[pt] Catalisadores de ferro suportados em sílica alumina e em sílica mesoporosa, além de nano partículas de ferro não suportadas, foram estudados. A preparação dos catalisadores suportados ocorreu pelo método de impregnação do ponto úmido incipiente com soluções aquosas de cloreto de ferro, para obter 2 por cento ou 5 por cento de metal, sendo um desses preparado pelo método da ureia, onde uma quantidade apropriada de uma solução aquosa de FeCl3·6H2O (99 por cento -Merck) foi misturada com ureia. As amostras foram caracterizadas por medidas de fisissorção de N2, difração de Raios-X (DRX), redução com temperatura programada (RTP) e microscopia eletrônica de transmissão (TEM). A quantidade de metal foi determinada usando espectroscopia de absorção atômica (EAA). Os suportes de sílica alumina e de sílica mesoporosa foram caracterizados ainda por análise termogravimétrica (ATG/DTG). As propriedades texturais mostraram que após a introdução do metal nos suportes, a área específica, o volume de poros e o diâmetro de poro decresceram conforme o teor metálico foi aumentado. As análises de DRX com refinamento de Rietveld detectaram a formação das fases de FeO, Fe3O4, Fe0, para todas as amostras suportadas. Os perfis de redução (RTP) para as amostras de ferro suportadas mostraram, principalmente, duas regiões de redução, a primeira atribuída a redução de Fe2O3 para FeO e a segunda a redução de FeO para Fe0. / [en] Iron catalysts supported on silica alumina and mesoporous material, beside non supported iron nanoparticles, were studied. The preparation of supported catalysts occurred by incipient wetness impregnation method with aqueous solutions of iron chloride to give 2 percent or 5 percent of metal. One iron catalyst supported on silica alumina was prepared by the method of urea, in which an appropriate amount of an aqueous solution of FeCl3·6H2O (99 percent - Merck) was mixed with urea for impregnation. The samples were characterized by measurements of N2 physisorption, X-ray diffraction (XRD), temperature programmed reduction with (TPR), transmission electron microscopy (TEM). The amount of metal embedded in each sample was determined using atomic absorption spectroscopy (AAS). The silica alumina and mesoporous silica supports were also characterized by thermogravimetric analysis (DTA/TGA). The textural properties showed that after introduction of the metal into the supports, the specific area, pore volume and pore diameter decreased as the metal content was increased. XRD analysis with Rietveld refinement showed the formation of phases the following phases FeO, Fe3O4, Fe0, for all supported samples. Reduction profiles (TPR) for the supported iron samples showed mainly two reduction regions, assigned for Fe2O3 to FeO and for FeO to Fe0, respectively.

[pt] Os catalisadores de platina, níquel e platina suportados em sílica-alumina e sílica mesoporosa (SBA-15) foram investigados para o hidrotratamento do óleo de coco para produção de bio-óleo. Os suportes foram carregados com 1 por cento de Pt e 5 por cento de Ni e os catalisadores resultantes foram caracterizados para determinar suas propriedades estruturais e de textura. Os catalisadores foram reduzidos e testados em um reator semi-descontínuo a 360 C sob 10 MPa de hidrogênio durante 4 horas. Foram obtidos 30-40 por cento de remoção de oxigênio. As curvas de destilação dos produtos e seu ponto de inflamação e gravidade específica (a 20 C) foram determinados pelos métodos oficiais ASTM e ABNT/NBR a serem comparados com o diesel derivado do petróleo. As curvas de destilação e as propriedades físico-químicas foram muito próximas das especificações estabelecidas pela legislação brasileira para o diesel comercial. Destilou-se 90 por cento do volume de cada produto na faixa de temperatura de 180-370 C, o ponto de inflamação ficou entre 76-81 e o número do índice de cetano foi calculado como 47-48, de acordo com as especificações do diesel comercial. Os produtos obtidos com os catalisadores Pt/SiO2Al2O3 e PtNi/SBA-15 também apresentaram gravidade específica dentro da faixa de especificação (865 e 860,0 kg/m3, respectivamente). Os catalisadores utilizados mostraram sua potencial aplicação para a produção de biocombustíveis na faixa de diesel de petróleo pelo processo de hidrotratamento de óleo de coco. / [en] Platinum, platinum nickel and nickel catalysts supported on silicaalumina and mesoporous silica (SBA-15) were investigated for hydrotreating of coconut oil to produce bio oil. The supports were loaded with 1 percent Pt and 5 percent Ni content and the resulted catalysts were caracterized to determine their strutural and textural properties. The catalysts were reduced and tested in a semi-batch reactor at 360 C under 10 MPa of hydrogen during 4 hours. It was obtainned 30-40 percent of oxygen removal. The distillation curves of products and their flash point and specific gravity (at 20 C) were determined by oficials ASTM, and ABNT/NBR methods to be compared with the petroleum-derived diesel. The distillation curves and physicochemical properties were very close to specifications stabilished by Brazilian legislation for comercial diesel. 90 percent of the volume of each product was distilled in the temperature range of 180-370 C, the flash point was between 76-81 and the cetane index number was calculated as 47-48 in agreement with the specifications for comercial diesel. The products obtainned using the Pt/SiO2Al2O3 and PtNi/SBA-15 catalysts also presented specific gravity within the specification range (865 e 860.0 kg/m3 respectively). The catalysts used showed their potential application for the production of biofuels in the petroleum diesel range by coconut oil hydrotreatment process.

[pt] A reação de síntese de Fischer-Tropsch tem despertado interesse pelo seu caráter tecnológico e científico uma vez que este processo é capaz de converter o gás natural em produtos de elevado valor agregado. No presente trabalho, catalisadores de ferro suportados em sílica alumina ou em SBA-15 foram sintetizados, caracterizados, ativados e empregados na síntese de Fischer Tropsch. Os catalisadores foram preparados via impregnação incipiente do ponto úmido utilizando cloreto de ferro III, obtendo-se catalisadores de porcentagem mássica próximos a 5%, 10% e, no caso da sílica alumina, 2% também. As amostras foram caracterizadas por análise termogravimétrica (ATG), por medidas de adsorção física de N2, difração de raios-X (DRX) e redução à temperatura programada (RTP). O teor de ferro foi determinado pela espectroscopia de raios X por dispersão de energia (EDX). A ativação dos catalisadores e, em seguida, os testes catalíticos foram conduzidos em um reator tubular de bancada e os produtos gasosos foram analisados através de cromatografia gasosa com detector por ionização de chama (CG-DIC), cuja análise mostrou a formação de hidrocarbonetos C1-C5. A adsorção física de N2 revelou que, a introdução de ferro nos suportes, diminuiu a área superficial específica e o volume de poro dos materiais. A difração de raios X foi realizada para os catalisadores após a calcinação, mostrando a presença das fases α-Fe2O3 e Fe3O4; após a ativação e após a reação, onde se encontrou Fe0 e carbetos de ferro Fe5C2 e Fe2C. Os testes catalíticos mostraram maior seletividade aos hidrocarbonetos C2-3 para os catalisadores suportados em SBA-15. / [en] The Fischer-Tropsch synthesis reaction has showed interest due to its technological and scientific character since the process is able to convert natural gas into high added value products. In the present work, iron catalysts supported on SBA-15 or silica doped alumina were synthesized, characterized, activated and employed in the Fischer Tropsch synthesis. The catalysts were prepared via incipient wetness impregnation method using iron III chloride, obtaining catalysts with a weight percentage of about 5%, 10% and, in the case of silica doped alumina, 20% as well. The samples were characterized by thermogravimetric analysis (ATG), with measurements of N2 physisorption, X-ray diffraction (DRX) and temperature programmed reduction (RTP). Iron content was determined by energy dispersive X-ray spectroscopy (EDX). The catalysts activation and, subsequently, their catalytic tests were conducted in a bench tubular reactor and the products were analyzed by gas chromatography with flame ionization detector (CG-DIC), where it was detected the formation of C1-C4 hydrocarbons. The N2 physisorption showed that the introduction iron in the supports decreased the specific surface area and the pore volume of the materials. X-ray diffraction was performed for catalysts after calcination, showing the presence of α-Fe2O3 and Fe3O4 phases, after activation and after reaction, where it was found crystals of Fe0 and iron carbides Fe5C2 and Fe2C. The catalytic tests showed greater C2-3 selectivity for SBA-15 supported catalysts.

Master of Science / Department of Chemistry / Kenneth J. Klabunde / Although Degussia-Huls P-25 TiO[subscript]2 semiconductor photocatalyst has high photodegradation rate for organic molecules, it works only under ultra-violet (UV) light. Mesoporous metal doped V-MCM-48 silica was synthesized under ambient conditions for use as a visible-light photocatalyst to convert toxic probe molecules to innocuous products: CO[subscript]2 + H[subscript]2O. The synthesis employed a modified Stober metal doped MCM-48 silica method. Powder X-ray diffraction (XRD), diffuse-reflectance-ultra-violet-visible (DR-UV-vis) spectroscopy, and N[subscript]2 adsorption-desorpton analysis characterization methods were completed on V-MCM-48 mesoporous material. These characterization methods indicate V-MCM-48 structure had formed with visible light absorption and mesoporous properties. Photocatalysis studies were completed with V-MCM-48 under dark, visible, and UV-light illumination conditions for the following probe molecules: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, and acetonitrile. Acetaldehyde over V-MCM-48 was converted to CO[subscript]2 under dark, visible, and UV-light conditions. Carbon monoxide photooxidation occurred over V-MCM-48 under visible and UV-light. Ethanol and acetonitrile had smaller photodegradation activity over V-MCM-48. Acetone and 2-propanol had no activity photocatalytically. Under dark and visible light illumination, V-MCM-48 consumed approximately one-half acetaldehyde and produced one-third CO[subscript]2 concentration as compared with the P-25 TiO[subscript]2 under UV-light. V-MCM-48 produced two-thirds of the amount of CO[subscript]2 in comparison to nanoparticle Au/ZnO catalyst under UV-light. The results infer V-MCM-48 might be useful in gas and liquid phase photocatalysis including water-splitting due to a high oxidation state (V[superscript]5+), visible light absorption, and high surface area. In conclusion, an extended literature review has been completed and literature employed extensively throughout the thesis with potential methods to further the research on V-MCM-48/Si-MCM-48 in catalysis, chromatography, adsorption/gas separation, and solar collection/water-splitting.

De nos jours, la modification de surface fait l'objet d'attentions particulières en raison de sa variété d'applications dans divers domaines. Dans ce contexte, l'objectif de cette thèse a été de traiter de la modification localisée de surfaces dans des conditions douces en utilisant le microscope électrochimique à balayage (SECM). En tant que preuve de concept pour l'écriture directe, différentes stratégies ont été menées pour la modification de surface par gravure de matériaux, greffage de couche organique et modification de la structure chimique surfacique. Des surfaces de verre et d'or ont été les principaux substrats qui ont été modifiés du fait de leur large utilisation notamment dans les nanotechnologies. Cette thèse est présentée sous forme de quatre chapitres et le premier est consacré à la technique SECM ainsi qu'à la modification de surface en général. Les trois autres parties concernent le travail effectué pour valider le concept d'écriture directe. Dans la première partie, une matrice de silice synthétisée par voie sol-gel et dopée avec un ion métallique (cuivre ou or) est utilisée comme matériau d'écriture à l'aide d'une sonde locale (ultramicroéléctrode). Le SECM est utilisé en mode de rétroaction avec des médiateurs tels que viologène de méthyle et le p-benzoquinone. Le diamètre de l'ultramicroélectrode (UME) et la durée d'hydrolyse ont été des facteurs pris en compte pour étudier l'effet sur la taille des plots métalliques électrogénérés. Dans la deuxième partie, la gravure par voie humide localisée de la surface de l'or a été réalisée en utilisant le SECM opérant dans un électrolyte à base de diméthylsulfoxide chargé avec de l'iode. Dans cette méthode, une UME est positionnée (à une distance connue) à proximité de la surface d'or pour générer électrochimiquement l'ion triiodure à la pointe de l'UME de platine, agissant comme oxydant à la surface d'or. La troisième partie comprend deux travaux expérimentaux différents mais complémentaires. Le premier porte sur la réduction électrochimique sur électrode d'or d'un sel de diazonium préparé à partir de l'éthylènediamine, une molécule aliphatique. Pour la première fois, la fonctionnalisation covalente sur or d'un sel de diazonium est démontrée via la diazotation d'un groupe amino de l'éthylènediamine. Dans la seconde partie, un substrat de verre a été greffé par un film à base de 3-aminopropyle silane qui a été réalisée par un procédé sol-gel. Ensuite, la lame de verre modifiée a été fonctionnalisée avec du glutaraldéhyde pour greffer la tyrosinase. Enfin, le mode de réaction du SECM a également été utilisé pour vérifier l’activité catalytique de cette enzyme. La pointe de l’UME est positionnée à proximité de la surface modifiée par l’enzyme afin de réaliser une mesure de courant de l’activité enzymatique à partir d’un balayage horizontal dans le plan x-y. / Nowadays, the modification of surfaces has drawn more attention due to its variety of applications in various domains. Therefore, the purpose of this thesis deals with the localized modification of surfaces in mild condition by using the scanning electrochemical microscope (SECM) instrument. As a proof of concept for direct writing, different strategies have been used for surface modifications through removing surface materials, grafted organic layer and changing the chemical structure of the surface. Gold wafer and glass surfaces were the main substrates which have been modified since these materials are very used especially in nanotechnologies. This dissertation is conducted in four chapters and the first one focuses on SECM technique and surface modifications in general. The three other parts concern the work performed to validate the concept of direct writing. In the first part, metal ion (copper and gold)-doped silica matrices have been prepared by the well-known sol-gel method. Copper and gold metallic particles are produced locally by using the SECM in feedback mode with mediators such as methyl viologen and p-benzoquinone. The diameter of ultramicroelectrode (UME) tip and hydrolysis period were factors taken into account to study the effect on the size of electrogenerated metallic spots. In the second part, the localized wet etching of gold surface has been achieved by using SECM where a dimethylsulfoxide-based electrolyte charged with iodine is used. In this method an UME probe is positioned (at a known distance) close to the gold surface. Friendly environment method was used as etching process to generate electrochemically triiodide ion at the platinum UME tip, acting as an oxidant for gold surface. he third part includes two different experimental works. The first one covers the electrochemical reduction on gold electrode of diazonium salt prepared from ethylenediamine, an aliphatic diamine molecule. For the first time, the covalent functionalization on gold of a diazonium salt is demonstrated, and required diazotization of one amine group from ethylenediamine. In the second work, glass substrate was grafted by 3-aminopropyl silane film which was performed by sol-gel method. Then the modified-glass slide was functionalized by glutaraldehyde solution in order to immobilize tyrosinase molecules. Finally, the feedback mode of SECM has also been used to monitor the catalytic activity of tyrosinase. The tip of ultramicroelectrode was positioned close to the enzyme-modified surface and was scanned horizontally in x-y plane while measuring current from re-generated mediator molecules was carried out.

La conception de solides à la fois stables en conditions hydrothermales, mais aussi capables de convertir des composés biosourcés en molécules plateformes dans un même lit catalytique, représente un défi majeur en science des matériaux.Dans ce contexte, des oxydes mixtes binaires et ternaires de silice dopée avec les éléments W, Ti, Zr, Nb, Ta et Mg (3 à 20%at.) ont été élaborés via la méthode non conventionnelle de synthèse Sol-Gel Non Hydrolytique (SGNH). Cette méthode permet d’obtenir des oxydes mixtes très homogènes et de moduler finement leurs propriétés via les paramètres de synthèse.Les solides sont majoritairement amorphes et mésoporeux. Les analyses en MET-EDS, FTIR et ToF-SIMS indiquent que les éléments dopants sont bien dispersés dans la silice et que les oxydes mixtes présentent majoritairement une homogénéité allant jusqu’à l’échelle nanométrique voire atomique.Les molécules sondes NH3 et CO révèlent la présence des sites acides de forces faible et moyenne, majoritairement de type Lewis pour l’ensemble des matériaux. La densité de sites acides peut être promue via : l’amélioration du degré d’homogénéité entre les oxydes, l’élaboration d’oxydes mixtes ternaires et l’augmentation de la teneur en éléments dopants.La caractérisation des solides par la réaction modèle de conversion du mélange cyclopentanol/cyclohexanone en phase gaz montre que la majorité des matériaux catalysent à la fois des réactions de déshydratation et de transfert d’hydrogène (réduction MPVO).Après traitement hydrothermal en phase gaz à 400°C, les solides conservent de bonnes textures, en particulier les oxydes mixtes ternaires et dopés à haute teneur.Cette étude montre la versatilité de la méthode de synthèse SGNH et son potentiel pour mettre au point des oxydes mixtes binaires et ternaires très homogènes. Les oxydes mixtes ternaires, contenant 20% d’éléments dopants et contenant du Nb, du Zr ou du Ta sont particulièrement prometteurs pour les applications visées. / The design of new heterogeneous catalysts with good hydrothermal stability that are able to transform bio-based components into building blocks in one single catalytic process is a main challenge in material science.In this context, binary and ternary mixed oxides of silica doped with W, Ti, Zr, Nb, Ta et Mg (3 to 20%at.) have been produced with the non-conventional Non-Hydrolytic Sol-Gel (NHSG) synthesis method. This method enables to obtain highly homogeneous mixed oxides and to finely shape the properties of the material with the synthesis parameters.The solids are mostly amorphous and mesoporous. TEM-EDS, FTIR and ToF-SIMS analysis indicate that the doping elements are highly dispersed in the silica and that most of the mixed oxides display nanometric or atomic scale homogeneity.The NH3 and CO bases show the presence of mostly Lewis weak and medium strength acid sites for these materials. The acid sites density can be improved through: increasing mixed oxide homogeneity, preparing ternary mixed oxides, increasing doping element content.The conversion of the mixture cyclopentanol/cyclohexanone in the gas phase shows that the majority of the materials perform both dehydration and hydrogen transfer reactions (MPVO reduction).After steaming at 400°C, the solids maintain good textures, particularly ternary mixed oxides and mixed oxides containing high dopant content.This study shows the versatility of the NHSG synthesis method and its applicability in order to design binary and ternary mixed oxides. The ternary mixed oxides containing 20%at. of doping elements with Nb, Zr and Ta are promising for the conversion of bio-based compounds.