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Reference: Chun Wong Aaron Chan, (2012). Ultraselective nanocatalysts in fine chemical and pharmaceutical synthesis. DPhil. University of Oxford.Citable link to this page:

 

Ultraselective nanocatalysts in fine chemical and pharmaceutical synthesis

Abstract: Surface catalysed reactions play an important role in chemical productions. Developments of catalyst requiring high activity whilst improving on product selectivity can potentially have a profound effect in the chemical industry. Traditional catalyst modifications were focused on tuning the size, shape and foreign metal doping to form well defined metal nanoparticles of unique functionalities. Here, we show new approach to engineering of metal nanocatalysts via a subsurface approach can modify the chemisorption strength of adsorbates on the surface. Carbon modified nanoparticles were synthesised using glucose to stabilise Pd nanoparticles at a molecular level. Upon heat treatment, the carbonised glucose encapsulated the Pd nanoparticles with carbon atoms take residence in the octahedral holes (15 at.%). These materials were tested in liquid phase stereoselective hydrogenations of 3-hexyn-1-ol and 4-octyne. The former has importance in the fragrance industry towards the production of leaf fragrance alcohol. It was shown for the first time that the geometrically and electronically modified Pd with interstitial carbon atoms reduced the adsorption energy of alkenes, ultimately leading to higher reaction selectivity. Boron modified Pd nanoparticles was synthesised using BH3.THF in the liquid phase. The material possess high B interstitial saturation (20 at.%), which can be synthesised for the first time below 100°C. These materials were tested in the liquid phase selective hydrogenation of various alkynes and 2-chloronitrobenzene, of which the latter has importance in the pesticides industry. Kinetic modelling on the hydrogenation of 4-octyne suggests these subsurface occupied B does play a pivotal role on increasing the reaction selectivity, as removal of these species lead to decreased selectivity. Au nanoparticles were synthesised and characterised using H13COOH NMR. The new liquid NMR characterisation method is successfully applied to examine the chemisorption strength of metal nanoparticles. An attempt to synthesise PVP capped B modified Pd nanoparticles with the above NMR characterisation was investigated. It is believed the examples of subsurface atom modifications as shown here may offer future catalyst developments in this area.

Digital Origin:Reformatted digital Type of Award:DPhil Level of Award:Doctoral Awarding Institution: University of Oxford

Contributors

Prof Shik Chi Edman TsangMore by this contributor

RoleSupervisor

 

Dr James CooksonMore by this contributor

RoleSupervisor

 Bibliographic Details

Issue Date: 2012

Copyright Date: 2012 Identifiers

Urn: uuid:866296af-5296-4d2e-8e52-6499dacaef0f Item Description

Type: thesis;

Language: en Keywords: heterogeneous catalyst selective hydrogenation liquid phase subsurface interstitial alkynes kinetic modelling 2-chloronitrobenzene formic acid nuclear magnetic resonanceSubjects: Inorganic chemistry Nanomaterials Surface chemistry Surface analysis Tiny URL: ora:11326

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Autor: Dr Chun Wong Aaron Chan - institutionUniversity of Oxford facultyMathematical,Physical and Life Sciences Division - Chemistry - I

Fuente: https://ora.ox.ac.uk/objects/uuid:866296af-5296-4d2e-8e52-6499dacaef0f



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