Thesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2016. / The use of ozone as an advanced oxidation process is gathering wide spread attention with the major limitation to its application being its cost of operation and design considerations. While the general approach of most researches is to buttress the already known fact of the efficacy of the process, little attention is given to studying the by-products of ozone reactions with organics. The aims of this study were to investigate the efficacy of the ozonation process for removing recalcitrant phenolics: phenol, 2-chlorophenol (2CP), 4-chlorophenol (4CP) and 2,4-dichloropheno (2,4DCP) from aqueous medium with a view of understanding various reaction pathways of the process and identifying possible intermediates and residual compounds using liquid chromatography-mass spectrometry (LC-MS). The choice of the selected chlorophenols would also elucidate the role of the positioning of the chlorine atoms in determining reaction rates, pathways and subsequent mechanisms and by-products. Sequel to this, oxy-hydroxy iron in β-phase (β-FeOOH, akaganite) and various β-FeOOH bonded composites on support metal oxides (Al2O3, NiO and TiO2) were prepared via hetero-junction joining, and explored as a possible promoter to improve the efficiency of the ozonation process. Apparent first order reaction rates constants of tested phenolics was in the order 2,4-DCP > 2-CP > Phenol > 4-CP, irrespective of the tested pH. The individual rates however increased with increasing pH. The position 4 chlorine atom was found to be least susceptible to hydroxylative dechlorination. Catechol intermediate and pathway was identified as the major degradation pathway for phenol and 2-CP, while 4-chlorocatechol pathways were more important for 4-CP and 2,4-DCP. The formation of polymeric dimers and trimers by all compounds was pronounced at alkaline pH. Heterogeneous catalytic ozonation using β-FeOOH reduced ozonation time for 4-CP by 32%. Mechanism for β-FeOOH/ozone catalysis showed that the catalyst suffered reductive dissolution in acidic pH and the kinetics of 4-CP removal using the catalyst was best described using a two stage kinetic model. The first stage was attributed to heterogeneous catalysis of ozone breakdown on β-FeOOH surface generating faster reacting radicals, while the second stage was due to homogeneous catalysis by reduced Fe2+ ions in solution. β-FeOOH stabilized on NiO at a 5% ratio exhibited superior catalytic property compared to the other tested composites. Characterization by high-resolution transmission electron microscopy (HRTEM) affirmed a β-FeOOH-NiO bonded interfaced composite which was stable as a iv catalyst over four (4) recycle runs. The mechanism of operation of the composite was via an increased ozone breakdown to radicals as monitored via photoluminescence experiments. The composite material produced satisfactory results when tested on real wastewater samples. Results from this study contribute to the current understanding on reaction mechanisms for ozone with phenols and chlorophenols, for the first time monitoring time captured intermediates via liquid chromatography-mass spectrometric method, which preserves the integrity of reaction intermediates. Also this study proposes heterogeneous catalysts; β-FeOOH and β-FeOOH bonded composites as possible improvements for simple ozone based water purification systems.

The general objective of this thesis is the analysis of selective reactions for group VI grafted metal complexes via methods and principles of SOMC. For this objective, three approaches have been chosen. The first chapter is an introduction to the topic of selectivity in catalysis, emphasizing heterogeneous catalysis and more specifically the different approaches to support catalysts on surfaces. The concept of catalysis by design is introduced as a new way to use the surface as a ligand. Chapter 2 presents the results of a library of well-defined catalysts of group VI with identical catalytic functionality, but different ligand environment. The results reveal, that metal-carbynes are able to switch their catalytic reactivity based on the substrate that they are contacted with. The difference in reaction mechanisms and the differing reactivities towards the substrates are presented. It can be concluded that the classical ROMP is selectively achieved with cyclic alkene substrates leading to polymers whereas cyclic alkanes yield exclusively higher and lower homologues of the substrate without polymeric products. Chapter 3 presents the study of olefin metathesis of cis-2-pentene with metal-carbynes of group VI, where the selectivity of the catalyst library towards yield of cis-/trans products is analyzed. It is presented, that the ligand environment of the catalysts is showing an influence in the selectivity. Rates of cis/trans isomerization of the products are high and are approaching thermodynamic equilibrium at high conversion. Product isomerization, thermodynamic equilibrium and reactivity differences between liquid phase and gas phase products are analyzed. Chapter 4 presents the full characterization of tungsten-hydrides by selective transformation into tungsten-hydroxides. These newly discovered well-defined tungstenhydroxides are fully characterized by ICP, TEM, DRIFT, double quantum and triple quantum solid-state NMR. The presented results allow to predict that tungsten-hydrides on KCC-1700 are present as two distinct species. Catalysis results with cyclooctane show, that due to burial of the complexes in the KCC-1700 surface the tungsten-hydrides are less active towards cyclic alkane metathesis reactions with bulky cyclooctane than the metalcarbyne complexes. Chapter 5 is giving a conclusion of results and an outlook for catalytic applications of the generated tungsten-hydroxides of chapter 4.

Since our society became industrialised, the levels of carbon dioxide in our atmosphere have been steadily rising, to the point where it in early 2020 at is 413 ppm. The high concentration is causing several troubling effects worldwide because of the increase in mean temperature that it creates, which causes longer draughts, more severe floods, and rising seawater levels to name a few. There are a few measures that can be taken to reduce carbon dioxide in the atmosphere, among which there are a number of methods that currently are being researched and/or used. The prospect of capturing carbon dioxide and using it as a carbon building block to make methanol is one solution that is particularly interesting, since it in theory could provide a fuel for combustion engines that is net neutral regarding carbon emission. Methanol can be synthesised from carbon dioxide using a heterogeneous catalyst consisting of copper, Cu, and zinc oxide, ZnO. This research is focused on one of the components of the catalyst, the metal oxide ZnO in the form of crystallites or nanoparticles (ZnO)n. Quantum chemistry is a branch of computational chemistry which is centered on solving the Schrödinger equation for molecular systems. Density functional theory, DFT, is an approach to quantum theory which in this study was used to calculate the geometry and energy of the particles. The supercomputer Tetralith in the National Supercomputer Centre, NSC, was used to carry out the calculations. The DFT calculations utilized the functional B3LYP and the basis set 6-31G (d,p). One of the largest particle sizes studied, (ZnO)20, with a structure that has a large, flat surface, was found to be the most energetically favourable. According to studies, the presence of an oxygen vacancy on the surface of ZnO reduces the amount of activation energy required for CO2 to bond to the particle, which increases the chance of forming CO and thus continuing the process of forming methanol. Two structures of (ZnO)20 were investigated in this regard, where oxygen atoms were removed at different locations, creating four versions of Zn20O19 in total. This proved yet again that the version with a large, flat surface yields the lesser amount of energy when an O atom is removed from the centre of its surface. The adsorption of CO2 to the ZnO clusters was studied by calculating the energy of adsorption, and this showed that it was the second version of (ZnO)20, without an O vacancy, that yielded the least amount of energy, thus being the most favourable species to engage in physisorption with CO2. Lastly, the activation energy was investigated, and a diagram of the reaction process of CO2 adsorbing to Zn20O19 forming (ZnO)20 and CO is presented in this paper, which shows that the required activation energy is 127 kJ/mol.

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第12931号 / 論工博第4124号 / 新制||工||1626(附属図書館) / 32141 / (主査)教授 北川 進, 教授 杉野目 道紀, 教授 濵地 格 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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This thesis focuses on the study of nickel boride as a catalyst in various coupling reactions. The nickel boride catalyst was investigated in three different coupling reactions, the experiments aimed at understanding the activity and catalytic properties of nickel boride. We successfully synthetized the nickel boride catalyst, alongside with the cobalt and iron boride. Different methods of preparation were compared and we concluded, that the differences in the preparation, such as solvent and atmosphere, influence the activity of the catalyst in coupling reactions. We found that the most suitable solvent for preparing nickel boride is anhydrous methanol, thus we proceeded our research with this catalyst. In the case of the Sonogashira cross-coupling we found that the homocoupling of the acetylene starting material is a side reaction we could not exclude. However, with the proper solvent it is possible to shift the reaction towards homocoupling, without the formation of the heterocoupling product. Thus, we decided to investigate the Glaser homocoupling between acetylenes. In the case of the Sonogashira coupling only TLC was used to examine the reaction mixture. However, in the case of Glaser coupling, after pre-investigations we developed a gas chromatography method for analyzing the reaction mixtures. We learned, that the homocoupling only results in trace amounts (2-4%) of product. Previous investigations in our research group showed, that the nickel boride could catalyze Suzuki-Miyaura-type couplings. Examining this reaction all three metal borides were tested; however, the reactions only led to the desired product with nickel boride. Analyzing the reaction with gas chromatography we learned that the choice of solvent influences the stability of the starting materials and the formation of side products. Reactions with different starting materials, in different solvents, with different bases were analyzed. The effect of microwave irradiation was also examined. Based on the results we concluded, that with nickel boride it is not possible to achieve high yields in coupling reactions.

The aim is to produce aliphatic liquid hydrocarbons using heterogeneous ethylene oligomerization. Thiscould potentially produce renewable synthetic fuels. Heterogeneous catalysis has some advantages overhomogeneous catalysis regarding some sustainability aspects. To achieve this, a setup was built using a heatedfixed bed reactor with an in-situ has chromatography to study conversion and gaseous products, and ex-situGC as well as NMR for analyzing liquid products. Ethylene was oligomerized on a commercial ZSM-5 zeoliteunder varying temperature conditions and feed gas dilution with hydrogen or helium. The gas and liquidproducts were analyzed and evaluated. Additionally, the ZSM-5 was studied at different silica to alumina ratios. The thesis discusses how conversion, liquid yield and selectivity of gas products using GC together withanalysis of liquid products using H-NMR can be used as a simple and quick evaluation. The liquid product isevaluated by the distribution of olefinic and aromatic hydrocarbon species using the hydrogen signal area inthe characteristic chemical shifts of olefinic and aromatic hydrogen. At 250-400oC, 6 bar of ethylene, with andwithout feed dilution, and WHSV of 204 h-1, conversion was consistently above 95% for the diluted 400oCruns. Though the liquid yield fell to around 6%, compared to the best yield at 18% for the pure 300oC run.Diluting the feed had a positive effect on increasing olefinic hydrogen signal while decreasing aromatichydrogen signal. The difference between diluting with H2 or helium had a surprisingly small effect. Decreasingthe Si/Al ratio had no significant effect on performance, while increasing the Si/Al ratio made the zeolite loseits catalytic ability. With a pure ethylene feed the lowest aromatic hydrogen signal was found at 350oC, whilethe olefinic signal did not vary too much with temperature. With diluted feed the higher temperature did leadto a lower olefinic hydrogen signal and higher aromatic hydrogen signal.

The abstract is the summary of three different projects all centered around the generalidea of catalysis which is the general theme of research in the Michaelis laboratory. The firstproject focuses on development of a new heterogeneous catalyst for selective catalysis. In theMichaelis lab, we were interested in the potential of nanoparticle catalysts for regioselectivetransformations. We showed that polymer supported ruthenium nanoparticles performed as areliable catalyst for regioselective reduction of azide to amine. In our study of regioselectivereduction of multiple azide containing substrates, we observed that in presence of ourruthenium nanoparticle catalysts, the least sterically hindered azide group reduced to aminefunctional group. The results were complementary to the conventional methods that employtriphenyl phosphine (Staudinger reaction) as the reductant and target the most electronicallyactive azide group.In the second project, we were looking to develop a new class of hetero-bimetallicNickel-Titanium complexes as an efficient catalyst for organic transformations. We designedand synthesized numerous bidentate ligands including NHC-Phosphine ligand. Our kineticstudies on the Suzuki cross coupling of allylic alcohols and phenyl boronic esters showed thatthe bidentate nature of the ligand was necessary for the success of the catalytic process. Theligand was proved to stabilize the catalyst in the solution by increasing the lifetime of thenickel (0) in the reaction medium. We also discovered a new cooperative titanium-nickelsystem for mild allylic amination of allyl alcohols. The system also represents an idealcatalyst for tandem cyclization amination process.In the Michaelis lab, we were also interested to explore the ability of bimetalliccomplexes in C-H functionalization process. Our efforts in this project led to the discovery ofnew Pallladium dimer complexes with two palladium centers in oxidation state of (I). Thecatalyst showed unique reactivity in C-C bond activation/functionalization. We have alsodiscovered that in presence of catalytic amount of triflic acid and stoichiometric amount ofphenyl boronic acid, cinnamyl alcohol undergoes a boron template dimerization/cyclization.The reaction represents a great synthetic pathway for the synthsis of bis homoallylic alcohols.

The reaction barrier and heat of formation of the various dehydrogenation reactions involved in the steam reforming of ethane is a critical concern in the applications and understanding of these reactions. Focusing on Ir-based catalyst, we report a comprehensive reaction network of dehydrogenation of ethane on Ir(100) based on extensive density functional theory calculations performed on 10 C-H bond cleavage reactions, utilizing the Vienna Ab Initio Package codes. The geometric and electronic structures of the adsorption of C2Hx species with corresponding transition-state structures is reported. We found that the C-H bond in CH3C required the most energy to activate, due to the most stable four-fold hollow adsorption site configuration. Ethane can easily dissociate to CH3CH and CH2CH2 on Ir(100) and further investigation of surface temperature dependence will contribute to the research effort in this area. By using the degree of dehydrogenation of the reactant species as a variable to correlate the C-H bond cleavage barrier as well as reaction energy. DFT studies reveal that the surface Ir(100) to a great extent promotes ethane dehydrogenation when compared to other surfaces.