Oxidative organic transformations using catalyst systems based on metal nanoparticles supported on organic/inorganic composite materials.
| dc.contributor.advisor | Mapolie, Selwyn Frank | en_ZA |
| dc.contributor.advisor | Malgas-Enus, Rehana | en_ZA |
| dc.contributor.author | Storm, Ené | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. | en_ZA |
| dc.date.accessioned | 2020-10-20T08:14:11Z | en_ZA |
| dc.date.accessioned | 2021-02-01T07:54:15Z | en_ZA |
| dc.date.available | 2020-10-20T08:14:11Z | en_ZA |
| dc.date.available | 2021-02-01T07:54:15Z | en_ZA |
| dc.date.issued | 2020-10 | en_ZA |
| dc.description | Thesis (PhD)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The use of metal nanoparticles as catalysts in a variety of transformations has been widely reported. Their prevalent use in catalysis is based on their increased surface area and thus an increase in active sites which could improve their catalytic ability compared to the respective bulk metals. This is specifically true for Au nanoparticles. Au and Pd nanoparticles have previously been successfully used as catalysts in oxidation reactions. Based on this, the dissertation describes the use of supported Au and Pd nanoparticles applied as catalysts in the oxidation of alcohols and the oxidative transformation of amines. A variety of support materials, including inorganic, organic and hybrid materials, have been reported in the literature to be able to stabilize metal nanoparticles. Organic support materials containing a high nitrogen content is envisaged to enhance the stability of metal nanoparticles, specifically in the case of Au and Pd nanoparticles. Introducing inorganic functional groups into an organic support material could also improve the thermal stability without significantly impacting on the high nitrogen content. With this in mind, two organic support materials and one hybrid silica-organic support material containing triazine units were prepared. The organic support materials, polymeric melamine formaldehyde microspheres (PMF) and polymeric melamine resorcinol formaldehyde microspheres (MRF), were synthesized through hydrothermal condensation. The hybrid support material, a triazine siloxane hybrid material (TSH), was prepared in a one-pot process with in-situ formation of the monomer followed by subsequent hydrolysis and condensation of the siloxane units to produce a highly cross-linked polymeric material. All three support materials were fully characterized employing solid-state characterization techniques and found to be thermally stable and insoluble in common organic solvents and water. Au and Pd monometallic nanoparticles were stabilized on all three support materials through an in situ chemical reduction method. Small and well-dispersed nanoparticles were prepared in all cases. The interaction between the TSH material and the Au nanoparticles supported on it was also investigated and revealed that the Au nanoparticles were stabilized by the Si atoms in the TSH material and not the N atoms as expected. The supported metal nanoparticles were then applied as catalysts in the oxidation of 1-phenylethanol and 2-octanol as well as the oxidative self- and cross-coupling of amines. 1-Phenylethanol could be fully converted to acetophenone under relatively mild conditions in the presence of TBHP as oxidant and Au/PMF as catalyst. Improved catalyst activity was observed using water as solvent compared to acetonitrile. This was attributed to the formation of a 3-phase emulsion droplet catalytic system. An investigation into the mechanistic pathway was also conducted, including a study into the factors that influence the decomposition of the oxidant, TBHP. The Au/PMF catalyst was also tested in the oxidative self-coupling of benzylamine and the oxidative cross-coupling of benzylamine with aniline to produce its corresponding imine products. Here, it was found that the use of excess aniline and longer reaction times increased the selectivity to the target imine product. The influence of the catalyst and oxidant on the reaction pathway was also explored. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die gebruik van metaal nanopartikels as katalisators in ‘n verskeidenheid transformasies is wyd berig. Hul algemene gebruik in katalise is gebasseer op hul verhoogde oppervlak area en dus verhoogde hoeveelheid aktiewe setels wat hul katalitiese vermoë verbeter in vergelyking met die van die onderskeie grootmaat metale. Hierdie is spesifiek van toepassing vir Au nanopartikels. Au en Pd nanopartikels was voorheen suksesvol gebruik as katalisators in oksidasie reaksies. Gebaseer hierop word die gebruik van Au en Pd nanopartikels gestabiliseer op draermateriale as katalisators in die oksidasie van alkohole en die oksidatiewe transformasie van amiene beskryf in hierdie verhandeling. ‘n Verskeidenheid van draermateriale, onder andere anorganiese, organiese en hibriede materiale, is al voorheen in die literatuur berig vir die stabilisering van metaal-nanopartikels. Organiese draermateriale wat ‘n hoë stikstof inhoud bevat word beoog om the stabiliteit van metaal-nanopartikels te verbeter, veral in die geval van Au en Pd nanopartikels. Deur anorganiese funksionele groepe in ‘n organiese draermateriaal te inkorporeer, kan dit ook die termiese stabiliteit van die materiaal verbeter sonder om die hoë stikstof inhoud noemenswaardig te beïnvloed. Met hierdie in gedagte was twee organiese draermateriale en een hibriede silika-organiese draermateriaal, wat almal triasien eenhede bevat, voorberei. Die organiese draermateriale, poli(melamien formaldehied) mikrosfere (PMF) en poli(melamien formaldehied resorsinol) mikrosfere (MRF), is gesintetiseer deur ‘n hidrotermiese kondensasie reaksie. Die hibriede draermateriaal, triasien siloksaan hibriede materiaal (TSH), is voorberei in ‘n eenpot proses deur in situ vorming van die monomeer en daaropvolgende hidrolise en kondensasie van die siloksaan eenhede om ‘n hoogs kruisgekoppelde polimeriese materiaal te produseer. Al drie draermateriale was ten volle gekarakteriseer deur gebruik te maak van vastetoestand karakteriserings tegnieke en was bevind om termies stabiel en onoplosbaar in algemene organiese oplosmiddels en water te wees. Au en Pd monometaal-nanopartikels is op all drie draermateriale gestabiliseer deur ‘n in situ chemiese reduksie metode. Klein en goed verspreide nanopartikels is voorberei in al drie gevalle. Die interaksie tussen die TSH materiaal en die Au nanopartikels wat daarop gestabiliseer is was ook geondersoek. Hierdie ondersoek het aan die lig gebring dat die Au nanopartikels deur die Si-atome in die TSH materiaal gestabiliseer word en nie deur die N-atome soos verwag nie. Die gestabiliseerde metaal-nanopartikels was daarna getoets as katalisators in die oksidasie van 1-finieletanol en 2-oktanol asook die oksidatiewe self- en kruis-koppeling van amiene. 1-Finieletanol kon ten volle omgeskakel word na asetofenoon onder relatiewe matige kondisies in die teenwoordigheid van TBHP as oksidant en Au/PMF as katalis. Verbeterde katalisator aktiwiteit was waargeneem deur van water as oplosmiddel gebruik te maak in teenstelling met asetonitriel as oplosmiddel. Hierdie waarneming kan toegeskryf word aan die vorming van ‘n 3-fase emulsie-druppel katalise sisteem. ‘n Ondersoek aangaande die reaksie meganisme was ook uitgevoer, insluitende ‘n studie van die faktore wat die ontbinding van die oksidant, TBHP, beïnvloed. Die Au/PMF katalisator is ook getoets in die oksidatiewe self-koppeling van bensielamien en die oksidatiewe kruis-koppeling van bensielamien en anilien om die ooreenstemmende imien produkte te produseer. Daar is gevind dat die gebruik van oortollige anilien en verlengde reaksie tye die selektiwiteit tot die teiken imien produk verhoog. Die invloed van die katalisator en oksidant op die reaksiepad is ook ondersoek. | af_ZA |
| dc.description.version | Doctorate | en_ZA |
| dc.embargo.terms | 2022-12-31 | en_ZA |
| dc.format.extent | xxvi, 184 pages : illustrations. | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/109415 | en_ZA |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Oxidation | en_ZA |
| dc.subject.lcsh | Catalysis | en_ZA |
| dc.subject.lcsh | Metal nanoparticles | en_ZA |
| dc.subject.lcsh | Composite materials | en_ZA |
| dc.subject.lcsh | UCTD | en_ZA |
| dc.title | Oxidative organic transformations using catalyst systems based on metal nanoparticles supported on organic/inorganic composite materials. | en_ZA |
| dc.type | Thesis | en_ZA |