The following thesis outlines work carried out during the past three years for the discovery and investigation of catalytic methodologies towards the synthesis and modification of heterocycles, namely cyclic carbamates, carbonates and their sulfur analogues. Chapter 1 summarises the current catalytic methods reported in the literature towards the synthesis and modification of functionalized 2-oxazolidinones. This introduction highlights the diverse range of methods and catalysts that have been developed and their scope and limitations. In addition the review highlights the importance of these structural motifs and suggests areas in which the following research fulfills unmet needs. Chapter 2 reports the discovery and development of a one-pot two-step copper-catalysed methodology towards the synthesis of N-aryl oxazolidinones from amino alcohol carbamates. The scope of both the N-aryl substituent as well as oxazolidinone functionalization is presented in addition to preliminary investigations into the mechanisms of both reactions. Chapter 3 presents the application of the previously reported one-pot process towards the synthesis of a number of medicinally active molecules and blockbuster pharmaceuticals. The one-pot two-step copper-catalysed reaction was utilized to synthesise a common intermediate in the synthesis of a number of oxazolidinone-based pharmaceuticals. The complete syntheses of Toloxatone, Linezolid, Tedizolid and Rivaroxaban are reported. Chapter 4 reports the modification of N-aryl oxazolidinones towards a diverse library of N-aryl oxazolidinethiones. The reactivity of these structures, in addition to N-alkyl oxazolidinethiones, towards transition metal catalysis was investigated and revealed a ruthenium catalysed O- to S-alkyl migration to afford structurally diverse thiazolidinones. Investigations into the substrate scope and mechanism were also carried out, suggesting a pseudo-reversible radical pathway drawing mechanistic parallels to the classic Barton-McCombie reaction. Chapter 5 details further development of the pseudo-reversible radical pathway for the regioselective rearrangement of dioxolane-2-thiones using Pd(PPh3)4 as a catalyst. The scope of the reaction is reported for the formation of highly selective, highly substituted sulfur-rearrangement products.

High-valent metal-oxo complexes are vital as active oxidants in enzymatic and synthetic catalytic oxidations. Inspired by the ubiquitous cytochrome P450 enzyme, researchers have explored the power of metalloporphyrins to mimic one of Nature’s premier catalytic entities. In this work, four manganese(III)porphyrin systems, including three electronwithdrawing ligands and one electron-donating ligand, were investigated with regard to their ability to form high-valent manganese(IV)-oxo porphyrin systems. The porphyrin ligands studied were 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin [H2(2,6-F2TPP)], 5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin [H2(4-CF3TPP)], 5,10,15,20-tetra(4- fluorophenyl)porphyrin [H2(4-FTPP)], and 5,10,15,20-tetra(2,6- dimethoxyphenyl)porphyrin [H2(TDMPP)]. All were synthesized purified and characterized spectroscopically. Using the mild oxidant iodobenzene diacetate, manganese(IV)-oxo porphyrins [MnIV(Por)O] were successfully generated in all systems as confirmed through spectroscopic methods. Meanwhile, a new photochemical approach was explored for its efficacy in producing the MnIV-oxo complexes by visible light irradiation of manganese(III) precursors containing the photolabile chlorate as the axial ligand. More importantly, the MnIV-oxo complexes obtained by chemical generation were tested for their abilities as oxygen atom transfer agents (OATs) with aryl alkenes, alkenes and thioanisoles in CH3CN. The apparent second-order rate constants for sulfoxidation ranged between (2.29 ± 0.08) and (12.9 ± 2.0) M-1s-1 x 10-2 which were, on average, a magnitude larger than the rates for epoxidation of the aryl alkenes. Most notably in reactions with substrate, the order of reactivity of [MnIV(Por)O] was [(4-F)TPP] > [(4- CF3)TPP] > [(2,6-F2)TPP], which is inverted from the expected result based on the electron-demands of the porphyrin ligands. The apparent rate constants for reaction with cyclohexene was found to be 1 to 2 orders of magnitude larger than those with sulfide substrates. The kinetic results are consistent with a reaction model involving disproportionation of MnIV(Por)O to give MnIII(Por) and MnV(Por)O species, the latter of the two being the active oxidant. Alternatively, the results from the sulfoxidations are consistent in part with a direct oxygen atom transfer by [MnIV(Por)O]

Catalytic combustion provides us an efficient approach for the utilization and mitigation of methane, the major component of natural gas as well as an important greenhouse gas in global warming. From the research of catalytic combustion of methane, better understandings as well as solutions to the current methane-related problems can be obtained. This study investigates lean methane combustion on palladium-based catalysts. Catalysts activities were tested through ignition and extinction experiments. Several pretreatments and their influence were studied. Instrumental neutron activation analysis (INAA) and x-ray diffraction (XRD) were used as characterization tools for the catalysts. It was found that after being reduced, catalysts had stable and excellent abilities for methane conversion. However, these abilities were strongly compromised by additional water in the feeds. XRD results, combined with other testing results, implied that reduction produced the most active samples, while INAA revealed the real Pd concentrations of these catalysts. / Chemical Engineering

In this thesis, the development and use of a transient heterogeneous 2D model for monolithic catalytic converter is presented. Study on the cold flow hydrodynamics, temperature effect and CO conversion and light off behaviour of different models is developed. Different models are studied based on different parameters such as monolith brick CPSI configuration, size of the converter, inlet cone sizing and inlet velocity of the converter. The results for both steady state and transient modes are presented in detail. It is shown that monolith brick CPSI has a significant effect on pressure drop and light-off behaviour of the converter. Also, converter size has a major effect on the performance of a converter. Inlet cone sizing showed to have a significant effect on the hydrodynamics of the converter but it did not have a major effect on light-off behaviour of the converter. / Chemical Engineering

La energía se ha convertido en una necesidad vital para garantizar el desarrollo de las sociedades modernas. Entre las diferentes posibles alternativas para producir energía, el hidrogeno presenta varias características que lo convierten en un atractivo vector energético: primero, se trata de una tecnología más eficiente para transformar la energía química en electricidad -por ejemplo, utilizando pilas de-combustible, las cuales también reducen de manera significativa los niveles de emisión de CO2 -; en segundo lugar, el hidrogeno puede ser producido a partir de una amplia variedad de materias primas, incluyendo recursos renovables y no renovables. Sin embargo, las tecnologías para producir hidrogeno para applicaciones con pilas de combustible aun requieren de un esfuerzo en investigación y desarrollo.El objetivo principal de esta tesis fue de evaluar técnicamente las opciones para preparar y utilizar catalizadores en placas insertados en un reactor de pared catalítica para producir hidrogeno mediante el reformado por vapor de etanol bajo condiciones de alta eficiencia térmica. Para completar el objetivo general y los objetivos específicos, se diseño un plan experimental sistemático, compuesto de tres partes: documentación, experimentación y simulación numérica. La información utilizada se puede clasificar en tres ramas: primero, una revisión detallada de las características generales que presentan las técnicas de reformado, seguido por una revisión descriptiva del reformado por vapor de etanol, enfocado en los principales aspectos de la preparación de catalizadores y la realización de la reacción química. A continuación en segundo lugar, se presenta una descripción acerca de reactores estructurados y los métodos para preparar catalizadores. Por último, en tercer lugar, se expone una explicación centrada en los materiales, equipos y métodos empleados para explorar el rendimiento de los catalizadores. Esta parte incluye la descripción de: algunas de las técnicas analíticas más comunes para caracterizar y evaluar tanto catalizadores como compuestos químicos y la descripción de las herramientas utilizadas en la simulación numérica.El primer bloque de simulación numérica tiene como fin evaluar las posibles restricciones termodinámicas por medio de análisis específicos basados en el equilibrio termodinámico, tanto del reactor como del proceso integrado. Luego, se ejecuta un mapeo del conjunto de condiciones operacionales, compuesto por cuatro variables principales: (temperatura, relación vapor carbón, presión y factor de recobro de hidrogeno en el separador de membrana). Ello con el fin de garantizar una operación auto-térmica del procesador de combustible. Se compara la habilidad y la ventaja entre los diferentes tipos de catalizadores publicados en trabajos previos en base a las condiciones termodinámicas ideales determinadas en el análisis termodinámico.Para los catalizadores en polvo, se realizo experimentos de caracterización y reacción mediante el empleo de un reactor de lecho fijo. Se ha efectuado un estudio sistematico para comparar la actividad y la selectividad de dos tipos de catalizadores, bajo condiciones moderadas de temperatura y relación vapor carbón. Los catalizadores basados en níquel (Ni/La2O3-Al2O3) y cobalto (Co-Fe/ZnO y Co-Mn/ZnO) han sido preparados y probados a las siguientes condiciones: temperatura en el rango de 400-500°C, relación vapor carbono entre 2 y 4, tiempo de contacto desde 4.3 hasta 1100 min·gcat molEtOH-1, cubriendo un rango de conversión de etanol desde 20 hasta 100%. Se ha efectuado un diseño de análisis multifactorial para establecer la influencia de las variables (temperatura, relación vapor carbón, tiempo de contacto y formulación del catalizador) en términos de la conversión de etanol y la selectividad hacia los diferentes productos.Por último, se ha efectuado la caracterización, simulación y experimentación utilizando una configuración de reactor de pared catalítica. Primero, se emplea un modelo en 2D para analizar las características principales del reactor de pared catalítica diseñado y construido para realizar la reacción sobre las placas con catalizador previamente preparadas. En segundo lugar, se expone de manera detallada el método seguido para preparar dos tipos diferentes de placas catalíticas. Estas placas con catalizador son caracterizadas de manera similar al método empleado con los catalizadores en polvo. Luego, se ha realizado un estudio sistemático para comparar la actividad y la selectividad de los dos tipos de placas catalíticas. Por último, mediante un modelo 1D se revelan aspectos fundamentales de la configuración del reactor de pared catalítica utilizando una configuración con dos canales paralelos, en los cuales se ejecutan una reacción endotérmica y otra exotérmica respectivamente.La principal conclusión de este trabajo es que el reformado por vapor de etanol puede ser realizado bajo condiciones de alta eficiencia térmica si se emplea un diseño basado en un reactor de pared catalítica con recobro de calor integrado a una unidad de separación para la purificación del hidrogeno. Las placas catalíticas han demostrado ser un elemento fundamental en este tipo de reactor porque incrementan de manera significativa el transporte de calor que se requiere para sostener las reacciones endotérmicas. / Energy has become a fundamental necessity to guarantee modern society development. Among different alternatives possible to produce energy, hydrogen presents several characteristics which make it an attractive energy vector: first, more efficient processes to transform chemical energy into electricity -such as Fuel Cells that, in addition, will help to reduce significantly CO2 emission levels-; and second, hydrogen can be produced from a large variety of feed stocks, including fossil and renewable resources. However, as hydrogen production technologies for Fuel Cell applications are not available commercially yet, it still requires additional R&D efforts.The principal objective of this thesis was to evaluate technical feasibility for preparing and using catalytic plates in a Catalytic Wall Reactor configuration to produce hydrogen by Steam Reforming of Ethanol under conditions of high thermal efficiency. To fulfill the overall and specific objectives, a systematic experimental plan was designed and executed. It was composed of three main parts: documentation, experimentation and numerical simulation. Background information is divided into three branches, first a detailed overview of technical features for reforming technology, followed by a descriptive review of Steam Reforming of Ethanol key aspects for catalysts preparation and reaction performance. Third is presented a comprehensive examination on structured reactor and catalyst preparation methods. In this part is exposed a detailed explanation of materials, equipments, and methods employed for screening catalyst and evaluating catalytic reactor performance. Also, is presented employed techniques for catalyst characterization and fluid analysis. Finally are described tools for numerical simulation.First component of numerical simulations evaluates possible thermodynamic constrains through specific analyses based on thermodynamic equilibrium of reactor and integrated fuel processor. Then, is performed a mapping for the set of four operational variables (temperature, steam to carbon ratio, pressure, and hydrogen recovery in the membrane separator), that allow an auto-thermal operation of the fuel processor. The suitability and advantages of the different catalysts preparations that are known from recent publications are discussed on the basis of the operation conditions determined on the thermodynamic analysis.Experimental work is performed for powder catalyst characterization and catalytic experimentation using a Packed Bed Reactor (PBR). It has conducted a systematic study to compare the activity and selectivity of two types of catalyst at moderate temperature and steam to carbon (SC) ratios. Nickel-based catalysts (Ni/La2O3-Al2O3) and novel Co-based catalysts (Co-Fe/ZnO and Co-Mn/ZnO) have been prepared and tested at temperatures of 400 and 500 °C, Steam to Carbon (SC) molar ratios of 2 and 4, and contact times from 4.3 to 1100 min·gcat molEtOH-1, covering a range of ethanol conversion from 20 to 100%. A multifactorial design analysis has been conducted to establish the significance of temperature, SC ratio, contact time and catalyst formulation on ethanol conversion and selectivity towards the different reaction products.At last, it is carried out the catalytic plate characterization, simulation and experimentation using a Catalytic Wall Reactor configuration. First, is used a 2D modeling to analyze main characteristics of the Catalytic Wall Reactor designed and constructed to perform reactions on the prepared catalytic plates. Prepared catalytic plates are characterize in a similar way to that employed for the powder catalysts. After that, it was conducted a systematic study to compare the activity and selectivity of two types of catalytic plates. 1D model reveals main aspects on thermal performance for a theoretical Catalytic Wall Reactor using two co-current channels with endothermic and exothermic reactions respectively.Main conclusion from this work is that Steam Reforming of Ethanol can be performed at high thermal efficiency if the design of the fuel processor is based on structured catalytic wall reactors with integrated heat recovery coupled to a separation unit for hydrogen purification. Catalytic plates have proven to be a key component on CWR because improves significantly the heat transfer which is required to sustain endothermic reactions.

Perchlorate is known to adversely affect the thyroid gland functions including iodide take up, thus perchlorate should be removed from drinking water. Bituminous coal-based activated carbon (AC) has been used for perchlorate removal in past years. Virgin carbon and carbon modified by oxidation with HNO3, NaOH and H2O2 were examined in this study for their ability to remove perchlorate by reduction or adsorption mechanisms. Surface functional groups formed on the modified AC (MAC) were examined with diffuse reflectance infrared spectrometry. Inhibition of perchlorate removal onto MAC by various anions ( - Cl , - 3 NO , and - 2 4 SO ) and solution pH (4.5, 7.2 and 10.5) were examined to characterize the MACs before an electrochemical reaction was performed. Surface functional groups were increased by oxidation. Groups that were found on the carbon include, but are not limited to lactone, quinine, carboxylate, and nitrogenoxygen groups. The effect of pH on removal of perchlorate by MAC was greatly affected by the change in the zero point charge (ZPC) induced on the carbon by modification. Virgin carbon also experienced difficulty in removing perchlorate when solution pH was above the ZPC. Anion inhibition varied with the modification process. - 3 NO inhibited perchlorate removal only by the virgin carbon. The other anions showed no major effects on the removal efficiency of perchlorate by the carbons. Electrochemical processes did not show favorable results in removal of perchlorate. The dominant mechanism of perchlorate removal during desorption tests was adsorption onto the carbon surfaces via ion exchange.

In general, the characteristics of stone are two: high regenerative thermal activity and low cost. In this study, isopropyl alcohol (IPA) was oxidized by metallic catalysts with stones as carriers. To discover the best removal efficiency of isopropyl alcohol, different catalysts with different ratios of metal (these metals were copper, manganese, and cobalt) and different loading (loading meant the ratio of the weight of metal to the weight of stone) were made. Moreover, others parameters such as different inlet concentration of IPA, inlet concentration of oxygen, space velocity, reaction temperature, and long-term test were also discussed. Finally, two kinetic models were introduced to prove the catalytic oxidation mechanism of IPA. The experimental results showed that the most effective catalyst is copper-cobalt catalyst, which ratio of metals is 6: 4 and loading is 10%. With this kind of catalyst, the optimal operational parameters could be easily found, and they were as follows: the inlet concentration of IPA was 1500 ppm, space velocity was 13500 hr-1, and reaction temperature was 350¢J. It was noticed that the conversion of IPA was all up to 95% in these conditions. In conclusion, the experimental results also indicated that conversion was increased with reaction temperature, inlet concentration of IPA and inlet concentration of oxygen increasing. On the contrary, the conversion was decreased as space velocity was increased. Besides, after long-term test of catalyst, the results showed that the performance of the catalyst acted still fairly well in oxidation. To realize the physical properties of catalysts, some analytic instruments such as SEM, EDS, EA, XRD were used. These analytic results could also tell us the difference between fresh and aged catalysts. Two kinetic models, Power rate law Model and Mars-Van Krevelen Model, were used to fit the kinetic mechanism of the decomposition of IPA. The fitting result was that Power rate law Model was rather suitable to describe the catalytic decomposition of IPA in the operational conditions in this work, and the reaction order was nearly first order.

In this work, a fundamental kinetic model for the catalytic reforming process has been developed. The complex network of elementary steps and molecular reactions occurring in catalytic reforming has been generated through a computer algorithm characterizing the various species by vectors and Boolean relation matrices. The algorithm is based on the fundamental chemistry occurring on both acid and metal sites of the catalyst. Rates are expressed for each of the elementary steps involved in the transformation of the intermediates. The Hougen-Watson approach is used to express the rates of the molecular reactions occurring on the metal sites of the catalyst. The single event approach is used to account for the effect of structure of reactant and activated complex on the rate coefficients of the elementary steps occurring on the acid sites. This approach recognizes that even if the number of elementary steps is very large they belong to a very limited number of types, and therefore it is possible to express the kinetics of elementary steps by a reduced number of parameters. In addition, the single event approach leads to rate coefficients that are independent of the feedstock, due to their fundamental chemical nature. The total number of parameters at isothermal conditions is 45. To estimate these parameters, an objective function based upon the sum of squares of the residuals was minimized through the Marquardt algorithm. Intraparticle mass transport limitations and deactivation of the catalyst by coke formation are considered in the model. Both the Wilke and the Stefan-Maxwell approaches were used to calculate the concentration gradients inside of the particle. The heterogeneous kinetic model was applied in the simulation of the process for typical industrial conditions for both axial and radial flow fixed bed reactors. The influence of the main process variables on the octane number and reformate volume was investigated and optimal conditions were obtained. Additional aspects studied with the kinetic model are the reduction of aromatics, mainly benzene. The results from the simulations agree with the typical performance found in the industrial process.

Thesis (Ph. D.)--University of Chicago, Department of Biochemistry and Molecular Biology, 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.