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International audience; NH4-dawsonite is a promising alternative precursor for the preparation of alumina catalyst supports. Since generally prepared by precipitation, a good knowledge of its thermodynamic properties and its solubility would allow a better control over its synthesis. However, only few research efforts have focused on this material aspect until now. We propose in this study to estimate the order of magnitude of the NH4-dawsonite Gibbs free energy at 25 °C by combining experimental solubility measurements and theoretical solubility calculations. The latter were performed within the pH range 3-14 and considering the predominant Al species Al 3+ , Al(OH) 3 0 and Al(OH) 4-. The NH4-dawsonite Gibbs free energy obtained with this method was-1564 ± 2 kJ.mol-1 .

In the framework of the cryogenic air separation, impurities such as CO2 and N2O may solidify at the reboiler-condenser placed between the two distillation columns.The formed solid could provide an additional strength to the heat and material transfers, and increase the pressure drops in the distillation columns.Furthermore, the presence of a solid phase can promote the accumulation of light hydrocarbons which may form flammable mixtures with liquid oxygen.Therefore, the presence of solid phases must be controlled see avoided within the cryogenic air distillation process.The main issue of this thesis is to develop a suitable model for representing solid phases and their equilibrium with the liquid and vapor phases at the operating conditions of the process, and to obtain full phase diagrams which would improve the knowledge of phase equilibria and the control of the risks associated to the presence of solid phases. Dans le cadre du procédé de séparation cryogénique des gaz de l'air (T< 100 K), impuretés telles que le CO2 et le N2O peuvent se solidifier au niveau de l'échangeur de chaleur placé entre les deux colonnes de distillation cryogénique.La formation du solide doit être évitée pour deux principales raisons:- au niveau opérationnel, le solide constitue une résistance supplémentaire aux transferts de chaleur et de matière, et augmente les chutes de pression dans les colonnes de distillation;- au niveau sécurité, la présence d'une phase solide peut également favoriser l'accumulation d'hydrocarbures légers qui forment avec l'oxygène liquide des mélanges potentiellement inflammables.Les conditions de formation thermodynamique de la phase solide doivent être parfaitement maitrisées dans le cadre de la distillation cryogénique. C'est pourquoi, il est indispensable de disposer d'une équation d'état adaptée qui permette de représenter les diagrammes de phases impliquant une phase solide dans les conditions opératoire du procédé.L'objectif principal de la thèse est de développer un modèle thermodynamique pour représenter les équilibres de phases solide – fluides. Ce travail nécessite de mettre au point des algorithmes de résolution des équilibres bi et triphasiques et de déterminer le meilleur jeu de paramètres du modèle en s'appuyant sur la disponibilité des données expérimentales dans les conditions cryogéniques.Le modèle permet d'améliorer la connaissance des équilibres et constitue un outil indispensable pour maîtriser les risques associés à la présence de phases solides pour le procédé de distillation cryogénique.

Networks of reactions inside the cell are constrained by the laws of mass and energy balance. Constrained-based modelling (CBM) is the most used method to describe the mass balance of metabolic network. The main key concepts in CBM are stoichiometric analysis such as elementary flux mode analysis or flux balance analysis. Some of these methods have focused on adding thermodynamics constraints to eliminate non-physical fluxes or inconsistencies in the metabolic system. Here, we review the main different approaches and how they tackle the different class of problems.

Mai 2004, qui a été le pionnier de l'étude des liens entre l'écologie, la thermodynamique et la théorie de l'information. La gentillesse personnelle de Ramon Margalef et sa façon stimulante et provocante d'enseigner et de discuter des questions d'écologie et de sciences naturelles ont été une grande source d'inspiration. Mayo de 2004, quien fue pionero en el estudio de los vínculos entre la ecología, la termodinámica y la teoría de la información. La amabilidad personal de Ramon Margalef y su forma estimulante y provocadora de enseñar y discutir temas de ecología y ciencias naturales han sido una gran fuente de inspiración. May 2004, who pioneered the study of the links between ecology, thermodynamics and information theory.The personal kindness of Ramon Margalef, and his stimulating and thought-provocative way of teaching and discussing issues in ecology and natural sciences have been a great source of inspiration. مايو 2004، الذي كان رائدًا في دراسة الروابط بين البيئة والديناميكا الحرارية ونظرية المعلومات. كان اللطف الشخصي لرامون مارغليف، وطريقته المحفزة والمحفزة للتفكير في تدريس ومناقشة القضايا في البيئة والعلوم الطبيعية مصدرًا كبيرًا للإلهام.

A set of models for estimating the enthalpy of formation, the entropy, the heat capacity and the volume of dehydrated phyllosilicates is presented. The model for entropy and heat capacity estimation is essentially based on a method of decomposition into polyhedral units, similar to that published by Holland (1989). The model for predicting the enthalpy of formation is based on the electronegativity scale, as previously developed by Vieillard (1994a, 1994b). For the sake of consistency, the models are parameterized using the same critical selection of thermodynamic properties from the literature. This includes a set of direct measurements especially dedicated to clay minerals that had not been taken into account in previous calculation methods. The accuracy of the predictions is tested for each property. The verification tests are also carried out for minerals that include different chemical elements than the phases used to derive the model constants, especially lithium-bearing micas. Verification tests also concern the Gibbs energy function that combines contributions from both models. Finally, the models are used in order to propose a complete thermodynamic database for clay mineral end-members. The consistency of the stability domains calculated on the basis of these thermodynamic properties is investigated by drawing relevant predominance diagrams for some chemical systems of interest. The models proposed represent a significant improvement with respect to previous works as regards the global accuracy of the estimates and because the developments were realized and tested using the same set of minerals, whose properties had been collected through a critical selection of the literature.

A new P-stabilized boryl radical [iPr2P(naph)BMes]• 2a was obtained by reduction of the corresponding phosphino-bromoborane 1a with Na(Hg). The persistent radical 2a has been characterized by EPR, and its structure has been thoroughly studied by DFT. The corresponding Gomberg-type dimer has been analyzed by NMR and XRD, and the Gibbs free energy associated with the dimerization process has been evaluated by VT EPR. The replacement of the Ph substituents at phosphorus for iPr groups has a slight but noticeable impact: it increases the spin density at boron and favors the radical over its Gomberg-type dimer. An original cross-coupling product between 2a and the trityl radical Ph3C• has also been authenticated crystallographically. The P-stabilized boryl radicals 2a,b are readily trapped by TEMPO to give the corresponding B–O adducts 3a,b (naphthyl-bridged phosphine-boranes without P → B interaction). The reaction of 2a,b with Ph3CCl substantiates their ability to participate in halogen transfer reactions.

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al0.975FeIII0.182FeII1.422Mg0.157Li0.035Mn0.002)(Si1.332Al0.668)O5(OH)4] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si2.633Al1.367)(Al1.116FeIII0.215Mg2.952FeII1.712Mn0.012Ca0.011)O10(OH)8]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738–4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature.

International audience