our objective is to obtain reliable thermodynamic data for different amines in order to correlate the amine structure and the absorption properties. More specifically the enthalpies of solution and the solubilities of acid gases in aqueous solutions of selected amines are determined simultaneously to the solution density and the amine dissociation constants. The enthalpies of solution are directly measured by a calorimetric method at temperatures 323 K and 373 K and pressures up to 2 MPa. The solubilities are deduced from the analysis of the enthalpic data. A customized flow mixing unit adapted to the SETARAM C-80 calorimeter [1] was used to measure the enthalpy of solution of CO2 with aqueous solutions of amine. The experiments are carried out at constant temperature and pressure for different gas loadings up to the saturation of the solvent. The densities of the solutions are determined at 303.15 K and different pressures using a vibrating tube densimeter DMA 620 from Anton Paar. The dissociation constants are determined at atmospheric pressure and temperatures between 298 K and 333 K using an automatic titrator from Mettler-Toledo equipped with a glass electrode. The influence of the structure of the amine on the thermodynamic properties will be discussed simultaneously to the intensive parameters. The compilation of all the data will be used to develop and optimize rigorous thermodynamic models. References [1] H. Arcis, L. Rodier, J.-Y. Coxam, J. Chem. Thermodyn. 39 (2007), 878-887