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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Identification and characterization of interferon-gamma induced ubiquitinated newly synthesized proteins

Wiemhoefer, Anne 20 July 2011 (has links)
Ein Schlüsselprozess in der Immunantwort ist die durch das proinflammatorische Zytokin Interferon-gamma (IFNg) induzierte transiente Akkumulation von neu synthetisierten defekten Proteinen, die durch Anknüpfen von Polymeren des Proteins Ubiquitin (Ub) post-translational modifiziert werden. Die Ubiquitinierung ist das Schlüsselsignal für den Abbau dieser Proteine. Die Abbauprodukte dienen unter anderem als Quelle für die Prozessierung von Antigenen. Um die frühe Immunantwort besser zu verstehen, wurden im Rahmen dieser Arbeit die Identität und Charakteristika dieser neu synthetisierten Proteine, sowie die Topologie ihrer post-translationalen Modifizierung durch Ub untersucht. Dazu wurde die massenspektrometrischen Analyse ubiquitinierter Proteine weiterentwickelt, indem die experimentellen Konditionen auf deren Analyse optimiert wurden. Insbesondere konnte gezeigt werden, dass die kombinierte Verdauung der Ub-Konjugate mittels zweier Peptidasen die Identifizierung der Proteinpeptide und der Indikatorpeptide für Ubiquitinierungsstellen entscheidend verbessert. Es wurde demonstriert, dass eine selektive Isotopenmarkierung der neu synthetisierten Proteine möglich ist. Mit Hilfe dieser Methode gelang es, Veränderungen der Ub Modifikationen bezüglich der Topologie sowie quantitative Unterschiede der ubiquitinierten Proteine aus humanen HeLa-Zellen in An- und Abwesenheit von IFNg zu identifizieren. Nach Induktion durch IFNg wurden drei polyubiquitinierte, drei mono- oder polyubiquitinierte und 111 potentiell ubiquitinierte Proteine identifiziert. Diese Proteine zeigten, dass keine generelle Ubiquitinierungspräferenz für die durch IFNg verstärkt transkribierten Gene besteht. Die Ergebnisse dieser Arbeit erweitern das Verständnis der frühen zellulären Immunantwort und tragen zum Verständnis von Krebs- und Autoimmunerkrankungen sowie chronischen Entzündungsprozessen bei. Möglicherweise bilden sie die Grundlage für die Weiterentwicklung entsprechender Therapien. / A key process within the immune response of organisms is the transient accumulation of newly synthesized defective proteins affected by the proinflammatory cytokine interferon-gamma(IFNg). These proteins are post-translationally modified by attachment of polymers of the protein ubiquitin (Ub), which represents the key signal for targeting them to degradation. The resulting peptides can serve as sources for antigen processing. In order to get an insight into the details of the cellular early immune response, the identity and characteristics of the newly synthesized proteins and the topology of their post-translational modification with Ub were investigated. An essential progress of the mass spectrometric approach was achieved by optimizing the experimental conditions with regard to the requirements of the analysis of the targeted proteins. In particular, it could be shown that a combined digestion of Ub-conjugates with two peptidases leads to an improved detection of protein peptides and indicator peptides for ubiquitination sites. It was shown that a selective isotopic labeling of the newly synthesized proteins was possible. With this method, a decisive step forward was made in the understanding of changes of the Ub modifications with respect to the topology and in clarifying the quantitative differences between Ub-conjugates from IFNg treated and untreated human HeLa cells. Three IFNg induced polyubiquitinated proteins, three mono- or polyubiquitinated as well as 111 potential Ub-substrates could be identified. These proteins did not show any general ubiquitination preference for genes whose transcription is enhanced in presence of IFNg. The results obtained in this work help to broaden and refine the general picture of the early cellular immune response. They contribute to the knowledge on molecular processes of cancer, autoimmune diseases or chronic inflammation and, potentially, can give hints for the continued development of corresponding therapies.
32

Membranas anisotrópicas de alumina sintetizada pelo método pechini para aplicações em processos de separação.

SILVA, Mirele Costa da. 25 June 2018 (has links)
Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-06-25T21:56:30Z No. of bitstreams: 1 MIRELE COSTA DA SILVA – TESE (UAEMa) 2015.pdf: 9764394 bytes, checksum: a51abce77e60acf4e1faa93511e08be8 (MD5) / Made available in DSpace on 2018-06-25T21:56:30Z (GMT). No. of bitstreams: 1 MIRELE COSTA DA SILVA – TESE (UAEMa) 2015.pdf: 9764394 bytes, checksum: a51abce77e60acf4e1faa93511e08be8 (MD5) Previous issue date: 2015-08-28 / Capes / As membranas cerâmicas anisotrópicas obtidas a partir de pós sintéticos estão ampliando suas aplicações industriais, devido principalmente as vantagens que apresentam em termos de permeabilidade e resistência (química, térmica e mecânica). Este trabalho tem como objetivo obter membranas anisotrópicas com a camada filtrante de alumina sintetizada pelo método Pechini para aplicações em processos de separação. Foram preparadas membranas com geometria na forma de discos e posteriormente membranas tubulares com os melhores parâmetros avaliados na geometria de discos. O suporte foi preparado com uma massa composta por alumina comercial e bentonita, a camada intermediária foi obtida com uma argila caulinítica e a camada filtrante com a alumina sintetizada. As massas utilizadas para obtenção das membranas foram caracterizadas por análise química e térmica, difração de raios X (DRX), distribuição granulométrica e microscopia eletrônica de varredura (MEV). A alumina foi sintetizada pelo método Pechini nas relações 2:1, 3:1 e 4:1 de ácido cítrico:cátion metálico, calcinadas em diferentes temperaturas e caracterizadas por análise térmica, DRX, distribuição granulométrica, MEV e análise textural por BET. Cada camada que compôs a membrana foi caracterizada por MEV, microscopia ótica, porosimetria por intrusão ao mercúrio e análises de fluxo com água dessalinizada. A camada intermediária e a filtrante foram obtidas através da deposição de dispersões por dip-coating. Os resultados apresentaram membranas confeccionadas com sucesso, atingindo permeabilidade de 317,53 L/h.m2 Bar. As membranas foram eficientes para aplicação no tratamento de água oleosa, reduzindo a concentração de 70 mg/L de óleo em água em 100%; para aplicação na separação de índigo blue a membrana atingiu 100% de rejeição das partículas sólidas de uma solução com concentração de 0,25 g/L de índigo blue em água; no tratamento de águas utilizando o efluente bruto de um rio a membrana reduziu entre outros a cor, turbidez, íons, amônia, sílica e ferro e para aplicação na separação da proteína caseína atingiu 97,4% de rejeição em uma solução com concentração de 3,08 mg/L da caseína em água. / The anisotropic ceramic membranes obtained from synthetic powders are expanding their industrial applications, mainly because the advantages that present in terms of permeability and resistance (chemical, thermal and mechanical). The aim of this work is to obtain anisotropic membranes with the filtering layer of alumina synthesized by Pechini method for applications in separation processes. Membranes were prepared in the form of discs and later with tubular geometry with the best parameters evaluated on disk geometry. The support has been prepared with a ceramic mass consisted by a commercial alumina and bentonite. The intermediate layer was obtained with kaolinite clay and the filtering layer with synthesized alumina. The ceramic masses used for obtaining the membranes were characterized by chemical and thermal analysis, X-ray diffraction, particle size distribution and scanning electron microscopy (SEM). Alumina was synthesized by Pechini method in ratios of 2:1, 3:1 and 4:1 of citric acid:metallic cation. It were calcined at different temperatures and characterized by thermal analysis, X-ray diffraction, particle size distribution, and textural analysis by BET. Each layer that composed the membrane was characterized by SEM and optical microscopy, by intrusion mercury porosimetry and flow analysis with desalinated water. The intermediate and filter layer were obtained through the deposition of dispersions by dip -coating. The results showed membranes made with success, free from defects, with permeability of 317.53 L/h m 2 Bar. The membranes were efficient for the application in the treatment of oily water, reducing the concentration of 70 mg/L of oil in water at 100%; for application in separation of indigo blue the membrane reached 100% of rejectio n of solid particles of a solution with concentration of 0.25 g/L of indigo blue; water treatment using the raw sewage of a river the membrane reduced color, turbidity, ions present, ammonia, silica and iron and for application in separation of casein has been reached 97.4% of rejection in a solution with concentration 3.08 mg/mL.
33

Inactivation of Microorganisms by Photocatalysis

Sontakke Sharad, M January 2012 (has links) (PDF)
Photocatalysis is an advanced oxidation process, which has shown to possess an enhanced capability to remove a wide range of contaminants. It involves the use of a semiconductor photocatalyst and a photon source. Photocatalysis has several advantages such as mild reaction conditions like ambient temperature and pressure, good control over the reaction and faster reaction kinetics. Semiconductor photocatalysts such as TiO2, ZnO, Fe2O3, CdS, ZnS, etc. absorbs light of energy greater than or equal to its band gap and the electron in the valence band gets excited to conduction band leaving behind the hole in valence band. These charge carrier pair results in the formation of various reactive oxygen species such as hydroxyl and superoxide radicals which results in the degradation of chemical contaminants and inactivation of microorganisms. TiO2 is the most widely used catalyst in photocatalytic studies because of its high photocatalytic activity, non-toxicity and wide availability. Anatase phase TiO2 has been reported to possess higher photocatalytic activity than the rutile phase. Although there are several methods to synthesize TiO2, solution combustion synthesis is a single step process to produce pure anatase phase TiO2. The catalyst produced by this method has been shown to be superior to the commercially available Degussa P-25 catalyst for the degradation of various chemical contaminants. The present investigation focuses on the use of combustion synthesized catalyst for the inactivation of microorganisms. The photocatalytic activity was compared with commercial Degussa P-25 catalyst. The various aspects of photocatalytic inactivation reactions studied in this dissertation are: i) photocatalytic inactivation of microorganisms in presence of UV light, ii) effect of various parameters on the inactivation, iii) photocatalytic inactivation in presence of visible light, iv) use of immobilized catalyst for the photocatalytic inactivation, v) understanding of mechanism and kinetics of inactivation. Combustion synthesized TiO2 (CS-TiO2), combustion synthesized 1% Ag substituted TiO2 (Ag/TiO2 (Sub)) and 1% Ag impregnated CS-TiO2 (Ag/TiO2 (Imp)) were used as photocatalysts. The catalysts were characterized by powder XRD, TEM, BET surface area, UV-Vis spectroscopy, TGA and photoluminescence spectroscopy. The photocatalytic inactivation experiments were carried out using E. coli (K-12 MG 1655), a bacterial strain and P. pastoris (X-33), a yeast strain, as model microorganisms. The results demonstrate higher photocatalytic activity of all the combustion synthesized catalysts than commercial Degussa P-25 catalyst. The optimum catalyst concentration was 0.25 g/L and the maximum inactivation was observed in the presence of Ag/TiO2 (Imp) catalyst. Rapid and complete inactivation of the microorganisms was observed at lower initial cell concentrations. A reduced photocatalytic inactivation was observed in presence of various anions (HCO3¯ , SO4 2¯ , Cl¯ and NO3¯ ) and cations (Na, K, Caand Mg). Even a small addition of H2O2 was observed to improve the photocatalytic inactivation. At higher dosage of H2O2, a 2 min exposure was sufficient to result in a complete inactivation. Changing the initial pH of the solution was observed to have no significant effect on the photocatalytic inactivation. All the combustion synthesized catalysts showed higher activity as compared to those obtained with commercial Degussa P-25 TiO2 in presence of visible light. The higher photocatalytic activity of combustion synthesized TiO2 can be attributed to the lesser crystallite size, higher surface area, large amount of hydroxyl groups and decreased band-gap energy of the catalyst. The present study demonstrates the potential use of catalyst immobilized thin films for the photocatalytic inactivation of E. coli in the presence of UV light. The CS-TiO2 catalyst was immobilized on glass substrate by LbL deposition technique. The performance of immobilized CS-TiO2 was compared to commercial Degussa Aeroxide TiO2 P-25 (Aeroxide) catalyst. The effect of various operating parameters like catalyst loading, surface area and number of bilayers on inactivation has been investigated. It was observed that increasing the number of bilayers and the concentration did not influence the inactivation but increased surface area led to an increase in inactivation. It was observed that the catalyst immobilized on glass slides can be used for repeated experimental cycles with the same efficiency. It was observed that the inactivation process can be studied in continuous mode by using catalyst immobilized on glass beads. The work also focused attention towards understanding the microorganism inactivation mechanism and kinetic aspects. Various microscopy techniques such as optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the inactivation mechanism. From the images obtained, it was suggested that the inactivation is caused due to rupture of cell wall. The mechanism was also examined by carrying out degradation experiments on cell component such as protein and media component such as dextrose. UV alone was observed to degrade protein and the presence of catalyst showed no additional effect. On the other hand, dextrose does not respond to photocatalytic degradation even at a lower concentration. The photocatalytic degradation of Orange G dye was reduced by addition of dextrose sugar or protein which shows a possibility of competitive degradation. The kinetics of inactivation was studied by various models available in literature such as the power-law model, Chick-Watson model, modified Hom model, GInaFIT tool and a Langmuir-Hinshelwood type model. It was observed that power-law based kinetic model showed good agreement with the experimental data. A mechanistic Langmuir-Hinshelwood type model was also observed to model the inactivation reactions with certain assumptions.
34

Sur la génération d'exemples pour réduire le coût d'annotation

Piedboeuf, Frédéric 03 1900 (has links)
L'apprentissage machine moderne s'appuie souvent sur l'utilisation de jeux de données massifs, mais il existe de nombreux contextes où l'acquisition et la manipulation de grandes données n'est pas possible, et le développement de techniques d'apprentissage avec de petites données est donc essentiel. Dans cette thèse, nous étudions comment diminuer le nombre de données nécessaires à travers deux paradigmes d'apprentissage~: l'augmentation de données et l'apprentissage par requête synthétisée. La thèse s'organise en quatre volets, chacun démontrant une nouvelle facette concernant la génération d'exemples pour réduire le coût d'annotation. Le premier volet regarde l'augmentation de données pour des textes en anglais, ce qui nous permet d'établir une comparaison objective des techniques et de développer de nouveaux algorithmes. Le deuxième volet regarde ensuite l'augmentation de données dans les langues autres que l'anglais, et le troisième pour la tâche de génération de mots-clés en français. Finalement, le dernier volet s'intéresse à l'apprentissage par requête synthétisée, où les exemples générés sont annotés, en contraste à l'augmentation de données qui produit des exemples sans coût d'annotation supplémentaire. Nous montrons que cette technique permet de meilleures performances, particulièrement lorsque le jeu de données est large et l'augmentation de données souvent inefficace. / Modern machine learning often relies on the use of massive datasets, but there are many contexts where acquiring and handling large data is not feasible, making the development of techniques for learning with small data essential. In this thesis, we investigate how to reduce the amount of data required through two learning paradigms~: data augmentation and membership query synthesis. The thesis is organized into four parts, each demonstrating a new aspect of generating examples to reduce annotation costs. The first part examines data augmentation for English text, allowing us to make an objective comparison of techniques and develop new algorithms. The second one then explores data augmentation in languages other than English, and the third focuses on the task of keyword generation in French. Finally, the last part delves into membership query synthesis, where generated examples are annotated, in contrast to data augmentation, which produces examples without additional annotation costs. We show that this technique leads to better performance, especially when the dataset is large and data augmentation is often ineffective.
35

Machine Learning for Speech Forensics and Hypersonic Vehicle Applications

Emily R Bartusiak (6630773) 06 December 2022 (has links)
<p>Synthesized speech may be used for nefarious purposes, such as fraud, spoofing, and misinformation campaigns. We present several speech forensics methods based on deep learning to protect against such attacks. First, we use a convolutional neural network (CNN) and transformers to detect synthesized speech. Then, we investigate closed set and open set speech synthesizer attribution. We use a transformer to attribute a speech signal to its source (i.e., to identify the speech synthesizer that created it). Additionally, we show that our approach separates different known and unknown speech synthesizers in its latent space, even though it has not seen any of the unknown speech synthesizers during training. Next, we explore machine learning for an objective in the aerospace domain.</p> <p><br></p> <p>Compared to conventional ballistic vehicles and cruise vehicles, hypersonic glide vehicles (HGVs) exhibit unprecedented abilities. They travel faster than Mach 5 and maneuver to evade defense systems and hinder prediction of their final destinations. We investigate machine learning for identifying different HGVs and a conic reentry vehicle (CRV) based on their aerodynamic state estimates. We also propose a HGV flight phase prediction method. Inspired by natural language processing (NLP), we model flight phases as “words” and HGV trajectories as “sentences.” Next, we learn a “grammar” from the HGV trajectories that describes their flight phase transition patterns. Given “words” from the initial part of a HGV trajectory and the “grammar”, we predict future “words” in the “sentence” (i.e., future HGV flight phases in the trajectory). We demonstrate that this approach successfully predicts future flight phases for HGV trajectories, especially in scenarios with limited training data. We also show that it can be used in a transfer learning scenario to predict flight phases of HGV trajectories that exhibit new maneuvers and behaviors never seen before during training.</p>
36

Мулти-резолуциона мера за објективну оцену квалитета синтетизованих слика ФТВ видео сигнала / Multi-rezoluciona mera za objektivnu ocenu kvaliteta sintetizovanih slika FTV video signala / Multi-scale metric for objective synthesized image quality assessment for FTV

Sandić-Stanković Dragana 19 September 2016 (has links)
<p>Основни допринос ове докторске дисертације је развој алгоритама за објективну процену визуелног квалитета слике синтетизоване применом ДИБР (Depth Image Based Rendering) техника које узрокују неуниформна изобличења у области ивица. Применом нелинеарних морфолошких филтара у мултирезолуционој декомпозицији слика код израчунавања предложене метрике, важне геометријске информације као што су ивице су добро очуване без помака и замућења у сликама на различитим скалама мултирезолуционе репрезентације. Израчунавањем МСЕ по подопсезима који садрже ивице, пиксел по пиксел, прецизно се мери разлика две мултирезолуционе репрезентације. Тако се највећи значај у процени квалитета додељује области ивица. Процене предложене метрике се добро поклапају са субјективним оценама.</p> / <p>Osnovni doprinos ove doktorske disertacije je razvoj algoritama za objektivnu procenu vizuelnog kvaliteta slike sintetizovane primenom DIBR (Depth Image Based Rendering) tehnika koje uzrokuju neuniformna izobličenja u oblasti ivica. Primenom nelinearnih morfoloških filtara u multirezolucionoj dekompoziciji slika kod izračunavanja predložene metrike, važne geometrijske informacije kao što su ivice su dobro očuvane bez pomaka i zamućenja u slikama na različitim skalama multirezolucione reprezentacije. Izračunavanjem MSE po podopsezima koji sadrže ivice, piksel po piksel, precizno se meri razlika dve multirezolucione reprezentacije. Tako se najveći značaj u proceni kvaliteta dodeljuje oblasti ivica. Procene predložene metrike se dobro poklapaju sa subjektivnim ocenama.</p> / <p>The main contribution of this doctoral thesis is the development of algorithms for objective<br />DIBR-synthesized view quality assessment. DIBR algorithms introduce nonuniform<br />geometric distortions affecting the edge coherency in the synthesized images.The non-linear<br />morphological filters used in multi-scale image decompositions of the proposed metric<br />maintain important geometric information such as edges across different resolution<br />levels.Calculating MSE pixel-by-pixel through subbands in which the edges are extracted,<br />the difference of the two multiresolution representations, the reference and the synthesized<br />image, is precisely measured. In that way the importance of edge areas which are prone to<br />synthesis artifacts is emphasized in the image quality assessment. The proposed metric has<br />very good agreement with human judgment.</p>
37

S?ntese de catalisadores nanoporosos na aus?ncia total e parcial de direcionadores org?nicos para pir?lise catal?tica de ?leos pesados e intermedi?rios

Costa, Maria Jos? Fonseca 03 June 2013 (has links)
Made available in DSpace on 2014-12-17T15:42:28Z (GMT). No. of bitstreams: 1 MariaJFC_TESE.pdf: 4007652 bytes, checksum: 7bb363c54641679d79bbff5c76de539f (MD5) Previous issue date: 2013-06-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The processing of heavy oil produced in Brazil is an emergency action and a strategic plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports the materials preparation that combine the high catalytic activity of zeolites with the greater accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by synthesis processes with less environmental impact than conventional ones. Innovative methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic template. The synthesis of hybrid with pore bimodal distribution took place from one-single organic directing agent aimed to eliminate the use of organic templates, acids of any kind or organic solvents like templating agent of crystalline zeolitic aluminosilicate together with temperature-programmed microwave-assisted, making the experimental procedures of preparation most practical and easy, with good reproducibility and low cost. The study about crystalline zeolitic aluminosilicate in the absence of organic template, especially MFI type, is based on use of H2O and Na+ cation playing a structural directing role in place of an organic template. Advanced characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Highresolution Transmission Electron Microscopy (HRTEM), Adsorption of N2 and CO2, kinetic studies by Thermogravimetric Analysis (TGA) and Pyrolysis coupled to Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) were employed in order to evaluate the synthesized materials. Achieve the proposed objectives, has made available a set of new methodologies for the synthesis of zeolite and hybrid micro-mesoporous material, these suitable for catalytic pyrolysis of heavy oils aimed at producing light fraction / O processamento do petr?leo pesado produzido no Pa?s ? uma a??o emergencial e estrat?gica para obter a auto-sufici?ncia e super?vits econ?micos. Neste sentido, ? indispens?vel o investimento em pesquisas de novos catalisadores para obten??o de derivados leves a partir de fra??es pesadas do petr?leo. O trabalho de doutorado aqui reportado dedicouse ? prepara??o de materiais que combinem, numa ?nica estrutura, a elevada atividade catal?tica de ze?litas, com melhor acessibilidade de materiais mesoporosos, como a estrutura h?brida HZSM-5/MCM-41, utilizando processos de s?ntese com menor impacto ambiental que os convencionais. Metodologias inovadoras foram desenvolvidas para a s?ntese do catalisador h?brido micro-mesoporoso ou ze?lito-mesoporoso por mecanismo de direcionamento estrutural via duplo agente diretor org?nico e tamb?m a partir de estrutura zeol?tica sintetizada na aus?ncia total de direcionador org?nico. Esse ?ltimo, tamb?m chamado de s?ntese do h?brido com distribui??o bimodal de poros a partir de um ?nico agente diretor org?nico, visou eliminar o uso dos direcionadores org?nicos, ?cidos de qualquer natureza ou solventes org?nicos como molde estrutural da estrutura zeol?tica em conjunto com o m?todo hidrot?rmico assistido por irradia??o via micro-ondas, tornando o procedimento experimental de prepara??o pr?tico e simples, com boa reprodutibilidade e menor custo. A metodologia de prepara??o da ze?lita MFI do tipo ZSM-5 utiliza H2O e c?tions Na+ no papel de direcionamento estrutural e compensa??o de cargas na estrutura. T?cnicas relevantes de caracteriza??o, como Difra??o de Raios-X (XRD), Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletr?nica de Varredura (SEM), Microscopia Eletr?nica de Transmiss?o de Alta Resolu??o (HRTEM), Adsor??o de N2 e CO2, estudos cin?ticos via An?lises Termogravim?tricas (TGA) e Pir?lise acoplada ? Cromatografia Gasosa/Espectrometria de Massas (Pyrolysis-GC/MS), foram empregadas no intuito de avaliar os materiais sintetizados. Alcan?ados os objetivos propostos, disponibilizou-se um conjunto de novas metodologias para s?ntese de catalisadores zeol?ticos e h?bridos micromesoporosos, estes adequados para pir?lise catal?tica de ?leos pesados visando ? produ??o de derivados leves
38

S?ntese e caracteriza??o de materiais nanoporosos para pir?lise catal?tica de ?leos pesados

Costa, Maria Jos? Fonseca 22 December 2008 (has links)
Made available in DSpace on 2014-12-17T15:41:45Z (GMT). No. of bitstreams: 1 MariaJFCpdf.pdf: 4931245 bytes, checksum: 45a7ea893d17f478c73adf56787579aa (MD5) Previous issue date: 2008-12-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work reports the study of nanoporous structures, aiming at their use in research directed to the current demand of the petroleum industry to value heavy oil. Initially, two ways were chosen for the synthesis of porous structures from the molecular sieves of type Si-MCM-41. In the first way, the structure MCM-41 is precursory for heteroatom substitutes of silicon, generating catalyst of the type Al-MCM-41 from two different methods of incorporation of the metal. This variation of the incorporation method of Aluminum in the structure of Si-MCM-41 was carried out through the conventional procedure, where the aluminum source was incorporated to the gel of synthesis, and the procedure post-synthesis, where the Aluminum source was incorporated in catalyst after the synthesis of Si-MCM-41. In the second way, the MCM-41 acts as a support for growth of nanocrystals of zeolite embedded in their mesoporous, resulting in hybrid MCM-41/ZSM-5 catalyst. A comparative analysis was carried through characterizations by XRD, FTIR, measures of acidity through n-butylamine adsorption for TGA, SEM-XRF and N2 adsorption. Also crystalline aluminosilicate with zeolitic structure MFI of type ZSM-5 was synthesized without using organic templates. Methodologies to the preparation of these materials are related by literature using conventionally reactants that supply oxides of necessary silicon and aluminum, as well as a template agent, and in some cases co-template. The search for new routes of preparation for the ZSM-5 aimed at, above all, the optimization of the same as for the time and the temperature of synthesis, and mainly the elimination of the use of organic templates, that are material of high cost and generally very toxic. The current study is based on the use of the H2O and Na+ cations playing the role of structural template and charge compensation in the structure. Characterizations by XRD, FTIR, SEM-XRF and N2 adsorption were also conducted for this material in order to compare the samples of ZSM-5 synthesized in the absence of template and those used industrially and synthesized using structuring / O presente trabalho relata o estudo de estruturas nanoporosas, visando o uso em pesquisas que atendam a atual demanda da ind?stria do petr?leo, de valorizar ?leos pesados. Inicialmente, optou-se por duas vertentes para a s?ntese de estruturas porosas a partir da peneira molecular do tipo Si-MCM-41. Na primeira vertente, a estrutura MCM-41 ? precursora para hetero?tomos substituintes do sil?cio, gerando catalisadores do tipo Al-MCM-41 a partir de dois diferentes m?todos de incorpora??o do metal. Essa varia??o do m?todo de incorpora??o do Alum?nio na estrutura do Si-MCM-41 se deu atrav?s do procedimento convencional, no qual a fonte de alum?nio foi incorporada ao gel de s?ntese e do procedimento p?s-s?ntese, no qual a fonte de Alum?nio foi incorporada ao catalisador ap?s a s?ntese do Si-MCM-41. Na segunda vertente, o MCM-41 age como suporte para o crescimento de nanocristais de ze?lita embutidos nos seus mesoporos, resultando no catalisador h?brido MCM-41/ZSM-5. Uma an?lise comparativa foi realizada atrav?s de caracteriza??es por XRD, FTIR, medidas de acidez atrav?s de dessor??o de n-butilamina por TGA, SEM-XRF e Adsor??o de N2. Tamb?m foi sintetizado um aluminossilicato cristalino com estrutura zeol?tica MFI do tipo ZSM-5, na aus?ncia total de direcionador org?nico. Metodologias relacionadas ? prepara??o desses materiais s?o relatadas pela literatura utilizando-se convencionalmente reagentes que forne?am os ?xidos de sil?cio e de alum?nio necess?rios, bem como um agente direcionador, e em alguns casos at? co-direcionadores. A busca por novas rotas de prepara??o para a ZSM-5 visou, sobretudo, a otimiza??o da mesma no que se refere ao tempo e ? temperatura de s?ntese, e principalmente a elimina??o do uso dos direcionadores org?nicos, que s?o materiais de alto custo e geralmente muito t?xicos. O atual estudo se baseia na utiliza??o da H2O e dos c?tions Na+ desempenhando o papel de direcionamento estrutural e compensa??o de cargas na estrutura. Caracteriza??es por XRD, FTIR, SEM-XRF e Adsor??o de N2 tamb?m foram realizadas para esse material, a fim de comparar as amostras de ZSM-5 sintetizadas na aus?ncia do direcionador e aquelas utilizadas industrialmente e sintetizadas utilizando estruturantes

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