Thermodynamic Study of ternary systems {CO2-AMINE-WATER} at temperature up to 353 K and pressure up to 2 MPa.
Résumé
The carbon dioxide released in the atmosphere is the supposed 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 combustion, 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 aabsorption properties against to theand amine structure. 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. This work is the continuation and the extension of a study concerning more classical alkanolamines in aqueous solutions [1]. The eEnthalpies of solution are directly measured by a calorimetric method at temperatures 323 K and 373 K and pressures up to 2 MPa. The sSolubilities are deduced from the analysis of the enthalpic data. A customized flow mixing unit adapted to the SETARAM C-80 calorimeter [2] is used to measure the enthalpy of solution of CO2 with aqueous solutions of amine. EThe experiments are carried out at constant temperature and pressure for different gas loadings up to the saturation of the solvent. The densities of the sSolutions densities are determined at 303.15 K and different pressures using a vibrating tube densimeter DMA 620 from Anton Paar. The dDissociation 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 chosen amines are: 3-dimethylamino-1-propanol (DiMAP), morpholine, and 1,2 bis (2-aminoethoxy)ethane (DiAEOE). All the amines are studied in aqueous solutions at the molar concentration of 2.5 mol.L-1. These solutes are respectively a primary amine, a secondary cyclic amine and a primary diamine. The influence of the structure of the amine structure on the thermodynamic properties will be discussed simultaneously to the intensive parameters. The compilation of all the data will used to develop and optimize rigorous thermodynamic models.