PhD - Science / Gold has been regarded as being inert and catalytically inactive for many years compared with for example the platinum group metals. However, for the past decade gold has attracted a growing attention as both a heterogeneous and homogeneous catalyst and it has been shown that it can catalyze a wide range of reactions such as oxidation, hydrogenation, reduction, etc. This project entails the synthesis, characterization and testing of a suitable gold catalyst for the oxidation of carbon monoxide (CO), and some hydrocarbons (methane). In this project 2 wt% Au/TiO2; Au/TiO2-ZrO2; Au/TiO2-CeO2 catalysts were prepared by both deposition-precipitation and co-precipitation methods. Different synthesis conditions such as pH, catalyst ageing, and catalyst pretreatment were investigated in order to find suitable conditions for the preparation of catalyst that would be more active at lower temperature range (25 oC – 100 oC). The techniques used for catalyst characterization include, TGA, XRD, BET, XPS, TPR, XANES, HRTEM etc. in order to elucidate the catalyst surface structure and its suitability in affecting adsorption and subsequently catalytic activity. Carbon monoxide and methane oxidation reactions were undertaken in a tubular glass flow reactor. It was observed that when gold is well dispersed on a suitable support, it can catalyze total oxidation of CO at room temperature, provided that certain preparation and pretreatment conditions are followed. An uncalcined catalyst was found to be more active than the catalyst calcined at higher temperatures. This is due to the agglomeration of gold particles on the surface of the support according to our High Resolution Transmission Electron Microscopy results. With Mössbauer spectroscopy, it was observed that the addition of the second support metal oxide such as zirconia resulted in the decrease in agglomeration of gold particles. In such iv catalysts, a considerable amount of ionic species were preserved even after calcination at 400 oC resulting in the higher activity. With Au/TiO2, a batch of uncalcined catalyst dried at 120 oC overnight was leached with cyanide to remove the bulk metallic gold particles, supposedly leaving mostly ionic, small, and well dispersed gold particles and the activity of such leached catalyst was higher than that of the unleached sample. Methane oxidation was found to be very difficult compared with carbon monoxide, and only 8% conversion was achieved at 450 oC whereas a total CO oxidation was achieved at lower temperatures with the same catalyst. It is conclusive that small, ionic well dispersed gold species are necessary for CO oxidation and the adsorption and the active sites for this reaction may be different from those involved in methane oxidation.

Ho-Fai Lee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 90-91). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abbreviations --- p.ii / Abstract --- p.iii / Chapter Part I. --- Chemoselective and Oxo-Controlled S-Oxidation of Sulfides Containing Pyridine Rings and Olefinic Double Bonds / Chapter 1.1. --- Introduction --- p.2 / Chapter 1.2. --- Results and Discussion --- p.5 / Chapter 1.3. --- Conclusion --- p.14 / Chapter 1.4. --- Experimental --- p.15 / Chapter 1.5. --- References --- p.32 / Chapter Part II. --- Directed Synthesis of all-Homocalix[n]arenes with Various Cavity Sizes / Chapter II. 1. --- Introduction --- p.35 / Chapter II.2. --- Previous Synthetic Routes for all-Homocalixarenes --- p.37 / Chapter II.3. --- Synthetic Plan --- p.39 / Chapter II.4. --- Results and Discussion --- p.41 / Chapter II.5. --- Conclusion --- p.55 / Chapter II.6. --- Experimental --- p.56 / Chapter II.7. --- References --- p.90 / Chapter Appendix --- 1H and 13C NMR Spectra / List of and 13C NMR Spectra of Part I --- p.92 / 1Hand 13C NMR Spectra of Part I --- p.93 / List of 1H and 13C NMR Spectra of Part II --- p.100 / 1H and 13C NMR Spectra of Part II --- p.102

Presented herein is the development, optimization and mechanistic investigation of an Fe-catalyzed reaction for the Cα-H oxidation of tertiary aliphatic amines to form amides, and related synthetic reactions. Traditional amide synthesis typically involves nucleophilic substitution, and thus produces stoichiometric waste. The need to develop safer, more efficient methodologies for amide synthesis is well documented. The field of transition metal catalysis has made progress toward meeting this synthetic need by developing a variety of transition metal-catalyzed reactions for the oxidation of primary, secondary and benzylic amines. However, tertiary aliphatic Cα-H amine oxidation had not been developed. Guided by literature precedent, and inspired by cytochrome P450, initial investigations involved the evaluation of Fe-based transition metal catalysts with a variety of mono- and bidentate ligands, oxidants and solvents. Ultimately, the ligands picolinic acid and pyridine, the oxidant tert-butyl peroxybenzoate, and water as additive were identified as key players in this catalytic reaction. Through the systematic evaluation of reaction conditions, the Cα-H oxidation of tripropylamine to form N,N-dipropylpropanamide was optimized to afford 63% yield. The Cα-H oxidation of a variety of other amine substrates, including the complex pharmaceutical amines Lidocaine and Donepezil, were optimized to afford amide product in synthetically useful yields. Preliminary mechanistic investigations revealed water to be the source of the O atom in amide formation. Furthermore, these studies suggested that the amine substrate forms an iminium ion after C-H activation, which then undergoes nucleophilic attack by water to form a hemiaminal intermediate. These results allowed us to hypothesize that other nucleophiles, such as CN-, may be used to attack the iminium ion intermediate and thus afford other products. Using slightly modified reaction conditions, this catalytic system was optimized to perform Cα -H cyanation of dimethylaniline. This finding expanded the utility of the reaction as well as supported the mechanistic hypothesis of the presence of an iminium intermediate. Once the Fe/picolinic acid-catalyzed reaction for the Cα-H oxidation of tertiary aliphatic amines was firmly established, detailed mechanistic investigations were conducted using tripropylamine as substrate. Using in-situ IR spectroscopy, the structure of the resting state of the catalyst was probed. These studies revealed that picolinic acid binds to the Fe center in a 1:1 ratio to produce the catalytically active species. Amine substrate as well as water and pyridine were also found to be coordinated to the Fe center. Furthermore, initial rate kinetics were used to establish the dependence of the reaction rate on the concentration of each reaction component. Through these investigations, the kinetic order in each reagent was established and a rate law determined. Additionally, a primary kinetic isotope effect was observed using deuterated substrate, which implicated C-H bond cleavage as the turnover-limiting step in the catalytic cycle. Finally, Eyring studies and oxidant radical probe reactions were conducted, and implicated a concerted 2e- turnover- limiting step. This finding is in contrast to many mechanisms of Fe-catalyzed oxidation reactions found in the literature and allowed us to propose the unprecedented, detailed mechanistic hypothesis described herein. The research presented here establishes an unprecedented amide synthesis methodology through the use of both simple and complex amines. Because this catalytic reaction selectively oxidizes the Cα-H bonds of amines, a high percentage of atoms in the starting material are incorporated into the amide product, and it thus affords a significant increase in atom economy. The mechanistic work offers unique insight into 2e- Fe-oxidation catalysis, and may serve as a foundation for additional optimization, including industrial scale-up.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 330-335. / by Koon Gee Neoh. / Sc.D.

Made available in DSpace on 2014-06-11T19:30:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2001-10-31Bitstream added on 2014-06-13T19:19:51Z : No. of bitstreams: 1 oprime_meag_dr_araiq.pdf: 1812682 bytes, checksum: 4b3b2df220ff32216f506ec44dfa28c9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A remoção de H2S de uma corrente gasosa proveniente de industrias (petroquímica, refinarias de petróleo, etc) ou de tratamento de esgotos domésticos e muito importante tanto sobre o ponto de vista econômico como de saúde pública. Alguns processos convencionais vem sendo estudados e utilizados porém, são processos que apresentam como inconveniente um alto custo operacional por utilizarem alto consumo de energia e catalisadores específicos. Alternativas biotecnológicas tem sido estudadas usando principalmente espécies do gênero Thiobacillus uma vez que essas espécies quimiolitotróficas oxidam compostos reduzidos de enxofre como fonte de energia para o seu crescimento. No presente trabalho foi investigado a oxidação direta do H2S por Thiobacillus ferrooxidans-LR e Thiobacillus thiooxidans-FG01 assim como um processo combinado usando separadamente etapas químicas e etapas biológicas. Este processo é baseado em uma rápida reação entre o íon Fe3+ e o H2S, o qual produz enxofre elementar e íon Fe2+, e a capacidade de T. ferrooxidans-LR oxidar Fe2+ como único caminho metabólica para obter energia, entre as espécies Thiobacillus. Ambas as espécies oxidaram diretamente H2S presente em solução acida (pH ~ 1,8) em concentrações no intervalo de 5 a 100 mg.L-1. O desprendimento deste gás em solução ácida foi considerável e a oxidação bacteriana foi somente detectada, em comparação com o frasco não inoculado, em concentrações abaixo de 5 mg.L-1 e após 150 min. Para estudar o processo combinado químico bacteriano, células de T. ferrooxidans-LR foi primeiramente imobilizada em fitas de PVC e anéis de vidro. Em ambos os suportes formou-se um espesso biofilme após cinco ciclos de oxidação do Fe2+. Durante os ciclos de imobilização celular houve o aparecimento... / Removal of H2S from gas streams of industrial sources or anaerobic treatment of domestic sewage is a imperative task under economic (corrosion in petrochemical industries), environmental and public healthy point of view. Conventional physicochemical processes are currently in use but they are very expensive since the necessity of energy in these processes are so high. Biotechnological alternatives have been studied using mainly species of Thiobacillus genus, since these chemolithotrophic species oxidize reduced sulfur compounds as energy source for their growth. In the present work it was investigated the direct H2S oxidation by Thiobacillus ferrooxidans-LR and Thiobacillus thiooxidans-FG01, as well as a combined process using separated chemical and biological steps. This process is based on the fast chemical reaction between Fe3+ and H2S, which produces elemental sulfur and Fe2+, and the capacity of T. ferrooxidans-LR to oxidize Fe2+ as a unique metabolic pathway to obtain energy, among Thiobacillus species. Both species oxidized directly H2S present in acid solutions (pH ~ 1.8) in concentrations ranged from about 5 to 100 mg.L-1. The gas volatilization in these acid...(Complete abstract, click electronic access below)

Orientador: Luiz Shiguero Matsubara / Resumo: A hemoglobina, o componente principal do citoplasma eritrocitário, está sujeita à oxidação, fisiologicamente ou por agentes externos, seja através da formação de Metahemoglobina, ou pela oxidação da cisteína β93 por agentes tiois. Impossibilitado de sintetizar proteína, o eritrócito depende primordialmente da via glicolítica, que, além de fornecer ATP, através da integração da formação de NADH e da Via da Hexose Monofosfato, mantém o potencial redutor extremamente eficiente. A presente investigação teve como finalidade avaliar o sistema de óxido-redução eritrocitário, à partir da oxidação da hemoglobina pelas seguintes drogas: a) Nitrito de Sódio, indutora da formação de Metahemoglobina; b) Azul de Metileno, utilizado terapeuticamente e em testes laboratoriais na redução de Metahemoglobina; c) Cistamina, agente tiol, que induz à formação do complexo Hemoglobina-Etilamina, através da oxidação da cisteína β93. Doadores de sangue da Divisão Hemocentro foram convidados a participar do trabalho e tiverem seu sangue coletado após consentimento - 96 - verbal e por escrito. Todos os indivíduos eram do sexo masculino, não anêmicos e sem deficiência de G6PD. Foram utilizados, para os testes, glóbulos lavados, ressuspensos em PBS, pH 7.45, com hemoglobina ajustada entre 11 e 13 g/dl, na presença de glicose e incubados a 37o C com as drogas testadas, nos momentos 10. 90 e 180 minutos de incubação... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Hemoglobin, the essential component of erythrocyte cytoplasm, is physiologically prone to oxidation by external agents, through the formation of Methemoglobin or the oxidation of β93 cysteine by thiol agents. Unable to protein synthesis, the erythrocyte depends essentially on glycolysis, which, besides producing ATP, maintains the highly efficient reduction potential through the integration of NADH production and the Hexose Monophosphate Shunt. The present investigation's purpose was to evaluate the erythrocyte antioxidant system by studying hemoglobin oxidation by the following substances: a) Sodium Nitrite (SN), a well known Methemoglobin-forming agent; b) Methylene Blue (MB), a Methemoglobin reductant reagent, available for therapeutic and laboratory tests; c) the thiol reagent Cystamine (CI), that reacts with hemoglobin through the β93 cysteine oxidation, forming the Hemoglobin-Ethylamine complex. After informed... (Complete abstract click electronic access below) / Doutor

Les alliages de titane possèdent une faible activation neutronique, une bonne tenue mécanique et une bonne résistance à la corrosion de manière générale. Ils sont susceptibles d’être utilisés comme matériau de structure de composants du circuit primaire des réacteurs nucléaires à eau pressurisée. Cette étude s’intéresse à leur durabilité dans ce milieu.Des échantillons de trois alliages de titane alpha (T40), alpha + beta (TA6V) et beta métastable (Ti10­-2-­3) ont été exposés au milieu primaire à 300 °C et à 350 °C pour des durées maximales de 11000 h et 1750 h respectivement. Des observations MEB et des analyses XPS, SDL, MET-ASTAR et de photoélectrochimie ont permis de proposer un mécanisme de corrosion impliquant simultanément la croissance interne et la dissolution dans le milieu d’une fine couche dense de TiO2 accompagnées de la précipitation de cristallites d’oxydes TiO2 et FeTiO3 liée à la saturation du milieu en hydroxydes. Il en résulte une consommation du métal estimée grâce à des analyses d’images et à la modélisation des prises de masse en fonction du temps de 2,9 µm.an­-1 à 300 °C et de 18 µm.an-­1 à 350 °C au maximum. Cette cinétique de corrosion est fortement ralentie lorsque les cristallites de FeTiO3 recouvrent la totalité de la surface des échantillons. L’exposition au milieu primaire des matériaux implique aussi une prise d’hydrogène d’autant plus importante que la température et le taux de phase beta sont élevés. Des essais de traction à température ambiante ont été réalisés sur des éprouvettes exposées au milieu primaire et sur des éprouvettes chargées en hydrogène ou traitées thermiquement. Ces essais ont mis en évidence une baisse de ductilité du Ti10­2­3 liée à son exposition au milieu primaire. Cette baisse de ductilité semble résulter de l’effet couplé du vieillissement thermique et de la présence d’hydrures aux interfaces alpha/beta. L’exposition au milieu primaire réalisée au laboratoire du T40 et du TA6V ne modifie que très peu leurs propriétés mécaniques étant donné que les prises d’hydrogène sont faibles devant les concentrations en hydrogène de transition ductile/fragile.L’utilisation des alliages de titane en milieu primaire paraît donc possible sur de longues durées sous réserve que leur phase beta soit stable et que les pièces possèdent un rapport surface/volume suffisamment faible pour limiter leur teneur en hydrogène. / Titanium alloys have a low neutron activation, good mechanical properties and good corrosion resistance in common environment. They could be good candidates for nuclear Pressurised Water Reactor (PWR) primary circuit structure components. This study deal with their durability in primary water.Samples of three titanium alloys alpha (Ti CP), alpha + beta (Ti 64) and metastable beta (Ti10­2­3) were exposed to primary water at 300 °C and 350 °C for maximum durations of 11000 h and 1750 h, respectively. Based on SEM observations as well as XPS, GD-OES, MET-ASTAR and photoelectrochemistry analysis, a corrosion mechanism was proposed. It involves the inward growth of a dense TiO2 layer and its simultaneous dissolution into primary water as well as TiO2 and FeTiO3 oxide crystallites precipitation. Image analysis and mass uptake modelling indicated a maximum resulting metal matrix corrosion rate of 2.9 µm.year-­1 at 300 °C and of 18 µm.year-­1 at 350 °C. An abrupt decrease of the corrosion rate was noticed as FeTiO3 oxide crystallites surface covering fraction reached 100 %. Materials exposure to primary water also led to a hydrogen uptake which increased with both temperature and beta phase ratio. Room temperature tensile tests were performed on primary water exposed specimens, hydrogen charged specimens and heat treated specimens. These tests highlighted a loss of ductility of Ti10­2­3 samples linked to their exposure to primary water. It could be due to the combined effects of both thermal ageing and hydride presence at alpha/beta interfaces. Primary water exposure performed in laboratory had little effect on T40 and TA6V mechanical properties because hydrogen uptake is low in comparison with hydrogen concentration leading to ductile/brittle transition.Long duration use of titanium alloys in primary water seems reasonable, provided that beta phase is stable and that the surface/volume ratio of the considered component is low enough.

The internal oxidation behaviour of Ni-base and Fe-base alloys containing approximately 5 at% Al and both with and without low concentration Cr additions in flowing low-oxygen atmospheres at 1273 K was studied. There were two groups of Febase alloys; ferritic alloys that were Fe-Al-Cr and others that also contained approximately 9.3 at% Ni in order to make them austenitic. Ni?base alloys were oxidised in oxygen partial pressures of either 4.6 ?? 10-11 atm or 9.8 ?? 10-13 atm and Febase alloys were oxidised in an oxygen partial pressure of 1.2 ?? 10-16 atm The aim of this investigation was to examine the effect of internal oxidation on Fe- and Ni-base alloys containing Al or Al with Cr. The morphology of the precipitates formed and rates of reaction were of interest. Oxidation of the ferritic Fe-base alloys produced internal oxidation only at lower solute concentrations. In these alloys steady state diffusion-controlled precipitation was prevented from occurring due to the formation of an oxide barrier at the reaction front, and cracking off of the internal oxidation zone. In all of the austenitic alloys (Ni-base and y-Fe-base) internal oxidation was observed after all exposures. In y-Fe-base alloys and in Ni-base alloys oxidised at the higher oxygen partial pressure (4.6 ?? 10-11 atm) precipitation zones were found to widen according to parabolic kinetics, indicating diffusion control. In Ni-base alloys oxidised at 9.8 ?? 10-13 atm, precipitation zones were observed to widen according to parabolic kinetics up to 40.9 hours. However, the rate slowed for longer reaction times due to coalescence of precipitates at the reaction front. The rate of internal oxidation decreased with increasing Cr, and thus total solute, concentration. The parabolic rate constants measured for internal oxidation were higher than predicted by Wagner's theory of internal oxidation, which is consistent with observations in previous studies. Kinetics were accelerated by the presence of elongated precipitates, aligned approximately normal to the alloy surface. Chromium alloy additions led to precipitate coarsening, and at lower oxygen partial pressures, to loss of elongated morphology. The precipitates formed were found to be a mixture of M2O3 and AM2O4, where M represents either Al or Cr, and A represents either Fe or Ni. Both oxide forms were detected at all depths within the internal oxidation zone. However, Cr-containing oxides were limited to the part of the internal oxidation zone closer to the alloy surface, while Al-containing oxides were present at all depths. This is consistent with thermodynamic predictions.

Offprints of 35 journal articles inserted / Bibliography: leaves 28-29 / 1 v. (various pagings) ; / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D. Sc.)--Dept. of Animal Science, University of Adelaide, 1985

Zugl.: Stuttgart, Univ., Diss., 2005