Mesure des enthalpies de solution du CO2 dans les solutions aqueuses d'alcanolamines primaires aux très faibles taux de charge

National audienceLa détermination des enthalpies de solution des gaz, en particulier CO 2 et H 2 S, dans les solutions aqueuses d'alcanolamines a permis d'obtenir de nombreuses données pour alimenter les modèles thermodynamiques et améliorer les procédés de captage de ces gaz dans les fumées industrielles. Cependant le dispositif utilisé jusqu'alors ne permettait pas d'obtenir des résultats fiables pour les faibles taux de charge en gaz ( inférieur à 0.2). Les chaleurs de solution de CO 2 dans les solutions aqueuses d'amine ont été obtenues en utilisant un calorimeter BT2.15 de type calvet de la société SETARAM. Les cellules utilisées pour réaliser le mélange sont des cellules à écoulement développées au laboratoire. Lors de la mesure, les deux fluides, respectivement le gaz et la solution aqueuse, sont injectés dans la cellule de mélange à l'aide de deux pompes seringues haute pression (ISCO), à température et à pression constantes. L'enthalpie de solution est obtenue à partir de la différence entre le flux thermique mesuré par les thermopiles lors du mélange et celui obtenu lorsque la solution aqueuse circule dans le calorimètre sans CO 2. En faisant varier le débit des pompes, il est possible de déterminer l'enthalpie pour différents taux de charge en CO 2 (, en mol CO 2 / mol Amine). Cependant, les débits respectifs de gaz et de liquide qui doivent être utilisés pour mesurer l'enthalpie de solution pour des taux de charge inférieurs à 0.2 sont extrêmement différents et le débit de liquide trop important pour pouvoir réaliser la mesure. Afin de réduire cette différence entre les débits, nous remplacé le CO 2 pur par des mélanges de gaz (CO 2-N 2) de composition connue. L'azote n'étant pas soluble dans la solution aqueuse d'amine, l'effet thermique obtenu lors du mélange est alors directement lié à l'enthalpie de dissolution du CO 2. L'azote est alors considéré comme un gaz de dilution du CO 2. Un exemple est présenté ici pour les systèmes aqueux contenant de la monoéthanolamine (MEA) ou de l'aminométhylpropanol (AMP), ou un mélange des deux amines. Les résultats obtenus sont en très bon accord avec ceux obtenus pour les mesures avec du CO2 pur

Assessment of health claims in the field of bone: a view of the Group for the Respect of Ethics and Excellence in Science (GREES)

Health claims for food products in Europe are permitted if the nutrient has been shown to have a beneficial nutritional or physiological effect. This paper defines health claims related to bone health and provides guidelines for the design and the methodology of clinical studies to support claims

Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1‑n‑Fluoro-alkyl-3-methylimidazolium Bis(n‑fluoroalkylsulfonyl)amide Ionic Liquids

International audienceThe effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis(perfluoroalkylsulfonyl)amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298–343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]), 1-octyl-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8mim][BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8H4F13mim][NTf2]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8H4F13mim][BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids

Calorimetric methods for key properties in refrigeration cycles.

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Thermodynamic Modeling and Experimental Study of CO 2 Dissolution in New Absorbents for Post-Combustion CO 2 Capture Processes

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Flow calorimetry: a technique for caracterisation of liquid-liquid and liquid-gas systems

International audienceThe laboratory develops projects on acid gas mitigation by capture and storage of carbon dioxide in post combustion industrial effluents. The systems investigated are complex and involve molecular and ionic species in solution and liquid-liquid or vapor-liquid phase equilibria. Then it is of interest to collect consistent experimental data to optimize parameters of theoretical models. In open literature, experimental data mainly concern phase equilibrium and solubility limits as function of temperature, pressure and phase compositions. The determination of energetic properties is more challenging and literature data become scarce. However, they are necessary for understanding chemical mechanisms (ARCIS). Our laboratory develops several calorimetric techniques for the determination of enthalpy of mixing. The description and principles of the techniques are illustrated by examples of applications in the domain of CO2 capture by dissolution in aqueous solutions of amines. The heat of gas dissolution is determined in dynamic mode (Mathonat Arcis MEA) using customized mixing flow unit adapted to Setaram heat conduction differential calorimeters (C80 or BT215). In order to represent the mechanism of chemical dissolution (Simond) the technique was adapted for the measurement of amine protonation constant. Recently it was used to investigate the gas dissolution in demixing amines of interest for breakthrough capture processes (Raynal). The particularity of such amines is a liquid-liquid phase separation in aqueous solution as function of temperature and CO2 gas loading. Such phase separation can be observed when determining excess enthalpies of binary {water + amine} mixtures. The presentation will report different examples in this field and will emphasis the limitations and difficulties associated to measurements at super ambient conditions. REFERENCES [1] Arcis, H.; Rodier, L.; Coxam, J.-Y. J. Chem. Thermodyn. 2007, 39, 878-887

Thermodynamic study of a phase-change solvent: New experimental data and modelling

International audienceThe 2,4,6-tris(dimethylaminomethyl)phenol shows a partial miscibility with water. The temperatures of liquid–liquid phase separation were experimentaly determined to establish the phase diagram. The specific heat capacities and densities of aqueous solutions of 2,4,6-tris(dimethylaminomethyl)phenol were measured to determine excess heat capacities and excess molar volume. Experiments have been carried out for temperatures range from 288 K to 338 K, at atmospheric pressure. The NRTL model was used to correlate liquid–liquid equilibria and, the UNIQUAC model to correlate heat capacities and predict excess molar enthalpies. The excess molar volumes were fitted to a Redlich–Kister polynomial

Calorimetric studies for development of CO2 Capture and Storage (CCS) processes

National audienceCarbon dioxide (CO 2) is a major anthropogenic greenhouse responsible of global warning and Intergovernmental Panel on Climate Change (IPCC) has encouraged nations to reduce emissions resulting from industry. The CO 2 Capture and Storage option proposed to reach this objective (Raynal, Bouillon et al. 2011) consists in a selective separation from industrial effluent followed by storage in secured sites. Our laboratory is particularly invested in CO 2 capture processes based on selective absorption in aqueous solution of amines (Arcis, Rodier et al. 2009) and storage process by dissolution in deep saline aquifers(Koschel, Coxam et al. 2006). The development of the industrial processes needs a thermodynamic characterization of systems composed of CO 2 , water, amine and electrolytes. The objectives of research studies are to predict gas absorption or dissolution properties, in order to design absorbent for CO 2 capture or to test capacity and safety of storage sites. Thermodynamic models representative of gas absorption or dissolution are currently used to describe chemical and physical mechanisms involved in gas capture or storage. Rigorous developments require adjustment of interaction parameters, in order to take into account system non-ideality. Acquisition of experimental data is necessary to adjust such semi-empirical parameters in classical models and, because of a lack of enthalpy data, most of the models are adjusted to fit solubility data (Arcis, Ballerat-Busserolles et al. 2012). They correctly represent vapor liquid equilibrium but usually fail to predict energetic properties. Our laboratory use specific calorimetric techniques to measure heat of mixing and determine enthalpy of absorption, enthalpy of solution or excess enthalpy. These properties represent severe test for the thermodynamic models, in terms of consistency and ability to predict accurate data used in process development. This presentation will focus on both theoretical and experimental tools implemented for the thermodynamic representation of CO 2 capture and storage