1) La descarga del recurso depende de la página de origen
2) Para poder descargar el recurso, es necesario ser usuario registrado en Universia

Opción 1: Descargar recurso

Detalles del recurso


The use of biomass as a resource to produce value-added products has garnered significant interest as a means of reducing reliance on fossil fuels. This task is complicated by the complex, highly functionalized nature of abundant biomass derivatives, such as glucose. Tin-containing zeolite Beta (Sn-Beta) has been investigated as a catalyst for isomerizing aldohexoses into ketohexoses through a Lewis acid mediated hydride shift (1,2-intramolecular hydride shift, 1,2-HS). Recent studies on the reactivities of Lewis base-doped and alkali-exchanged Sn-Beta samples have conclusively demonstrated that the open tin site performs the glucose isomerization reaction. With Lewis base doped Sn-Beta, glucose conversion is almost completely eliminated and product selectivity is shifted predominantly to mannose, formed through a 1,2-intramolecular carbon shift (1,2-CS). To understand the structure-activity relationships between the conditions of the active sites in the zeolite, three molecular models (tin silsesquioxanes) of the tin sites in the zeolite are synthesized. Two tin silsesquioxanes that contain an octahedral tin site with and without an adjacent silanol group are prepared and used as catalysts for the reaction of glucose. The catalyst that contains the adjacent silanol group selectively forms fructose through a 1,2-HS while the catalyst without the silanol group yields mannose through a 1,2-CS. These results provide further evidence for the nature of the active sites in Sn-Beta. A methyl-ligated tin silsesquioxane is experimentally and theoretically examined to examine possible reactivities at the closed site. This compound is an active glucose conversion catalyst that selectively produces mannose, although the rates of reaction are far below those obtained from Sn-Beta. Additionally, a hybrid quantum mechanical/molecular mechanics model is constructed, and the complete catalytic cycle is computationally examined via considering ring-opening, three distinct pathways for each hydride- and carbon-shift reaction, and ring-closing. The combined experimental and computational results suggest that there could be reaction pathways that involve Si-O-Sn cleavage that give much slower reaction rates than the open tin site in Sn-Beta.

Zeolite and zeolite-like molecular sieves are being used in a large number of applications such as adsorption and catalysis. Achievement of the long-standing goal of creating a chiral, polycrystalline molecular sieve with bulk enantioenrichment would enable these materials to perform enantioselective functions. In part II of this thesis, the synthesis of enantiomerically enriched samples of a molecular sieve is reported. Enantiopure organic structure directing agents (OSDAs) are designed with the assistance of computational methods, and used to synthesize enantioenriched, polycrystalline molecular sieve samples of either enantiomer. Computational results correctly predicted which enantiomer is obtained, and enantiomeric enrichment is proven by high-resolution transmission electron microscopy. The enantioenriched and racemic samples of the molecular sieves are tested as adsorbents and heterogeneous catalysts. The enantioenriched molecular sieves show enantioselectivity for the ring opening reaction of epoxides and enantioselective adsorption of 2-butanol (R enantiomer of the molecular sieve shows opposite and approximately equal enantioselectivity from the S enantiomer of the molecular sieve, while the racemic sample of the molecular sieve shows no enantioselectivity).

Pertenece a



Brand, Stephen Kramer - 

Id.: 69832502

Versión: 1.0

Estado: Final

Tipo:  application/pdf - 

Tipo de recurso: Thesis  -  NonPeerReviewed  - 

Tipo de Interactividad: Expositivo

Nivel de Interactividad: muy bajo

Audiencia: Estudiante  -  Profesor  -  Autor  - 

Estructura: Atomic

Coste: no

Copyright: sí

Formatos:  application/pdf - 

Requerimientos técnicos:  Browser: Any - 

Relación: [References] http://resolver.caltech.edu/CaltechTHESIS:04182017-134255198
[References] http://thesis.library.caltech.edu/10141/

Fecha de contribución: 12-may-2017


* Brand, Stephen Kramer (2017) I. Tin Silsesquioxanes as Analogs for the Open and Closed Sites in Tin-Containing Zeotype Beta and II. Enantiomerically Enriched, Polycrystalline Molecular Sieves. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z96T0JPX. http://resolver.caltech.edu/CaltechTHESIS:04182017-134255198

Otros recursos que te pueden interesar

  1. Guerra e tradição : os argumentos conservadores em defesa das instituições armadas do Estado brasileiro no período 1964-1988 A lo largo del 2014, una serie de publicaciones, dentro de las cuales se cuenta un informe de la Com...
  2. Effects of amino acid supplementation of lysine and methionine on body biochemical composition and amino acid profile of Sobaity sea bream (Sparidentex hasta) juveniles In this study that lasted to 8 weeks, was conducted to determine the effects of dietary supplementat...
  3. Ecological study of zooplankton communities in the Persian Gulf Martyrs Lake (Chitgar-Tehran) and the first report of the freshwater jellyfish Craspedacusta sp. (Cnidaria, Limnomedusae) in Iran This study focused on zooplankton structure, biodiversity, relationship between a biotic parameters ...
  4. The effect of different feeding rates on growth indices, feed conversion ratio and body composition of Oriental River prawn Macrobrachium nipponense (De Haan, 1849) This research was carried out in accordance with identification of effects of different feeding rate...
  5. The evaluation of the quality of beta-carotene derived from Azolla filiculoides in the Anzali Wetland using the alkaline hydrolysis method in summer The present project was aimed at determining the content, quality, and purity of β-carotene extracte...

Otros recursos de la mismacolección

  1. Chemical Exchange in Nuclear Magnetic Resonance

    Nuclear magnetic resonance spectra of molecules undergoing chemical exchange have traditionally ...

  2. Genetic Sequences by Electron Microscopy

    Part I: Sequence homology between the DNA molecules of the two temperate Bacillus subtilis b...

  3. High Energy Heavy Ion Beam Enhanced Adhesion of Gold Films to GaAs

    Improvement of the adhesion of gold films to GaAs substrates by irradiation with a beam of high e...

  4. Unit Activity in the Hypothalamus and Striatum of the Rat during Learning Unit activity was recorded from the hypothalamus and striatum of 80 freely moving rats during an app...
  5. High Alumina Metamorphic Rocks of the Kings Mountain District, North Carolina and South Carolina

    The Kings Mountain district is located in the center of the Piedmont province at the North Carol...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.