Silica-alumina composite membranes for hydrogen separation and high temperature chemical reactions were prepared using both conventional and modified dip-coating techniques. These were deposited on commercially available a.-alumina macroporous support of 10 millimetre (mm) outer diameter, 7 mm inner diameter and average pore size of 6000 nanometre (nm) wash coated with Titania. The reactants of the coating technique were silicone elastomer and isopentane promoted by a catalyst. The catalyst (silicone curing agent) was added as a templating agent to control the eventual adhesion and densification of the elastomer sol. In particular, the microporous membranes were prepared by creating suction in the bore side of the membrane and involved continuous stirring of the coating mixture during the process, and their pore characteristics were analysed. Then, the effects of thermal treatment on the gas transport and micro pore structure of the resulting membranes were investigated. The pore size of the silica membrane prepared by conventional technique was in the range of approximately 8 to 11 nm while that prepared by modified dip-coating was in the range of about 3 to 4 nm. In addition, the membranes were segmented into five categories; silica membrane for hydrogen reaction, silica membrane for separation, silica membrane for purification, palladium (Pd)-impregnated membrane and silica on gamma -alumina (y-alumina). The hydrogen permeation of the silica membrane prepared for hydrogen reaction was of the order of 10-7 mol/m2.s.pa, while the nitrogen permeance was of the order of 10- mollm2.s.pa. at pressure differential of 0.5-2.0 bar and temperature range of 323-473 Kelvin (K). The maximum hydrogen I nitrogen (H2 I N2) selectivity, determined from single-component permeances to H2 and N2 was approximately 3.58. These permeances were decreased for the silica membrane prepared for hydrogen separation when the dip coating, drying and calcination was applied 7 times instead of 3 times as in the case of the hydrogen reaction membrane. The silica membrane for H2 separation provides permeances of about 5.8 x 10-9 mole.meter-2.second-l.pascarl (mol!m2.s.pa) for H2 and 9.4 x 10-10 mol/m2.s.pa for N2, with higher H21N2 selectivity of about 8. Higher mixed gas separation factors of H2:N2 > 400 and H2 permeance of 4.1 x 10-9 ol!m2.s.pa were achieved with silica membrane for H2 purification prepared with the modified dip-coating using suction technique with silicone elastomer as precursor. This technique was especially effective in plugging the macroporous support which possessed a wide pore size distribution. The membrane permeated gases except propane (C3Hg) by the activated diffusion mechanism at permeation temperature range of 298 -573 K, and the activation energies are in the order of 10.6 - 13 kilojoules I mole (kJ/mol) and 26.1-28.7 kJ/mol for H2 and N2 respectively. The tests have demonstrated that this composite membrane has the capability to separate hydrogen from gas mixtures with almost complete H2 selectivity and to produce high purity H2 (up to 99.0 %) from a 50 I 50 % H21N2 mixture stream. A theoretical model for a propane dehydrogenation reaction scheme in tubular and annular membrane reactors is developed. This model is applied to three different membranes namely: a silica-alumina membrane, a silica-y-alumina membrane and a Pd impregnated membrane. Results indicate that the Pd impregnated membrane provided very high theoretical conversions (82 % at 600°C) compared with the other two composite membranes.

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The H⁺₃ ion is the simplest and most fundamental of polyatomic molecules consisting of three protons and two electrons. H⁺₃ is an important molecule playing a key role in many areas of Physics, Chemistry and Astronomy. The astrophysical importance of H⁺₃ lies in the fact that most of the universe is made up of hydrogen, and molecular hydrogen in the cool regions. H⁺₃ is rapidly formed by the reaction H₂+H⁺₂→H⁺₃+H. Thus H⁺₃ is usually the dominant ion in environments containing molecular hydrogen. Furthermore, multiple deuterated species have been observed in the interstellar medium recently. These species are thought to have been formed via deuterium fractionation effects, in which the isotopomers H₂D⁺ and D₂H⁺ play a significant role. More than two decades have passed since Carrington and co-workers produced a remarkably rich spectrum of the H⁺₃. Over 27,000 absorption lines in a region between 872cm⁻¹ to 1094cm⁻¹. This experiment still remains largely unexplained. This work calculates intensities of transitions of states near dissociation. Thus will help illuminate the Carrington spectrum. Within this work I present a method of calculating line strengths for the H⁺₃ system. Several improvements on previous methods are presented, including the use of discrete variable representation, symmetry and a parallel algorithm. The implementation of this method on massively parallel computers is also discussed. Several applications of the synthetic spectra of H⁺₃ and isotopomers are presented. This will include where possible how they have aided other work and the results of this other work.

Ce document contient un rapport scientifique résultant de plus de quatre années de recherche théorique et expérimentale sur un type particulier de systèmes physico-chimiques appelés hydrates de clathrates de gaz. Ces systèmes sont des composés d'inclusion constitués d'un cadre aqueux tridimensionnel contenant des molécules de gaz avec de faibles moments dipolaires dans leurs cavités. Les hydrates de clathrate de gaz sont très importants dans une grande variété de domaines scientifiques liés aux sciences de la vie ou à la planétologie, et ils sont également considérés comme une ressource naturelle principale pour l'industrie de l'énergie. Habituellement, les hydrates de clathrate de gaz nécessitent une pression élevée et une température basse pour être thermodynamiquement stables. En fonction de ces conditions, différentes phases ont été détectées, les plus courantes étant les structures cubiques sI et sII, la sH hexagonale et la structure de glace remplacée orthorhombique (FIS). Notre étude a considérablement progressé dans la connaissance du comportement du méthane et des hydrates de clathrate de dioxyde de carbone dans différentes conditions de pression et de température. En particulier, nous avons contribué à : (i) la détermination et la compréhension des régions thermodynamiques de stabilité, (ii) la caractérisation d'une structure haute pression controversée et (iii) la mise en place d'un nouvel équipement expérimental pour les mesures Raman dans une gamme de pression jusqu'à 1 GPa [...] / This document contains a scientific report resulting from more than four years of theoretical and experimental research on a particular kind of physicochemical systems called gas clathrate hydrates. These systems are inclusion compounds constituted by a three dimensional water framework hosting gas molecules with low dipolar moments in its cavities. Gas clathrate hydrates are very important in a great variety of scientific fields related to life sciences or planetology, and they are also considered as a main natural resource for the energy industry. Usually, gas clathrate hydrates need high pressure and low temperature to be thermodynamically stable. Depending on these conditions, differentphases have been detected being the most common ones the cubic structuressI and sII, the hexagonal sH, and the orthorhombic Filled Ice Structure(FIS). Our study has substantially advanced in the knowledge of the behaviorof methane and carbon dioxide clathrate hydrates under different pressure andtemperature conditions. In particular, we have contributed to: (i) the determination and understanding of stability thermodynamic regions, (ii) the characterizationof a controversial high-pressure structure, and (iii) setting up a new experimental equipment for Raman measurements in a pressure range up to 1 GPa [...] / Este documento contiene el informe científico resultante después de más de cuatro años de investigación teórica y experimental sobre un tipo particular de sistemas físico-químicos llamados clatratos hidratos de gas. Estos sistemas son compuestos de inclusión constituidos por un armazón tridimensional de agua que aloja en sus cavidades moléculas de gas con momentos dipolares bajos.Los clatratos hidratos de gas son muy importantes en una gran variedad de campos científicos relacionados con las ciencias de la vida o la planetología, y también se consideran como uno de los principales recursos naturales para la industria energética. Por lo general, los clatratos hidratos de gas necesitan alta presión y baja temperatura para ser termodinámicamente estables.Dependiendo de estas condiciones, se han detectado diferentes fases siendo las más comunes las estructuras cúbicas sI y sII, hexagonal sH y la estructura ortorrómbica de hielo relleno (FIS). Nuestro estudio ha avanzado sustancialmente en el conocimiento del comportamiento de los clatratos hidratos de metano y dióxido de carbono en diferentes condiciones de presión y temperatura, proporcionando (i) regiones termodinámicas de estabilidad, (ii) la caracterización de una estructura de alta presión controvertida y (iii) un nuevo equipo experimental para mediciones Raman en un rango de presión de hasta 1 GPa [...]

Dans le cadre de la recherche de vecteurs d'énergie “propres”, le borazane et ses dérivés amine-boranes sont devenus des candidats intéressants en tant que matériaux de stockage de l'hydrogène en raison de leur pourcentage massique relativement élevé en hydrogène (19,6% pour borazane) et de la réversibilité potentielle de la réaction de déshydrogénation. Pour des applications réelles, le contrôle des réactions se produisant à la température ambiante est fondamental. Dans ce contexte, la compréhension du processus de la déshydrogénation/déshydrocouplage catalytique de l'amine-borane apparaît comme un élément important. Dans cette thèse, les catalyseurs de types métallocènes du Groupe IV (Cp2M, M = Ti, Zr et Hf) sont étudiés en détail. Le déshydrocouplage de HMe2N·BH3 catalysé par le titanocène a été étudié à la fois expérimentalement et théoriquement mais aucun accord n'avait été atteint auparavant. Dans ce travail, les caractérisations systématiques des interactions 3-centre 2-électron M···H-B impliquées dans les intermédiaires réactionnels ont été réalisées avec des approches topologiques QTAIM et ELF. Par la suite, des mécanismes réactionnels détaillés ont été étudiés. Les résultats théoriques ont démontré que la méthode DFT corrigée avec la dispersion (DFT-D) étaient nécessaire et suffisantes pour une description énergétique correcte des chemins réactionnels. Mon travail a également permis l'identification d'un complexe de van der Waals jouant un rôle clé dans le mécanisme réactionnel en accord avec les observations expérimentales. / With the increasing demand of clean energy carriers, ammonia borane and its related amine-borane compounds have emerged as attractive candidates for hydrogen storage materials due to their relatively high weight percentage of available hydrogen (19.6% for ammonia borane) as well as the potential reversibility for the hydrogen release reactions. Actual applications would benefit from controlled reactions occurring close to room-temperature. In this context, catalytic dehydrogenation/dehydrocoupling of amine-borane appears as a promising solution. In this thesis the Group IV metallocene (Cp2M, M = Ti, Zr and Hf) are mainly discussed. The dehydrocoupling of HMe2N·BH3 catalyzed by titanocene was investigated both experimentally and theoretically but no agreement were reached. In this work, systematic characterization of M···H-B 3-center 2-electron interactions involved in reaction intermediates were carried out with QTAIM and ELF topological approaches. Afterwards, detailed mechanisms were further studied. Computational results have demonstrated that the dispersion corrected DFT (DFT-D) method was indispensable for a correct enegetic prediction for reaction pathways. The identification of a van der Waals complexe also plays a central role for a reaction mechanism with good agreement with experimental observations.