Dissertations / Theses on the topic 'Hydrogène – Solubilité'

Les surfaces métalliques sont au centre des mécanismes de fissuration par corrosion sous contrainte et de fatigue corrosion. Celles-ci s'avèrent être le lieu principal de l'initiation de l’endommagement des métaux, tout en faisant preuve d'une grande réactivité vis-à-vis de leur environnement. Agissant en portes d'entrée pour les solutés, comme l'hydrogène ou l'oxygène,vers le cœur de la matrice métallique, les surfaces jouent un rôle clé dans les processus de fragilisation par l'hydrogène (FPH). Afin d'identifier les états métallurgiques résistants à la FPH, une compréhension des interactions H-surface sous contrainte est nécessaire. En étudiant les mécanismes physiques élémentaires impliqués aux premiers stades de fatigue-corrosion, ces travaux de thèse visent à proposer un début d'évaluation de l'impact de l'apparition de défauts de surface dus à une sollicitation en fatigue(dislocations de surface, bandes de glissement, lacunes) sur la diffusivité locale apparente et solubilité de l'hydrogène près de la surface du nickel. La première étape de cette étude nécessite cependant d'identifier l'effet de l'orientation cristallographique des surfaces sur ces propriétés locales. Cette étude constitue la majorité de cette thèse. Pour cela, nous travaillons sur des surfaces monocristallines {100}, {110} et {111} du nickel non déformé en premier lieu, à la fois par approches numériques et expérimentales. Expérimentalement, un gradient de diffusion d'hydrogène est observé pour chaque orientation en chargeant des monocristaux de nickel en hydrogène avec une technique électrochimique pulsée. Contrairement aux techniques de perméation habituelles, cette technique potentiostatique en deux étapes permet de caractériser la mobilité de l'hydrogène à l'entrée de l'échantillon qui s’avère être le principal endroit de piégeage de l’hydrogène, et donc de fragilisation. Une corrélation entre les défauts émergents en surface et en subsurface (caractérisés par MO/AFM/TEM) et la diffusivité locale de l'hydrogène est ensuite discutée dans le cas de Ni{110}. En parallèle, des calculs à l'échelle atomique sont effectués (DFT + Phonons) afin de déterminer l'évolution des énergies libres de migration de l'hydrogène du voisinage des surfaces {100}, {110} et {111} vers le nickel massif. La solubilité locale de l'hydrogène est calculée et discutée en termes d'énergie d’origine élastique liée à la relaxation différenciée des atomes de surface pour les trois orientations. Une confrontation avec la théorie élastique met en évidence l'évolution des propriétés élastiques locales. Enfin, des calculs à plus grande échelle par potentiels empiriques (EAM) sont initiés pour étudier des systèmes plus complexes en ajoutant des défauts, tels que des marches de surface, amorçant l’analyse des interactions entre l'hydrogène et les défauts émergeant en surface lors d’une sollicitation en fatigue
Metallic surfaces are at the central place of stress corrosion cracking and corrosion fatigue mechanisms. These latter turn out to be the initiation site of materials damage, while exhibiting great reactivity to their environment. As they act as front doors for solutes, like hydrogen or oxygen, towards the bulk, surfaces play a key role in hydrogen embrittlement (HE) processes. In order to identify HE-tolerant metallurgical states, an understanding of H-surface interactions under stress is necessary. By investigating elementary physical mechanisms implied at the first stage of corrosion fatigue, this thesis work aims to propose a beginning in assessing the impact of the emergence of surface defects due fatigue stress (surface dislocations, slip bands, vacancies) on the apparent local diffusivity and solubility of hydrogen near the surface of nickel. The first step of this study requires however to identify the surfaces crystallographic orientation effect on these local properties, which is the raw material of this thesis. For this, we work on monocrystalline {100}, {110} and {111} surfaces of undeformed nickel at first sight, using both numerical and experimental approaches. Experimentally, a hydrogen diffusion gradient is observed for each orientation by charging nickel single crystals with a pulsed electrochemical technique. Conversely to usual permeation techniques, this double-step potentiostatic one enables the characterization of hydrogen mobility at the entrance side of the sample which was proven to be the main location for H-trapping and embrittlement. A correlation between emerging surface and subsurface defects (characterized by MO/AFM/TEM) according to the degree of cyclic deformation and the local hydrogen diffusivity is then discussed in case of Ni{110}. In parallel, calculations at the atomic scale are carried out (DFT + Phonons) in order to determine the evolution free energies of hydrogen migration from near the {100}, {110} and {111} surfaces towards the bulk. The local solubility of hydrogen is calculated and discussed in terms of lattice elastic distortion energy related to the differentiated relaxation of the surface atoms for the three orientations. A confrontation with elastic theory approach highlights the evolution of local elastic properties. Finally, bigger scales calculations through EAM are initiated to study more complex systems by adding defects, such as surface steps, giving a start for a reliable basis to interpret the interactions between hydrogen and part of the surface defects involved with a fatigue solicitation

La présence d’hydrogène en solution dans l’aluminium liquide entraîne la formation de porosités une fois celui-ci solidifié. C’est pourquoi il est important de bien mesurer la quantité de gaz dissous dans le métal. La méthode de Sieverts, utilisée par d’autres expérimentateurs dans le passé, montre certaines faiblesses et une nouvelle méthode plus fiable et versatile est proposée afin de valider les résultats obtenus précédemment. Après plusieurs tests et améliorations au montage et à la méthodologie, des résultats prometteurs ont été obtenus. En fait, un phénomène attribuable à la dissolution de l’hydrogène dans l’aluminium a été observé. En faisant quelques hypothèses, ces résultats ont permis de valider le modèle mathématique en obtenant une valeur de la solubilité de l’hydrogène dans l’aluminium près de celle des autres expérimentateurs. Suite à ces essais, de nouvelles améliorations ont été apportées au montage et une nouvelle méthodologie de mesure est proposée pour les expérimentations futures.
La présence d’hydrogène en solution dans l’aluminium liquide entraîne la formation de porosités une fois celui-ci solidifié. C’est pourquoi il est important de bien mesurer la quantité de gaz dissous dans le métal. La méthode de Sieverts, utilisée par d’autres expérimentateurs dans le passé, montre certaines faiblesses et une nouvelle méthode plus fiable et versatile est proposée afin de valider les résultats obtenus précédemment. Après plusieurs tests et améliorations au montage et à la méthodologie, des résultats prometteurs ont été obtenus. En fait, un phénomène attribuable à la dissolution de l’hydrogène dans l’aluminium a été observé. En faisant quelques hypothèses, ces résultats ont permis de valider le modèle mathématique en obtenant une valeur de la solubilité de l’hydrogène dans l’aluminium près de celle des autres expérimentateurs. Suite à ces essais, de nouvelles améliorations ont été apportées au montage et une nouvelle méthodologie de mesure est proposée pour les expérimentations futures.
The presence of hydrogen in solution in liquid aluminium leads to the formation of porosities after the solidification. For this reason, a good measurement of the quantity of gas dissolve in the molten metal should be made. The Sieverts’ method, used by the precedents experimenters, shows some weaknesses and a new method more reliable and versatile is proposed to validate the results formerly obtained. After several tests and ameliorations to the measurement system, some promising results were obtained. A phenomenon that can be attributed to the dissolution of hydrogen in liquid aluminium was observed. By making some assumptions, these results were used to validate the mathematical model by obtaining a value of the solubility of hydrogen in aluminum near the other experimenters. Following that, new ameliorations were made to the system and that a new measurement methodology is proposed for the future experimentations.
The presence of hydrogen in solution in liquid aluminium leads to the formation of porosities after the solidification. For this reason, a good measurement of the quantity of gas dissolve in the molten metal should be made. The Sieverts’ method, used by the precedents experimenters, shows some weaknesses and a new method more reliable and versatile is proposed to validate the results formerly obtained. After several tests and ameliorations to the measurement system, some promising results were obtained. A phenomenon that can be attributed to the dissolution of hydrogen in liquid aluminium was observed. By making some assumptions, these results were used to validate the mathematical model by obtaining a value of the solubility of hydrogen in aluminum near the other experimenters. Following that, new ameliorations were made to the system and that a new measurement methodology is proposed for the future experimentations.

L’adsorption des gaz dans les solides micro/mésoporeux et la solubilisation des gazdans les liquides sont des phénomènes physiques très bien connus. En revanche, lasolubilisation des gaz dans un liquide confiné à l’intérieur d’un solide (système hybride) estun domaine très peu étudié, malgré des applications importantes, notamment dans l’extractiondu pétrole, les ciments ou encore les réacteurs catalytiques triphasiques. Nous avons montréexpérimentalement que la solubilité du CO2 et H2 augmente quand la taille de pores du solideest de l’ordre du nanomètre. Un des objectifs de cette thèse était d’optimiser le couple solidesolvant(système hybride) et les conditions de température et de pression pour augmenter lestockage de H2 pour les applications de stockages. Dans le système Aérogel/éthanol à 50 barset 0°C, la solubilité de H2 est 8,5 fois supérieure à la solubilité mesurée dans le liquide seul,représentant une masse de 6,2g d’hydrogène stocké par kg de solide. Le second objectif étaitde comprendre les paramètres clefs de ce phénomène apparent de « sursolubilité » dans lessystèmes hybrides. En comparant différents solides poreux (zeolithes, MOF, MCM, silice),nous avons montré le rôle majeur des propriétés d’interfaces. Les phénomènes desolubilisation ont été modélisés à l’échelle moléculaire par GCMC et validéesexpérimentalement. Il apparait que le mécanisme de sursolubilisation provient d’unestructuration en couche des molécules de solvants en interactions avec les parois dumésopore
The adsorption of gases in micro/mesoporous materials and solubility of gases inliquids are physical phenomena well known. On the other hand, solubility of gases in liquidsconfined inside a solid (hybrid system) has not been entensively studied, despite the importantapplications such systems can have in the areas of oil extraction, cement and triphasiccatalytic reactors. We have shown experimentally that the solubility of CO2 and H2 increaseswhen the size of the pores of the solid is in the nanometer range. One of the objectives of thisthesis was to optimize the couple a solid and a solvent into a hybrid system and the conditionsin which to increase the H2 storage capacity. In an aerogel/ethanol hydrid system at 50 barand 0 ° C, the solubility of H2 is 8.5 times greater than the solubility measured in the singleliquid, representing a mass of 6.2 g of hydrogen stored per kg of solid. The second objectivewas to understand this apparent phenomenon of oversolubility and the key parameters in thehybrid systems. By comparing different porous solids (zeolites, MOFs, MCM-41 and silica),we have shown the major role of the properties of interfaces. The phenomena of solubilsationwas modelled by GCMC and experimentally validated. It appears that the mechanism ofoversolubilisation comes from structuring the solvent molecules in interactions with the wallsof the mesopore layered

La volonté de réduction des émissions de gaz à d'effet de serre est à l'origine de l'étude de la capture du CO2 dans les systèmes de production d'électricité à base de gazéification du charbon intégrée à un cycle combiné. Une étude comparative des procédés de capture de CO2 retenus dans la littérature (MEA-MDEA, AMP, N-Méthyl- Pyrrolidone et méthanol) a conduit au choix de l'absorption physique par le méthanol. La simulation du fonctionnement de l'IGCC avec capture de CO2 a été réalisée à l'aide du logiciel Aspen Plus

Les viroles en acier microallié 18MND5, destinées aux générateurs de vapeur, présentent une composition hétérogène à plusieurs échelles. Un écart au procédé de fabrication ou une teneur en hydrogène excessive, peuvent conduire à la formation des Décohésions Dues à l’Hydrogène. Ces DDH résultent de la désorption de l’hydrogène interne lors du refroidissement jusqu’à température ambiante. La pression interne n’étant pas mesurables expérimentalement, une modélisation du phénomène est requise. Afin de préciser les mécanismes sous-jacents, il est proposé un scénario de formation de ces défauts s’appuyant conjointement sur une expertise et la modélisation des processus de diffusion-désorption-propagation. Les observations ont révélé une corrélation entre les DDH, les zones ségrégées et les amas de MnS (sites préférentiels d’initiation). Un modèle de diffusion dans un milieu hétérogène a été proposé afin d’évaluer la pression interne associée. La pression maximale excède ainsi 8600 bar en considérant une loi d’Abel-Noble optimisée du gaz réel. Le couplage de ce modèle avec la mécanique de la rupture a permis de quantifier l’évolution des paramètres relatifs à la propagation (pression interne, taille finale, vitesse, …). Un scénario de formation des DDH industriel a ainsi pu être formulé sur la base d’une étude paramétrique. Bien que les simulations préliminaires corroborent le retour d’expérience, le modèle raffiné et la prise en compte du gonflement de la DDH semblent sous-estimer la cinétique. Le caractère multi-fissuré des amas de MnS (homogénéisation des propriétés mécaniques) associé à un critère de rupture à l’échelle locale permettrait d’ajuster ce modèle
Heat generators are manufactured from ingots of 18MND5 (A508cl3) low alloy steel and present composition heterogeneities at different scales. Under specific conditions (non-respect of guidelines or high initial content of H), Hydrogen Induced Cracks (HIC) may result from diffusion-desorption of internal hydrogen during cooling down to room temperature. Since neither hydrogen redistribution nor its internal pressure within cavities could be measured by experimental techniques, quantitative investigation is based on the modelling of related physical phenomena. A scenario of HIC formation, based on industrial feedback and modelling, has been proposed. A correlation between these defects, segregated areas and clusters of MnS (preferred initiation sites) has been revealed by expertise of HIC. A model of diffusion in heterogeneous alloys has then been proposed to assess the maximal pressure of H2 in such HIC. Simulation has shown that internal pressures above 860MPa are reached by considering an optimized Abel-Noble real gas behavior. The previous model has then been coupled to a failure mechanics procedure to characterize and quantify the crack growth parameters. Based on a parametric study, a scenario of HIC formation during the cooling has been proposed regarding process. Although results from preliminary simulations matched with feedback, the refined model based on the pressure induced elastic deformation of HIC has been developed but provided an underestimated kinetic of crack growth. Consequently, the multi-cracked nature of MnS clusters (homogenization of mechanical properties) and the updated local failure criterion appear to be a viable path to adjust predictions

It is a worldwide priority to reduce emissions of greenhouse gases such as CO2. One solution for reducing these emissions is to improve the efficiency of energy production units by increasing their operating temperature. However, in order to increase operating temperature, new austenitic materials based on the Fe-Ni-Cr system have to be designed. In addition, these materials need to exhibit good protection against high temperature oxidation, which is achieved by the formation of a slow growing chromium oxide or alumina scale on the metal. However, to predict the formation of a protective scale, knowledge of the oxygen permeability, the product of oxygen solubility and diffusivity, in the base alloy is required. The objective of this study is to measure the permeability, solubility and diffusivity of oxygen in Fe- Ni alloys at temperatures above 1,000°C. In order to obtain the best results, the formation of an external oxide layer during the experiment has to be avoided. To achieve this, the oxygen partial pressure was fixed at the Fe/FeO equilibrium pressure in all experiments. In addition, two types of atmospheres were used: one dry and one wet, in order to investigate the effect of water vapour on oxygen permeability, solubility and diffusivity. The dry atmosphere was achieved using the Rhines Pack technique. The samples were oxidised in vacuum-sealed quartz capsules, which contained a mixture of powdered iron and wüstite. The humid atmosphere was obtained by using H2/H2O gas mixtures with the appropriate water vapour to hydrogen ratio to fix oxygen partial pressure at the Fe/FeO equilibrium. The maximum oxygen solubility was found in pure iron, and decreased continuously with nickel additions to the alloy. The dependence of solubility on alloy composition is non-ideal, and cannot be predicted from simple models. Moreover, the presence of water vapour in the atmosphere seems to increase the solubility by a factor of 2 in alloys with nickel content lower than 80 at.% at temperatures near 1,000°C. However, at 1,150°C the solubility of the oxygen is independent of the environment. The oxygen permeability was determined by measuring the internal oxidation kinetics of Fe-Ni-Cr alloy. These kinetics were evaluated by measuring the internal oxidation zone depth by optical microscopy, or by continuous and discontinuous thermogravimetry. Results showed that the oxygen permeability exhibits the same variation with alloy composition as the oxygen solubility, independent of the atmosphere. In particular, no significant effect of water vapour on oxygen permeability values was observed. In the present study, the oxygen diffusion coefficient was also determined using permeability, in addition to the independent measurement of the oxygen solubility carried out in the present study. For temperature above 1,000°C, the variation of oxygen diffusion coefficient with the alloy composition is similar in all environments tested, and a maximum is observed for alloys with a nickel content of 40 at.%. However, for a given nickel content up to 60 at.%, the presence of water vapour in the atmosphere decreases the value of the oxygen diffusion coefficient by a factor of 2-3 at 1,000°C. In addition, this difference between diffusion coefficients measured in a dry and wet atmosphere increases as the temperature decreases. Overall, it was found that the water vapour has no effect on the way in which oxygen permeability, solubility and diffusivity vary with the alloy composition. However, the presence of water vapour in the environment appears to increase the oxygen solubility and decrease the oxygen diffusivity in iron-rich alloys, the effect being more significant at low temperatures. These results suggest further research into interactions between O, H and metal vacancies, particularly for temperature around 1,000°C and below, as the latter defect is thought to change the diffusion and solubility properties of interstitial species.

The AQUAFAC (Aqueous Functional Group Activity Coefficients) method for predicting aqueous activity coefficients proposed by Myrdal et al. (1992) is expanded to include for hydrogen bonding groups: hydroxy, carboxy, nitro and amino. Activity coefficients can be used to estimate aqueous solubility. Using aqueous solubility data, from a number of sources, for a set of subsituted aromatic compounds, group or q values are derived. Group values have been generated for a number of substituents, none have included hydrogen bonding groups (Myrdal et al., 1992,1993). Q values are related to activity coefficients through the following relationship: log gammaw = Sigmaniqi where log gammaw is the log of the activity coefficient, qi is the group value subtituent i and ni is the group frequency. Ortho effects between hydrogen bonding groups is also examined. Intramoleculat hydrogen bonding involving carboxy substituted compounds, in this research, does appear to affect aqueous solubility.

In the present thesis a study of the mechanisms of hydrogen control pickup during ladle treatment was undertaken. Previous studies showed that the presence of hydroxyl ions in the ladle slag resulteds in hydrogen transfer from the slag back into the steel bath. The main focus of the present work was therefore to gain deeper knowledge of the ladle slag, its properties and impact on hydrogen concentration in the liquid steel. For this purpose a number of slag compositions were examined in order to clarify whether these slags were single liquids at 1858 K. 14 out of 27 compositions in the Al2O3-CaO-MgO-SiO2 system werewas completely melted, while the rest had solid shape present . These results were in disagreement with the existing phase diagram.   Water solubility measurements were carried out by employing a thermo gravimetric technique. The temperature was found to have negligible effect in the water solubilities. The experimental results showed that the water capacity values varied between 1·103 and 2·103 in the majority of the composition range. However, for compositions close to CaO saturation the water capacity value could reach higher than 3·103. The experimental determined water capacity was further used to develop a water capacity model for the quaternary slag system Al2O3-CaO-MgO-SiO2. The model was constructed by considering the effects of the binary interactions between the cations in the slag on the capacity of capturing hydroxyl ions. The model calculations agreed reasonably well with the experimental results as well as with the literature data.   The water capacity model was used in the last part of the present thesis in order to determine the major source for hydrogen pick-up of the steel after vacuum degassing but before casting. For this purpose, samples of slag and metal were taken at different stages ofduring ladle treatment at SSAB. Hydrogen increase after vacuum treatment was observed. Moisture contents of the industrial slag were analysed and the water capacities of the slags were calculated. It could be seen that the hydrogen increase was correlated to the amount of moisture in the slag and the water capacity. The study showed that the slag containing most water was also the heat having the largest hydrogen increase. The slag with most water had the highest water capacity. It could be concluded that the major source for hydrogen coming back into the steel was due to the slag-metal reaction. A tentative process model to predict the final contents of hydrogen and nitrogen after tundish process was attempted. More work is needed to improve the model.

QC 20150825

This thesis presents the results of an experimental study of the solubility of Au in reduced sulphur-bearing vapours at elevated temperature and pressure, as well as the PVTx properties of H2O-H2S gas mixtures. The solubility of gold was measured in pure H2S gas and H2O-H2S gas mixtures. Results of the experiments demonstrate that the fugacity of gold increases with the fugacity of H2S, and that reactions involving the formation of volatile sulphide species control the solubility of gold in the gas phase. The results obtained for pure H2S gas indicate that solvation of sulphide gold species by molecules of H2S significantly increases the dissolution of gold, whereas the experiments with H2O-H2S vapour mixtures showed that this dissolution is further enhanced by hydration of the gold sulphide. The reactions of formation of solvated and hydrated gaseous complexes AuS(H2S)n and AuS(H2O)m are interpreted to control the solubility of gold in H2O-H2S gas mixtures. Equilibrium constants and the solvation or hydration numbers (n or m) for these reactions were determined by minimizing the errors between the results for an optimized solvation/hydration model and the experimental data. The fugacity of H2S and H2O required for the model calculation were determined from the experimentally determined PVTx properties of the H2O-H2S fluid mixtures; the latter were modeled using cubic equations of state with composition- and density-dependent mixing rules and adjusted binary interactions parameters.Under the experimental conditions of this study, i.e., temperatures from 300 to 400 °C, pressures up to 265 bar, and hydrogen fugacity constrained by the reaction H2+S=H2S, the solubility of gold in reduced sulphur-bearing vapour is relatively high (up to 1 ppb), and the results obtained provide strong evidence that H2S plays an important role in the vapour transport of gold. As most natural hydrothermal vapours are water rich (>90% H2O), gold will be transported in the vapour dominantly as an hydrated gold sulphide, provided that there is sufficient reduced sulphur (H2S) in the vapour for complexation. The stoichiometry and stability of the gold complexes determined in this study represent an important contribution to our knowledge of the chemical properties of volatile metal species and permit accurate modeling of vapour-related processes involved in the mobilization, transport and deposition of gold in magmatic hydrothermal systems, notably those of epithermal environments.
Cette thèse présente les résultats d'une étude expérimentale sur la solubilité de l'or dans des vapeurs contenant du souffre à l'état réduit à haute pression et température, ainsi que les propriétés PVTx de mélanges gazeux de H2O-H2S. La solubilité de l'or a été mesurée dans du H2S gazeux pur et dans des mélanges gazeux de H2O-H2S. Les résultats de cette expérience démontrent que la fugacité de l'or augmente avec la fugacité de H2S, et que les réactions qui mènent à la production d'espèces volatiles de souffre contrôlent la solubilité de l'or dans la phase gazeuse. Les résultats obtenus pour le gaz de sulfure d'hydrogène à l'état pur indiquent que la solvatisation des espèces de sulfure d'or par les molécules de sulfure d'hydrogène augmente de façon significative la dissolution de l'or, alors que les résultats issus des expériences utilisant des mélanges gazeux de H2O et de H2S montrent que cette dissolution est davantage augmentée par l'hydratation du sulfure d'or. Nous proposons que les réactions de formation de solvates et hydratée complexes gazeux AuS(H2S)n et AuS(H2O)m contrôlent la solubilité de l'or dans des mélanges de H2O-H2S. Les constantes d'équilibre ainsi que le degré de solvatisation ou d'hydratation (n ou m) pour ces réactions furent déterminés par minimisation de l'erreur entre les résultats obtenus d'un modèle de solvatation/hydratation optimisé et les données expérimentales. Les fugacités de H2S et de H2O requises pour les calculs du dit modèle furent établies en utilisant les propriétés de PVTx expérimentalement déterminées pour les mélanges fluides de H2O-H2S; ces dernières furent modélisées en utilisant des équations d'état cubiques avec des lois de mélange sur la dépendance de composition et densité, ainsi que des paramètres sur les interactions binaires spécialement ajustées.Dans les conditions de cette étude, c'est- à -dire à 300-400 °C et à des pressions jusqu'à 265 bars, la fugacité de l'hydrogène étant contrainte par la réaction chimique H2+S=H2S, la solubilité de l'or dans des vapeurs de soufre à l'état réduit est relativement élevée (jusqu'à 1 ppb), et les résultats démontrent que le sulfure d'hydrogène joue un rôle important dans le transport de l'or par la vapeur. La plupart des vapeurs hydrothermales dans la nature sont riches en eau (>90% H2O), donc l'or sera transporté par la vapeur sous la forme de sulfure d'or hydraté si il y a assez de sulfure d'hydrogène à l'état réduit pour qu'il y ait complexation. La stœchiométrie et la stabilité des complexes d'or déterminés dans cette étude représentent une contribution essentielle à la caractérisation des propriétés chimiques sur les espèces métalliques volatiles et permettent une modélisation précise des processus à l'état vapeur et inhérents à la mobilisation, le transport et le dépôt de l'or dans des systèmes hydrothermaux magmatiques, en particulier les environnements épithermaux.

The purpose of this dissertation is to investigate the thermochemical properties of nonelectrolyte solutes dissolved in ternary solvent mixtures, and to develop mathematical expressions for predicting and describing behavior in the solvent mixtures. Forty-five ternary solvent systems were studied containing an ether (Methyl tert-butyl ether, Dibutyl ether, or 1,4-Dioxane), an alcohol (1-Propanol, 2-Propanol, 1-Butanol, 2-Butanol, or 2-Methyl-1-propanol), and an alkane (Cyclohexane, Heptane, or 2,2,4-Trimethylpentane) cosolvents. The Combined NIBS (Nearly Ideal Binary Solvent)/Redlich-Kister equation was used to assess the experimental data. The average percent deviation between predicted and observed values was less than ± 2 per cent error, documenting that this model provides a fairly accurate description of the observed solubility behavior. In addition, Mobile Order theory, the Kretschmer-Wiebe model, and the Mecke-Kempter model were extended to ternary solvent mixtures containing an alcohol (or an alkoxyalcohol) and alkane cosolvents. Expressions derived from Mobile Order theory predicted the experimental mole fraction solubility of anthracene in ternary alcohol + alkane + alkane mixtures to within ± 5.8%, in ternary alcohol + alcohol + alkane mixtures to within ± 4.0%, and in ternary alcohol + alcohol + alcohol mixtures to within ± 3.6%. In comparison, expressions derived from the Kretschmer-Wiebe model and the Mecke-Kempter model predicted the anthracene solubility in ternary alcohol + alkane + alkane mixtures to within ± 8.2% and ± 8.8%, respectively. The Kretschmer-Wiebe model and the Mecke-Kempter model could not be extended easily to systems containing two or more alcohol cosolvents.

The purpose of this dissertation is to investigate the behavior of polycyclic aromatic hydrocarbons (PAHs) in binary solvent systems and determine and/or develop predictive mathematical expressions for describing solutions in which hydrogen-bonding occurs.

Experimental mole fraction solubilities of several carboxylic acids (2-methoxybenzoic acid, 4-methoxybenzoic acid, 4-nitrobenzoic acid, 4-chloro-3-nitrobenzoic acid, 2-chloro-5-nitrobenzoic acid,2-methylbenzoic acid and ibuprofen) and 9-fluorenone, thianthrene and xanthene were measured in a wide range of solvents of varying polarity and hydrogen-bonding characteristics. Results of these measurements were used to calculate gas-to-organic solvent and water-to-organic solvent solubility ratios, which were then substituted into known Abraham process partitioning correlations. The molecular solute descriptors that were obtained as the result of these computations described the measured solubility data to within an average absolute deviation of 0.2 log units. The calculated solute descriptors also enable one to estimate many chemically, biologically and pharmaceutically important properties for the ten solutes studied using published mathematical correlations.

The cocrystallization of two or more pure compounds by crystal engineering to create a new functional material is of a great academic and industrial interest. Pharmaceutical cocrystallization has allured a lot of attention by means of altering the physicochemical properties of Active Pharmaceutical Ingredient (API) such as solubility, stability and bioavailability. Crystal engineering of nutraceuticals can produce novel compounds such as pharmaceutical cocrystals. To establish the importance of nutraceutical cocrystallization and its use; polyphenols, a major class of nutraceuticals and potential disease preventing agents, are the appropriate targets. The work herein focuses on two polyphenols, protocatechuic acid and quercetin, which are strong antioxidants. The cocrystals of quercetin have been synthesized, aiming to modify its poor water solubility and bioavailability which limits its usage. On the other hand, cocrystals of water soluble protocatechuic acid are also prepared to establish its use as a cocrystal former. Seven novel cocrystals of protocatechuic acid and two novel cocrystals of quercetin are obtained and are characterized by FTIR, DSC (Differential Scanning Calorimetry), PXRD (Powder X-Ray Diffraction), single crystal x-ray diffraction and TGA (Thermo Gravimetric Analysis). The new crystal forms have also been studied via dissolution. Dissolution studies show alteration in solubility of a target molecule by its cocrystal irrespective of solubility of the cocrystal former. Overall, the study helps in understanding the role of crystal engineering and its utility.

The synthesis method for PEG/alkyl-based imidazolium/pyridinium ionic liquids was studied. Four steps were used to fabricate the membranes: polymerization, chloromethylation, linkage of the polymers with the pendent groups and membrane cast. Permeabilities and CO2/N2 selectivity of two membranes were examined and each showed remarkable CO2/N2 selectivity. CO2 permeability of the [PSM-MIM][Cl] membrane is better than that of the [PSM-MEIM][Cl] membrane, which is due to the steric hindrance of the methoxyethyl group. The syntheses of PEG/alkyl-based imidazolium/pyridinium ionic liquids (IL) were studied. PEG-based ILs were demonstrated to have better H2S solubilities than the alkyl-based ILs. H2S solubilities of the imidazolium ILs and pyridinium ILs were compared. The anion effects on H2S solubilities have been investigated, while the temperature effects on H2S solubilities will need to be studied in the near future.

Pharmaceutical cocrystals use principles of crystal engineering for the design of crystalline forms of drugs and can improve their solubility, bioavailability, stability and other important properties without changing the efficacy of the drug. Herein reported are pharmaceutical cocrystals of two API's, caffeine and Pentoxifylline. Research has indicated that caffeine has the ability to reverse AB; plaque deposition in the brain (believed to be the primary cause of Alzheimer's pathogenesis) and thus revert memory and improve cognitive impairment. But owing to the fast absorption rate and short half life, a controlled release formulation of caffeine would be clinically beneficial. Thus, novel cocrystals of caffeine are presented with varying solubilities with respect to caffeine. The pharmaceutical cocrystals of caffeine used herein include: caffeine.cyanuric acid monohydrate, caffeine.syringic acid tetrahydrate, caffeine.chlorogenic acid and caffeine.catechin hydrate. Three caffeine cocrystals were prepared in our lab previously which include caffeine.ferulic acid, caffeine.ethyl gallate dihydrate and caffeine.caffeic acid. In addition, six caffeine cocrystal forms were reproduced from the literature and included in the solubility study: caffeine.quercetin, caffeine.salicylic acid, caffeine.1-hydroxy-2-napthoic acid, caffeine.gallic acid hemihydrate, caffeine.ellagic acid monohydrate and caffeine.coumaric acid. Dissolution studies were performed in aqueous media at room temperature. All of the cocrystals decreased the solubility of caffeine with the highest being a 278 fold decrease in the solubility of caffeine. Analysis of melting point, crystal packing efficiency and solubility of cocrystal former with solubility was also done to determine if they influenced the solubility. Presented herein are the results of the analyses. It was seen that solubility of the cocrystal former had no effect on the decrease in cocrystal solubility. Moreover melting point and solubility of the cocrystal could not be correlated probably due to the variability in the cocrystal formers. Crystal packing efficiency though did not show a high correlation with solubility but it was seen that highest solubility achieved by pure caffeine achieved the lowest crystal packing efficiency and vice versa suggesting its role in cocrystal solubility. Pentoxifylline is contraindicated for its use in autism. But owing to high solubility of the drug, a less soluble form of the drug would help in decreasing the half life and thereby help in forming a sustained form of the drug by modifying the inherent solubility of the API. Here, novel cocrystals of Pentoxifylline are presented with varying solubilities with respect to the API. The pharmaceutical cocrystals used herein include: pentoxifylline.benzoic acid, pentoxifylline.1-hydroxy-2-napthoic acid, pentoxifylline.salicylic acid, pentoxifylline.gallic acid, pentoxifylline. salicylamide, pentoxifylline.coumaric acid, pentoxifylline.caffeic acid and pentoxifylline.catechin hydrate. Dissolution studies were also performed in aqueous media at room temperature. All of the cocrystals decreased the solubility of Pentoxifylline with the highest being a 99 fold decrease in the solubility with pentoxifylline.coumaric acid. On analyzing melting point, crystal packing efficiency and relation of solubility of cocrystal former with solubility of cocrystal, as was done in the case of caffeine, the parameters showed no effect on solubility of the cocrystal.

Hydrogen peroxide is a versatile oxidizing agent with several industrial applications. It is also one of “greenest”, since its oxidation by-product is only water. The global demand of the peroxide is increasing, due to its recent usage in new large scale oxidation processes, such as the epoxidation of propylene to propylene oxide and the synthesis of caprolactam. Nowadays most of the world production of H2O2 is carried out by the anthraquinone autoxidation process. Though very safe (H2 and O2 are never in direct contact), the costs related to the high energy consumption for the extraction and purification of the peroxide produced, together with the usage and periodic replacement of toxic and expensive solvents, stimulated the interest in new production paths. Among the several alternatives proposed, the most fascinating one is the direct synthesis (DS) from H2 and O2. It is a environmentally friendly process that would be economically profitable for an in-situ production, requiring lower investments and operating costs. During the last thirty years this system has been under intensive study both by industries as well as academia. However, it has not been commercialized yet, mainly because of poor selectivity and safety concerns. While most of the efforts on improving DS must address the catalyst, there are reaction engineering aspects that deserve attention. DS is frequently carried out in solvents other than water, both to improve H2 solubility and isolate the undesired product (H2O). Further, CO2 is used for safety, H2 solubility and H2O2 stability. However, the lack of information about the solubility of the reagents makes it difficult to develop a realistic kinetic description of the reactions involved in the DS process. Hence, the first step of the research presented herein dealt with solubility measurements, at temperatures in the range 268-288 K and pressures between 0.37 and 3.5 MPa. Measurements were focused on H2, i.e. the limiting reagent during the reaction. At all conditions investigated a linear relation between hydrogen partial pressure and concentration was observed. Increasing the temperature resulted in an enhanced H2 solubility at the same H2 partial pressure. At constant H2 fugacity, the presence of CO2 favored the dissolution of hydrogen in the liquid phase. Correlation and generalization of the measurements were provided through an EoS-based thermodynamic model for the estimation of H2 solubility at reaction conditions. A batch apparatus for the direct synthesis of hydrogen peroxide was developed, to carry out activity measurements on new catalysts and develop a quantitative model of the kinetics. Hydrogenation, disproportionation and direct synthesis reactions were studied on a commercial 5 wt.% Pd/C catalysts at temperatures in the range 258-313 K and pressure up to 2 MPa. Separate experiments were performed to highlight the role of each reaction. An enhanced H2O2 production was obtained adopting different H2 feeding policies, although selectivity did not exceeded 30%. A model of the gas bubbling, batch slurry reactor for H2O2 direct synthesis was developed. A sensitivity analysis on the mass transfer coefficients excluded any limitations occurring at experimental conditions. Comparable temperature dependence was observed for H2O production, hydrogenation and disproportionation (activation energies close to 45 kJ mol-1), while H2O2 synthesis had a much lower activation energy (close to 24 kJ mol-1), suggesting that a higher selectivity is achievable at low temperature. Disproportionation reaction had a very limited influence on the overall peroxide production rate, while hydrogenation was the most rapid side reaction. Water formation was significant, prevailing at higher temperatures. Following these results, Pd and PdAu catalysts supported on SBA15 were prepared and investigated for H2O2 direct synthesis. Catalysts were doped with bromine, a promoter in the H2O2 direct synthesis. Productivity and selectivity decreased when bromine was incorporated in the catalysts, suggesting a possible poisoning due to the grafting process. A synergetic effect between Pd and Au was observed both in presence and absence of bromopropylsilane grafting on the catalyst. Three modifiers of the SBA15 support (Al, CeO2 and Ti) were chosen to elucidate the influence of the surface properties on metal dispersion and catalytic performance. Higher productivity and selectivity were achieved incorporating Al into the SBA15 framework, whereas neither Ti nor CeO2 improved H2O2 yields. The enhanced performance observed for the PdAu/Al-SBA15 catalysts was attributed to the increased number of Brønsted acid sites. Supported catalysts were also synthesized depositing Pd on a highly acidic, macroporous PS-DVB resin (Lewtit K2621). Catalysts with active metal content in the range 0.3-5 wt.% were tested batchwise for the direct synthesis of H2O2. Preliminary H2O2 measurements and X-ray photoelectron spectroscopy (XPS) analysis revealed that the reduced form of Pd was more selective than PdO towards the peroxide. Transmission electron microscopy (TEM) images showed that smaller nanoclusters favored the production of H2O, likely due to their O-O bond breaking aptitude
Il perossido di idrogeno è un potente agente ossidante, molto usato nella pratica industriale. E’ uno dei meno tossici, dal momento che l’unico sottoprodotto della sua ossidazione è l’acqua. A livello mondiale, la domanda di H2O2 è in costante aumento, non da ultimo grazie a recenti usi in nuovi processi ossidativi, quali l’epossidazione del propilene e la sintesi del caprolattame. Attualmente l’acqua ossigenata viene prodotta quasi esclusivamente attraverso l’auto-ossidazione dell’antrachinone. Sebbene molto sicuro (non vi è mai contatto diretto tra idrogeno ed ossigeno), questo processo presenta alcuni svantaggi, quali ad esempio gli alti costi di esercizio, dovuti in particolare all’alta richiesta energetica per la separazione e la purificazione del perossido prodotto. Si tratta inoltre di un processo potenzialmente inquinante, in quanto fa uso di costosi solventi tossici, e dagli alti costi d’investimento, essendo economicamente vantaggioso solo per grandi produzioni (>4*104 tonnellate all’anno). Pertanto l’H2O2 è attualmente prodotta in pochi grandi impianti e trasferita per grandi distanze all’utente finale. Il trasporto aggiunge costi e rischi, in quanto soluzioni concentrate di H2O2 possono decomporre violentemente. Nelle ultime decadi vi è stato un notevole interesse nella ricerca di nuovi processi di produzione del perossido di idrogeno, che fossero contemporaneamente meno costosi ed inquinanti. Tra le varie alternative proposte, la più affascinante è sicuramente la sintesi diretta a partire da H2 ed O2. Si tratta di un processo “verde”, che si propone di eliminare i sottoprodotti inquinanti e, allo stesso tempo, ridurre i costi di produzione, rendendo economicamente vantaggiosa la produzione in situ presso l’utilizzatore finale. Nonostante il grande interesse sia industriale che accademico suscitato da tale processo negli ultimi trent’anni, a tutt’oggi non vi è nessuna applicazione industriale. Il motivo di ciò è da ricercarsi principalmente nei problemi di sicurezza e selettività che a tutt’ora restano irrisolti. La mancanza di informazioni sulla solubilità dei reagenti alle condizioni di reazione rende difficoltoso ottenere una descrizione cinetica precisa delle reazioni coinvolte nella sintesi diretta. Pertanto i primi passi della ricerca qui presentata sono stati mossi con l’obiettivo di raccogliere dati di solubilità alle condizioni di reazione (temperatura compresa tra i 268 e i 288 K e pressione tra 0.37 e 3.5 MPa). In particolare, si era interessati all’H2, in quanto reagente limitante del processo. A tutte le condizioni indagate, è stata riscontrata una relazione lineare tra la pressione parziale e la concentrazione di H2. Contrariamente a quanto normalmente avviene, l’incremento di temperatura ha avuto l’effetto di aumentare la solubilità nella fase liquida (a parità di pressione parziale). Inoltre, a parità di fugacità di H2, la presenza di CO2 ha favorito la concentrazione dell’H2 nel liquido. I risultati ottenuti sono stati generalizzati sviluppando un modello per stimare la solubilità dell’H2 alle condizioni di reazione. E’ stato poi realizzato un apparato batch per la sintesi diretta di acqua ossigenata. Un catalizzatore commerciale a base di Pd (5 wt.%) su carbone è stato utilizzato per studiare le reazioni di idrogenazioni, dismutazione e sintesi a temperature comprese tra 258 e 313 K e pressioni fino a 2.0 MPa. Il ruolo di ciascuna reazione è stato studiato attraverso esperimenti specifici. Appropriate politiche di alimentazione dell’H2 hanno permesso di realizzare un aumento di produzione rispetto a condizioni tipicamente batch. Tuttavia il catalizzatore testato ha rivelato limiti di selettività, non superando valori del 30% ca. Per studiare le cinetiche di reazione, è stato sviluppato un modello per il reattore batch. Un’analisi di sensitività sui coefficienti di trasporto di materia (sia dalla fase gassosa alla liquida che dalla liquida al catalizzatore) ha permesso di escludere ogni limitazione tra le fasi coinvolte nelle reazioni. Le reazioni indesiderate (formazione di H2O, dismutazione ed idrogenazione) hanno rivelato una simile dipendenza dalla temperatura (con un’energia di attivazione di circa 45 kJ mol-1). Una minore energia di attivazione è stata ottenuta per la reazione di sintesi diretta di H2O2 (24 kJ mol-1), il che suggerisce che la selettività è favorita alle basse temperature. Un confronto tra le velocità delle reazioni coinvolte ha permesso di identificare la dismutazione come la reazione più lenta di distruzione del perossido. Inoltre, la formazione di acqua era sempre significativa, compromettendo la selettività. A seguito di questi risultati, si è deciso di focalizzare l’attenzione sul catalizzatore. Catalizzatori mono e bi-metallici sono stati realizzati depositando Pd e PdAu su SBA15, una silice macroporosa e strutturata. Tali catalizzatori sono stati anche dopati con l’aggiunta di bromo, un noto promotore della reazione di sintesi diretta. Sia la selettività che la produttività sono diminuite modificando i catalizzatori con l’alogenio, probabilmente a causa di un avvelenamento durante la procedura di innesto del bromo. Una sinergia tra i metalli Pd e Au è stata osservata sia nei catalizzatori con e che senza bromo. Tre modifiche sono state apportate al miglior catalizzatore sviluppato (PdAu/SBA15) per evidenziare l’influenza delle proprietà superficiali sulla reazione di sintesi diretta. Tre modificatori sono stati incorporati nel supporto: Al, CeO2 e Ti. Un aumento sia di selettività che di produttività è stato riscontrato solo con l’aggiunta di Al. Tale risultato è stato attribuito al maggior numero di siti acidi di Brønsted riscontrati su questo catalizzatore. Un'altra famiglia di catalizzatori, con un contenuto di metallo attivo variabile tra lo 0.3 ed il 5 wt.%, è stata sintetizzata depositando del Pd su una resina acida e macroporosa, miscela di PS e DVB. I risultati preliminari dei test catalitici e delle analisi di spettroscopia fotoelettronica a raggi X (XPS) hanno rivelato che lo stato di ossidazione del palladio più selettivo verso il perossido è quello ridotto, mentre il PdO porta più facilmente alla formazione di H2O. Le immagini al microscopio elettronico a trasmissione (TEM) hanno mostrato che i nanocluster di Pd più piccoli portato alla formazione preferenziale di H2O, il che è probabilmente legato alla loro propensione alla rottura del legame O-O

Le but de notre travail est de contribuer à la compréhension des interactions entre les gaz acides et la glace, à la fois pendant la phase atmosphérique de la glace, c'est à dire dans les nuages, et dans la neige après dépôt au sol. Les gaz polaires en général, et les acides en particulier, interagissent fortement avec la glace dans la quelle ils peuvent se dissoudre. Dans les nuages, ces interactions peuvent modifier fortement la composition de l'air, et ce point reste une inconnue majeure en chimie atmosphérique. La compréhension de la relation entre la composition de l'air et celle de la glace, appelée fonction de transfert air-neige, est également indispensable pour reconstituer la composition des paléoatmosphères à partir des carottes de glace. Afin de contribuer à élucider ces problèmes, nous avons étudié l'incorporation dans la glace des composés gazeux HCI et HN03. Les compositions à l'équilibre thermodynamique des solutions solides HCl-glace et HN03-glace, en fonction de la température et de la pression partielle du gaz, ont été obtenues expérimentalement en mesurant les profils de diffusion du gaz dans des monocristaux de glace. A -15 °C, le coefficient de diffusion est de l'ordre de 10-12 cm2/s pour HCI et de 10-10 cm2/s pour HN03. A la même température, sous une pression de 6 x 10-3 Pa, HN03 est environ 25 fois moins soluble que HCI avec pour solubilité respectives de 2,2 x 10-7 et 5 x 10-6 fraction molaire. Ces données ont été appliquées à différents phénomènes d'intérêt atmosphérique. Dans le cadre de la fonction de transfert air-neige, nos résultats ont été comparés à des données de terrain obtenues au Groenland. Il apparaît que, dans les flocons de neige, HCI en solution solide n'est pas en équilibre avec HCI en phase gazeuse. La teneur en HCI dans la neige est déterminée par des facteurs cinétiques lors de la formation des cristaux. Les résultats concernant HN03 suggèrent en revanche que, dans les flocons analysés, HN03 est en équilibre avec la phase gazeuse sans doute grâce à sa cinétique de diffusion plus rapide. Suite à ces résultats, nous avons proposé un mécanisme d'incorporation des gaz dans la glace lors de la croissance des cristaux. Celui-ci suggère que la relation liant la composition atmosphérique à la composition de la glace des nuages est fortement influencée par la dynamique atmosphérique et, en particulier, par les paramètres température et vitesse de refroidissement lors de la phase de formation du nuage. Les données obtenues au laboratoire intéressent aussi le domaine de l'hydrologie appliqué à la composition des eaux de fonte des neiges. Les résultats sur les solubilités de HCI et de HN03 et leur localisation probable dans le névé en cas de sursaturation expliquent semi quantitativement le phénomène observé d'élution préférentielle de l'ion nitrate par rapport à l'ion chlorure.

A goal of the Swedish government is to increase the usage of renewable fuels and biomass-based fuels. Fuel cells, and especially the MCFC, are useful for these types of fuels. The Swedish market may benefit from the MCFC in two ways: increased efficiency of the biofuels and also utilisation of produced heat in district heating. Most of the commercial MCFC systems today are optimised for use with methane. The possibility to utilise biomass in Sweden makes it important to study how the MCFC may be adapted or optimised for good performance and low degradation with gas produced from biomass or other renewable fuels. This thesis is focused on methods that may be used to investigate and evaluate MCFC electrodes and electrolytes with renewable fuels i.e. CO2-containing gases. The methods and results are both experimental and mathematically modelled. The objectives of this thesis are to better understand how the performance of the anode is dependent on different fuels. Anode kinetics and the water-gas shift reaction have been investigated as well as the possibility to increase cell lifetime by increasing the initial electrolyte amount by having the anode as a reservoir. The effect of segregation of cations in the electrolyte during operation has also been studied. It was found that if the gas composition at the current collector inlet is in equilibrium according to the water gas-shift reaction the gas composition inside the electrode is almost uniform. However, if the gas is not in equilibrium then the concentration gradients inside the current collector have a large effect on the gas composition inside the electrode. The conversion of the gas in the gas flow channels according to the water-gas shift reaction depends on the gas flow rate. For an anode used in a gas mixture of humidified hydrogen and carbon dioxide that are not in equilibrium some solubility of Ni in a (Li/Na)2CO3 mixture was found. To have the anode act as an electrolyte reservoir to prolong cell lifetime the anode pore size should be carefully matched with that of the cathode and a bimodal pore-size distribution for the anode is preferable to have as good performance as possible for as large electrolyte filling degree interval as possible. Modelling results of segregation of cations in the electrolyte during operation indicate that the electrolyte composition changes during operation and that the lithium ions are enriched at the anode for both types of electrolyte used for the MCFC. The electrolyte composition changes are small but might have to be considered in long-time operation. The results from this thesis may be used to better understand how the MCFC may be used for operation with renewable fuels and how electrodes may be designed to prolong cell lifetime.
Ett av den svenska regeringens mål är att öka användandet av förnyelsebara bränslen och bränslen från biomassa. Bränsleceller och framförallt MCFC är användbara för dessa typer av bränslen. Den svenska marknaden kan dra fördelar av MCFC på två sätt; ökad bränsleutnyttjandegrad och utnyttjande av producerad värme för fjärrvärme. De flesta kommersiella MCFC-systemen idag är optimerade för användning av metan. Möjligheten att använda biomassa på den svenska marknaden gör det viktigt att studera hur MCFC kan anpassas eller optimeras för bra prestanda och låg degradering för användning med gas från biomassa eller andra förnyelsebara bränslen. Fokus i denna avhandling är på metoder som kan användas för att undersöka och utvärdera MCFC-elektroder och -elektrolyter med förnyelsebara bränslen, dvs. gaser innehållande CO2. Metoderna och resultaten är både experimentella och matematiskt modellerade. Målet med denna avhandling är att bättre förstå hur anodens prestanda beror på användningen av olika bränslen. Anodens kinetik och vattengasskiftreaktionen har studerats liksom möjligheten att förlänga cellens livstid genom att öka den initiala mängden elektrolyt medelst användning av anoden som reservoar. Effekten av segregation av katjoner i elektrolyten under last har också undersökts. Om gassammansättningen är i jämvikt enligt vattengasskiftreaktionen vid inloppet till strömtilledaren kommer gassammansättningen att vara nära uniform inuti elektroden. Om ingående gas inte är i jämvikt kommer stora koncentrationsgradienter uppkomma i strömtilledaren och påverka gassammansättningen i elektroden. Omsättningen med avseende på vattenskiftreaktionen av gasen i flödeskanalen verkar vara beroende av gasens flödeshastighet. För en anod som används i en uppfuktad blandning av vätgas och koldioxid som inte är i jämvikt befanns det att Ni har en viss löslighet i (Li/Na)2CO3. För att kunna använda anoden som reservoar för elektrolyt för att förlänga livstiden för MCFC skall anodens porstorleksfördelning överensstämma med katodens och ha en bimodal porstorleksfördelning för att ge en tillräckligt god prestanda i ett så stort elektrolytfyllnadsgradsintervall som möjligt. Modelleringsresultat för segregering av katjoner i elektrolyten under drift visar att litiumjoner anrikas i anoden för båda typerna av elektrolyt som används i MCFC. Elektrolytkoncentrationsförändringarna är små men kan behövas tas i beaktande vid långa driftstider. Denna avhandlings resultat kan användas för att bättre förstå hur MCFC skall anpassas för drift med förnyelsebara bränslen och hur elektroder kan utformas för att förlänga livstiden.
QC 20100630

The solubility of H in single crystals and polycrystalline samples of $\rm Ni\sb{3}Al$ has been measured in equilibrium with $\rm H\sb2$ gas at atmosphere. In all cases the solubility exhibits a maximum at 750 K. A structural transformation from $\rm Ll\sb2$ (cubic) to $\rm Ll\sb2$ (tetragonal) in hydrogenated $\rm Ni\sb3Al\ (Ni\sb3Al$-H) was observed. The transformation temperature was found to be between 720 K and 870 K. No enthalpy change during this transformation was detected in the DTA experiment. The diffusivity of hydrogen in $\rm Ni\sb3Al$ has been measured in the temperature range of 588 K to 1214 K using a method involving the outgassing of hydrogen charged spheres. The diffusivity of hydrogen exhibits discontinuity in the temperature range of 753 K to 793 K. Finally, the addition of Pd (0.5 wt) is shown to significantly suppress the hydrogen embrittlement of $\rm Ni\sb3Al.$ Microstructure analysis indicates no second phase is formed due to the small amount of Pd. The addition of Pd alters the fractography of $\rm Ni\sb3Al$ charged with hydrogen. It is suggested that Pd may play a role of trapping hydrogen atoms in lattice and result in reducing the hydrogen concentration around crack tips and grain boundaries, thus improving the susceptibility of $\rm Ni\sb3Al$ to hydrogen embrittlement.

Poly (Ethylene Oxide) (PEO, with a general formula (CH₂-CH₂-O)[subscript pi] ) is completely soluble in water at room temperature over an extremely wide molecular weight range and has been widely studied by experiment and theory. The objective of our work is to study the solubility behavior by the method of Monte Carlo simulation. The insertion factor lnB, which is equivalent to the infinite dilute Henry's Law Constant, is used to represent the solubility of various molecules in water. Our research started with simple fluid and aqueous solutions of small molecules including hard spheres, inert gases, hydrocarbons and dimethyl ether (DME, as a precursor for PEO). Solubility consists of a favorable energy term and an unfavorable entropy term. Against the common belief of entropy-dominating-hydrophobicity effect, it is actually the ability of the solute to interact with solvent (or the energetic factor) that dominates solubility. The solubility minimum appearing for both hydrophobic and hydrophilic solutes along the water coexistence curve is the result of competition between the favorable energy contribution and the unfavorable entropy contribution. Normal alkanes with carbon number from 1 to 20 have been modeled by LJ chains to study the solubility of non-polar polymer chains in water. Various constraints have been put on the LJ model to evaluate their effect on solubility. No significant difference was observed for LJ chain with or without fixed bond angles, but torsional interaction changed the chain solubility dramatically. The temperature and chain-length effect on chain solubility has been examined and it can be explained by the balancing between the intra-chain interaction and entropy penalty. By choosing the right torsional interaction parameters we may be able to reproduce by simulations the solubility minimum of normal alkanes at C₁₁. PEO was modeled by united atom chains with length up to 30. The most probable distance between two nearest ether oxygens in both vacuum and aqueous solutions matches the hydrogen bond length in bulk water. Hydrogen bonding plays an important role in the unique water solubility behavior of PEO since the water-PEO interaction effectively increases the total number of hydrogen bonds and results in a favorable change in energy. A trans-gauche-trans conformation along the O-C-C-O bonds does enable hydrogen bond formation between one water molecule and two nearest or next nearest ether oxygens. A helix structure is not required for the PEO to have favorable interactions with water. Two polymers with similar structure as PEO but are insoluble in water: Poly (methylene oxide) (PMO) and Poly (propylene oxide) (PPO) have been studied to compare with PEO. Their difference in structure from PEO, though slight, reduces the chance of hydrogen bond forming between water and chains so as to decrease the solubility.
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碩士
中原大學
化學工程研究所
82
The solubilities of the mixtures of CO2 and H2S in aqueous MEA (monoethanolamine) / AMP (2-amino-2-methyl-1-propanol) solutions have been measured. The systems studied are CO2/MEA/ AMP/H2O,H2S/MEA/AMP/H2O,and CO2/H2S/MEA/AMP/H2O. For CO2/MEA/ AMP/H2O and H2S/MEA/AMP/H2O solutions,six blended amines solut ions(a total of 30 wt%) were selected for measurements for tem peratures 40 to 100 C. For CO2/H2S/MEA/AMP/H2O systems, the va por-liquid equilibrium studied are 3M MEA + 2M AMP and 2M MEA +3 M AMP at temperatures 40 and 80 C and for the partial press ures of the acid gases (CO2 or H2S) ranging from 1.0 to 160 kP a. THe obtained vapor-liquid equilibrium data have been correl ated based on the method of Kent and Eisenberg. The binary par ameters in the model were determined by fitting to the equilib rium solubility data.Satisfactory results were obtainded for calculation of the solubility of CO2 and H2S in MEA + AMP aque ous solutions for the systems tested. The use of blended amine s in gas-treating process has been shown to be attractive and with great potenial.The results of this study can be used as an important vapor-liquid equilibrium data base for design of the gas treating process units using MEA / AMP as absorption fluids. Also,the data can also be used to develop thermodynami ces model involving the solubilities of CO2 and H2S in MEA + AMP +water systems.

碩士
中原大學
化學工程研究所
84
The solubilities of the mixtures of CO2 and H2S in aqueous AMP (2-amino-2-methyl-1-propanol) / MEA(monoethanolam-ine) solutions have been measured. The system studied is CO2/H2S/ AMP/MEA/H2O . For CO2/H2S/AMP/MEA/H2O systems, six blended amines solutions (a total of 30 wt %) were selected for measurements at temperat- ures 40 and 80℃ and for the partial pressures of the acid gases ( CO2 or H2S ) ranging from 0.1 to 129 kPa. The obtained vapor- liquid equilibrium data have been correlated based on the method of Deshmukh and Mather. The binary parameters in the model were determined by fitting to the equilibrium solobility data.Satisf- actory results were obtained for calculation of the solobility of CO2 and H2S in AMP + MEA aqueous solutions for the systems tested. The use of blended amines in gas-treating process has been shown to be attractive and great potential. The results of the study can be used as an important vapor-liquid data base for design of the gas treating process units using AMP / MEA as absorption fluids. Also, the data can also be used to develop thermodynamics model involving the solubilities of CO2 and H2S in AMP+MEA +water systems.

碩士
國立中央大學
化學工程與材料工程研究所
99
It is well-known that crystalline materials obtain their fundamental physical properties from the molecular arrangement within the solid, and altering the placement and/or interactions between these molecules. Most studies were interested in the formation and structure of co-crystal/salt compound, the hydrogen bonding played an important role to affect physical properties. In crystal engineering for screening co-crystals/salts, this thesis focused on relating the physical properties such as the heat of fusion, the enthalpy of dissolution, the entropy of dissolution, and the solubility in water. Common laboratory analytical tools such as PXRD, DSC, TGA, FT-IR, OM, and SXD were used to understand the supramolecular architectures and to ensure the quality of co-crystals. 2:1 co-crystal of cytosine-fumaric acid, 2:1 co-crystal of cytosine-acetylenedicarboxylic acid, and 2:1 salt of cytosine-tartaric acid were manufactured. The significance of our research is to offer concept to study the solid state hydrogen bonding. In the experimental process, we used hydrogen bonding number in the solid-state to attempt to explain the co-crystal solubility in the liquid state, rather than using the solubility product in the liquid state to explain the co-crystal solubility in the liquid state.

Nuclear-based hydrogen production via thermochemical water decomposition using a copper-chlorine cycle consists of a series of chemical reactions that split water into hydrogen and oxygen. This is accomplished through reactions involving intermediate copper and chlorine compounds, which act as catalysts that are recycled in the process. In this thesis, analytical and numerical solutions are developed to predict the behaviour of aqueous cupric chloride droplets in a solution undergoing spray-drying in the Cu-Cl cycle. The aqueous CuCl2 is present as a slurry within the cycle, which will later generate oxygen and hydrogen as a net result. The efficiency of the cycle can be increased by utilizing low-grade waste heat from any industrial source or nuclear power plant to assist in the drying process. There are many different methods employed in industry for drying of solutions. Each method has its own advantages and disadvantages, depending on the application and conditions. In this thesis, analytical correlations of heat and mass transfer are developed for the aqueous solution, subject to various drying conditions. The analysis is performed for moist air in contact with a sprayed aqueous solution of CuCl2(2H2O). Validation of the model is performed by comparisons with experimental results obtained from a Niro-spray dryer for CuCl2 and previous experimental and theoretical data for different fluids, on the basis of non-dimensional analysis.
UOIT

Yes
Literature solubilities and NMR and IR studies have been used to obtain properties or descriptors of edaravone. These show that edaravone has a significant hydrogen bond acidity so that it must exist in solution partly as the OH and NH forms, as found by Freyer et al. Descriptors have been assigned to the keto form which has a low hydrogen bond acidity, and which is the dominant form in nonpolar solvents. Physicochemical properties of the keto form can be been calculated such as solubilities in nonpolar solvents, partition coefficients from water to nonpolar solvents, and partition coefficients from air to biological phases.
The full-text of this article will be released for public view at the end of the publisher embargo on 3 Mar 2022.

碩士
國立中央大學
化學工程與材料工程研究所
92
Abstract In this study, the solubilities of hydrogen in mixtures of toluene, norbornene, and cyclic olefin copolymer (COC) were measured at various temperatures (between 323.15 and 423.15 K), pressures (between 5 and 25 bar), concentrations of norbornene (between 0 and 85 wt %), and concentrations of COC (between 0 and 40 wt %). The experiments were conducted by the pressure decaying method using a newly designed apparatus. The experimental results show that the solubility of hydrogen increases with increasing system pressure but decreases with increasing system temperature in the above mixture. Another interesting observation is that the solubility decreases when the concentration of reaction product, COC, is increased. Thus, in addition to temperature and pressure, the COC concentration affects the reaction extent, and beyond a certain COC concentration, further reaction favoring COC generation is impossible because of the opposite effect on hydrogen solubility. Also, in this study, the experimental solubility data were expressed in vapor-liquid equilibrium relationship and correlated by bubble-pressure calculations with the Peng-Robinson equation of state incorporating the modified van der Waals one-fluid(vdW-1) mixing rules and the Zhong-Masuoka mixing rules, including the consideration of binary interaction parameters. The average absolute deviation percentages (AAD) of the correlation are less than 7 %, except that of pressure with the Z-M mixing rules.

碩士
中原大學
化學工程研究所
84
The equilibrium solubility of carbon dioxde and hydrogen su- lfide in aqueous mixtures of monoethanolamine(MEA) with methyld- iethanolamine(MDEA) has been correlated on the basis of the met- hod of Deshmukh and Mather. The extended Debye- Huckel expression given by Guggenheim has been used to calculate the activity co- efficients of both ions an dmolecules inivolved in the solution. The fugacity coefficients of the acid gas were determined using the Peng- Robinson equation of state. The interaction parameters among pair species were determined from the vapor-liquid equili- um data. The data base used in this study are MEA/MDEA/H2O/H2S/ CO2 from literatures at temperatures ranging from 40 to 100℃, pressures ranging from 0.8-1000kPa, concentrations of MEA rangi- ng from 0.5 to 5N and MDEA ranging from 1 to 4.2N. Statisfactory results were obtained for calculation of the solubility of carb- on dioxide and hydrogen sulfide in aqueous MEA/MDEA solutions tested. When performing the vapor- liquid equilibrium calculatio- ns for the systems which are not included in the data base, the correlation yields reasonably well results. The correlation obt- ained in this study can be used as a computation tool for the vapor-liquid equilibrium calculations for designing the acid ga- ses process using the aqueous MEA/MDEA solution as the absorpti- on fluid.

The design and discovery of sources for alternative energy such as coal liquefaction has become of major importance over the past two decades. One of the major problems in such design is the lack of available data, particularly, for gas solubility in polycyclic aromatics at high temperature and pressure. Static and gas-liquid partition chromatographic methods were used for the study of hydrogen-phenanthrene and methane-phenanthrene systems. The static data for these two binaries were taken along 398.2, 423.2, 448.2, 473.2 K isotherms up to 25.23 MPa. Pressure versus liquid mole fraction plots were presented as well as linear ln(f$\sbsp{\rm i}{\thinspace\rm g}$/x$\sb{\rm i}$) versus P-P$\sbsp{\rm s}{\rm vap}$ graphs. Using estimates of the partial molar volume in the liquid phase, V$\sbsp{\rm i}{\infty}$, the latter plots indicated both pressure and small liquid mole fraction deviations from ideal solution. Gas-liquid partition chromatography was used to study the infinite dilution behavior of methane, ethane, propane, n-butane, and carbon dioxide in the hydrogen-phenanthrene system as well as hydrogen, ethane, n-butane, and carbon dioxide in the methane-phenanthrene binary. The principle objective was to examine the role of the elution gas. Temperatures were along the same isotherms as the static data and up to 20.77 MPa. Comparison of the hydrogen and methane elution gas results indicated that the PK$\sbsp{\rm i}{\infty}$ product increases much more rapidly with pressure for the methane carrier data. However, plots of ln(PK$\sbsp{\rm i}{\infty}\phi\sbsp{\rm i}{\infty}$) versus P-P$\sbsp{\rm s}{\rm vap}$ were the same in both elution gases for ethane and n-butane. Using V$\sbsp{\rm i}{\infty}$ estimates, the plots displayed deviations from ideal solution due to pressure effects alone, with carrier gas absorption having essentially no effect. This was contrary to previous conclusions for infinitely dilute data in the hydrogen-9-methylanthracene system. Analysis of this data also indicated hydrogen solubility was not important. With the exception of carbon dioxide, Henry's constants were calculated for all systems. Expressions for the heat of solution as a function of pressure were derived for both binary and chromatographic data. Estimates of $\Delta$H$\sbsp{\rm i}{\rm sol}$ at high pressure were presented.

碩士
中原大學
化學工程研究所
84
The equilibrium solubility of mixture of carbon dioxide and hy- drogen sulfide in aqueous mixtures of diethanolamine ( DEA) with sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP) has been measured at 40 ℃ and 80 ℃ at partial pressure of the acid gases between 0.1 and 200kPa.The systems selected for this study are six blended amines solutions (total 30wt％) consisting of 30 wt﹪ DEA, 24 wt﹪DEA＋6 wt﹪AMP, 18 wt﹪DEA ＋12 wt﹪AMP, 12 wt﹪ DEA＋18wt﹪AMP,6wt﹪DEA＋24 wt﹪AMP,30wt﹪ AMP.The solubility mo- del of Deshmukh and Mather has been used to represent the data. The model reproduces reasonably the equilibrium partial pressur- es of CO2 and H2S above the solutions for the systems tested.

Yes
A new type of self-assembled polyelectrolyte complex nanocarrier composed of chondroitin (CHON) and protamine (PROT) was designed and the ability of the carriers to bind salmon calcitonin (sCT) was examined. The response of sCT-loaded CHON/PROT NPs to a change in the properties of the liquid medium, e.g. its pH, composition or ionic strength was studied and in vitro peptide release was assessed. The biocompatibility of the NPs was evaluated in Caco-2 cells. CHON/PROT NPs were successfully obtained with properties that were dependent on the concentration of the polyelectrolytes and their mixing ratio. X-ray diffraction determined the amorphous nature of the negatively charged NPs, while those with the positive surface potential were semi-crystalline. sCT was efficiently associated with the nanocarriers (98-100%) and a notably high drug loading (13-38%) was achieved. The particles had negative zeta potential values and were homogenously dispersed with sizes between 60 and 250 nm. CHON/PROT NPs released less than 10% of the total loaded peptide in the first hour of the in vitro release studies. The enthalpy of the decomposition exotherm correlated with the amount of sCT remaining in NPs after the release experiments. The composition of medium and its ionic strength was found to have a considerable influence on the release of sCT from CHON/PROT NPs. Complexation to CHON markedly reduced the toxic effects exerted by PROT and the NPs were compatible and well tolerated by Caco-2 cells.