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. Reconstruction of an Acid Water Spill in a Mountain Reservoir The Olivargas Reservoir is located in a remote and scarcely monitored area in the Odiel River Basin ...
  2. Structure, Function and Dynamics in Adenovirus Maturation Here we review the current knowledge on maturation of adenovirus, a non-enveloped icosahedral eukar...
  3. Omics Meets Biology: Application to the Design and Preclinical Assessment of Antivenoms Snakebite envenoming represents a neglected tropical disease that has a heavy public health impact w...
  4. Application of an E-Tongue to the Analysis of Monovarietal and Blends of White Wines This work presents a multiparametric system capable of characterizing and classifying white wines ac...
  5. Airborne Hyperspectral Images and Ground-Level Optical Sensors As Assessment Tools for Maize Nitrogen Fertilization Estimating crop nitrogen (N) status with sensors can be useful to adjust fertilizer levels to crop r...

Otros recursos de la mismacolección

  1. On the Evolution of Field Galaxies

    This thesis presents the analysis of spectroscopic and photometric data on faint galaxies in an 8...

  2. Neutron Stars Observations as Astrophysical Probes

    Several aspects of observations of neutron stars and compact extragalactic radio sources are cons...

  3. Cryogenic Strain Application to Two-Dimensional Electron Systems and the Stripe State Electrons confined to move in a plane are collectively known as a two-dimensional electron system (2...
  4. Unveiling the Physical Conditions in Star-Forming Galaxies at Peak of Galaxy Assembly

    Galaxies at the peak of cosmic star formation (z~2-3) exhibit significantly higher star fo...

  5. Development of Synthetic Strategies for the Total Synthesis of Ent-Kauranoid and Diterpenoid Alkaloid Natural Products

    As part of an ongoing synthetic effort directed towards biologically active ent-kauranoid ...

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.