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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Investigation of Secondary Coordination Sphere Effects for Cyanohydrin Hydration with Transition Metal Catalysts

Knapp, Spring Melody, Knapp, Spring Melody January 2012 (has links)
The synthesis of high value acrylic monomers is currently done industrially via cyanohydrin hydration using concentrated acids, resulting in large quantities of useless byproducts. This current process is energy intensive and lacks atom economy; therefore, alternative cyanohydrin hydration strategies are under investigation. Ideally, cyanohydrin hydration would be done using organometallic nitrile hydration catalysts. Cyanohydrin hydration with these catalysts is challenging, because it needs to be done at low temperatures and under acidic conditions to reduce cyanohydrin degradation and catalyst poisoning with cyanide. This dissertation describes the reactivity of [Ru(#951; / 10000-01-01
2

An Investigation of Transition Metal Catalysts for Cyanohydrin Hydration: The Interface of Homogeneous and Heterogeneous Catalysis

Downs, Emma 29 September 2014 (has links)
Acrylic monomers are important materials that represent a large portion of the economy. The current industrial synthesis hydrates cyanohydrins with sulfuric acid, a process which results in large amounts of waste and significant energy costs. A transition metal catalyzed, acid free hydration of cyanohydrins would be beneficial from both economic and environmental standpoints. However, this reaction is challenging, as many catalysts are poisoned by the cyanide released when cyanohydrins degrade. Therefore the development of a catalyst that is resistant to cyanide poisoning is the ideal method to circumvent these difficulties. This dissertation describes several cyanohydrin hydration catalysts, with an emphasis on nanoparticle catalysts. These are at the interface between the homogeneous and heterogeneous catalysts that have been explored previously for this reaction. Chapter I surveys previous studies on nanoparticle catalysts for nitrile hydration and their implications for the hydration of cyanohydrins. Chapter II reports on the homogeneous platinum catalysts [PtHCl(P(NMe2)3)2] and [PtH2(P(NMe2)3)2], exploring secondary coordination sphere effects to enhance nitrile hydration. Chapter III describes another example of this type of complex, [PtH2(P(OMe)3)2], that forms catalytically active nanoparticles under reaction conditions. Explorations of the reactivity of this catalyst with nitriles and cyanohydrins are also described in this chapter. Chapter IV investigates a silver nanoparticle catalyst with a water soluble phosphine (1,3,5-triaza-7-phosphaadamantane) ligand for its activity towards the hydration of nitriles and cyanohydrins. The results of the degradation of the nanoparticles in the presence of cyanide are also described. Chapter V reports on the preparation and examination of a solid supported nickel catalyst for cyanohydrin hydration. Finally, Chapter VI describes how these investigations have made progress towards the development of a cyanide resistant nitrile hydration catalyst. This dissertation includes previously published and unpublished co-authored material. / 2015-09-29
3

Investigations into the Oxidative Desulfurization Activity in a Film-Shear Reactor, the Source of Enhanced Reactivity, and Other Potential Applications

Fox, Brandy R., 1981- 06 1900 (has links)
xviii, 242 p. : ill. (some col.) / Fuel purification is an extremely active area of research in today's green world. Specifically, desulfurization of fuels is an important area of research for two reasons. First, any sulfur present in fuels generates SOx pollutants that are hazardous to human health and also contribute to acid rain. Secondly, even trace sulfur contaminants prohibit the use of fuel streams in fuel cells. However, achieving near-zero sulfur levels with existing technology is impractical. The work in this thesis investigates a new process for the removal of sulfur from fuel streams using a film-shear reactor (based on a process known as oxidative desulfurization), and goes on to investigate the mode of activation for the process within the reactor through a study of the reactor conditions. Additionally, other applications of the film-shear reactor, including mechanical activation of molecules and controlled nanoparticle synthesis are explored. Chapter I outlines the current status of oxidative desulfurization research, highlighting the strengths of the method, innovative approaches and drawbacks to the various approaches. Chapters II and III go on to discuss the enhancement of the process in the film-shear reactor using model fuels and a variety of substrates. This method was found to significantly enhance the oxidative desulfurization process, reducing both the time and temperature required to achieve considerable sulfur removal. Levels of desulfurization that require hours at elevated temperatures by conventional stirring methods were obtainable on the scale of seconds at or below room temperature. Chapter IV offers investigations into the conditions within the film-shear reactor, and also presents studies of the ability of the high shear rates obtained in the reactor to mechanically activate molecules. Chapter V extends the applicability of the film-shear reactor to nanoparticle synthesis through investigation of two titania synthesis methods utilizing the film-shear reactor. Appendices A and B offer supplementary information to enhance the studies presented in Chapters II and III, while Appendices C, D, and E highlight work done investigating the ability of platinum complexes to hydrate nitriles and cyanohydrins. This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Victoria J. DeRose, Chairperson; David R. Tyler, Advisor; Kenneth M. Doxsee, Member; Catherine J. Page, Member; Mark H. Reed, Outside Member
4

Systèmes supramoléculaires biomimétiques : les complexes bols, synthèse, propriétés et réactivité / Biomimetic supramolecular systems : bowl complexes, synthesis, properties and reactivity

Parrot, Arnaud 16 December 2015 (has links)
Le ligand Rim3, constitué d’une cavité resorcinarène fonctionnalisée par 3 groupements méthylimidazole a été synthétisé et étudié. Ce ligand est capable de coordiner différents métaux de transitions comme le zinc et le cuivre. Ces complexes possèdent des propriétés hôte-invité intéressantes et une sélectivité avec la taille de la cavité. La complexation d’invités acides nécessite l’addition d’une base exogène. De plus, la présence de base peut être nécessaire pour réaliser des réactions d’hydratation ou d’hydrolyse. Dans ce manuscrit sont présentés différents ligands cavitaires resorcinarène avec 4 imidazoles greffés. Chaque ligand et complexe associé présente des solubilités différentes. Nous étudierons d’abord la synthèse et la caractérisation des systèmes en milieu organique ou aqueux. Les études de complexation montreront la forte affinité associée à ces complexes en milieu organique. L’étude des propriétés hôte-invité montre que le complexe est capable de coordiner un invité acide de manière quantitative dans les conditions RMN. Cette coordination ne nécessite pas l’addition de base. Le 4e imidazole joue le rôle de base intramoléculaire et n’est pas nécessaire à la coordination. Deux positions labiles en cis sont également disponibles, attesté par la coordination de ligands bidentes. Le complexe zincique [Rim4ZnII(EtOH)](ClO4)2 montre des propriétés d’hydratation des nitriles. Dans l’acétonitrile avec 35% d’eau à 70°C, le complexe forme de l’acétamide de manière catalytique. L’addition de base n’est pas nécessaire et le pH n’évolue pas avec la réaction. Dans l’eau avec 10% d’acétonitrile, [WRim(OH)44 Zn(H2O)](NO3)2 catalyse l’hydratation en acétamide mais est inhibé par l’hydrolyse successive en acétate. / In this manuscript, we present the synthesis and caracterisation of three tetradentate bowlshaped ligand. These ligands are resorcin[4]arene functionnalized by four methylimidazole. Each ligand is soluble in a different medium, such as organic solvent, water and mixed solvent. The four methylimidazoles are able to coordinate several metal ions, such as zinc, copper and iron. We then present the host-guest properties of the complexes. The complexes are able to coordinate acidic guests without addition of an exogenous base, thanks to the fourth imidazole. Two labiles positions are avalaible in cis, and bidentate ligands are able to coordinate the metal ions. Finally, we present the reactivity of the complexes. The zinc complex, [Rim4Zn]2+ catalyses the acetonitrile hydration with 35% water at 70°C. In an aqueous media with 10% water,[WRim(OH)44 Zn(H2O)](NO3)2 catalyses not only the acetonitrile hydration but also it’s subsequent hydrolysis into acetate.

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