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Catalytic application of gold and palladium nanoparticles supported on mesoporous transition metal oxides in oxidation and hydrogenation reactions

Investigating cyanogen-rich Manihot esculenta efficacy for Au and Ru phytomining and applications in catalytic reactions

  • Authors: Dube, Sifelani
  • Date: 2021
  • Subjects: Catalysis , Manihot
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/483930 , uj:43937
  • Description: Abstract: The research was focused on phytomining using gold (Au) and ruthenium (Ru) in a biomatrix from Manihot Esculenta, a cyanogen-rich plant species. The catalytic reactions based on furfural conversion to furfural alcohol and the various aspects were explored and observations made. The work focused on using artificially contaminated garden potting soils as models of mine tailing and metal-rich dumps. Soils were contaminated with aqueous Ru(III) and Au(III) solutions to deposit soluble metal ions... , M.Sc. (Chemistry)
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A high-throughput, combinatorial and robotic approach to catalysis

Bicyclic phosphine ligands derived from limonene and their applications in palladium-catalysed Heck reactions

  • Authors: Setati, Boitumelo
  • Date: 2020
  • Subjects: Catalysis , Heck reactions , Ligands , Palladium catalysts
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/474412 , uj:42761
  • Description: Abstract: Transition metal catalysts which involve the use of electron rich, bulky trialkylphosphine ligands such as P(t-Bu)3 and P(Cy)3 have been successful in various Pd cross-coupling reactions. However, trialkylphosphine ligands are susceptible to rapid oxidation, presenting serious challenges during handling. Researchers in academia and industry have directed efforts in developing novel phosphines, and this resulted in remarkable breakthroughs in discovering several bulky trialkylphosphines and biaryldialkylphosphines. Of these, biaryldialkylphosphine ligand systems developed by Buchwald and Hartwig provide high, stable catalytic ability and efficiency. These ligands systems also feature electron donating and steric bulk properties. In this work we, report the use of limonene (Lim) derived, electron rich, bicyclic phosphine ligands in Pd-catalysed Heck cross-coupling and its application in synthesis of industrially valuable products (Figure 1)... , M.Sc. (Chemistry)
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Design and development of low cost materials for water electrolyzers

  • Authors: Munonde, Tshimangadzo Saddam
  • Date: 2020
  • Subjects: Electrocatalysis , Electrochemistry, Industrial , Reactivity (Chemistry) , Catalysis
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/418369 , uj:35469
  • Description: Abstract: The construction and modifications of highly active, stable and low cost electrocatalysts promoting the oxygen and hydrogen evolution reactions (OER and HER) in water splitting are the key areas of research in energy generation and conversion. Given the significance of the HER and OER electrocatalysts, the objective of this study was to fabricate low-cost materials that are capable of being used as cathode and anode electrocatalysts in water splitting. Thus, nanomaterials and nanostructures provide unique properties that have allowed then to play an essential role in recent developments in energy-related applications. As known, the structural and electronic properties of nanomaterials/nanostructures stimulate their physical and chemical properties, and therefore their catalytic activity. Thus, tailoring the morphology of nanomaterials/nanostructures either during the synthesis or post the synthesis process, have been known to promote their structural and electronic properties, thus leading to enhanced catalytic activity... , Ph.D. (Chemistry)
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Synthesis and characterization of metal/metal oxide supported nano-catalysts for nitro arenes reduction

Synthesis of tungsten and molybdenum promoted mesoporous metal oxides by inverse micelle approach for the evaluation of catalytic behavior on different reactions

  • Authors: Hlatshwayo, Xolani Sibusiso
  • Date: 2020
  • Subjects: Tungsten , Molybdenum , Catalysis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/473948 , uj:42703
  • Description: Abstract: Tungsten and molybdenum promoted mesoporous metal oxides (ZrO2 and SiO2) were synthesized by inverse micelle method. Some of the as-synthesized bimetallic mesoporous catalysts were further converted to ternary mesoporous catalysts via deposition-precipitation whereby palladium nanoparticles were deposited or introduced in the system. The main objective of this investigation was to alterative hetero-catalyst for the modified homogeneous system of aminolysis of epoxides, acetylation of alcohols, and methoxycarbonylation of phenylacetylene by employing the as-synthesized Lewis acid catalysts. A variety of reactions such as aminolysis of epoxides, acetylation of alcohols and methoxycarbonylation of phenylacetylene were investigated. A total of six catalysts were fully characterized by BET, p-XRD, TPR, TPD, TGA, TEM, SEM, and EDX. Interestingly, the as-synthesized catalysts were active in the investigated reactions, with the promoted ones showing molybdenum promoted catalysts with greater activity than the tungsten. The binary mesoporous metal oxide catalysts were utilized for the aminolysis of epoxides, and the acetylation of alcohols, while the ternary mesoporous metal catalysts were employed in the investigation of methoxycarbonylation reaction. The advantage of these heterogenized systems is that the catalysts possess a higher potential of recyclability. , M.Sc. (Chemistry)
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Hybrid designed porous carbon dispersed gold/metal oxide nanocomposites for catalytic synthesis of biomass-derived chemicals

Novel porous organic polymer supported gold-based nanocatalysts for production of biopolymer chemicals

  • Authors: Sebati, Ngwanamohuba Wilhemina
  • Date: 2019
  • Subjects: Biomass chemicals - Synthesis , Polymers , Catalysis
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/418742 , uj:35515
  • Description: Abstract: Catalytic synthesis of value-added chemicals from renewable biomass-derived platform chemicals is an important way to reduce current dependence on fossil-fuel resources. The main objective of this study was to synthesize magnetic functionalized porous organic polymers (POPs), gold incorporated POPs and bifunctional gold incorporated POPs acid catalysts and use them for the catalytic upgrade of biomass derived model compounds to valuable chemicals. The high surface area, stable and amorphous nanoporous polytriphenylamine polymer (PPTPA) was synthesized as a POPs based support under a microwave assisted method. The synthesized PPTPA was sulfonated with chlorosulfonic acid to introduce acidic groups on the surface of the material to form SPPTPA acid catalysts which were further incorporated with magnetic Fe3O4 nanoparticles to form FeSPPTPA catalysts. The neat PPTPA support and SPPTPA materials were incorporated with gold nanoparticles to form AuPPTPA and bifunctional AuSPPTPA nanocatalysts. The morphological characterization showed that the prepared materials showed nanofiber-like, flake-like and nanorods morphologies. The magnetic solid acid catalysts (FeSPPTPA) successfully dehydrated fructose to 5-hydroxymethyl furfural (HMF) as a valuable compound with highest HMF yield of 96.61% and the best catalyst could be reused for 4 consecutive catalytic runs. The magnetic solid acid catalysts (FeSPPTPA) also showed that levulinic acid could be converted to diacids as the products even though levulinic acid could not be fully converted to possible products under the reaction conditions used. , Ph.D. (Chemistry)
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Synthesis, characterisation and catalytic evaluation of novel palindromic O^N^O and non-palindromic O^N^S palladium pincer complexes

  • Authors: Awe, Babatunde
  • Date: 2019
  • Subjects: Organopalladium compounds , Polycyclic compounds , Catalysis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/416517 , uj:35237
  • Description: Abstract: Novel cationic Pd(II) O^N^S and O^N^O pincer complexes have been successfully synthesized and detailed evaluation of their catalytic activity was carried out for crosscoupling reactions. Cross-coupling reactions, most importantly C-C coupling reactions, have grown into key methodologies for the synthesis of a wide range of biaryl natural products and biologically active compounds. In view of several advances made to make the methods more excellent and environmentally conducive. Designing stable ligands, since conventionally employed phosphine-based ligands are unable to tolerate high temperature and exposure to air and moisture, is still a present-day challenge. However, Pincer complexes are reported to be stable to the harsh conditions; but they are less explored in cross-coupling reactions. .. , M.Sc. (Chemistry)
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Iodine mediated preparation of beta-acetoxysulfides and stereoselective synthesis of (E)-1,3-diphenyl-1-butene dimers

  • Authors: Marakalala, Mokgethwa B.
  • Date: 2018
  • Subjects: Sulfur compounds , Catalysis , Chromatographic analysis , Stereochemistry
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279618 , uj:30031
  • Description: Abstract: -Hydroxysulfides comprise a significant segment of sulfur-containing natural products. Owing to their biological importance, their presence in a number of natural products in addition to their use as key intermediates in the synthesis of pharmaceuticals and substrates for the preparation of allylic alcohols, benzoxathiepines, benzodiazepines, thioketones, -substituted unsaturated enones, and -hydroxysulfoxides [15b], a number of methodologies have been reported for the synthesis of β-hydroxysulfides. Regioselective epoxide ring opening and 1,2-difunctionalization of alkenes are the commonly employed routes in the synthesis of such compounds. However, most of the reported methods suffer from one or more limitations including the use of transition metals, poor regioselectivity, long reaction times, limited substrate scope, the need for expensive and toxic reagents as well as the need for the preparation of an epoxide precursor and the formation of undesirable side products via rearrangement of epoxides and the oxidation of thiols, especially in the thiolysis of epoxides. In addressing some of these issues, we herein report in the current study a transition metal-free iodine catalysed preparation of acetate masked -hydroxysulfides (-acetoxysulfides) in the presence of a disulfide and a diacetoxyiodobenzene. The scope and limitations of the methodology are investigated in detail. In demonstrating the importance of (-acetoxysulfides) in organic synthesis, the methodology was fine tuned to provide styrene dimers that incorporate a sulfur heteroatom via a head-to-tail dimerization. The importance of sulfur in the synthesis of advanced materials, the scarcity of methodologies for the incorporation of sulfur to styrene monomers, as well as the attractiveness of the head-to-tail dimerization which generates an allylic chiral centre that is reported to be present in a number of biologically important organic molecules, makes the current method attractive in organic synthesis and thus, the results from the investigation of the scope and limitations of the reaction are reported along with full experimental details. , M.Sc. (Chemistry)
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Lanthanide organic frameworks of Azole type linkers as catalysts for the epoxidation of olefins

  • Authors: Belay, Yonas Habtegiorghies
  • Date: 2018
  • Subjects: Alkenes , Catalysis , Azoles
  • Language: English
  • Type: Doctoral (Thesis)
  • Identifier: http://hdl.handle.net/10210/416766 , uj:35269
  • Description: Abstract: The aim of the project is the synthesis of lanthanum metal organic frameworks with azole based linkers as catalysts for the oxidation of olefins to aldehydes and epoxides. The organic struts of azole based linkers 4-((1-(4-carboxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-3- methoxybenzoic acid (18), 5-((1-(4-carboxyphenyl)-1H-1,2,3-triazol-4- yl)methoxy)isophthalic acid (23), 5-(4-((3,5-dicarboxyphenyl)methyl)-1H-1,2,3-1-yl) isophthalic acid (26) and 4,4ˈ-(2H-tetrazole-2,5-diyl)dibenzoic acid (28) were successfully synthesized using copper-catalyzed click chemistry reaction of azides and alkynes. Their structures were confirmed using nuclear magnetic resonance spectroscopy (NMR), high resolution electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. The metal organic frameworks were synthesized by mixing lanthanum nitrate hexahydrate and the azole based linker organic struts in dimethylformamide solvent using solvothermal technique. Other synthesis methods such as solvent evaporation and diffusion techniques were also attempted for the synthesis of crystalline metal organic frameworks. The slow evaporation method of synthesis provided UJMOF-1 (La-triazole 18 MOF) as a crystalline product suitable for single X-ray diffraction analysis. All the attempted synthesis methods for UJMOF-2, UJMOF-3 and UJMOF-4 did not provide crystalline product suitable for single crystal X-ray diffraction analysis. However, the solvothermal synthesis for all the MOFs provided microcrystalline powder solid products. The products were characterized using different characterization techniques such as acid digestion 1H NMR, EA, IR, ESI-MS, SEM-EDX, PXRD, ICP-OES, BET, TGA and DSC methods, which provided substantial support for the formation of the proposed lanthanum based metal organic frameworks. The MOFs showed good catalytic activities for the oxidation of olefins to aldehydes and epoxides, using hydrogen peroxide and tert-butyl hydroperoxide, respectively, as oxidizing agents in the presence and absence of additives after heating at 70-80 °C in acetonitrile solvent for 24 hours. , Ph.D. (Chemistry)
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Polymer nanocomposites-based sensors for the detection of lung cancer volatile organic biomarkers

  • Authors: Mgwenya, Tintswalo N.
  • Date: 2018
  • Subjects: Catalysis , Chromatographic analysis , Stereochemistry
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279521 , uj:30019
  • Description: M.Sc. (Nanoscience) , Abstract: Cancer has been and is still of great interest and a disease that draws researcher’s attention. Exhaled breath biomarkers are a promising solution for early detection of lung cancer on its early developmental stages. The analysis of specific Volatile Organic Compounds (VOCs) in exhaled breath give insight of metabolic and physiological activities of an individual. Application of nanoscience using metals oxides and polymer nanocomposites through gas sensing is an interesting research path that brings cost-effectiveness and fast results using the non-invasive route for the detection of biomarkers. This mode of detection was employed for the detection of lung cancer exhaled breath biomarkers. This study aimed at developing polymer-metal-oxide-nanocomposites based sensors of high sensitivity and tuneable selectivity towards specific targeted lung cancer VOC biomarkers to improve the detection methods for lung cancer VOCs. Materials such as Manganese dioxide, Titanium dioxide and Tin dioxide, carbon nanoparticles and polymer nanocomposite based Volatile Organic Compounds sensors were utilized. Synthesized materials were characterized using BET, SEM, XRD and Raman spectroscopy. Sensors were fabricated by solution mixing method of metal-oxide, carbon nanoparticles and a biopolymer to produce a nanocomposite. The prepared nanocomposites were drop-casted onto electrodes and dried under room temperature. Prepared sensors were tested on VOCs 2-Hexanal, Hexanal and Dodecane. Overall, our result suggested the sensors were responsible for lung cancer VOCs.
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Synthesis and characterization of new pyrazolyl and ferrocenyl-pyrazolyl Ru(II) and Ru(0) complexes as catalyst precursors for the hydroformylation of 1 - Octene

  • Authors: Sekati, Kagiso M.J.
  • Date: 2018
  • Subjects: Pyrazoles , Ruthenium compounds - Synthesis , Ruthenium catalysts , Catalysis
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/279311 , uj:29993
  • Description: M.Sc. (Chemistry) , Abstract: A series of pyrazolyl and ferrocenyl-pyrazolyl ligands were synthesized. These ligands were reacted with ruthenium dimeric metal complex [RuCl2(Cy)]2 (where Cy = p – cymene) and a ruthenium carbonyl dimer [(ղ4-Ph4C4C=O)(CO)2Ru]2 to produce a series of monometallic and heterobimetallic Ru(II) arene complexes, as well as monometallic and heterobimetallic Ru(0) carbonyl complexes respectively. All the complexes were characterized by various spectroscopic and analytical techniques including 1H NMR and 13C NMR spectroscopy, FT-IR spectroscopy, mass spectrometry, elemental analysis (CHN) and single-crystal X-ray diffraction (complex C1). These techniques revealed that the proposed structures were indeed what had been formed. The techniques were also able to show that the various complexes were chemically different and displayed different chemical traits (such as functional groups). All the complexes, including the ferrocenyl-pyrazolyl ligands were tested as catalyst precursors in the hydroformylation of 1-octene. The Ru(II) and Ru(0) complexes were all active hydroformylation catalyst precursors and converted 1-octene to mainly aldehydes and alcohols, with minimal amounts of internal alkenes and octane produced. Branched and linear aldehydes as well as alcohol products were produced as a result of hydroformylation, followed by hydrogenation, while internal octenes and octane were produced via isomerization and hydrogenation reactions respectively. Of the various catalysts, Ru(II) complexes C1 and C2 displayed better hydroformylation/hydrogenation activity than their Ru(0) analogues, with C2 being the better of the two. On the contrary, catalyst precursors C4 – C6 possessed a higher degree of isomerization. The Ru(0) complexes showed no hydrogenation activity throughout the reactions conduted. Collectively, Ru(II) catalysts C1 – C3 favoured a regioselectivity for branched aldehydes compared to the Ru(0) catalysts C4 – C6. The substituents (tBu and Ph) on the pyrazolyl ring of the monometallic complexes have an influence on the regioselectivity of the catalyst. The tBu substituent favoured the formation of branched aldehydes in a minority of instances whereas the phenyl group resulted in an exclusive preference of linear aldehydes produced. Branched aldehydes were more favoured with the Ru(II) heterobimetallic catalyst precursor whilst the Ru(0) analogue yielded linear aldehydes...
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Carbon dioxide conversion via modified Fischer Tropsch Synthesis (FTS) over cobalt-based catalyst

  • Authors: Bopape, Abegail Tebogo
  • Date: 2017
  • Subjects: Fischer-Tropsch process , Catalysis , Cobalt catalysts , Carbon dioxide , Atomic emission spectroscopy
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/242783 , uj:25053
  • Description: Abstract: Human population is drastically increasing; in turn, it increases human activities that contribute to CO2 emissions, resulting in global warming. Effective CO2 mechanisms that can mitigate CO2 emissions to the environment are in high demand. One among the other approaches would be to develop processes that can utilize CO2 as feedstock to produce useful products. In this study CO2 is used as feedstock for hydrocarbons production via modified FTS over a cobalt-based (Co/γ-Al2O3) catalyst in a fixed bed reactor. The catalyst was prepared by precipitation-deposition method and characterized by using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and temperature programmed reduction (TPR) analysis. The feed to the reactor consisted of CO2/H2/N2 with a H2 to CO2 ratio of 3:1. The project aimed at evaluating the effect of operating temperature, pressure and mixing cobalt-based catalyst with methanol synthesis catalyst (Cu/ZnO/ZrO2) on CO2 conversion and product selectivity during CO2 hydrogenation. The effect of operating temperature was studied in a range of 200-250 ⁰C in two ways: i) step-up experiment where the temperature was increased from 200-250 ⁰C in steps of 10 ⁰C and ii) step-down where the reverse temperature variation was used. The effect of operating pressure was studied over a pressure range from atmospheric to 20 bar at an operating temperature of 220 ⁰C while the other operating parameters were kept unchanged. The effect of methanol synthesis catalyst (Cu/ZnO/ZrO2) on CO2 hydrogenation over the Co/γ-Al2O3 catalyst was studied by physically mixing the two catalysts in equal proportions. CO2 conversions were found to increase with the increase in operating temperature and went through a maximum at 230 ⁰C and started decreasing due to catalyst deactivation. The methane selectivity decreased while the CO selectivity increased as the operating temperature was increased suggesting that high temperatures favoured the RWGS reaction. CO2 conversions were higher at high operating pressures with no clear trend on methane selectivity. CO was only detected at atmospheric pressure suggesting that at high pressures CO is readily hydrogenated to hydrocarbons. When the methanol synthesis catalyst was mixed with the Co/γ-Al2O3 catalyst the CO2 conversion was observed to increase with the increase in operating temperature up to 300 ⁰C above which rapid decline in catalyst activity was observed. The presence of Cu/ZnO/ZrO2 shifted the deactivation temperature of the Co/γ-Al2O3 catalyst to higher temperature, i.e. above 300 ⁰C compared to 230 ⁰C... , M.Tech. (Chemical Engineering)
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Coordination chemistry of functionalized triazole lanthanide complexes and their catalytic application

Application of monometallic and bimetallic dendrimer encapsulated nanoparticles (DENs) and their catalytic evaluation on reduction of 4-nitrophenol

  • Authors: Patala, Rapelang
  • Date: 2016
  • Subjects: Dendrimers , Dendrimers - Synthesis , Catalysis , Inorganic compounds - Analysis , Nanostructured materials
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/226086 , uj:22850
  • Description: M.Sc. (Chemistry) , Abstract: The compound 4-nitrophenol found in wastewater streams is mainly the result of industrial and agricultural production. Having adverse health effects associated with it, 4-nitrophenol should be removed from the environment or converted to less hazardous forms as efficiently as possible. Feasible techniques to get rid of this chemical compound are of great research interest. The synthesized nanoparticles encapsulated inside dendrimers (DENs) will be evaluated for catalytic activity against the reaction of 4-nitrophenol reduction. Transition metal nanoparticles find their application in catalysis; this makes them to be of great technological importance. They can be synthesized by evaporation, condensation and chemical or electrochemical reduction of metal salts in the presence of stabilizers. Dendrimers were used as templates for the synthesis of both monometallic and bimetallic nanoparticles which were evaluated as catalysts for the reduction of 4-nitrophenol. We also focused on comprehensive kinetic analysis of 4-nitrophenol reduction using dendrimer encapsulated metal nanoparticles (DENs). The adsorption rates and reaction rates were found and evaluated, and it could be concluded that bimetallic catalysts were more catalytically active than monometallic ones. Different ratios of bimetallic (AuPd) nanoparticles were also supported on different mesoporous metal oxides (MMOs) and their catalytic activity evaluated on reduction of 4-nitrophenol. The results were interpreted in the light of Langmuir Hinshelwood model. The AuPd bimetallic nanoparticles supported on MMOs showed synergistic effect. With the use of power rate law it was shown that 4-nitrophenol reduction follows first order kinetics.
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Fischer-Tropsch reaction over alumina-supported cobalt catalyst : activation using H2 and CO

  • Authors: Khangale, Phathutshedzo Rodney
  • Date: 2016
  • Subjects: Fischer-Tropsch process , Catalysis , Cobalt catalysts
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/212944 , uj:21058
  • Description: Abstract: The catalytic activity for Fischer-Tropsch (FT) reaction over cobalt-based catalysts mainly depends on two parameters, namely the reducibility of cobalt precursors and cobalt dispersion. Therefore, a perfect catalyst would comprise of an optimal combination of these two parameters. Cobalt precursor’s reduction is usually performed in the presence of H2 and is usually limited by metal-support interactions which, in some cases, lead to the formation of metal-support compounds that are not reducible under a practical reduction temperature range. The water vapour that is formed during cobalt-based reduction by H2 has been reported to promote the formation of these metal-support compounds in some cases. An investigation on a reduction process that does not produce water would potentially offer opportunities for better cobalt-based catalyst reduction. Therefore, the aim of this project was to investigate the effect of activating Co/Al2O3 FT catalyst using H2 or CO on the catalyst structure and performance for FT reactions. The catalyst was prepared by impregnation of the support (Al2O3) with a cobalt nitrate (Co(NO3)2•6H2O) solution and calcined in air at 500°C for 10 hours to decompose and transform the cobalt nitrate to cobalt oxide. XRD analysis was performed to determine the structure of the catalyst prepared. BET analysis was performed to determine the surface area and porosity of the catalyst. Temperature programmed reduction (TPR) was performed on calcined Co/Al2O3 catalyst using a H2 and CO containing gas mixture respectively to study the reduction behaviour of the catalyst. The catalyst morphology was studied using scanning electron microscopy (SEM) analysis. The catalyst was tested for FT reaction in a fixed bed reactor and the outlet gas products were analysed using a Dani master gas chromatograph (GC) equipped with thermal conductivity detector (TCD) and flame ionisation detector (FID). It was found that CO activates the Co/Al2O3 catalyst at a lower temperature than H2 and is accompanied by carbon deposition on the catalyst surface. The main forms of cobalt species in catalyst samples reduced by CO or H2 at 300 oC were CoO. Co0 and CoO were the major cobalt phases for the catalyst samples respectively reduced by CO and H2 at 350 oC. The highest catalytic activity for FT reaction with the highest rate of C5+ hydrocarbons formation were measured on CO-activated catalyst samples. The deposited carbon on COreduced samples is believed to be a precursor for possible cobalt carbide formation during FT reaction that led to high methane selectivity. , M.Tech. (Chemical Engineering)
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Functional silver nanoparticle catalysed [3+] cycloaddition reaction : greener route to substituted-1,2,3-triazolines

Template synthesis of palladium and platinum nanoparticles by dendrimer and reverse microemulsions for the catalytic evaluation on various reactions

  • Authors: Noh, Ji-Hyang
  • Date: 2015-11-09
  • Subjects: Palladium catalysts , Chemical reactors , Chemistry, Inorganic , Nanostructured materials , Platinum , Catalysis
  • Type: Thesis
  • Identifier: uj:14524 , http://hdl.handle.net/10210/15047
  • Description: PhD. (Chemistry) , Well-defined palladium and platinum nanoparticles were synthesized by two template methods, namely dendrimer template and reverse microemulsions. For dendrimer template, three dendrimers, generation 4, 5, and 6 hydroxyl terminated poly(amidoamine) dendrimers (PAMAM), G4-OH, G5-OH, and G6-OH, were used as stabilizing agent, with PdCl4 2- or PtCl4 2- metal ions to dendrimer ratio of 40, 80, and 160, respectively. For reverse microemulsions, we employed water/AOT surfactant/isooctane system with water to surfactant ratios (ω0) of 5, 10, and 13, capped with thiol, to produce Pd and Pt nanoparticles. A total of twelve catalysts were characterized by techniques such as UV-Vis spectroscopy, TEM, EDX, and p-XRD. In the dendrimer template method, the synthesis of Pd and Pt nanoparticles in lower concentrations produced smaller sizes with narrower size distributions (2.02 ± 0.45 ~ 2.35 ± 0.58 nm Pd nanoparticles, 1.90 ± 0.44 nm ~ 2.48 ± 0.60 nm Pt nanoparticles) compared to those in higher concentrations (2.74 ± 0.44 ~ 3.32 ± 0.86 nm Pd nanoparticles, 2.81 ± 0.70 nm ~ 3.03 ± 0.47 nm Pt nanoparticles). In the case of thiol-capped Pd and Pt nanoparticles by reverse microemulsions, the range of average particle sizes were 3.47 - 7.51 nm and 3.51 - 4.23 nm for Pd and Pt nanoparticles, respectively. This indicated that a wider size regime was obtained by the reverse microemulsion method as compared to the dendrimer template method. Overall, smaller sizes with narrower size distributions were achieved by using the dendrimer-templated synthetic method rather than reverse microemulsions for both Pd and Pt nanoparticles.
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