Made available in DSpace on 2014-07-29T15:12:43Z (GMT). No. of bitstreams: 1 dissertacao rafael gomes da silveira 2010.pdf: 606651 bytes, checksum: c482224a3bb2815edeb926f5afa40486 (MD5) Previous issue date: 2010-11-29 / Neste trabalho, sílica gel com área superficial especifica (S BET ) de 407 m 2.g-1 foi modi cada com a mol ecula de 3-cloropropiltrimetoxissiliano (CPTMS), seguida da reação de funcionalização com os ligantes N-benzoiltioureia (BT) e N-benzoil- N' -amino-N"-(2-piridil)-guanidina (BG) via rota heterogênea, obtendo os materiais Si- BT e Si-BG, respectivamente. Os ligantes e os materiais funcionalizados foram caracterizados por ponto de fusão, espectroscopia de infravermelho, análises elementares de cloreto e de nitrogênio, medidas de porosidade e termogravimetria. A anáalise de nitrogênio indicou a presença de 2,14.10 ??4 e 8,30.10-6 mols de BT e BG por grama de materiais - Si-BT e -Si-BG, respectivamente. As medidas de área superficial, volume de poros e de diâmetro médio dos poros dos materiais, mostraram uma diminuição de sua área superficial em relação ao material de partida. Os espectros de infravermelho apresentaram bandas características dos ligantes N-benzoiltiouréeia, N-benzoil-N'-amino- N" -(2-piridil)-guanidina, bem como dos grupos cloropropil e dos grupos BT e BG covalentemente ligados na sílica. As superfícies funcionalizadas adsorveram íons Cu(II) e Co(II), em soluções aquosas e etanólicas num sistema de batelada, a 25 C. Os dados cinéticos mostraram que o tempo necessário para que o sistema atinja o equilíbrio foi de aproximadamente 60 minutos em ambos os casos. As isotermas de adsorção dos íons metálicos em equilíbrio com - Si-BT e -Si-BG mostraram que os sistemas estão de acordo com o modelo proposto por Langmuir, onde a capacidade máaxima de adsorção N f .g-1 (mol.g-1) (experimental e teórico) mostra que o Cu(II) tem a nidade ligeiramente maior que o Co(II), tanto em solução aquosa quanto em etanólica, para ambas as superfícies funcionalizadas. palavras chave: sílica, funcionalização, N-benzoiltiour eia, N-benzoil-N'-amino-N"-(2-piridil)-guanidina, adsorção de íons.

Due to the wide application of silica based systems ranging from microelectronics to nuclear waste disposal, detailed knowledge of water-silica interactions plays an important role in understanding fundamental processes, such as glass corrosion and the long term reliability of devices. In this dissertation, atomistic computer simulation methods have been used to explore and identify the mechanisms of water-silica reactions and the detailed processes that control the properties of the water-silica interfaces due to their ability to provide atomic level details of the structure and reaction pathways. The main challenges of the amorphous nature of the silica based systems and nano-porosity of the structures were overcome by a combination of simulation methodologies based on classical molecular dynamics (MD) simulations with Reactive Force Field (ReaxFF) and density functional theory (DFT) based ab initio MD simulations. Through the development of nanoporous amorphous silica structure models, the interactions between water and the complex unhydroxylated internal surfaces identified the unusual stability of strained siloxane bonds in high energy ring structure defects, as well as the hydroxylation reaction kinetics, which suggests the difficulty in using DFT methods to simulate Si-O bond breakage with reasonable efficiency. Another important problem addressed is the development of silica gel structures and their interfaces, which is considered to control the long term residual dissolution rate in borosilicate glasses. Through application of the ReaxFF classical MD potential, silica gel structures which mimic the development of interfacial layers during silica dissolution were created A structural model, consisting of dense silica, silica gel, and bulk water, and the related interfaces was generated, to represent the dissolution gel structure. High temperature evolution of the silica-gel-water (SGW) structure was performed through classical MD simulation of the system, and growth of the gel into the water region occurred, as well as the formation of intermediate range structural features of dense silica. Additionally, hydroxylated silica monomers (SiO4H4) and longer polymerized silica chains were formed in the water region, indicating that glass dissolution is occurring, even at short time frames. The creation of the SGW model provides a framework for a method of identifying how interfacial structures which develop at glass-water interfaces can be incorporated into atomistic models for additional analysis of the dissolution of silicates in water.

Reactions of catalytic hydrogenations and polymerizations are widely used in industry for manufacture of fine chemicals, pharmaceuticals, and plastics. Homogeneous catalysts for the processes that have low stability and their separation is difficult. Therefore, the development of new highly active and stable catalysts for hydrogenations and polymerizations is a necessity. The objective of this research was the development of a strategy for immobilization of heterogeneous metallocene catalysts. First, a methodology of immobilization of bis-indenyl ligands on the surface of mesoporous silica gel was designed. Four bis-indenyl ligands containing functionalized tethers of various lengths with terminal alkene groups were synthesized. All bis-indenyl ligands were immobilized on the surface of mesoporous functionalized silica gel by two methods: hydrosilylation and thiol-ene coupling of the double bond. After comparing the results, the second strategy was chosen as more efficient. The materials can be used further as intermediates for synthesis of supported metallocene catalysts.

This research investigated parameters that can affect the use of nanoporous silica gel as a media for accumulating a detectable amount of uranium. The unique fluorescence of the Uranyl (UO22+) ion was used to evaluate the transport kinetics and accumulation within silica gel in a static fluid and under pressure driven flow. The addition of fluid flow decreased the time constant from on the order of an hour to approximately 2s with a very low fluid velocity of 0.36cm/s. The 0.36cm/s fluid velocity was found to be the critical velocity above which there was no gain in time constant. A table top instrument was developed that can detect trace amounts of uranium in solution. The table top instrument was used to investigate how the time constant depends on the uranyl concentration, which led to the development of a new time-based method for quantifying the uranyl concentration. The time-based method of detection uses a preset threshold and, based on the time it takes to reach that threshold, the concentration in the water sample can be determined. The lifetime of uranyl in complex with silica increased to approximately 120us, allowing for gated detection and background discrimination. In addition to the fluorescent contaminants, competing cations were tested to determine how they affect the fluorescence and transport kinetics of the uranyl. The cations tested were Mn2+, Ca2+, Mg2+, Na+, K+, and Li+. The result shows that within the natural concentrations, Mg2+, Na+, and K+ did quench the fluorescent of the uranyl ions by collision quenching. The time constant was also examined in the presence of each cation and showed that Ca2+, Mg2+, Na+, and K+ decreased the adsorption time constant. Future studies in this area should be directed toward the development of a portable version of the instrument.

In this thesis, yearly performance of the solar adsorption cooling system which is proposed to be installed to a residential building in Antalya is theoretically investigated in detail. Firstly, thermodynamic designs of the adsorption cooling cycle for three different types of cycles which are intermittent, heat recovery and heat &amp / mass recovery cycles are presented. Secondly, adsorption characteristics of three adsorbent/adsorbate pairs which are zeolite-water, silica gel-water and activated carbon-methanol are given. Following this, load side (i.e., building) of the system is designed and parameters that should be considered in building design are presented. Then, solar-thermal cooling system design methodology with an emphasis on solar fraction is presented. In addition, system parameters effecting the performance of the adsorption cooling system are analyzed and results are presented. Finally, economic analysis is done in order to understand the economic feasibility of the solar-thermal cooling systems compared to conventional cooling systems. TRNSYS is used for the yearly simulations and an integrated model of the overall system is developed in TRNSYS. Since energy consumption and performance investigations of environment-dependent systems such as building HVAC, refrigeration systems and solar collectors usually require weather information, typical meteorological year (TMY) data for Antalya is also generated in order to be used in the analysis of the system parameters.

Grâce à un mécanisme coopératif d'auto-assemblage électro-assisté ("Electro-Assisted Self-Assembly" : EASA), l'électrogénération de couches minces sol-gel à partir d'un sol constitué d'alcoxysilanes et d'un tensioactif cationique (bromure de cétyltriméthylammonium : CTAB) permet l'accès à des films mésostructurés présentant des mésopores orientés perpendiculairement au support. Des films mésostructurés à base de silice méthylée présentant une porosité organisée et "verticalement" orientée ont été électrogénérés en réalisant la co-condensation en une étape d'un alcoxysilane et d'un organo-alcoxysilane en présence de CTAB. Une étude des transferts de matière au sein de ces couches minces démontre que leur perméabilité peut être modulée par la teneur en groupements -CH3. Le procédé EASA a ensuite été étendu à l'utilisation de sols principalement aqueux. Ceci permet l'accès à de nouvelles structures, au contrôle de l'orientation du réseau poreux et à la possibilité de moduler la morphologie du matériau déposé en faisant varier les contre-anions associés aux édifices micellaires. Différentes stratégies de synthèse visant à augmenter la porosité de films électrogénérés ont été évaluées (utilisation d'agents gonflants et d'un copolymère triblocs). Des résultats probants concernant l'électrogénération de couches minces à porosité hiérarchisée (interconnexion de mésopores et de macropores) sont aussi présentés. Enfin, la dernière partie s'attache à étendre le concept EASA à l'échelle locale (micrométrique) par l'utilisation d'un microscope électrochimique à balayage en tant que moyen de synthèse, ceci ouvrant la voie à l'électromicrolithographie sol-gel / Thanks to an Electro-Assisted Self-Assembly (EASA) cooperative process, the sol-gel electrogeneration of silica thin films from sols containing alkoxysilanes and cationic surfactant molecules (cetyltrimethylammonium: CTAB) allows to obtain mesostructured films exhibiting mesopore channels orthogonal to the substrate. Organized methylated silica thin films with "vertically"-aligned mesopores were electrogenerated by performing a one-step co-condensation between alkoxysilanes and organo-alkoxysilanes in the presence of CTAB. Monitoring mass transport issues inside these thin layers demonstrates that their permeability can be modulated by the -CH3 moieties ratio. The EASA process was then extended to the use of mainly aqueous sols. This permits the electrogeneration of new structures, the control of the porous network orientation and a modulation of the deposited material morphology by changing the CTA+ counter-anion. Various synthesis strategies aiming at increasing the porosity of electrogenerated films were evaluated (use of swelling agents and a triblock copolymer). Some convincing results dealing with the electrogeneration of silica films exhibiting a hierarchical porosity (combination of mesopores with macropores) are also presented. Finally, the last part of this work demonstrates how the EASA process can be applied at the local scale (micrometric) by using a scanning electrochemical microscope as a synthesis tool, thus opening the way to the sol-gel electromicrolithography

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-06-28T12:13:34Z No. of bitstreams: 1 arquivototal.pdf: 5054699 bytes, checksum: b0c36e922ea87a1775b247b54f1978c1 (MD5) / Made available in DSpace on 2017-06-28T12:13:34Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5054699 bytes, checksum: b0c36e922ea87a1775b247b54f1978c1 (MD5) Previous issue date: 2016-02-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In this work, cytochrome P450-inspired biomimetic oxidation systems were developed for aliphatic C–H bond activation and triclosan oxidation. Heterogenization of Mn(III) N-pyridylporphyrin derivatives onto silica gel resulted in three groups of catalysts. Immobilization of Mn(III) N-pyridylporphyrins (MnT-X-PyPCl, X = 2, 3, 4) on chloropropylfunctionalized silica gel (Sil-Cl) yielded the first group of catalysts, Sil-Cl/MnT-X-PyPCl. The second group was prepared by in situ methylation of Sil-Cl/MnT-X-PyPCl materials resulting in the Sil-Cl/MnT-X-PyPCl/MeOTs materials. Finally the third group of catalysts were prepared via electrostatic immobilization of Mn(III) N-methylpyridiniumporphyrins (MnTM-X-PyPCl5, X = 2, 3, 4) onto unfunctionalized silica gel to yield SiO2/MnTM-XPyPCl5 (X = 2, 3, 4). These materials were studied as catalysts for iodosylbenzene-based hydroxylation reactions of the model substrate cyclohexane. The heterogenized catalysts proved to be more efficient, selective and oxidatively stable than the corresponding homogeneous systems for cyclohexane oxidation. No significant loss in catalytic efficiency was observed upon recycling of these materials. The increase in Mn(III)/Mn(II) reduction potentials associated with the alkylation of the pyridyl moieties of Sil-Cl/MnT-XPyPCl/MeOTs (X = 2, 3, 4) materials did not result in significant changes in catalytic efficiency as compared with the non-methylated starting materials Sil-Cl/MnT-X-PyPCl (X = 2, 3, 4). The PhIO-oxidation of the emerging contaminant triclosan under homogenous conditions was carried out using Mn porphyrins as biomimetic catalysts for P450-based xenobiotic degradation. The second generation catalyst Mn(III) meso-tetrakis(2,6- dichlorophenyl)porphyrin chloride, MnTDCPPCl, was more efficient and oxidatively stable than its first generation analogue Mn(III) meso-tetraphenylporphyrin chloride, which was considerably destroyed during the reactions. GC-FID, HPLC-DAD and LC-MS/MS analyses were used to confirm the formation of two products already identified as in vivo metabolites of triclosan: 4-chlorocatechol and 2,4-dichlorophenol. LC-MS/MS spectra of reation mixture indicated the formation of four additional triclosan degradation products (m/z 270, 323, 448, and 483), whose structural identity and biological relevance have yet to be confirmed. / Neste trabalho foram desenvolvidos modelos biomiméticos dos citocromos P450 pela heterogeneização das N-piridilporfirinas de Mn(III) em sílica-gel, resultando em três classes de catalisadores. A primeira classe descreve a imobilização das N-piridilporfirinas de Mn(III) (MnT-X-PyPCl, X = 2, 3, 4) em sílica-gel funcionalizada com o grupo cloropropila (Sil-Cl), a segunda classe envolve a metilação in situ dos materiais obtidos anteriormente e a terceira classe corresponde ao ancoramento eletrostático das N-metilpiridinioporfirinas de Mn(III) (MnTM-X-PyPCl5, X = 2, 3, 4) em sílica-gel in natura, sendo denominados como Sil-Cl/MnT-X-PyPCl, Sil-Cl/MnT-X-PyPCl/MeOTs e SiO2/MnTM-X-PyPCl5 (X = 2, 3, 4), respectivamente. Estes materiais foram empregados em reações de hidroxilação do substrato modelo cicloexano por iodosilbenzeno (PhIO). Os catalisadores heterogeneizados mostram-se mais eficientes, seletivos e resistentes à destruição catalítica do que os sistemas em fase homogênea, além de não serem observadas perdas significativas na eficiência catalítica após reúsos desses materiais. O aumento do potencial de redução Mn(III)/Mn(II) associado ao aumento do grau de alquilação nos catalisadores Sil-Cl/MnT-X-PyPCl/MeOTs (X = 2, 3, 4) não levaram a alterações significativas na eficiência catalítica desses materiais em comparação aos materiais de partida Sil-Cl/MnT-X-PyPCl (X = 2, 3, 4). A investigação da atividade catalítica das Mn-porfirinas de primeira e segunda geração, cloreto de mesotetrafenilporfirinatomanganês (III) (MnTPPCl) e cloreto de meso-tetraquis(2,6- diclorofenil)porfirinatomanganês (III) (MnTDCPPCl), na oxidação do contaminante emergente triclosan revelou que estes modelos biomiméticos podem efetuar a degradação deste xenobiótico. A MnTDCPPCl mostrou-se mais eficiente do que seu análogo de primeira geração MnTPPCl, que foi mais degradado durante as reações. Pelas técnicas de GC-FID, HPLC-DAD e LC-MS/MS foi possível confirmar a formação de dois produtos já identificados na literatura como metabólitos in vivo: 4-clorocatecol e 2,4-diclorofenol. Ainda por LC/MS-MS pode-se identificar a formação de mais quatro produtos de degradação do triclosan ainda não definidos (m/z 270, 323, 448 e 483)

The present research work caters to two important needs of rural India: i) desalination of subsoil/coastal brackish water and ii) basic refrigeration for short term preservations of agro-produce, medicines etc. Fortunately, such places are blessed with abundant solar insolation and/or low grade thermal energy (< 100°C) is available which may be tapped for this purpose instead of relying solely on grid electricity. Both the objectives of desalination and cooling are realized by evaporating brackish water at a low pressure (~1 kPa) and thermally compressing the water vapour to a higher pressure before condensing it. Adsorption route is chosen for compression where silica gel is the adsorbent and water to be desalinated as the refrigerant. The objective of this study is to develop a laboratory prototype of a two-stage adsorption cooling cum desalination system driven by low grade heat source. The entire system is air-cooled which is necessitated by non-availability of heat exchange grade cooling water. Initially various experimental and theoretical studies are carried out for characterizing silica gel + water pair which is fundamental to the system design. RD type silica gel is used in this study due to its high uptake capabilities. The uptakes for this adsorption pair at various pressure and temperature conditions are measured using a specially designed isothermal adsorber cell connected to an evaporator. Subsequently, a modelling study of adsorption kinetics is performed for a monolayer of silica gel in order to estimate the adsorption time scale. This time scale is used as an input for the scaling analysis of columnar packed silica gel bed. The scaling analysis showed that the thermal diffusion time scale limits the adsorption process. It also showed that for a given thermal length scale, the bed has a unique vapour flow length scale beyond which the adsorption phenomenon gets limited due to pressure drop. The scaling results are validated by simulation studies. A shell-and-tube heat exchanger is chosen for the adsorber which closely mimics the columnar silica gel packing studied in scaling analysis. The heat exchanger is designed for radial entry of vapour. A modelling study is performed on ANSYS® Fluent platform for optimising the tube pitch by minimising the overall thermal capacitance of the bed. The shell diameter is determined for this tube pitch based on the vapour flow length criterion established through scaling. To experimentally study the effect of pressure drop on bed performance, the radial entry of vapour is closed for 1 bed/stage (out of the 4 beds/stage) enforcing the vapour to flow along the longer axial dimension. The system is generously instrumented for precise measurements and control over the various experimental parameters. For the functioning of the adsorber system, various vapour valves and water (heat transfer fluid) valves need to be operated in a cyclical and synchronized manner. Individual components are fitted with pressure, temperature and water flow sensors. The entire operation and data acquisition for the adsorption system has been automated using National Instruments® (NI) PXIe controller executing an in-house developed code written on NI Labview® platform. To simulate solar/waste heat input, multiple electrical heaters are used in this study and a constant temperature bath is used to simulate the cooling load at the evaporator. Prior to conducting experiments a 4-bed lumped dynamic model is developed based on the design data of the system to simulate the two-stage system performance for various input conditions. The study helped to optimise the performance of a two-stage system. The study also compares the two-stage and single-stage system performance for various ambient temperatures (25–40°C). The study revealed that for pressure lifts higher than 5 kPa a two-stage system is preferable. A detailed experimental study is conducted on the developed prototype by operating it in various conditions namely 2, 3 and 4–bed modes for single and two-stage operations; with 1.0–1.7 kPa evaporator pressures, half cycle time varying between 1200–3000s and source temperature in the range of 75–85°C. The system is operated indoors during summer conditions wherein the ambient temperature is found to be 36±1°C which is significantly higher than the design point of 25°C. This resulted in lower than expected throughput; however, the system performance variation is qualitatively similar to as predicted by the lumped model. A comparison between the experimental and simulated bed temperature revealed that the thermal wave during the switching of hot/cold water plays a significant role causing a large deviation from the simulation results. A comparative study is carried out between the beds with radial vapour flow to that with axial flow and the results validate the scaling criterion. Experimental results also depict that two-stage operation is favourable when the pressure lift required is larger than 5 kPa. Such large pressure lift is encountered when air-cooling is used in a tropical country like India.

Since a large number of polar and often ionizable anthropogenic organic trace compounds, such as pharmaceutical residues, can be detected in various stages of the water cycle, there is a need to elucidate the effects and behavior of such substances in the aquatic environment. Despite the fact that numerous studies on the sorption behavior of ionizable organic trace compounds have already been carried out, reliable sorption models, which allow a sufficiently accurate prediction of the sorption of organic cations, are not yet available. For this reason, the general objective of this thesis was to improve the fundamental process understanding of the interactions between dissolved cationic organic substances and solid surfaces including relevant influence parameters. The investigations were based on a differentiated process consideration in order to ultimately provide the essential prerequisites for a future reliable prediction of the sorption behavior of cationic organic compounds. Due to the complex superposition of several mechanisms, the basic relationships cannot be clearly elucidated with heterogeneous sorbents. Therefore, it was consciously worked with largely homogeneous, synthetic sorbents. The use of well-defined sorbents with different properties as well as the variation of background electrolyte concentration and the targeted use of different sorbates were the 'tools' that were used to identify and to separate the underlying sorption processes. / Da eine Vielzahl polarer und oftmals ionisierbarer anthropogener organischer Spurenstoffe, wie z. B. Pharmakarückstände, in verschiedenen Bereichen des Wasserkreislaufes nachweisbar ist, besteht die Notwendigkeit die Wirkung und das Verhalten solcher Spurenstoffe in der Umwelt näher aufzuklären. Trotz der Tatsache, dass bereits zahlreiche Untersuchungen zum Sorptionsverhalten ionisierbarer organischer Spurenstoffe bestehen, sind zuverlässige prognosefähige Sorptionsmodelle, welche eine ausreichend genaue Vorhersage der Sorption von organischen Kationen ermöglichen, zurzeit noch nicht verfügbar. Das generelle Ziel dieser Arbeit bestand daher darin, das grundlegende Prozessverständnis der Wechselwirkungen zwischen gelösten kationischen organischen Substanzen und festen Oberflächen einschließlich relevanter Einflussgrößen zu verbessern. Die Untersuchungen basierten auf einer differenzierten Prozessbetrachtung, um letztlich die wesentlichen Voraussetzungen für eine zukünftig zuverlässige Prognose des Sorptionsverhaltens kationischer organischer Verbindungen zu liefern. Aufgrund der komplexen Überlagerung mehrerer Mechanismen können die grundlegenden Zusammenhänge mit heterogen zusammengesetzten natürlichen Sorbentien nicht eindeutig aufgeklärt werden. Daher wurde bewusst mit weitgehend homogenen, synthetischen Sorbentien gearbeitet. Die Verwendung wohldefinierter Sorbentien mit unterschiedlichen Eigenschaften sowie die Variation der Elektrolytkonzentration und der gezielte Einsatz verschiedener Sorptive waren die 'Werkzeuge', die verwendet wurden, um die zugrunde liegenden Sorptionsprozesse zu identifizieren und zu separieren.

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