Dissertationen zum Thema „Catalyse – Teneur en silicium“
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Pascaretti, Mathieu. „Catalyse synergique οr/silicium par activatiοn d’οrganοsilanes et d’hydrοsilanes au mοyen de cοmplexes d’Au(Ι) : dévelοppements et applicatiοns“. Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH01.
Der volle Inhalt der QuelleSince the early 2000s, gold catalysis has developed particularly well in organic chemistry, offering new highly efficient synthetic methods, generally under very mild conditions. These advances have also led to abundant use in glycoscience, but despite important breakthroughs, the application of gold catalysis in glycochemistry is typically limited to conventional modes of sugar donor activation, in which the gold complex remains strictly confined to the role of a σ- or π-Lewis acid. The research work presented through this manuscript tends to introduce a new paradigm in gold-catalysed glycosylation reactions, by developing catalytic alkynylation reactions in which the gold complex should overcome the intrinsic difficulties of these couplings by contributing to the simultaneous activation of the sugar donor and the alkyne aglycone, based on an original gold/silicon synergistic catalysis strategy. The ideal combination of gold catalyst and counterion was sought (L and X) to achieve optimum catalytic reactivity and stereochemical control both for the alkynylation reaction of simple saturated glycosides and for the alkynylation of glycals. The discovery of a major impact of a hitherto unexploited Au(I) complex counterion in synergistic gold/silicon catalysis associated with a strongly deactivating phosphine has made it possible to extend the field of application of synergistic gold/silicon catalysis beyond the alkynylation of glycosides
Hoàng, Quoc Lam. „Séparation sélective de la cellulose, des hémicelluloses et des lignines par le système catalyseur-solvant : acide formique-acide acétique, de matières végétales à teneur variable en silicium“. Toulouse, INPT, 2000. http://www.theses.fr/2000INPT002C.
Der volle Inhalt der QuelleGuntzer, Flore. „Impact de la culture intensive de céréales sur les stocks de silice biodisponible dans les sols européens“. Aix-Marseille 3, 2010. http://www.theses.fr/2010AIX30064.
Der volle Inhalt der QuelleSilicon is found in the same proportions as most macronutrients in plants and is known to be beneficial for their growth. Although silicon is one of the main constituents of soil, most of the forms under which it is found are not available for plants. In natural ecosystems, phytoliths (amorphous silica particle recycled by plants) are one of the main sources of silicon for plants as their dissolution cinetic is way faster than that of other silicate minerals at pH > 4. However in cultuvated soils where the crops are exported, phytoliths do not come back to the soil. We studied soils cultivated with cereals to asses the impact of the exportation of crops on the amorphous silica stock. All studied soils were poor in amorphous silica. We also studied the effect of different Si fertilization. Restoration of straw to the soil, even for a short period of time, has a real impact on the stock of amorphous silica. This means the restitution of straw could be a simple remediation for the decrease of the bioavailable silica stock of cultivated soils
Ducos, Paul. „Synthèse de nouveaux acides de Lewis silylés pour la catalyse organique“. Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0439/document.
Der volle Inhalt der QuelleIn contrast with carbocations which existence was unambiguously proven in the early 60’s, silylium ions (R3Si+) have remained for a long time elusive species and putative intermediates in many transformations involving organosilicon compounds. It was only in 2002 that the first structural proof (X-ray crystallography) dispelled any doubt about the existence of tricoordinated silicon cations in the condensed phase. Silylium ions are extremely electrophilic, able to coordinate to weak Lewis bases including solvent molecules such as benzene. The possibility to tame this acidity through an appropriate labile coordination even widens the scope of applications of these reactive species and allows their use as catalysts for organic synthesis. The aim of this thesis was to synthesize new stabilized silyliums ions and rationalize the impact of this stabilization onto the reactivity. In a first part, we focused on the use of hindered nitrogen derivatives to stabilize the silicon center. The nature and the strength of the interaction were assessed by NMR spectroscopy and theoretical calculations. In a second part, the introduction of chirality onto the silicon cation has been studied. A series of binaphtyl templated silyliums bearing an intramolecular Lewis base were synthesized. According to the strength of the stabilization, the chiral information present on the silicon can be persistent and used for asymmetric catalysis
Wang, Huiyuan. „Quantification et distribution du bore dans le silicium implanté“. Rouen, 2013. http://www.theses.fr/2013ROUES042.
Der volle Inhalt der QuelleThis work is composed by three parts. In the first part, we have studied theoretically the influence of the temperature on the nucleation rate of precipitates in a supersaturated binary alloy. The more elaborate theory of Zeldovich has shown that the nucleation rate present a single maximum as function of temperature, which is similar to the classical theory of Volmer-Weber. A comparison between those two theories has shown that the regression effects (the supercritical germs can dissolve in a small area around the critical size) have a strong influence on the nucleation rate. We have applied this theoretical study into the Si-B system. Due to the high activation energy of B in the Si, the study has shown a weak influence of the regression effects, resulting in a slight decrease in temperature giving the maximum of the nucleation rate in the Si-B system. In the second part, the secondary ion mass spectrometry (SIMS), Scanning transmission electron microscopy - Electron energy loss spectroscopy (STEM-EELS) and the atom probe tomography (APT) have been combined for the quantification of B in high concentration implanted Si, their strengths and weaknesses have been shown in the characterization of B in Si. Concerning the multi-hit detection in APT, a new method of treatment of signals coming from the detection system of the atom probe has been applied. An important progress concerning the multi-hit detection and the quantification of B in the Si has been demonstrated by our experiences. In the third part, we have studied the precipitation of B in the Si weakly supersaturated and highly supersaturated. The studies of the precipitation of B in the Si weakly supersaturated have shown that it is very difficult to study only the precipitation due to the presence of implantation defects (dislocation loops…). To privilege the precipitation, the study of the precipitation of B in the highly supersaturated Si has shown that there is phase separation after the implantation. At low thermal budget, the composition of the precipitates is much lower than the one of the equilibrium phase SiB3, but at high temperature, a regime of Si-B spinodal decomposition is suspected for the more concentrated alloys
Leroux, Denis. „Polystyrène sulfoné supporté sur silice poreuse : greffage et activité en catalyse acide“. Lyon 1, 1994. http://www.theses.fr/1994LYO10290.
Der volle Inhalt der QuelleDavach, de Thèze Jean-François. „Vapoconversion catalytique sélective de produits aromatiques en présence de composés soufrés“. Lyon 1, 1986. http://www.theses.fr/1986LYO10521.
Der volle Inhalt der QuelleBrouty, Marie-Sophie. „Recherche de nouveaux catalyseurs acides supportés de type polyphénylsilsesquioxanes chlorés sulfonés greffés sur silices“. Lyon 1, 1995. http://www.theses.fr/1995LYO10135.
Der volle Inhalt der QuelleLecomte, Sandrine. „Préparation des diénolates de potassium à partir des diénoxysilanes et du tertiobutylate de potassium : Etude de leur condensation régiosélective avec les dérivés carbonylées. Mise au point d'une méthode de prénylation“. Rouen, 1997. http://www.theses.fr/1997ROUES072.
Der volle Inhalt der QuelleMadani, Behrang. „Synthèse de Fischer-Tropsch sur catalyseur à base de cobalt supporté sur carbure de Silicium“. Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/MADANI_Behrang_2005.pdf.
Der volle Inhalt der QuelleThe Fischer-Tropsch synthesis (FTS) leads to various products, mainly alkanes as well as olefins and alcohols, starting with precise mixture of CO and H2. Currently, natural gas is recovered as a by-product of oil extraction and directly burnt, which leads a non negligible economic loss as well as an atmospheric pollution due to the production of CO2. The reaction of FTS is one of the ways permitting valorisation of natural gas after its transformation in gas of synthesis (mixture of CO and H2). The SFT reaction is exothermique and requires fast evacuation of heat from the catalytic sites in order to avoid the problem of hot spots formation and subsequent cracking of formed products. The supports used traditionally for the FTS are insulating supports, such as alumina and silica, which does not permit a good evacuation of heat. In this work, we replaced the insulating support by a conducting support based on SiC, which permits a better homogenisation of the temperature in the catalytic bed. In this study, different reaction parameters- the Co content, the total pressure and contact time, have been optimized in order to obtain the best activity, selectivity and stability of the catalysts. We also studied the influence of the morphology of the support on the catalyst performance. Among the different shapes of support based on SiC (grain, extrudes and foam), the support as foam seems to have the best performance. We finalised the procedures of regeneration of the catalyst as well as the doping by molybdenum. The thus obtained catalysts present the best activity and selectivity
Garcia, Cervantes Gabriela. „Préparation et caractérisation de catalyseurs palladium sur supports thermoconducteurs (Si3N4, SiC, Cdiamant) : performances en catalyse d'hydrogénation du butadiène-1,3 et/ou d'oxydation totale du méthane“. Lyon 1, 2004. http://www.theses.fr/2004LYO10074.
Der volle Inhalt der QuelleDe, Tymowski Benoît. „Synthèse de Fischer Tropsch sur support conducteur à base de carbure de silicium“. Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00855282.
Der volle Inhalt der QuelleA, Ahad Hadad Caroline. „Valorisation de pentoses via la synthèse de glycodendrimères“. Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000979.pdf.
Der volle Inhalt der QuelleWith the aim of developing renewable ressources from the region of Champagne-Ardenne, we synthesized glycodendrimers, starting from two pentoses (D-xylose and L-arabinose), usable in micellar reactions or like artificial receptors in biomedical field. The first part of this memory relates to the synthesis of nitrogen-based glycodendrimers starting from PAMAMs (PolyAMidoAMines) or PPIs (PolyPropylene Imines) having both the functions amines on the surface. By reaction of condensation between these functions and the pentonolactones, resulting from the two pentoses, we succeeded in obtaining glycodendrimers of first generation. However optimization with the higher generations remains to be developed. Then, in a second part, we wanted to obtain silicon glycodendrimers starting from three kinds of reaction: hydrosilylation, silylation and click chemistry. No convincing results were obtained starting from the reactions of hydrosilylation some either catalyst used and some length of the chain. On the other hand, small molecules and dendrimers of first generation were obtained by a sequence “hydrosilylation/condensation” and by reaction of silylation. Glycodendrimers of generation 1 to 3 were obtained by click chemistry but the method of purification remains to be developed. Lastly, the third part appeared much more encouraging because we succeeded in obtaining the phosphorated first glycodendrimers, starting from a derivative of D-xylose, of generations 1 to 3 by reaction of substitution with quantitative yields. A simple method of purification by successive precipitations was also developed as well as the deprotection of the acetyls groups
Berthet, Agnès. „Propriétés du palladium déposé par jet atomique et par pulvérisation plasma sur des supports réfractaires (SiC et Si3N4) : texture, structure et réactivité en catalyse“. Lyon 1, 1999. http://www.theses.fr/1999LYO10156.
Der volle Inhalt der QuelleHelsens, Sylvie. „Comportement vis à vis de la corrosion aqueuse d'aciers inoxydables austénitiques à 12% de chrome et à teneur variable en silicium“. Toulouse, INPT, 1988. http://www.theses.fr/1988INPT019G.
Der volle Inhalt der QuelleHelsens, Sylvie. „Comportement vis-à-vis de la corrosion aqueuse d'aciers inoxydables austénitiques à 12% de chrome et à teneur variable en silicium“. Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376142243.
Der volle Inhalt der QuelleZidelmal, Nacim. „SILIPOLYSALEN : étude du greffage par polymérisation contrôlée de complexes de salen sur silicium pour une application en catalyse asymétrique hétérogène“. Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS058.
Der volle Inhalt der QuelleChiral metal complexes of salen type are known for their efficient catalytic activity leading to the preparation of enantioselective enriched synthons. In accordance with the concept of green chemistry, one of the main challenge is to establish a procedure for the recovery and reuse of these catalysts. In this context, the objective of this work is to functionalize the silicon surface by grafting these catalysts by controlled polymerization especially by Atom Transfer Radical Polymerization (ATRP) to facilitate their recovery and reuse.Thus, styrene copolymers containing 5 to 50 mol % of an disymmetric salen comonomer were synthesized by ATRP in solution. The controlled nature of the polymerizations is obtained only when the incorporation of the salen comonomer is less than or equal to 10%.After complexation with cobalt, these complexes are shown to be capable of effective cooperative activation, leading to the targeted product with high yields and selectivities as catalysts in Hydrolytic Kinetic Resolution (HKR) of epibromohydrin.Constantio Constantini fratre imperatoris, matreque Galla.We also reported the polymerization of styrene on the silicon surface by ATRP after grafting of the initiator. Several methods of initiator grafting have been used either directly from the hydrogenated surface or indirectly from an acid or ester surface. Styrene has been successfully mass polymerized in a controlled manner on silicon with thicknesses of 9-29 nm of the layer obtained by ellipsometry and Atomic Force Microscopy
Sauvageot, Elodie. „Nouveaux complexes d’Ir(III) à ligands azotés : catalyse photoredox (enantiosélective) et inhibition du TNF-alpha“. Caen, 2015. http://www.theses.fr/2015CAEN2061.
Der volle Inhalt der QuelleIn the context of green and sustainable chemistry, visible light-mediated photoredox catalysis has become a rapidly growing field in the last few years. This new tool allowed to achieve numerous and diverse chemical transformations in mild conditions. However, stereoselective reactions are still rare and require the presence of polarized bonds on the substrates. The aim of this thesis was to develop new chiral catalysts, especially artificial metalloenzymes, for stereoselective applications on a broad range of substrates. This work was completed in two steps: (i) synthesis and catalytic evaluation of iridium(III) and ruthenium(II) complexes bearing adjustable dipyridylamine ligands; (ii) incorporation of the complexes exhibiting the best photocatalytic activity within protein, such as glucosidases and streptavidin. The activity of the new biohybrids catalysts was then assessed in photoredox catalysis. Anti-inflammatory properties of iridium(III) complexes were also evaluated in vitro as potent inhibitors of TNF-/TNFR-1 interaction. The results obtained during this work pave the way toward a new class of photoredox catalysts and TNF-inhibitors
Béal, Maxime. „Compréhension et maîtrise de la mise en œuvre par fabrication additive (LPBF) d'un alliage d'aluminium à basse teneur en silicium pour l'aéronautique“. Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2022. http://www.theses.fr/2022ECDL0026.
Der volle Inhalt der QuelleAdditive manufacturing is becoming more and more mature and has shown its capacity to be a disruptive technology in terms of industrial innovation. Indeed, additive manufacturing allows to obtain a functional part from a 3D file. Laser Powder Bed Fusion (LPBF) is one of the additive manufacturing processes. Thales® is very interested in this type of process and would like to develop LPBF to increase its competitiveness in the aeronautical market. An aluminium alloy has been developed for the LPBF process and patented by Thales in 2019. The objective of the thesis work presented in this manuscript is to continue the work carried out on this alloy and to facilitate the industrialisation process of this alloy by the LPBF process for aeronautical and aerospace parts. The manuscript is divided into 4 parts, the first one focusing on the bibliography and the methods used. The second part deals with laser-material interaction and roughness optimisation. Part three deals with the life cycle of the powder by analysing the effect of reuse and storage on the process. Finally, the fourth and last part focuses on the optimisation of the chemical composition of the alloy and the search for a suitable heat treatment. The optimisation of the laser interaction showed the relationship between the parameters used and the geometry of the molten pool formed. It was also shown that it was harder to use the 6061-Zr alloy than a cast aluminium alloy such as Al-Si alloy. This chapter also highlighted the focal shift phenomenon and the importance of the plate altitude which has a strong impact on the process. Subsequently, a roughness optimisation was carried out by applying contours. A very good surface finish was obtained, however, this method was tested on more complex geometries than cubes and showed its weaknesses. The life cycle of the powder was then discussed. The reuse of the powder leads to an increase in oxygen content and chemical modification of the powder. Sieving is essential to ensure particle size and avoid these phenomena. The storage of powders is critical for the intended applications. Indeed, storage as carried out in this study has shown a strong impact on the process reducing the density, elongation and resilience of the parts while degrading the surface finish. As the patent for 6061-Zr is quite broad, the zirconium content was optimised to meet the specifications as much as possible while avoiding hot cracking. Subsequently, heat treatments were applied to alloys with different levels of Zirconium in order to observe the impact of these treatments as a function of temperature, duration and the level of Zirconium content. All of these results helped to remove scientific obstacles and thus facilitate the progression of this technology into controlled industrialisation for aeronautical and space applications
Guellil, Imene. „Nano-fonctionnalisation par FIB haute résolution de silicium“. Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0361.
Der volle Inhalt der QuelleThe goal of this work is to develop a process for the elaboration of silicon-germanium (SiGe) quantum dots (QDs) with compositions ranging from Si to pure Ge, and allowing to obtain semiconducting QDs with sufficiently small sizes to obtain quantum confinement. For this purpose, we have used a combination of different techniques: molecular beam epitaxy, focused ion beam lithography (FIBL) and heterogeneous solid state dewetting. In this context, the aim of this research is on the one hand to develop a new FIB that can be coupled to the ultra-high vacuum molecular beam epitaxy growth chamber, and on the other hand to realize two applications: (i) nanopatterns for the self-organisation of Si and Ge QDs and (ii) nano-implantations of Si and Ge. We used FIBL with energy-filtered liquid metal alloy ion sources (LMAIS) using non-polluting ions (Si and Ge) for the milling of conventional microelectronic substrates such as SiGe on silicon-on-insulator (SGOI). The nanopatterns must be totally free of pollution and with variable and perfectly controlled characteristics (size, density, depth). The morphology of the nanopatterns is then characterized in-situ by scanning electron microscopy (SEM), and the depth is determined ex-situ by atomic force microscopy (AFM). The nanopatterns made by FIBL were compared on the one hand to plasma etchings with He and Ne and on the other hand to the etchings obtained by electronic lithography (EBL). Nanoimplantations of Si and Ge ions were realised in diamond and in ultra-thin SGOI for the fabrication of local defects
Thomas, Shibin. „Elaboration par électrodépôt en liquide ionique de films minces et de nanofils de silicium / Silicium-Terre Rare et propriétés optiques associées“. Thesis, Reims, 2017. http://www.theses.fr/2017REIMS032.
Der volle Inhalt der QuelleThanks to their specific physical properties different from the massive materials, nanostructured materials have led to important technological progress. Since silicon is the predominant material in microelectronics, and due to a large surface to volume ratio, silicon nanowires are promising in many fields of applications such as optoelectronics or biological sensors. Nevertheless, the synthesis techniques currently used are still relatively complex to implement and thus costly and there is still a huge gap between the synthesis and the development of laboratory demonstrators and the realization of functional and marketable devices.This thesis work deals with the study of a new low cost synthesis technique, the electrodeposition in ionic liquid, to grow nanowires of silicon or silicon incorporating Earth-Rare ions with emission properties of emission in the visible or the near infrared range. One of the objectives of this thesis was to understand the influence of the different electrodeposition parameters on the growth of pure silicon thin films and to see if it was possible to synthesize silicon/terbium films, the terbium emitting in the visible, and Silicon/Erbium, erbium emitting at 1.55 μm. Thanks to different electrochemical studies and structural characterization of thin films, we have shown that this mode of synthesis makes it possible to obtain thin films of amorphous silicon of very good quality and without impurity. By controlling the deposition potential, temperature, and active species concentration, we were able to control and optimize the growth conditions, which allowed us to obtain amorphous silicon nanowires with diameters ranging from a few tens to a few hundred nanometers using nanoporous membranes as a mold. These nanowires are passivated by a surface oxide layer after dissolution of the membrane and exposition to air. An interesting property of these amorphous silicon nanowires is that they have a high luminescence in the red range at room temperature, in particular for diameters in the order of 100 nm. Optical and structural studies showed that this emission was due to the amorphous nature of the nanowires and that a mechanism of band-tail recombination and the spatial confinement of the carriers whitin the nanowires made it possible to explain the intense emission observed.The second important part of the thesis was the possibility of making films and nanowires of the silicon/rare earth type. We have shown for the first time that it was possible to synthesize simultaneous co-deposited films of silicon and rare earth elements for Tb and Er. By varying the deposition potential, we have shown that it is possible to tune the incorporated rare earth concentration by a few % to 20%. The structural studies show that this incorporation is carried out homogeneously in the thickness of the films and without changing the morphology. Thanks to this homogeneity, the thin films obtained emit at ambient temperature and at the expected wavelengths for the rare earth ions. Following this study as thin films, we then carried out the growth of Si/Tb and Si/Er nanowires using nanoporous membranes. We have obtained nanowires of silicon incorporating terbium or erbium with varying concentrations. The nanowires thus synthesized are also homogeneous in composition over the entire length and emit with high intensities at ambient temperature for terbium. For Si/Er nanowires, the emission intensity is low at ambient temperature but thermal annealing makes it possible to activate the terbium ions and to obtain an intense emission at ambient temperature
Roumanie, Marilyne. „Microréacteur pour la catalyse hétérogèneApplications : Stockage d'hydrogène dans les hydrocarbures Filtre pour capteur gaz“. Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2005. http://tel.archives-ouvertes.fr/tel-00012119.
Der volle Inhalt der QuelleRey, Nadège. „Synthèse de silices hybrides méso-structurées par auto-assemblage : vers des applications en catalyse“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2019. https://theses.enscm.fr/interne/ENSCM_2019_REY.pdf.
Der volle Inhalt der QuelleHybrid Silica-based materials have been investigated for many applications, ranging from micro-lenses for optics to drug encapsulation for health. In particular, the incorporation of metal cations in organized silica-based network is essential to the design of supported catalysts. Si-based matrices exhibit tunable mechanical properties, thermal stability and porosity. These matrices can be prepared with different shapes that play a role in their applications. Rods, stars, dumbbell, layer or polymeric network, that can be categorized in 2D or 3D architectures, are among the shapes encountered in the literature. For the construction of 2D and 3D architectures, several families are studied, such as bridged silsesquioxanes, polyhedral oligomeric silsesquioxanes (POSS) and lamellar silica.Lamellar silica is used as scaffolds or 2D building blocks to create functional materials. Crystalline layered silicates are easily modified by the intercalation of guest molecules and ions in the interlayer. Covalent modification is achieved by silylation of the interlayer Si–O- / Si–OH groups with organosilanes. Moreover POSS consists of a cage-like structure and formula (RSiO3/2)n, R being an organic group. T8 structure is the most common one which when it is octa-substituted can be used as a node in a polymer-like self-assembly by connection to other POSS. In the case of a mono-substituted cage, two scenarios are available: functionalization of the substituted corner or synthesis of dumbbell-like object formed by grafting of another POSS.In this work, the aim is to provide new functional hybrid materials involving original 2D and 3D architectures.2D self-structure assemblies, made of lamellar silica and silylated organic linkers, will be used for complexation reactions and catalysis For this purpose, there is a need for new functional linkers. Here, we present the original synthesis of linkers for the assembly of the 2D structures. Inspired by previously reported bis-urea compounds, we designed and prepared bi-functional urea-thiourea monosilylated linkers. The originality of these flexible molecules comes from the combination of four key sites allowing interactions or complexation: (i) the silyl moiety will serve as a single grafting anchor to the lamellar silica, (ii) the urea moiety will promote order in the self-assembled layer via H-bonding, (iii) the thiourea moiety will mainly serve for the coordination of metallic cations and (iv) in the case of the monosilylated precursors, the terminal functional R group will offer the possibility of self-organization of the pillars within the layer. Hence long alkyl chains are likely to interact through Van der Waals interactions and to tune the interlayer distance and thus the size of the cations possibly hosted within the layers while aryl R groups will enable the self-assembly thanks to the-conjugated system.3D self-structure assemblies will be synthesized from POSS and bis-silylated organic linkers. We used a bis-silylated version of the urea-thiourea compound as well as various bis-silylated malonamide compounds. The panel of malonamide compounds will allow to tune the flexibility of the final structure offering more or less accessibility for the metal complexation in the system. Prior to the materials synthesis, we investigated the feasibility of various dumbbell systems as models for the future studies and for a better understanding of the possible arrangement of these units within the final corresponding materials. We also demonstrate the formation of polymeric-like self-assembled hybrid silica by using Si-H functionalized POSS/POS connected with the same bridging units
BEN, TAYEB AMAR. „Influence de la teneur en silicium sur la solubilite et la diffusion de l'hydrogene (deuterium) dans les alliages pd#1#0#0##xsi#x amorphes“. Paris 6, 1990. http://www.theses.fr/1990PA066405.
Der volle Inhalt der QuelleO'Donnell, Benedict. „Plasma grown silicon nanowires catalysed by post-transition metals and applications in radial junction solar cells“. Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/76/15/66/PDF/ODonnell_-_PhD_2012.pdf.
Der volle Inhalt der QuelleIn this thesis, disordered arrays of vertical silicon nanowires are used to trap light in PECVD-deposited silicon solar cells. The abrupt surface which they present can absorb light efficiently and be manufactured in the same vacuum run as the other layers of the cell, offering the prospect of dispensing with the additional fabrication steps conventionally required to texture the substrates of thin-film photovoltaics. Drops of liquid tin and indium, designed to catalyze the growth of silicon nanowires, were deposited and rearranged on transparent conducting oxide substrates under vacuum to obtain metal drop configurations with diameters and densities spanning several orders of magnitude. In discussing the suitability of different metals to catalyze the growth of silicon nanowires, we have highlighted distinctions between the behavior of transition and non-transition metals for vapor-liquid-solid growth and studied in particular the case of silicon nanowires catalyzed by tin. Nanowires doped P-type with the appropriate morphology were covered in conformal layers of intrinsic and N-type hydrogenated amorphous silicon, and an indium-tin-oxide electrical contact to produce networks of 107 radial PIN junctions connected over areas of 3. 1 mm². Optimizing the fabrication process of these devices has led to open-circuit voltages of 0. 8 V and short-circuit currents of 13 mA/cm². The cells are deposited over untextured substrates using techniques which are compatible with a single pump-down process. Their ability to trap light rivals that of established texturing techniques and their performance comes close to that of planar PIN structures
Ksiaa, Mariem. „Étude de l’effet du silicium chez Hordeum marinum sous déficiences nutritionnelles“. Electronic Thesis or Diss., Sorbonne université, 2022. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/NNT.pdf.
Der volle Inhalt der QuelleSilicon (Si) is a ubiquitous element; it is considered to be the second most abundant element in the lithosphere after oxygen. It is not considered as an essential element for plants. However, the addition of Si in crops under abiotic stress gives them a better tolerance to stress. The first objective of this work was to study the effect of Si in Hordeum marinum, a plant species known to accumulate Si, under iron deficiency. This Poaceae species is of interest for livestock fodder and valorization of marginal zones. Our results indicate that growth parameters, water status, photosynthetic gas exchange, photosynthetic pigment contents, chlorophyll fluorescence and iron accumulation are improved by Si treatment when plants are grown under iron deficiency. We also investigated the effect of seed priming with Si in H. marinum seeds as an inexpensive and easy method to alleviate the effect of stress. Our results showed that germination rate, growth parameters, membrane integrity, activities of antioxidant enzymes and soluble sugar content are all improved by Si pre-treatment in plants growing under iron deficiency. The last objective of this work aimed to understand the behavior of Arabidopsis thaliana, a non-accumulating Si species, in response to stress. Interestingly, our results show that silicon acts positively on germination, development and antioxidant stress in A. thaliana, possibly through a modulation of proline metabolism
Tymowski, Benoît de. „Fischer Tropsch synthesis on conductive silicon carbide based support“. Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF019/document.
Der volle Inhalt der QuelleThe Fischer-Tropsch synthesis (FTS) allows the transformation of a mixture of synthesis gas, i.e. H2 and CO, into valuable liquid hydrocarbons. The catalysts generally used in FTS are based on iron or cobalt supported on alumina or silica. ln the present work, silicon carbide (SiC) has been proposed as a replacement media to traditional supports. The results obtained indicate that the mesoporous SiC containing cobalt catalyst exhibits a good FTS activity and an extremely high selectivity towards liquid hydrocarbons compared to other FTS catalysts supported on alumina or silica. The FTS activity on the Co/SiC catalyst can be improved by changing the impregnation solvent or by promoting the cobalt phase with trace amount of noble metal. The doping of the SiC support with Ti02 phase also significantly improves the FTS activity keeping a similar high selectivity thanks to the formation of small cobalt particles in contact with the Ti02 phase
Gombert, Bertrand. „Etude de l'oxydation par l'ozone en présence de catalyseurs solides de molécules organiques en milieu aqueux“. Poitiers, 1999. http://www.theses.fr/1999POIT2292.
Der volle Inhalt der QuelleLescure, Régis. „Synthèse et propriétés de cétones aliphatiques à longue chaîne et de leurs dérivés azotés“. Montpellier 2, 1995. http://www.theses.fr/1995MON20212.
Der volle Inhalt der QuelleRuiz, Johal. „Nouvelles synthèses par catalyse de composés organosilicés et leur transformation en fragments de polycétides“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S138/document.
Der volle Inhalt der QuelleThe aldol reactions is one of the most important and commonly used methods to form C-C bonds. The catalytic tandem isomerization-aldol reaction of allylic alcohols allows to perform this reaction with many synthetic advantages. Thus, we have prepared by this method beta-hydroxyacylsilanes from alpha-hydroxyallylsilanes. First, we have attempted to develop a catalytic asymmetric version of this reaction, and also to synthesize beta-hydroxyacylsilanes by direct aldol reaction. Then, we used alpha-hydroxyallylsilanes to prepare alpha-silyl aldols trough epoxidation reactions. Next, we synthesized aldols from protected beta-hydroxyacylsilanes in a simple and efficient fashion which allowed us to perform iterative aldol reactions. We have illustrated the potential of this method by the synthesis of a fragment of (±)-pironetine. Finally, we have synthesized, from the same protected beta-hydroxyacylsilanes, silyl enol ethers that next have been used successfully as substrates for Mukaiyama aldol reactions
Jeon, Taewoo. „Nanostructured hybrid solar cells based on PECVD grown SiNWs and organic semiconducting polymers“. Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/91/78/26/PDF/Thesis_Taewoo_JEON_EP_PICM.pdf.
Der volle Inhalt der QuelleSolar cells are an exciting alternative energy technology due to the infinite energy source, the Sun. Many types of solar cells based on inorganic or organic materials are currently developed with the objective of higher efficiency and lower cost. In this context, this thesis suggests to study nano-structured hybrid solar cells based on silicon nanowires (SiNWs) and organic active materials to benefit advantages of both materials. SiNWs are grown by PECVD on transparent conducting oxide via Vapor-Liquid-Solid (VLS) mechanism with careful control of their nano-morphology. The organic materials made of polymers or blend polymers are then deposited by spin-coating on top of SiNWs. In these hybrid solar cells the SiNWs are used as light-trapping medium and/or electron acceptor material. For better solar cell performance, the optimization of SiNWs array is carried out by removing residual catalyst and etching parasitic hydrogenated amorphous silicon. Their effects on hybrid solar cells have been fully analyzed and discussed. Furthermore, the electron-acceptor properties of the nano-structured SiNWs have been estimated with Bismuth-doped n-type SiNWs. The results clearly reveal the potential of this type of hybrid solar cells, namely, 1) power conversion efficiency improvement by enhancing external quantum efficiency in longer wavelength regime and 2) variety uses of SiNWs by tuning their electrical property and morphology
O'donnell, Benedict. „La croissance plasma de nanofils de silicium catalysée par l'étain et l'indium et applications dans les cellules solaires à jonctions radiales“. Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00761566.
Der volle Inhalt der QuelleGodou, Timothé. „Mimer la chimie des hydrosilanes et hydroboranes par l’activation catalytique de dérivés silylés et borés de l’acide formique“. Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS307/document.
Der volle Inhalt der QuelleGlobal energy needs are mostly covered by the use of fossil fuels such as oil, coal or gas. The use of these fossil resources in the field of energy or the chemical industry causes a high accumulation of CO2 in the atmosphere and causes climatic disturbances. In addition to posing a major ecological problem, these fossil resources are not renewable and will pose a problem of availability in the long term. To overcome these difficulties, one possible solution is to limit or even stop the use of fossil resources in favor of renewable carbon sources such as CO2 or biomass. These resources could be used as a source of chemicals and / or storage of intermittent energies. These uses require the conversion of oxygenates with C=O (such as CO2) and C–O (such as biomass) and require energy input into reduction reactions. Few reducers are compatible with this use which requires the use of compounds both renewable and having a redox potential adapted to the reduction of C–O bonds. These are essentially dihydrogen and formic acid. In this context, this doctoral work aims to define and meet the specifications of a renewable reducer. In the first place, the use of silyl formates is explored, through reactions mimicking the behavior of hydrosilanes. This strategy is used in dehydrogenating coupling reactions and for the reduction of ketones by transfer hydrosilylation. Finally, this concept is transposed to transfer hydroboration with the use of boryl mono formate compounds and a catalyst involving a participative ligand. The boryl and silyl formates thus appear as attractive renewable reducers, which combine a source of renewable hydride (formic acid) with an oxophilic element of the main group whose stereo-electronic properties are easily adjustable
Batt-Coutrot, Delphine. „Recherche de nouveaux catalyseurs isospécifiques destinés à la polymérisation du propylène : catalyse Ziegler-Natta et métallocène“. Nancy 1, 2000. http://www.theses.fr/2000NAN10070.
Der volle Inhalt der QuelleJeon, Taewoo. „Cellules solaires hybrides à base de polymères et de nanofils de silicium fabriqués par dépôt chimique en phase vapeur assisté par plasma“. Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00917826.
Der volle Inhalt der QuelleCarreras, Virginie. „Réactions d'insertion énantiosélective de composés diazoïques dans la liaison silicium-hydrogène et synthèses de cyclopropènes via la cycloaddition [2+1] d’alcynes avec des diazirines en flux continu“. Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69597.
Der volle Inhalt der QuelleThe insertion of diazo compounds into the Si–H bond is a direct and efficient method of synthesizing organosilanes. Various methods employing catalysts, in particular asymmetric catalysts, have been studied in the past. The common issue, detailed in the first part of this thesis, is the use by existing methods of complex and expensive chiral catalysts. This can make the synthesis and use of chiral organosilanes less attractive. This is why in Chapter 1 a green method of asymmetric catalysis for the synthesis of chiral organosilanes is developed, using diazo compounds. This route employs an inexpensive CuI catalyst system, an easy-tosynthesize ligand, mild reaction conditions and which show excellent results. A wide range of chiral organosilanes have been synthesized with yields up to 98% and enantioselectivities up to 98:2 er. To get insight into the reaction mechanism of this reaction, isotopic, competition or computational studies allowed us to understand the key steps of this transformation. The second part of this thesis was to develop an innovative method for the synthesis of gem-difluoro alkenes via an 1,2-desilylative defluorination reaction of organosilanes. This gem-difluorinated alkenes are real synthetic tools, often used in many subsequent reactions. This is why simplifying its synthesis by the 1,2-desilylative defluorination of trifluoromethylated organosilanes represents a real potential. This transformation arises from the possible application to the synthesis of organosilanes via the insertion of diazo compounds into the Si–H bond. The addition of a catalytic amount of fluoride on trifluoro-methylated organosilanes activates the catalytic system that provides excellent yields of gem-difluoro alkenes. Various examples and applications have been demonstrated. This method promotes the use of polyfluoromethylated organosilanes for the synthesis of perfluorinated alkenes. The third chapter of this thesis was about the cyclopropenation of alkynes by cycloaddition [2+1] with the use of carbene precursors. The first part consisted in studying the photochemical decompositions of the diazo compounds and diazirines, using a continuous flow system. The aim was to present a new pathway for the synthesis of trifluoromethylated cyclopropenes. This transformation has shown excellent results with the use of trifluoromethylated diazirines, for the synthesis of new cyclopropenes. Different ranges of LEDs were used to be suitable for a wide range of diazirines. Control experiments were carried out, and comparison of diazo compounds vs diazirines reactivities, and also comparisons of cyclopropenation vs cyclopropanation transformations could be evaluated. We were also able to benefit from the advantages of using continuous flow by allowing us to work on several grams, while remaining safe. Lastly, using synchronous measurements of infrared spectra, we were able to illustrate the presence of diazo compounds during the decomposition of diazirines by photochemistry, allowing us to raise certain hypotheses about the reaction mechanism The second part of chapter 3 illustrates the development of an asymmetric synthesis of chiral cyclopropenes by repeating the concepts developed above for the Si–H insertion. This reaction involving trifluoromethylated diazo compounds has not yet shown satisfactory results. This part is still under study and other approaches are being considered to date.
Lec, Jean-Christophe. „Les thioltransférases, des agents doubles impliqués dans le métabolisme du sulfure d’hydrogène : de la catalyse aux rôles physiologiques“. Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0305.
Der volle Inhalt der Quelle3-mercaptopyruvate sulfurtransferases (3-MSTs) and thiosulfate sulfurtransferases (TSTs) are ubiquitous enzymes that belong to the rhodanese sulfurtransferase family and catalyze the transfer of a sulfur atom from a donor to an acceptor substrate via a cysteine-persulfide intermediate. While 3-MSTs are involved in the biogenesis of hydrogen sulfide (H2S), a gasotransmitter known to be toxic at high concentration, TSTs are likely responsible of its degradation. My project mainly focused on deciphering the sulfurtransferase-dependent molecular mechanisms to better define their physiological functions. To address these questions, their catalytic mechanisms and substrate specificities were investigated. This was achieved through the development of kinetic approaches (fluorescence, stopped-flow, H2S specific probe) to study each step of the reaction catalyzed by human (3-MST, TSTD1 and Rhodanese) and Escherichia coli (3-MST, GlpE) enzymes and structure-function relationship studies performed in collaboration for the theoretical chemistry and the X-ray crystallography parts. Here, I show that the active site of these enzymes is optimized to perform an efficient S0 transfer from non-activated sulfur compounds. Moreover, the mechanisms leading to formation of the persulfide intermediate do not depend on the enzyme but rather on the donor substrate. Indeed, the cleavage of the carbon-sulfur bond of 3-mercaptopyruvate critically depends on the CysX5 catalytic loop acting as a thiolate hole to favor the deprotonation of the essential Cys and the substrate, and on a water-mediated protonation step. In the presence of thiosulfate, the Cys activation mode remains unchanged and the reaction of sulfur transfer is only driven by the neutralization of the negative charges of the substrate. In addition, we propose a new physiological function for the human 3-MST in the cytoplasmic elimination of sulfite, a toxic compound for the cells. Finally, the two human mitochondrial TSTs are likely to be involved in the H2S-mediated cellular signaling, through the formation of polysulfide entities, but also in H2S catabolism
Houda, Sara. „Oxidative desulfurization of marine fuels : optimization of reaction conditions and development of efficient catalysts“. Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R064.
Der volle Inhalt der QuelleThe International Maritime Organization (IMO) has limited marine fuel sulfur content in Sulfur Emission Control Areas (SECAs) from 1 to 0.1 wt.% in 2015 and will limit marine fuel sulfur content from 3.5 to 0.5 wt.% in all maritime areas by 2020. Marine fuels consist of heavy oils characterized by high sulfur content with refractory sulfur compounds difficult to remove using existing conventional high pressure hydrodesulfurization processes. However, these sulfides molecules appeared more reactive in oxidative desulfurization (ODS) process, carried out at mild conditions without hydrogen consumption. The objective of this thesis is to propose an oxidative desulfurization method of marine fuels. Nevertheless, ODS on heavy fuels is still immature and marine fuels are poorly studied with only few publications reported in literature. This work first focused on the development of a reliable methodology for the analysis of sulfur compounds in marine fuels before the study of an appropriate and efficient catalyst for marine fuel ODS reaction with optimized operating conditions. Among a large variety of marine fuels, three marine fuels were chosen with high viscosities that varied from 380 to 700 cSt. The results of chemical analysis revealed high sulfur content ranging from 0.6 to 3.2 wt.% reflecting the variability of the composition of marine fuels. ODS reaction was carried out by heterogeneous catalysis using MoO3/Al2O3-H2O2 system in batch reactor. The effects of reaction time, oxidant to sulfur molar ratio (Ox/S) and extracting solvent were investigated. Ultrasound assisted oxidative desulfurization coupled to normal mixing provided better desulfurization rates due to the synergetic effect provided by ultrasounds. Studies on the effects of molybdenum loading, phosphorus and/or vanadium doping and molybdenum precursor type were carried out on the alumina-supported molybdenum catalyst. Others oxide carriers were also employed, remarkably improving catalytic performances. Under the optimum conditions and with the most efficient catalysts, it was possible to oxidize and desulfurize all selected feeds making them compatible with the 2020 new regulations
Houda, Sara. „Oxidative desulfurization of marine fuels : optimization of reaction conditions and development of efficient catalysts“. Electronic Thesis or Diss., Université de Lille (2018-2021), 2019. http://www.theses.fr/2019LILUR064.
Der volle Inhalt der QuelleThe International Maritime Organization (IMO) has limited marine fuel sulfur content in Sulfur Emission Control Areas (SECAs) from 1 to 0.1 wt.% in 2015 and will limit marine fuel sulfur content from 3.5 to 0.5 wt.% in all maritime areas by 2020. Marine fuels consist of heavy oils characterized by high sulfur content with refractory sulfur compounds difficult to remove using existing conventional high pressure hydrodesulfurization processes. However, these sulfides molecules appeared more reactive in oxidative desulfurization (ODS) process, carried out at mild conditions without hydrogen consumption. The objective of this thesis is to propose an oxidative desulfurization method of marine fuels. Nevertheless, ODS on heavy fuels is still immature and marine fuels are poorly studied with only few publications reported in literature. This work first focused on the development of a reliable methodology for the analysis of sulfur compounds in marine fuels before the study of an appropriate and efficient catalyst for marine fuel ODS reaction with optimized operating conditions. Among a large variety of marine fuels, three marine fuels were chosen with high viscosities that varied from 380 to 700 cSt. The results of chemical analysis revealed high sulfur content ranging from 0.6 to 3.2 wt.% reflecting the variability of the composition of marine fuels. ODS reaction was carried out by heterogeneous catalysis using MoO3/Al2O3-H2O2 system in batch reactor. The effects of reaction time, oxidant to sulfur molar ratio (Ox/S) and extracting solvent were investigated. Ultrasound assisted oxidative desulfurization coupled to normal mixing provided better desulfurization rates due to the synergetic effect provided by ultrasounds. Studies on the effects of molybdenum loading, phosphorus and/or vanadium doping and molybdenum precursor type were carried out on the alumina-supported molybdenum catalyst. Others oxide carriers were also employed, remarkably improving catalytic performances. Under the optimum conditions and with the most efficient catalysts, it was possible to oxidize and desulfurize all selected feeds making them compatible with the 2020 new regulations
Commandeur, Claude. „Chimio-et stéréosélectivité induites par le silicium dans des réactions d'allylation catalysées par le palladium : application aux cyclisations 5-et 6-endo-trig“. Paris 6, 2003. http://www.theses.fr/2003PA066066.
Der volle Inhalt der QuelleChauvier, Clément. „Nouvelles réactions d'hydroboration et d'hydrosilylation par transfert avec des réducteurs renouvelables à base d'acide formique“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS359/document.
Der volle Inhalt der QuelleThe utilization of cheap and abundant sustainable resources such as carbon dioxide or biomass derivatives as source of fuel and chemicals imposes the development of efficient reduction methods, able to promote the conversion of C-O bonds (π and σ) into C-H bonds in an energy and atom efficient manner. Within the realm of C-O reduction methods, the utilization of main group element-based hydrides (e.g. LiAlH₄ or NaBH₄) has proven highly beneficial in terms of selectivity and versatility in the reduction of various functional groups, including poorly electrophilic CO₂. This behavior not only stems from the positive kinetic attributes of these reductants in hydride transfer reactions but also from the oxophilicity of the main group elements that ensures the reductions are downhill processes. Yet, the latter appealing features comes at an energetic price, and the preparation of main group hydrides mainly relies on energy-demanding processes, which in turn limit the recyclability of these reductants. With the goal in mind to circumvent these limitations while preserving the beneficial properties of the main-group element during reduction, one of the major objectives of the research project presented therein was to study the unknown reductive chemistry of boryl formate and silyl formates. The latter indeed combine a renewable hydride source (formic acid can be obtained by 2e electroreduction of CO₂) linked directly to the main group element by the oxygen atom of the formate, which hints at the recyclability of this class of main group element-based reductants. Through a joint experimental and theoretical study, it will be demonstrated that these compounds can advantageously replace non-renewable hydroboranes or hydrosilanes in various reducing processes, which will be unified behind the more general concept of transfer hydroelementation
Boniface, Maxime. „Suivi à l'échelle nanométrique de l'évolution d'une électrode de silicium dans un accumulateur Li-ion par STEM-EELS“. Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY051/document.
Der volle Inhalt der QuelleOver the last 25 years, the performance increase of lithium-ion batteries has been largely driven by the optimization of inactive components. With today’s environmental concerns, the pressure for more cost-effective and energy-dense batteries is enormous and new active materials should be developed to meet those challenges. Silicon’s great theoretical capacity makes it a promising candidate to replace graphite in negative electrodes in the mid-term. So far, Si-based electrodes have however suffered from the colossal volume changes silicon undergoes through its alloying reaction with Li. Si particles will be disconnected from the electrode’s percolating network and the solid electrolyte interface (SEI) continuously grows, causing poor capacity retention. A thorough understanding of both these phenomena, down to the scale of a single silicon nanoparticle (SiNP), is critical to the rational engineering of efficient Si-based electrodes. To this effect, we have developed STEM-EELS into a powerful and versatile toolbox for the study of sensitive materials and heterogeneous systems. Using the low-loss part of the EEL spectrum allows us to overcome the classical limitations of the technique.This is put to use to elucidate the first lithiation mechanism of crystalline SiNPs, revealing Li1.5Si @ Si core-shells which greatly differs from that of microparticles, and propose a comprehensive model to explain this size effect. The implications of that model regarding the stress that develops in the crystalline core of SiNPs are then challenged via stress measurements at the particle scale (nanobeam precession electron diffraction) for the first time, and reveal enormous compressions in excess of 4±2 GPa. Regarding the SEI, the phase-mapping capabilities of STEM-EELS are leveraged to outline the morphology of inorganic and organic components. We show that the latter contracts during electrode discharge in what is referred to as SEI breathing. As electrodes age, disconnection causes a diminishing number of SiNPs to bear the full capacity of the electrode. Overlithiated particles will in turn suffer from larger volumes changes and cause further disconnection in a self-reinforcing detrimental effect. Under extreme conditions, we show that SiNPs even spontaneously turn into a network of thin silicon filaments. Thus an increased active surface will compound the reduction of the electrolyte and the accumulation of the SEI. This can be quantified by summing and averaging STEM-EELS data on 1104 particles. In half-cells, the SEI volume is shown to increase 4-fold after 100 cycles without significant changes in its composition, whereas in full cells the limited lithiation performance understandably leads to a mere 2-fold growth. In addition, as the operating potential of the silicon electrodes increases in full cells – potential slippage – organic products in the SEI switch from being carbonate-rich to oligomer-rich. Finally, we regroup these findings into an extensive aging model of our own, based on both local STEM-EELS analyses and the macro-scale gradients we derived from them as a whole
Raachini, Rita. „Nanoparticles of Ni strongly embedded in porous silica : towards the design of efficient catalysts for lignin hydrogenolysis“. Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS540.
Der volle Inhalt der QuellePhenols may be obtained from lignin instead of petroleum. Here, improving lignin conversion by hydrogenolysis, while limiting side hydrogenation of produced phenols using nickel-based catalysts instead of noble metals, was our main concern. Porous materials made of highly dispersed nickel onto silica were synthesized by different ways, characterized before and after reduction under H2, then tested in the hydrogenolysis of three compounds bearing C-OAr bonds, as in the β-O-4 linkage of lignin, using isopropanol as H-donor. In a first series of materials, Ni was introduced by the impregnation of Aerosil-380 in the presence of ammonia and similar materials were prepared with Rh. The latter favored phenol formation but resulted in much slower C-OAr cleavage. In fact, the most active catalyst was found to be the Ni-based one, affording high phenol productivity could be reached by reducing the Ni-based catalyst at high temperature. Unlike Ni, no Rh-phyllosilicates were detected, this was related to the counterion in the precursor and the metal itself. Secondly, designing highly dispersed nickel-based mesoporous monoliths with different pore structures (Sx) (wormlike, hexagonal or cubic pore structures) through an original sol-gel method. Divergences were observed between the reduced forms of NiII@Sx, with better yields with the more open cubic structure. The resulting solids were compared to two materials obtained by the impregnation of either aerosil silica or a hexagonal silica monolith with Ni(II) in the presence of ammonia in order to study the effect of the support and the incorporation method. the best catalyst with respect to phenol selectivity, avoiding its hydrogenation to cyclohexanol, was Ni-based aerosil silica. Lastly, studying the effect of adding a second metal with Ni (Co or Fe) by three methods, impregnation of Co or Fe on Ni@SBA-15 like monolith, a direct one-pot synthesis introduction or co-impregnation of both metals Ni and Co or Fe on blank SBA-15 like monolith. The incorporation method of metals is the most critical parameter. Incorporation Co or Fe by “two-solvents” method on Ni@SBA-15 like monolith led to the best catalytic activity in terms of selectivity towards phenol. In fact, not all active species were sufficiently reduced and it would be interesting to increase the reduction temperature of these solids and to optimize the reaction conditions
Janisch, Daniel. „Geo-inspired pathways towards ternary non-noble metal (pre-)catalysts for water splitting and CO2 reduction“. Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS387.pdf.
Der volle Inhalt der QuelleA full transition from fossil-based energy sources towards green energy production requires storage systems compensating for the intermittency of renewables. The production of green hydrogen from electrolysis of water powered by surplus electricity from solar or wind attracts a lot of attention as an abundant, clean and renewable energy vector. Beyond the electrolysis of water, surplus renewable energy can further be stored in more complex fuels or chemicals. Related to electrolysis, the electroreduction of CO2 (CO2R) yields energy-dense hydrocarbons storing also energy in chemical bonds. A lack of economic viability, however, still blocks widespread industrial use of these processes. The benchmark electrodes in water electrolysis cells are platinum group metals that are expensive and not abundantly available. Compounds of more common transition metals represent a much cheaper alternative as potential electrocatalysts for water splitting. It was shown that activity and stability in both acidic and alkaline electrolytes is enhanced most notably in binary transition metal borides (TMBs), silicides (TMSs) and carbides (TMCs). Covalent bonds between p-block elements and between these elements and the transition metals, and the resulting modifications of the metal charge density have been identified as key factors responsible for augmented catalytic activity. Nevertheless, the structure-activity relationship remains obscure and whether catalytic properties could be further boosted by a twofold combination of p-block elements with a transition metal has not been answered. Low CO2R selectivity is the current bottleneck in this process as intricate downstream product separation renders an industrial process unprofitable. Copper is the only metal electrocatalyst able to form substantial amounts of C+2 hydrocarbons. Again, p-block elements such as sulphur are reported to increase selectivity in copper sulphides to one-carbon products. Yet, the role of sulphur during CO2R remains unclear and whether a second p-block element could tune the charge state of copper to favour a single reduction pathway towards C+2 products has not been explored. To resolve these open questions, we have designed reaction pathways towards ternary compounds combining a transition metal with two p-block elements. The reaction processes are inspired by geological processes and rely on the use of molten salts as reaction media. Compared to classical solid-state synthesis, molten salts increase diffusivity of reactants and enable overall lower temperatures and reaction times. As a result, the process is prone to deliver nanostructured materials with high surface-to-volume ratio and without organic surface ligands, which is ideal for catalytic applications. In the first part of this work, the synthesis of four ternary transition metal silicoborides Ni6Si2B, Co4.75Si2B, Fe5SiB2 and Mn5SiB2 is presented, together with a detailed study of the electrocatalytic properties for alkaline water oxidation (OER). Synchrotron radiation-based in situ XRD resolves the formation mechanisms during the synthesis and sheds light on structural relationships between reaction intermediate and the final products. The second part is dedicated to the investigation of the influence of silicon, boron and carbon on molybdenum in three ternary compounds, Mo2BC, Mo4.8Si3C, Mo5SiB2, as electrocatalysts of hydrogen evolution from acidic and alkaline aqueous electrolytes. XPS and XAS point out the relationship between the oxidation state of molybdenum and the electrocatalytic activity. The assessment of two ternary copper silicosulphides Cu8SiS6 and Cu2SiS3 as catalysts for CO2R constitutes the topic of the third part of this work. The crystallisation sequence during synthesis was monitored during in situ XRD measurements and electronic configurations were assessed by XPS and XAS. Finally, in situ XAS during CO and CO2 reduction reactions shows how the materials evolve during electrocatalysis
Lacroix, Maxime. „Optimisation et caractérisation d’un nouveau support catalytique à base de mousses alvéolaires de β-SiC : Application à la synthèse de Fischer-Tropsch“. Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/restreint/theses_doctorat/2009/LACROIX_Maxime_2009.pdf.
Der volle Inhalt der QuelleThe catalytic Fischer Tropsch Synthesis (FTS) enables the transformation of synthetic gas, i. E. Mixture of H2 and CO, into a distribution of hydrocarbons (CnH2n+2 with 1 < n < 60-100), more or less saturated and more or less oxygenated. The Gas to Liquids way, including FTS, is consequently an opportunity allowing the transformation of the flared and/or stranded gas into liquid hydrocarbons for car or plane fuelling. This could first reduce the CO2 release in the atmosphere and secondly increase the oil resources by the transformation of natural gas. The classical catalysts used in Fischer-Tropsch processes are composed of cobalt or iron supported on alumina or silica, and, although they present good performances, they are highly constricted by the high exothermicity of the reaction inducing high temperature on the catalyst surface, leading to low selectivity towards desired products (i. E. Long chained parafins). In this context, silicon carbide (β-SiC) has been proposed as replacement support to alumina and silica in order to better evacuate the heat released by the reaction and thus keeping higher selectivity even at high conversion levels. Moreover, always in order to optimize the process, the impact of the catalytic support morphology (extrudates, cellular foams) on the Fischer-Tropsch reaction has been studied. It appeared that the intrinsic properties of the cellular supports (high effective thermal conductivity, low pressure drops) could let foresee new perspectives in the fixed bed FT reaction. In this work, silicon carbide as catalyst support revealed to be far more attractive than alumina both in the form of extrudates or cellular foams. Indeed, thermal runaway have been observed on alumina whereas the use of β-SiC allowed better control of the temperature and thus better selectivity towards C5+ products. A study on the influence of the active phase charge on the catalytic performances of the catalyst supported on β-SiC foams has been performed. A simple geometric model of the foam as been developed in order to estimate the pressure drop induced by the cellular supports. A correlation with classical packed beds was showed to be able to model the pressure loss induced by a gaseous flow in the cellular material. Finally, a study on the biphasic behaviour of β-SiC foams has evidenced higher liquid hold-ups compared to classical packed beds. The influence of this property on the FT reaction has here not been made and will be the subject of a next study
Char, Joëlle. „Nouvelles réactions de couplages des organosilanes pour la synthèse d’esters à partir du CO₂ et de sulfones à partir du SO₂“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS262/document.
Der volle Inhalt der QuelleCross coupling reactions are well studied reactions and their development was awarded a Nobel price. These reactions aim at coupling organometallic nucleophiles and electrophiles compounds and are the best way to form a little to none polarized bond such as C–C and C–S bond. They however make use of strong nucleophiles, decreasing their selectivity and tolerance. On one hand, among all available nucleophiles, organosilanes are very attractive because of their abundance, selectivity, stability and tolerance towards functional groups, they are also less toxic, easy to handle, and cheap. Their use though is a challenge because of their lower reactivity. On the other hand, for the sake of increasing the atom economy of a reaction, carbon dioxide (CO₂) is the best source of carbon and ester functional group; and sulfur dioxide (SO₂) is the best source of sulfur and sulfone functional group. In this manuscript, we herein report several coupling reactions between organosilanes giving a direct access to esters from CO₂ and to sulfones from SO₂. Experimental and theoretical studies have been carried out to develop a coupling reaction between arylsilanes, CO₂ and alkyl halides catalyzed by a copper(I) complex. SO₂ being more electrophilic and more nucleophilic, is used in a catalyzed less coupling reaction with arylsilanes and alkyl halides and in a coupling reaction with allylsilanes and aryl halides catalyzed by a palladium(II) complex, known as sulfonylating Hiyama coupling
Wardag, Alam Rahman Khan. „Filtration and Catalytic Reaction in Trickle Beds - Use of Solid Foam Guard Beds to Mitigate Fines Plugging“. Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29089/29089.pdf.
Der volle Inhalt der QuelleNemaga, Abirdu woreka. „Synthèse par électrodépôt en milieu liquide ionique de nanostructures de Si/TiO2, Al/TiO2 et Si-Al/TiO2 nanotubes pour électrode négative de batterie Li-ion“. Thesis, Reims, 2019. http://www.theses.fr/2019REIMS004.
Der volle Inhalt der QuelleAmong the various electric energy storage systems studied for more than two centuries, the electrochemical storage battery type Li-Ion is probably the most relevant and most effective. however locks remain for Li-Ion batteries respondents to current needs, and limitations comes from the electrode materials. Silicon is a prime candidate to meet the challenges posed batteries, however its resistance to cycling is short and synthesis methods are often very restrictive. Combining two research laboratories major players in the fields of nanoscience (the LRN to URCA) and materials and batteries (the LRCS to UPJV) the multidisciplinary project NanoSiBL a period of 36 months set the objective of provide solutions to the above two points: 1, the realization of negative electrodes in silicon by a synthetic route down original and innovative cost developed LRN (electrodeposition in ionic liquid medium), 2 increased lifetime of the electrode through two types of structuring (or one electrode made of nanowires / nanotubes Si monolithic or a composite nanostructured electrode Si / TiO2). The expertise in the field of LRCS of batteries should allow this second point to determine the geometry and ideal configuration of the electrode in terms of performance. Based methods developed by electrochemistry low cost and original NanoSiBL aims, through the sharing of expertise and technology between physicists and chemists involved, to initiate an inter-establishment new theme focused on valuation and silicon nanostructures composite nanostructured silicon. The scientific interest of this project lies in the implementation and control of the intrinsic properties of these nanostructures based on silicon for making efficient negative electrodes of Li-Ion battery. In the literature, the negative electrodes based on silicon or silicon composite (type Si / TiO2) have already demonstrated improvement compared to bulk silicon electrodes. However, the transition to operational devices remains uncommon for ways to contain the expansion in volume of the silicon are experiencing and because the methods used to develop these silicon nanowires (chemical vapor deposition, reactive evaporation ...) remain very restrictive both in terms of growth conditions (the need to use metal precursors and highly toxic gases) that manufacturing costs (labor UHV, many steps for the realization of devices with the need for contacts post- growth…). NanoSiBL proposes an alternative in real technological break with the current methods of synthesis. growth techniques (electrodeposition in ionic liquid) and nanostructuring (in polycarbonates or TiO2 nanotube membranes) used in the project will enable the development of electrodes at low cost efficient for application referred Li-Ion battery. Furthermore the consequent variety of possible geometries offered by the nanoporous membranes to be used in the project (polycarbonate or TiO2 nanotubes) will establish a critical comparison of the impact of the nanostructure or composition of electrodes to contain expansion by volume of the silicon during the cycling and improve the life of such electrodes (battery)
Colin, Boris. „Développement de méthodes de criblages et d'analyses en parallèle appliquées aux polymères modifiés silanes“. Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S145.
Der volle Inhalt der QuelleThe aim of this work is to discover new catalytic systems to replace organotin compounds. The strategy used on our laboratory exploits tools of high throughput experiments to test a large number of catalysts in the same time in order to discover new catalytic systems more quickly
Thibault, Marc. „Élaboration et caractérisation de revêtements formés par hydrolyse et condensation d'alcoxysilanes sur tôles magnétiques à grains orientés et non orientés“. Lille 1, 1995. http://www.theses.fr/1995LIL10110.
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