Dissertationen zum Thema „Silicon catalysis“
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Chigondo, Fidelis. „Continuous flow synthesis of silicon compounds as feedstock for solar-grade silicon production“. Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/4529.
Der volle Inhalt der QuelleBeveridge, Nicola Louise. „Characterisation of silicon-silicon hydroxide catalysis bonds for future gravitational wave detectors“. Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3526/.
Der volle Inhalt der QuelleLeung, Jane Jing. „Molecular hybrid photocathodes based on silicon for solar fuel synthesis“. Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288001.
Der volle Inhalt der QuelleTymowski, 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
Rae, James. „Copper-catalysed silicon and boron functionalisation of heterocycles and allenes“. Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/coppercatalysed-silicon-and-boron-functionalisation-of-heterocycles-and-allenes(a86718c0-18b4-4092-a2bd-b978797153db).html.
Der volle Inhalt der QuellePap, A. E. (Andrea Edit). „Investigation of pristine and oxidized porous silicon“. Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514277759.
Der volle Inhalt der QuelleWieting, Joshua Merlin. „Silanediol-Catalyzed Stereoselective Functionalization of Heterocycles“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448891366.
Der volle Inhalt der QuelleLee, Kang-sang. „New Concepts and Catalysts for Enantioselective Synthesis of C-C, C-Si, and C-B Bonds“. Thesis, Boston College, 2010. http://hdl.handle.net/2345/1739.
Der volle Inhalt der QuelleChapter 1. The development of chiral monodentate N-heterocyclic carbenes (NHCs) is presented. Structurally varied twenty-eight new chiral imidazolinim salts, NHC precursors, were synthesized and characterized. Chapter 2. The first example of Cu-catalyzed enantioselective conjugate additions of alkyl- and arylzinc reagents to unactivated cyclic enones is presented. Transformations are promoted in the presence of 2.5-15 mol % of a readily available chiral NHC-based Cu complex, affording the desired products bearing all-carbon quaternary stereogenic centers in 67-98% yield and in up to 97% ee. Catalytic enantioselective reactions can be carried out on a benchtop, with undistilled solvent and commercially available (not further purified) Cu salts. Chapter 3. A new class of enantioselective conjugate addition (ECA) reactions that involve aryl- or alkenylsilylfluoride reagents and are catalyzed by chiral non-C2-symmetric Cu-based NHC complexes are presented. Transformations have been designed based on the principle that a catalytically active chiral NHC-Cu-aryl or NHC-Cu-alkenyl complex can be accessed from reaction of a Cu-halide precursor with in situ-generated aryl- or alkenyl-tetrafluorosilicate. Reactions proceed in the presence of 1.5 equivalents of the aryl- or alkenylsilane reagents and 1.5 equivalents of tris(dimethylamino)sulfonium difluorotrimethylsilicate. Desired products are isolated in 63-97% yield and 73.5:26.5-98.5:1.5 enantiomeric ratio (47%-97% ee). Chapter 4. An efficient Cu-catalyzed protocol for enantioselective addition of a dimethylphenylsilanyl group to a wide range of cyclic and acyclic unsaturated ketones, esters, acrylonitriles and dienones is presented. Reactions are performed in the presence of 1-5 mol % of commercially available and inexpensive CuCl, a readily accessible monodentate imidazolinium salt as well as commercially available (dimethylphenylsilyl)pinacolatoboron. Cu-catalyzed 1,4- and 1,6-conjugate additions afford the enantiomerically enriched silanes in 72%-98% yield and 90:10->99:1 enantiomeric ratio (er) with up to >25:1 of Z:E selectivity. Chapter 5. A Cu-catalyzed method for enantioselective boronate conjugate additions to trisubstituted alkenes of acyclic a,b-unsaturated carboxylic esters, ketones, and thioesters is presented. All transformations are promoted by 5 mol % of a chiral monodentate NHC-Cu complex, derived from a readily available C1-symmetric imidazolinium salt, and in the presence of commercially available bis(pinacolato)diboron. Reactions are efficient (typically, 60% to >98% yield after purification) and deliver the desired boryl carbonyls in up to >98:2 enantiomer ratio (er). In addition, metal-free, nucleophilic activation of a B-B bond has been exploited in the development of a highly efficient method for conjugate additions of commercially available bis(pinacolato)diboron to cyclic or acyclic a,b-unsaturated carbonyls. Reactions are readily catalyzed by 2.5-10 mol % of a simple NHC. A variety of cyclic and acyclic unsaturated ketones and esters can serve as substrates. Transformations deliver boryl carbonyls bearing tertiary as well as quaternary B-substituted carbons in up to >98% yield
Thesis (PhD) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
Douglas, Rebecca Claire. „Aspects of hydroxide catalysis bonding of sapphire and silicon for use in future gravitational wave detectors“. Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7993/.
Der volle Inhalt der QuelleMungondori, Henry Heroe. „Development of a visible light active, photo-catalytic and antimicrobial nanocomposite of titanium dioxide and silicon dioxide for water treatment“. Thesis, University of Fort Hare, 2012. http://hdl.handle.net/10353/471.
Der volle Inhalt der QuelleNaha, Sayangdev. „Growth Model, Synthesis of Carbon Nanostructures and Alteration of Surface Properties Using Them“. Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28559.
Der volle Inhalt der QuellePh. D.
Han, Tingting. „Highly active and efficient metal-decorated silicon-based nanostructured photoelectrodes for water splitting solar cells“. Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670880.
Der volle Inhalt der QuelleLa quema de grandes cantidades de combustibles fósiles para satisfacer la demanda energética stá empeorando la contaminación ambiental cada vez más, y la crisis energética se está volviendo más grave. La división de agua mediante fotoelectroquímica (PEC, por sus siglas en inglés) utilizando luz solar es uno de los métodos más prometedores para producir combustible hidrógeno de forma limpia, debido a la estructura simple, el bajo costo de fabricación y el buen rendimiento. En las células fotoelectroquímicas, un fotoelectrodo semiconductor se sumerge en un electrolito y, cuando se ilumina, se puede generar hidrógeno y/u oxígeno en su superficie mediante electrólisis. Para obtener un mejor rendimiento, es extremadamente importante seleccionar semiconductores adecuados para absorber la luz, catalizadores para mejorar el rendimiento, y electrolitos que contienen varios iones. El silicio ha suscitado mucho interés debido a su bajo costo y a sus propiedades eléctricas (banda prohibida de 1.1eV). Sin embargo, debido a su inestabilidad en el electrolito, los catalizadores metálicos a menudo se usan para evitar la degradación de los fotoelectrodos de silicio y para mejorar su actividad en el electrolito. Dado que el grado de protección se puede reducir después de algunos períodos de tiempo, la vida útil de los fotoelectrodos de semiconductores sigue siendo el principal cuello de botella de esta tecnología de división de agua PEC. Además, ajustar el pH o la composición química de los electrolitos, incluidas las especies especiales, podría mejorar la actividad y la estabilidad de las células. En esta tesis, he estudiado el uso de niquel como capa protectora y catalizadora sobre fotoelectrodos de silicio, y hemos analizados su envejecimiento bajo condiciones de funcionamiento reales. También he desarrollado un electrolito avanzado (una mezcla de hidróxido de potasio [KOH] e hidróxido de litio (LiOH), pH 12.5) que muestra una buena actividad y estabilidad para los fotoelectrodos de silicio a base de metal. Además, también diseñamos, fabricamos y testeamos fotocatodos n-3C-SiC/p-Si cubiertos con nanopartículas de metales nobles para la división de agua PEC en KOH, y observamos una mejora en el rendimiento de PEC debido a los efectos de resonancia catalítica y plasmónica de las nanopartículas introducidas.
Rosenthal, Daniel Jay. „Estimating the acid site density of silica-alumina by infrared spectroscopy using a selective reactant poison“. Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10222.
Der volle Inhalt der QuelleNasrallah, Houssein. „Immobilisation de complexes à base de ruthénium par des interactions non-covalentes pour le recyclage en métathèse des oléfines“. Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS005.
Der volle Inhalt der QuelleRuthenium complexes immobilization by non-covalent interactions for the recycling in olefin metathesisAbstractThe aim of this thesis is the development of new ruthenium complexes immobilization strategies onto insoluble supports by non-covalent interactions, for their easy recycling in olefin metathesis reactions.First, a bibliographic part is devoted to the development of the olefin metathesis from the discovery until now. Then, three different approaches of metathesis catalysts immobilization are described in order to achieve efficient recycling, considering the important challenges associated to this reaction. Firstly, an immobilization procedure of catalysts by formation of reversible charge transfer complexes (CTC) is described between the appropriated tagged catalyst and the support. Based on the results obtained in these conditions, a more economical approach involved the immobilization of a commercially available catalyst by formation of hydrogen bonds with the silanol sites present in silica. Finally, another type of support namely a structured carbon based support (rGO), was used for the pyrene tagged ruthenium complexes immobilization via formation of non-covalent π- π interactions (π-stacking).The catalytic performances of these solid materials were firstly evaluated in the benchmark reaction of olefin metathesis (RCM of DEDAM). Then, other olefin metathesis reactions were applied to extend the application of these materials (enyne, CM, self-metathesis of methyl oleate).The development of these approaches has also been accompanied by mechanistic studies, based on the boomerang effect, already known for these reactions.This work was performed as part of the ANR project CD2I CFLOW-OM, in collaboration with academic (ENSC-Rennes, LGPC Lyon, CPE Lyon-Caen LCMT) and industrial (ITERG, NOVANCE, OMEGA-CAT- SYSTEM) partners
Motos, Blanca. „Silices fonctionnalisées contenant des espèces ioniques pour la catalyse hétérogène“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0015.
Der volle Inhalt der QuelleHeterogenous catalysis is an area in continuous development due to economical, health and environmental issues. This thesis deals with the preparation of i-silica materials for the posterior application in heterogeneous catalysis. First, di-aryl imidazolium containing silica materials were synthesized by post-grafting reactions on mesoporous SBA-15. Moreover, di-alkyl imidazolium containing PMO films were prepared in presence of an anionic surfactant. Then, supported copper and palladium N-heterocyclic carbenes were synthesized from di-aryl imidazolium silica and applied to A3 reactions (Cu-NHC) and Suzuki cross-coupling reactions (Pd-NHC). Imidazolium functionalized silicas were also utilized as heterogeneous organocatalysts in Henry reactions and in reactions of cycloaddition of carbon dioxide to epoxides. Finally, PMO type materials containing amine/ammonium and zwitterionic substructures were applied to Henry and Biginelli organocatalysed reactions, respectively
Chauvier, 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
Nguyen, Joseph Vu. „Design, synthesis, and optimization of recoverable and recyclable silica-immobilized atom transfer radical polymerization catalysts“. Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6860.
Der volle Inhalt der QuelleHarms, Stefan Mathias. „The oligomerisation of propene over nickel oxide silica alumina“. Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/22157.
Der volle Inhalt der QuelleA synthesis techniQue was developed for the preparation of a nickel oxide sil ica alumina catalyst. The propene oligomerisation activity and the selectivity of the catalysts prepared by homogeneous decomposition deposition (HDD) were investigated and compared with nickel oxide silica alumina catalysts prepared by the techniQues of impregnation (IMP) and co-precipitation (SG). Amongst others. the effect of the nickel content. reacti6n temperature and pressure, and water content of the feed, on the activity and selectivity. were investigated. Also investigated were the lifetime of the various catalysts and, in the case of HDD type catalysts. the ability to oligomerise high molecular weight hydrocarbons (Cb). Nickel oxide silica alumina prepared by the HDD method is more active for the propene oligomerisation than catalysts prepared by the IMP and SG methods. The product spectrum in the case of IMP and HDD type catalysts are similar, with a propene dimer (Cb) being the main product. In the case of SG type catalysts. however. a shift to heavier products was observed, i.e., propene dimer (Cb) and trimer (Cq) were formed in eQual Quantities. It is proposed that the increase in activity of HDD type catalysts was due to a large extent of metal dispersion and distribution and a stronger interaction between the metal and the support. It is also proposed that the metal is readily accessible to the reactant molecules. The activity and selectivity of catalysts prepared by the HDD method were independent of the nickel content. This was not the case for IMP and SG type catalysts. both of which showed decreasing activity with increasing nickel content when the nickel content was increased beyond 5 wt%. The lifetimes of the various catalysts were also examined. From the results obtained. over the first 10 h. the lifetime of HOD type catalysts was superior to that of the other catalysts studied. The activity and selectivity of the various catalysts were sensitive to the reaction conditions. Thus moving into the vapour phase. by either increasing the temperature at a fixed pressure or decreasing the pressure at a fixed temperature. was in each case acCompanied by a shift to heavier products and a decrease in activity.
Battisti, Marcos Valerio. „Investigação teórica sobre a possibilidade dos porfirinatos de silicio(IV) catalisarem O2 e NO: uma abordagem termodinâmica“. Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-14092007-143358/.
Der volle Inhalt der QuelleThe search for catalytic materials out of the transition metals was the objective of this thesis. Mainly if we consider the scarcity of noble metals as raw materials for the catalysis of diatomic molecules, especially oxygen and nitrogen oxides. The first molecule is directly related to the getting of energy in fuel cells, specifically, the anode of the fuel cells. The second molecule is related directly to the electroreduction of nitrate ions, in other words, in the formation of a very stable diatomic molecule and also very poisonous. Therefore, DFT was used (Density Functional Theory) for the accomplishment of several simulations, at 298,15K and 1 atm, with molecules in the gaseous state of silicon porphyrinatos (IV) reacting with O2 and NO for their catalytic confirmation. For that, the bases 3-21G, 6-31G, 6-31G * and 6-31G(d) were used to study the catalytic tendencies of the porphyrinatos here studied. For instance, the tendency of hydrolysis of silicon porphyrinato (IV) can be evidenced through theoretical calculations, as already observed and demonstrated through experimental works. Silicon porphyrinatos (IV) and silicon octaethilporphyirinatos (IV) showed the same tendency of forming a chemical bond with O2. They form a \"bridge\" changing the absolute values for DG and DH, and form a O2 bond with the porphyrinic ring. With porphyrinatos, the oxygen binds to silicon and to meso carbon; but with octaethilporphyirinato, the O2 binds to silicon and to the nitrogen of the ring, promoting a rupture between the silicon (present in the center of the porphyrins) and the nitrogen of the ring. The same tendency was observed when hydroxyls were added in the meso carbons of the porphyrinic ring showing that the presence of donor groups of electrons in the meso carbons does not strengthen the silicon and nitrogen bonds presented in the system, and a chlorine counter-ion does not influence the final result of the reaction as well. When we reacted the system with hydrogen, the formation of two weak molecules of water bound to the system is observed. Silicon octaethilporphyrinato (IV) just reacted with two NO molecules, and was observed the formation of a pentagonal structure on silicon breaking two bonds between silicon and nitrogen of the porphyrinic ring. When one puts hydroxyls and chlorine in the system silicon octaethilporphyrinato (IV), the reaction was only observed with a molecule of NO bound to the nitrogen of the ring without the formation of NO+ common in porphyrinic systems where the central atom is iron, for example. Also, it was observed the tendency of formation of the ammonium ion and water when we put in the system molecules of hydrogen to react with the NO linked to the porphyrin ring. In practice, as the silicon porphyrinatos (IV) as the silicon octaethilporphyrinatos (IV) possess counter-ions, where the most common is with chloride. Therefore, the study of the lability of the ion chloride with the studied molecules was of fundamental importance in the determination of the tendency of these molecular systems. From there, for instance, we could observe that the chloride is substituted by the oxygen molecule in a reaction between the two reactants. To conclude, CO and H2 did not react with the silicon porphyrinatos (IV) showing a strong tendency to repulsion due to the phase difference in the atomic orbitals.
Shiels, Rebecca Anne. „Synthesis, characterization, and evaluation of silica and polymer supported catalysts for the production of fine chemicals“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29629.
Der volle Inhalt der QuelleCommittee Chair: Dr. Christopher Jones; Committee Member: Dr. Dennis Hess; Committee Member: Dr. Hang Lu; Committee Member: Dr. Marcus Weck; Committee Member: Dr. Pradeep Agrawal. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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
Müller, Robert [Verfasser], Martin [Akademischer Betreuer] Kaupp und Carsten [Akademischer Betreuer] Strohmann. „Quantum-chemical studies of inorganic electronic structure and reactivity : from unusual silicon and germanium compounds to transition-metal catalysis / Robert Müller. Gutachter: Martin Kaupp ; Carsten Strohmann. Betreuer: Martin Kaupp“. Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066163480/34.
Der volle Inhalt der QuellePeiris, Thelge Manindu Nirasha. „Development and characterization of silica and titania based nanostructured materials for the removal of indoor and outdoor air pollutants“. Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14891.
Der volle Inhalt der QuelleDepartment of Chemistry
Kenneth J. Klabunde
Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized photocatalytic activity. In contrast, our xerogel system shows comparatively high visible light photocatalytic activity for the titania based system, showing the importance of non-localized nature of photocatalysis. The Cobalt doped silica system shows interesting dark catalytic activity towards acetaldehyde and several other pollutants. Thus, in summary, based on the different activities we observed during our studies these materials could be successfully used to improve the quality of both indoor and outdoor air.
Wojcik, Karolina. „D-glucosamine as "green" substrate in synthesis of ligands for asymetric catalysis“. Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00974873.
Der volle Inhalt der QuelleChiaranussati, Preeyanuj. „NMR studies of silicas and platinum/ silica catalysts“. Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319580.
Der volle Inhalt der QuelleAttoui, Mariam. „Nanocatalyseurs hélicoïdaux chiraux à base de polyoxométallates pour les réactions d’oxydation énantiosélectives“. Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0447/document.
Der volle Inhalt der QuelleChiral polyoxometalates (POMs)-based materials have attracted particular attention in recent years due to their remarkable properties and potential application, especially in the field of catalysis. The goal of this thesis is to design a series of enantiopure nanohelical structures based on polyoxometalates (NANOPOM), for their use as heterogeneous oxidation catalysts. Two approaches were used to prepare these new materials. The first one based on the immobilization of POMs on silica nanohelices and nanoribbons by electrostatic and direct adsorption grafting. These inorganic structures increase the stability and make them less sensitive to external environment. The second approach is to include POM units within the structure of organic nanoribbons and nanohelices during self-assembly of 16-2-16 (L)- or (D)-tartrate gemini amphiphile and POM in water. The characterization of these NANOPOM hybrids by using various techniques such as 31P NMR, UV-Vis, DRIFT, Raman, TEM, HR-TEM and EDX was performed and confirms the structure of these materials, especially the grafting of POM to helical supports. These materials are generally stable, and the induction chirality to the POM anion was confirmed by circular dichroism, highlighting the enantiopurity of these NANOPOM materials. The catalytic properties of these POM hybrids have been tested in the oxidation of sulfides. They are active and recoverable catalysts, unfortunately with no significant enantioselectivity observed in the condition used. We expect that new NANOPOM systems in which POM units are introduced within the structure of nanostructure during gel formation, followed by silica transcription will be more stable, an important feature for their use as recoverable catalyst
Elbert, Bryony L. „The synthesis and applications of cyclic alkenylsiloxanes“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a332365e-22f2-4449-b517-3fd8a62ea8a3.
Der volle Inhalt der QuelleAçıkel, Müge Artok Levent. „Silica Supported N-Heterocyclic Carbenes:Active and Reusable Heterogeneous Catalysts for Mizoroki-Heck Reactions/“. [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/kimya/T000496.pdf.
Der volle Inhalt der QuelleO'Brien, Jeannette M. „New Catalysts and Catalytic Methods for Cycloadditions and Conjugate Additions to Alpha, Beta-Unsaturated Carbonyls“. Thesis, Boston College, 2012. http://hdl.handle.net/2345/bc-ir:103617.
Der volle Inhalt der QuelleChapter 1. A Practical Synthesis of 3-Acyl Cyclobutanones by [2 + 2] Annulation. Mechanism and Utility of the Zn(II)-Catalyzed Condensation of alpha-Chloroenamines with Electron-Deficient Alkenes. We have developed a catalytic method for the synthesis of highly functionalized 3-acyl cyclobutanones which are useful building blocks for a variety of natural products. Methods for cyclobutanone synthesis have traditionally been limited to Lewis-acid promoted rearrangement of oxaspiropentanes or cyclizations of ketene and syntheses involving keteneiminium salts have required stoichiometric quantities of a Lewis acid. Furthermore, the mechanism for these types of cyclizations remains unknown. This portion of my research focused on an efficient, catalytic method for the synthesis of 3- acyl cyclobutanones and providing insight into the mechanism for cycloaddition. Chapter 2. Enantioselective Synthesis of Boron-Substituted Quaternary Carbons by NHC-Cu-Catalyzed Boronate Conjugate Additions to Unsaturated Carboxylic Esters, Ketones, or Thioesters. We have developed an enantioselective NHC-Cu-catalyzed conjugate addition of boronate esters to acyclic, trisubstituted alpha, beta-unsaturated carbonyl compounds. Enantioselective conjugate addition of a boronic acid pinacol ester through the use of bis(pinacolato)diboron [B2(pin)2,] to alpha, beta-unsaturated aliphatic and aryl esters promoted by 5 mol % of an NHC-Cu catalyst afforded tertiary beta-boryl carbonyls in high efficiency and enantioselectivity. Trisubstituted alpha, beta-unsaturated esters and thioesters were found to be reactive substrates in the presence of a stoichiometric quantity of methanol. Chapter 3. Metal-Free Catalytic C-Si Bond Formation in an Aqueous Medium and C-B Bond Formation in a Protic Medium. Enantioselective NHC-Catalyzed Silyl and Boryl Conjugate Additions to Cyclic and Acyclic alpha, beta-Unsaturated carbonyls. We have developed a method for enantioselective metal-free silyl conjugate additions through the use of dimethylphenylsilyl) boronic acid pinacol ester [PhMe2SiB(pin)] catalyzed by chiral N-heterocyclic carbenes (NHCs) in basic aqueous thf. Optimization of metal-free conditions demonstrated that the presence of water was required for high efficiency. alpha, beta-Unsaturated cyclic ketones and lactones were examined as substrates, and acyclic ketones, esters and aldehydes were also competent substrates for silyl conjugate addition. beta-Silyl carbonyls were isolated in up to >98% yield and >98:2 er. Chapter 4. Elucidation of Mechanism for Enantioselective NHC-Catalyzed Silyl Conjugate Addition. We propose a catalytic cycle for NHC-catalyzed enantioselective silyl conjugate addition. Mechanistic studies of NHC-catalyzed enantioselective silyl conjugate additions are presented. Optimization of conditions for an inefficient alpha, beta-unsaturated electron-deficient ketone provided insight into the roles for dbu and water. Kinetic data indicate that conjugate addition is first order in PhMe2SiB(pin) and carbene, and DFT calculations support the formation of an NHC-silyl anion as a reactive intermediate in the catalytic cycle
Thesis (PhD) — Boston College, 2012
Discipline: Chemistry
Lopes, Silva Susana. „Développement de nouveaux catalyseurs d'hydrotraitement basés sur l'encapsulation d'hétéropolyoxometallates dans des silices mésostructurées : application à la production de carburants propres“. Thesis, Lyon, École normale supérieure, 2013. http://www.theses.fr/2013ENSL0799/document.
Der volle Inhalt der QuelleEconomic growth in the developing countries over the past decade has increased the global demand for crude oil. It is projected that the global crude slate will become sourer, with a sulfur content above 1.3 wt%. An overall aim of policymakers is thus to ensure that transportation fuels do not surpass a sulfur content of 10 ppm. Several solutions are possible to achieve the nowadays goals, that affect either the process or the catalyst. The latter solution, which does not involve significant additional costs for refiners, is therefore the most studied. One way to improve the nowadays catalysts would be to increase the content of active metal (eg cobalt and molybdenum in the case of CoMo systems). Nevertheless, at higher metal loadings, the formation of refractory species such as CoMoO4 or Co3O4 by sintering during calcination and/or sulfidation steps has been reported for alumina-Supported catalysts. This PhD project is based on the development of new hydrotreating catalysts, through a 2-Step one-Pot method : synthesis of polyoxometalates-Containing mesoporous SBA-15 materials, followed by incipient wetness impregnation of active phase promoter. The encapsulation of these species within the silica matrix would prevent the agglomeration of large particles during sulfidation reactions and could thus lead to systems with high content of active metal well dispersed over the support. One aim of this study was to evaluate the potential of these catalysts in the hydrotreating of several feedstocks, such as diesel oil, gasoline or vegetal oil. A second objective was the understanding of the nature of the different interactions between the active phase precursors and the support, according to each preparation technique.The non-Promoted hybrid catalyst showed a better dispersion of the metallic phase in the oxide state, compared to the catalysts prepared by incipient wetness impregnation, which can be correlated with stronger interactions between encapsulated POM and silica functionalities, such as siloxanes and silanols, as evidenced by Raman spectroscopy. However, the wide-Angle XRD showed the presence of MoO3 crystallites. HRTEM analyzes of the sulfided catalysts showed different species on this catalyst: small MoS2 slabs and metal particles (∼ 1 nm) mainly in the walls but also on the surface of pores; curved MoS2 slabs at mesopores surface leaving the entrance of the pore free; MoS2 hanks blocking the pores.This catalyst showed a relatively low sulfidation rate (determined by XPS), which could be associated with the presence of refractory species already present before activation. Thus, the toluene conversion represented per MoS2 clearly showed the interest of the catalyst prepared by this innovative method, presenting an intrinsic activity two-Fold higher than that of the catalyst prepared by dry impregnation.The subsequent impregnation of the active phase promoter of the hybrid catalyst (Pr(NO3)2, Pr = Ni or Co; 4
Launez, Rémy. „Immobilisation d'organocatalyseurs sur supports inorganiques et évaluation de leur activité en condition de flux continu“. Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS212/document.
Der volle Inhalt der QuelleThe aim of our project was to develop an eco-friendly process based on heterogeneous asymmetric organocataysis in continuous flow conditions. To succeed in this development, we chose to use a quinine-derived bifunctional organocatalyst: cupreine. Silica, a mesoporous inorganic material, was chosen as the support to immobilize this organocatalyst. The grafted cupreine was then tested as catalyst for the asymmetric Michael addition between the trans-β-nitrostyrene (Michael acceptor) and the dimethyl malonate (Michael donor) in continuous flow condition.First, we immobilized the catalyst on two types of silica, following three different strategies. The various cupreine-grafted silicas we obtained were functionnalized with 0.2 to 0.4 mmol of cuprein per gram of silica. Each one of them possessed specific characteristics depending of the followed strategy.The assessment of the catalytic activity of immobilized silica was then performed in batch condition. Different bio-based solvents were used for the Michael addition. 2-MeTHF was chosen as the best solvent among those tested and used in continuous flow. Immobilized cupreine proved to be as efficient in heterogenous condition as in homogenous (enantiomeric excess was superior or equal to 85 % and conversion better than 96 %), except for turn over frequency (TOF, mol of converted substrate/mol of catalyst/reaction time) which is three times lower in hetereogeneous condition (0.2h-1 to 0.6 h-1 in homogenous condition).Michael addition of trans-β-nitrostyrene to dimethyl malonate was then realized in continuous flow condition, using the various silica-supported catalysts. Turn over frequency of cupreine was doubled (0.4 h-1) and the turn over number (mol of converted substrate/mol of catalyst) increased from 16 to 63 in continuous flow condition. Derivatives of trans-β-nitrostyrene (chlorinated, phenolic and methoxylated in position 4) were successfully tested in continuous flow.To the best of our knowledge, we realized the first asymmetric Michael addition between trans-β-nitrostyrene and the dimethyl malonate, catalysed by silica-supported cupreine in batch and in continuous flow, using a bio-based solvent.We successfully developed an eco-friendly process based on heterogeneous organocatalysis in continuous flow. This process favorited an efficient recycling of the supported catalyst, and increased the productivity of grafted cupreine compare to the heterogeneous condition in batch. The enantioselectivity of the cupreine for this reaction was similar in both homogeneous and heterogeneous conditions
Wu, Xianchun. „Acidity and catalytic activity of zeolite catalysts bound with silica and alumina“. Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/561.
Der volle Inhalt der QuelleWidyaningrum, Rosalia Nugraheni. „Mesoporous silica-supported catalysts to enhance hydrogen production during cellulose pyrolysis“. Thesis, The University of Sydney, 2011. https://hdl.handle.net/2123/28917.
Der volle Inhalt der QuelleHondow, Nicole S. „The synthesis of new heterogeneous Fischer-Tropsch catalysts : the incorporation of metal aggregates in mesoporous silicas“. University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0083.
Der volle Inhalt der QuelleRoussey, Arthur. „Preparation of Copper-based catalysts for the synthesis of Silicon nanowires“. Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10164.
Der volle Inhalt der QuelleThe work presented in this PhD thesis aimed at the preparation of copper nanoparticles of controllable size and their utilization as catalysts for the growth of silicon nanowires in a process compatible with standard CMOS technology and at low temperature (< 450°C). The growth of silicon nanowires by Chemical Vapor Deposition (CVD) via the catalytic decomposition of a silicon precursor on metallic nanoparticles at low temperature (Vapor Solid-Solid process) was demonstrated to be possible from an oxidized Cu thin film. However, this process does not allow the control over nanowires diameter, which is controlled by the diameter of the nanoparticle of catalyst. In this PhD is presented a fully bottom-up approach to prepare copper nanoparticles of controllable size directly on a surface without the help of external stabilizer by mean of surface organometallic chemistry. First, the preparation of copper nanoparticles is demonstrated on 3D substrates (silica and titanium nitride nanoparticles), along with the fine comprehension of the formation mechanism of the nanoparticles as a function of the surface properties. Then, this methodology is transferred to planar (2D) substrates typically used in microelectronics (silicon wafers). Surface structure is demonstrated to direct the Cu nanoparticles diameter between 3 to 40 nm. The similarities between the 2D and 3D substrates are discussed. Finally, the activity of the Copper nanoparticles in the growth of Silicon nanowire is presented and it is demonstrated that in our conditions a critical diameter may exist above which the growth occurs
Kaya, Sarp. „Structural and catalytic investigations on vanadium oxide nanoparticles supported on silica films grown an a Mo(112) substrate“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15639.
Der volle Inhalt der QuelleThe widespread use of model systems for understanding the heterogeneous catalytic processes is based on bridging the structural complexity gap between present generation of supported metal and metal oxide technical catalysts and crystalline metal and planar metal/oxide systems, which are utilized to investigate structure-reactivity relationships by a large variety of surface science techniques. In this thesis, we focused on a concept of so-called ''monolayer'' vanadium oxide catalysts, which have been introduced particularly for methanol oxidation reactions. Following a bottom-up approach, silica supported vanadium oxide model catalysts were investigated. Combining a number of experimental techniques, the surface of Mo(112) used as a substrate for the silica films was characterized in detail and the atomic structure of the silica film was determined. Adsorption of water and growth of vanadium oxide nanoparticles on the silica films, and finally the reactivity of vanadium oxide/silica systems towards methanol were studied. In contrast to the previously suggested models, an oxygen induced p(2×3) superstructure formed on a Mo(112) surface should be considered as one dimensional surface oxide where Mo=O groups are formed preferentially along the [-1-11] direction of the Mo(112) surface. Monolayer silica films grown on Mo(112) surfaces are composed of two-dimensional network of SiO4 tetrahedra. Depending on the film preparation conditions, the structure can be altered by additional oxygen atoms adsorbed on the Mo substrate. The defect structure includes antiphase domain boundaries which form by a half-lattice shift along the [-110] direction and a low density of point defects, most probably silicon vacancies. Water does not dissociate on the monolayer silica film. An ordered structure of water with respect to silica film was observed at 140 K owing to good lattice matching between the silica film and hexagonal ice. Amorphous solid water layers homogenously covering the surface at 100 K were used as reactive layers for vanadium oxide particles in order to mimic ''wet chemistry'' used in preparation of technical catalysts. The results revealed that ice layer assisted the formation of hydrated vanadium oxide nanoparticles partially terminated by V=O and V-OH groups. The dehydration takes place above 500 K, thus exposing V-terminated surface. Methanol dissociates on dehydrated vanadium oxide particles and methoxy species are stable on the surface up to 500 K only in the presence of vanadium terminated surface sites. Formaldehyde production which takes place at ~550 K is strongly affected by the surface structure of the vanadium oxide particles and exhibits a maximum at specific ratio between V- and V=O sites on the surface. The results presented may have a strong impact on our understanding of the catalytic reactions at the molecular level.
Aksın, Özge Artok Levent. „The activity of silica immobilized palladium N-heterocyclic carbene complexes toward Mizoro-Heck reaction and their characterization/Özge Aksın;thesis advisor Levent Artok“. [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/kimya/T000341.pdf.
Der volle Inhalt der QuelleKeywords: Palladium, Immobilization, Heck Reaction, Palladium-N-Heterocyclic Carbene, Carbon-Carbon Coupling. Includes bibliographical references (leaves. 89-104).
Zamboulis, Alexandra. „Silices hybrides pour l'organocatalyse asymétrique“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2010. http://www.theses.fr/2010ENCM0004.
Der volle Inhalt der QuelleAsymmetric organocatalysis is a blossoming area of research. Immobilisation of this kind of catalysts could present numerous advantages. This thesis deals with the sol-gel synthesis of organic/inorganic hybrid silicas and their applications in asymmetric organocatalysis. The first part of this work is dedicated to a bibliographic presentation of this area of research. In the second part, the use of L-proline as a model is described. Hybrid materials containing a L-proline component were prepared and their catalytic performances were evaluated in an asymmetric aldolisation reaction. The processes accounting for the moderate performances of these materials are discussed. The third part relates the synthetic strategies used to prepare silylated derivatives of the Takemoto catalyst, a bifunctional catalyst containig a H-bond donnor and a tertiary amine. Finally the nanostructuring of bridged silsesquioxanes through H-bonding interactions between thiourea cross-linkers is presented
Kababji, Ala'a Hamed. „Effects of Diluent Addition and Metal Support Interactions in Heterogeneous Catalysis: SiC/VPO Catalysts for Maleic Anhydride Production and Co/Silica Supported Catalysts for FTS“. Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/2035.
Der volle Inhalt der QuelleMoitra, Nirmalya. „Silices hybrides fonctionnelles : matériaux dérivés d'alcaloïdes pour organocatalyse ; réactions "click" pour le sol˗gel“. Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0003.
Der volle Inhalt der QuelleThis thesis deals with the preparation of organic-inorganic hybrid silica based on cinchona alkaloids fragments and with a new method of synthesis for hydrolysable silylated precursors via CuAAC “click” reactions. The first part of this work is dedicated to a bibliographic presentation of the area of supported catalysis on hybrid materials and is mainly focused on supported organocatalysis, an emerging area of research. In the second part, different methods for immobilization of alkaloids within a silica matrix are described aiming at using them as organocatalysts for an asymmetric decarboxylation reaction. The third part is devoted to a new method of preparation of silylated precursors by CuAAC “click” reactions. This methodology shows a high potential in the formation of new functional compounds. Finally the synthesis of mesoporous silica nanoparticles bearing azide or alkyne groups and their post-functionalization by CuAAC reactions are presented
Popoff, Nicolas. „Préparation et caractérisation de complexes du groupe IV supportés sur silice et silice mono-fonctionnalisée : catalyseurs pour la polymérisation des oléfines“. Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10229.
Der volle Inhalt der QuelleThis work deals with the preparation and characterization of new, neutral or cationic group IV complexes, supported on silica or mono-functionalized silica, for alpha-olefins polymerization. In a first part, a new preparation for an olefin polymerization catalyst based on TiCl4, was proposed. Grafting on silica dehydroxylated at 200 and 700°C (SiO2-200 and SiO2-700) yielded the unique species [≡SiO-TiCl3] which, upon activation by Mashima’s reductant, led to a neutral active polymerization catalyst, following an oxidative coupling mechanism, and reaching an activity of 260 kgPE.molTi -1.h-1. Similarly, neutral catalysts acting along the same mechanistic pathways, were developed by grafting M(CH2Ph)4 (M=Ti, Zr) to yield the well defined species [(≡SiO)2M(CH2Ph)2] and [≡SiO-M(CH2Ph)3] on SiO2- 200 and SiO2-700 respectively. The ensuing activation by B(C6F5)3 in order to yield cationic species, did not increase the activity considerably.In the second part of this work, a new material was prepared in order to introduce of a phenoxy spacer between the surface and the complex. Reaction of AliBu3 with SiO2-700 yielded the unique species [(≡SiO)2AliBu.(Et2O)] which was then reacted with hydroquinone. The tetrabenzyl Ti and Zr complexes were successfully grafted on this support. These species were then activated by B(C6F5)3 and a notable increase in the resulting polymerization activities were observed. This methodology was extended to 100\% enriched complexes (C5Me5)Zr(13CH3)3 following three approaches. Either direct grafting on this new material, followed by B(C6F5)3 activation, or by reaction with the support, previously altered by HB(C6F5)2 or [B(C6F5)3][NEt2Ph]. Either way, the active cationic active species obtained presents a covalent Zr-O bond with the surface, with the associated counter-ion [MeB(C6F5)3]- with a maximum activity of 510 kgPE.molZr-1.h-1, higher than its the silica counterpart
Wang, Zichun. „Catalytic conversion of biomass- and petrochemical-derived model compounds over acidic catalysts“. Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13679.
Der volle Inhalt der QuelleTichauer, Ruth Elena. „In silico screening of NRas protein oncogenic mutations : new structural and physico-chemical insights into the catalytic activity“. Electronic Thesis or Diss., Toulouse 3, 2019. http://www.theses.fr/2019TOU30028.
Der volle Inhalt der QuelleRas subfamily of small GTPase proteins holds a key position in cell proliferation pathways. Indeed, the transmission of cell growth signals is controlled by proteins belonging to it. In their GTP-bound conformation, these proteins interact and activate downstream effectors of cell replication and differentiation. The hydrolysis reaction that takes place in their center, terminates these interactions, thereby leading to the GDP-bound inactive state. Point mutations of key residues lead to a hydrolysis rate drop that keeps Ras in a GTP-bound active state. Now, high concentrations of active Ras have been associated to abnormal cell proliferation, emblematic of cancerous tissues dissemination. With this into consideration, the elucidation of Ras mechanisms for accelerating GTP cleavage appears as a major step in the development of cancer targeted therapies that would consist in restoring the hydrolysing capabilities within oncogenic Ras to a wild-type rate. In an attempt to gain insight into Ras catalysing properties at the atomic level, unconstrained Molecular Dynamics (MD) simulations describing the G domain at different levels of theory (Molecular Mechanics (MM), Semi-empirical and Density Functional Theory (DFT)) were carried out for NRas member in its wild-type and Gln 61 mutated forms. These simulations were coupled to biomechanic characterisations of the complexes under inspection employing the static modes approach. The latter method, allows the identification of hot spots {\it i.e.} responsive residues of the biomolecule, that have a mechanical influence on the GTPase function of the protein. Hence, they could serve as suitable sites to host drug-like molecules containing specific chemical groups that would facilitate GTP hydrolysis. The obtained results show that water molecules positioning is crucial for efficiently catalysing the reaction that takes place in NRas center. Indeed, the precise positioning observed within the wild-type is lost within the mutants studied here. Furthermore, the active site structural modifications undergone upon Gln 61 substitutions, together with solvent distribution in it, impact directly GTP electronic density. The latter is accommodated to a GDP-like state within the wild-type protein only, as experimentally determined in previous investigations. Thus, oncogenic Gln 61 mutations impair this major catalysing effect. Among three engineered NRas proteins of the Q61R mutated form, proposed during this thesis, one is presented during the defence while the three are described in the manuscript. The chemical groups inserted at the identified site enable the recovery of water distribution as within the wild-type. To end, during the defence only, an alternative reaction pathway of the enzymatic reaction is proposed
Scriba, Manfred R. „Silicon nanoparticle sysnthesis through thermal catalytic pyrolysis“. Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6550.
Der volle Inhalt der QuelleNanoparticles are considered as fundamental building blocks of nanotechnology and, silicon nanoparticles in particular, will form the basis of applications in single electron transistors, floating gate memory devices, solid state lighting, chemical sensors and flexible electronics, including solar cells and luminescent materials, printed on paper. A remaining key challenge however in the development of applications is the reproducible and reliable production of nanomaterial in sufficient quantities. Historically nanoparticles have been manufactured by top-down approaches such as milling, laser ablation or etching, and bottom-up synthesis such as colloidal chemistry and gas phase pyrolysis. The chemical processes in the latter are generally equivalent to those in the chemical vapour deposition (CVD) of compact films. Due to its simplicity and the relatively straight-forward construction of the hot wire chemical vapour deposition (HWCVD) reactor, this method is further investigated as a suitable route to nanoparticle production. The objective of this research is thus to produce Si nanoparticles (powder) in sufficient quantities, through thermal catalytic pyrolysis, while maintaining control of the important properties namely size, size distribution, composition and crystallinity.
Nzahou, Ottou Winnie. „Organopolymérisations du méthacrylate de méthyle induites par les carbène N-hétérocycliques et par des paires de Lewis organiques“. Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0303/document.
Der volle Inhalt der QuelleThe reactivity of imidazol-ylidene N-heterocyclic carbenes (NHCs) as direct initiators for the polymerization of miscellaneous (meth)acrylic monomers, mainly methylmethacrylate (MMA), has been screened in the absence of any other co-activator.Different reactivities have been observed according to the structure of the NHC and thenature of the substrate. Computational studies allowed rationalizing steric and electroniceffects involved in these reactions.The use of a peculiar NHCs as catalyst for the polymerization of MMA using alcohols as initiators has then been investigated. This simple and efficient method also allows achieving amphiphilic block copolymers by using hydroxylated poly(ethylene oxide)s asmacro-initiators. Combined computational and experimental investigations have provided insights into the mechanism of polymerization.Various Lewis pairs including a silicon-based compound as acid and NHC or a trialkyl(aryl)phosphine as base, have been investigated to trigger an efficient polymerization of MMA.In this case, the polymerization is expected to proceed via a cooperative/dual activation mechanism
Modiba, Fortunate Mofao. „Tin Catalyst preparation for Silicon Nanowire synthesis“. University of the Western Cape, 2018. http://hdl.handle.net/11394/6516.
Der volle Inhalt der QuelleSolar cells offer SA an additional energy source. While Si cells are abundantly available they are not at an optimal efficiency and the cost is still high. One technology that can enhance their performance is SiNW. However, material properties such as the diameter, porosity and length determine their effectiveness during application to solar cell technology. One method of growing SiNW uses Sn catalysts on a Si substrate. As the properties of the Sn nanoparticle govern the properties of the SiNW, this thesis investigates their formation and properties by depositing a Sn layer on a Si wafer and then subjecting it to different temperatures, during process the layer forms into nanoparticles. At each temperature the morphology, composition and crystallinity will be determined using XPS, SEM, TEM and EDS. Thus, in Chapter 1 there is an overview, Chapter 2 deals with techniques used in this study, Chapter 3 will give the quantitative and qualitative results on the XPS analysis and Chapter 4 will illustrate the structural behaviour of the annealed Sn film samples.
Polisski, Sergej. „Porous silicon/noble metal nanocomposites for catalytic applications“. Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545317.
Der volle Inhalt der QuelleUtting, Katherine Alice. „Silica supported mild base catalysts“. Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423602.
Der volle Inhalt der QuellePeyralans, Jerome Jean-Pierre. „Silasultones as silicon-based Lewis acid catalysts : synthesis and activity“. Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412759.
Der volle Inhalt der QuellePapafilippou, Alexandros. „Development of low-oxidation state nitrogen, carbon and silicon catalysts“. Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23646.
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