O gás carbônico é a fonte primária de carbono ideal para se obter novos compostos, devido principalmente à sua abundância, atoxidade e ao fato de ser renovável. Desta forma, novos métodos de introduzir o CO2 em rotas sintéticas se fazem necessários. Dentre os possíveis métodos, nesta tese foram estudadas duas rotas diferentes de utilização do gás carbônico: uma, empregando complexos bimetálicos como catalisadores da inserção do CO2 em alcenos e alcanos e outra utilizando enzimas imobilizadas em partículas magnéticas, atuantes no ciclo de redução do CO2 ao metanol. Os complexos bimetálicos foram construídos a partir do ligante de ponte, bispirrolidyl- fenil (BPP) incorporando grupos difenilmetanol e difenilfosfino em suas arquiteturas moleculares. Sua inspiração partiu de sistemas biomiméticos para a redução do CO2, e foi direcionada para a carboxilação de hidrocarbonetos. Nas reações de acoplamento carbono-carbono, observou-se que com o iodeto de metila, os complexos foram capazes de transformar o gás carbônico e produzir acetato de metila. Já nas reações com 1-deceno, isobutano e iso-octano, apenas três complexos se mostraram eficientes: BPP(ONi,ONi), BPP(OZn,OPPh2Pd) e BPP(OPPh2Pd,OPPh2Pd). Na rota enzimática, fez-se uso de enzimas imobilizadas do tipo desidrogenase e três tipos de nanopartículas magnéticas (MagNP) como suporte (MagNP-APTS, MagNP@SiO2-APTS e MagNP-APTS/Glioxil-Agarose, APTS = aminopropiltrimetoxissilano). Observou-se que para a imobilização da álcool desidrogenase e da formaldeído desidrogenase, o melhor suporte foi a MagNP@SiO2- APTS, enquanto para a formato desidrogenase, o melhor suporte de imobilização foi a MagNP-APTS. Para a glutamato desidrogenase, um sistema com imobilização via múltiplos pontos, como na MagNP-APTS/Glioxil-Agarose, conduziu a um melhor desempenho, . Os melhores sistemas enzima-suporte foram utilizados em uma reação multi-enzimática com CO2, NADH e glutamato para a obtenção de formaldeído e metanol. Os dois métodos de redução do gás carbônico se mostraram capazes de realizar o objetivo da tese, que é a transformação do CO2 em produtos de maior valor agregado / CO2 is a primary world carbon source readily available for the production of new compounds, under sustainable conditions due to its great abundance and non-toxic, renewable characteristics. Hence, there is a compulsive interest to develop new methodologies capable of introducing carbon dioxide in the chemical synthetic routes. Among the many possible alternatives, two different strategies were pursued this thesis: one using bimetallic complexes as catalysts, and the other one using enzymes supported on superparamagnetic nanoparticles. The bimetallic complexes were based on the bridging bis-pyrrolidyl-phenol (BPP) architecture encompassing diphenylmethanol and diphenylphosphino groups. They were inspired in biomimetic systems for the chemical reduction of CO2 and employed in the carboxylation of hydrocarbons. In such carbon-carbon coupling reactions, the bimetallic complexes were able to catalyse the reaction between CO2 and methyl iodide in order to obtain methyl acetate. However, in the reaction with 1- decene, isobutene and iso-octane, only three of them were efficient: BPP(ONi,ONi), BPP(OZn,OPPh2Pd) and BPP(OPPh2Pd,OPPh2Pd). In the studies focusing on immobilized enzymes, dehydrogenase-like enzymes and three different kind of magnetic particles (MagNP) were employed (MagNP-APTS, MagNP@SiO2-APTS and MagNP-APTS/Glioxyl-Agarose, APTS = aminopropyltrimethoxisylane). The best immobilization support for alcohol dehydrogenase and formaldehyde dehydrogenase was MagNP@SiO2-APTS, while for formate dehydrogenase the best immobilization support was MagNP-APTS. For glutamate dehydrogenase a multi-point immobilization was required, turning MagNPAPTS/ Glioxyl-Agarose the best catalytic support. These enzyme-support systems were used in a multi-enzymatic reaction using CO2, NADH and glutamate in order to obtain methanol and formaldehyde. Both CO2 redution methods were successful explored, and the results fulfilled the major objective of this thesis, which is the conversion of CO2 into higher value products.

O gás carbônico é a fonte primária de carbono ideal para se obter novos compostos, devido principalmente à sua abundância, atoxidade e ao fato de ser renovável. Desta forma, novos métodos de introduzir o CO2 em rotas sintéticas se fazem necessários. Dentre os possíveis métodos, nesta tese foram estudadas duas rotas diferentes de utilização do gás carbônico: uma, empregando complexos bimetálicos como catalisadores da inserção do CO2 em alcenos e alcanos e outra utilizando enzimas imobilizadas em partículas magnéticas, atuantes no ciclo de redução do CO2 ao metanol. Os complexos bimetálicos foram construídos a partir do ligante de ponte, bispirrolidyl- fenil (BPP) incorporando grupos difenilmetanol e difenilfosfino em suas arquiteturas moleculares. Sua inspiração partiu de sistemas biomiméticos para a redução do CO2, e foi direcionada para a carboxilação de hidrocarbonetos. Nas reações de acoplamento carbono-carbono, observou-se que com o iodeto de metila, os complexos foram capazes de transformar o gás carbônico e produzir acetato de metila. Já nas reações com 1-deceno, isobutano e iso-octano, apenas três complexos se mostraram eficientes: BPP(ONi,ONi), BPP(OZn,OPPh2Pd) e BPP(OPPh2Pd,OPPh2Pd). Na rota enzimática, fez-se uso de enzimas imobilizadas do tipo desidrogenase e três tipos de nanopartículas magnéticas (MagNP) como suporte (MagNP-APTS, MagNP@SiO2-APTS e MagNP-APTS/Glioxil-Agarose, APTS = aminopropiltrimetoxissilano). Observou-se que para a imobilização da álcool desidrogenase e da formaldeído desidrogenase, o melhor suporte foi a MagNP@SiO2- APTS, enquanto para a formato desidrogenase, o melhor suporte de imobilização foi a MagNP-APTS. Para a glutamato desidrogenase, um sistema com imobilização via múltiplos pontos, como na MagNP-APTS/Glioxil-Agarose, conduziu a um melhor desempenho, . Os melhores sistemas enzima-suporte foram utilizados em uma reação multi-enzimática com CO2, NADH e glutamato para a obtenção de formaldeído e metanol. Os dois métodos de redução do gás carbônico se mostraram capazes de realizar o objetivo da tese, que é a transformação do CO2 em produtos de maior valor agregado / CO2 is a primary world carbon source readily available for the production of new compounds, under sustainable conditions due to its great abundance and non-toxic, renewable characteristics. Hence, there is a compulsive interest to develop new methodologies capable of introducing carbon dioxide in the chemical synthetic routes. Among the many possible alternatives, two different strategies were pursued this thesis: one using bimetallic complexes as catalysts, and the other one using enzymes supported on superparamagnetic nanoparticles. The bimetallic complexes were based on the bridging bis-pyrrolidyl-phenol (BPP) architecture encompassing diphenylmethanol and diphenylphosphino groups. They were inspired in biomimetic systems for the chemical reduction of CO2 and employed in the carboxylation of hydrocarbons. In such carbon-carbon coupling reactions, the bimetallic complexes were able to catalyse the reaction between CO2 and methyl iodide in order to obtain methyl acetate. However, in the reaction with 1- decene, isobutene and iso-octane, only three of them were efficient: BPP(ONi,ONi), BPP(OZn,OPPh2Pd) and BPP(OPPh2Pd,OPPh2Pd). In the studies focusing on immobilized enzymes, dehydrogenase-like enzymes and three different kind of magnetic particles (MagNP) were employed (MagNP-APTS, MagNP@SiO2-APTS and MagNP-APTS/Glioxyl-Agarose, APTS = aminopropyltrimethoxisylane). The best immobilization support for alcohol dehydrogenase and formaldehyde dehydrogenase was MagNP@SiO2-APTS, while for formate dehydrogenase the best immobilization support was MagNP-APTS. For glutamate dehydrogenase a multi-point immobilization was required, turning MagNPAPTS/ Glioxyl-Agarose the best catalytic support. These enzyme-support systems were used in a multi-enzymatic reaction using CO2, NADH and glutamate in order to obtain methanol and formaldehyde. Both CO2 redution methods were successful explored, and the results fulfilled the major objective of this thesis, which is the conversion of CO2 into higher value products.

Les nanoparticules bimétalliques supportées sont des catalyseurs particulièrement attractifs en raison d’une activité et d’une stabilité accrues par rapport à leurs homologues monométalliques. Dans cette thèse des solides à base d'or ont été étudiés en tant que catalyseurs de l'oxydation sélective du glucose en absence de base. Il a été mis en évidence que la variation du ratio molaire entre l’or et le second métal (Pd, Pt, or Cu) a un impact différent sur les performances catalytiques en fonction de la nature du second métal, du support et de la méthode de préparation. Les séries Au-Pd supportés sur TiO2 et préparés par la méthode de sol-immobilisation et Au-Cu supportés sur TiO2 et préparés par la méthode de précipitation-réduction ont montré un effet synergique important, en particulier lorsque le rapport entre les deux métaux était de 1. Ces catalyseurs convertissent sélectivement le glucose en acide gluconique et leur activité a été trouvée supérieure à celle des contreparties monométalliques. L'analyse XPS a démontré que les espèces Au+δ, Pd+2 et CuOH jouent alors un rôle important dans la réaction étudiée en absence de base. Le bismuth en tant que second métal n'a montré aucun effet bénéfique, au contraire du palladium et du cuivre. Les catalyseurs à base d’Au et de Pt supportés sur ZrO2 se sont avérés quant à eux très stables lorsque la teneur en or était inférieure à 0,3% en masse. La nature du support a un impact très important sur le mécanisme de la réaction conduite en absence base sur des catalyseurs à base d’or. La raison réside dans les interactions que ce support développe avec la phase bimétallique favorisant ainsi la formation des espèces actives / The supported bimetallic nanoparticles are particularly attractive catalysts due to the increased activity and stability over their monometallic counterparts. In this thesis, gold-based solids have been studied as catalysts for the selective base-free oxidation of glucose. It has been demonstrated that the variation of the molar ratio between gold and the second metal (Pd, Pt, or Cu) has a different impact on the catalytic performances depending on the nature of the second metal, the support and the method of preparation. TiO2 supported Au-Pd series prepared by the sol-immobilization method and Au-Cu series prepared by the precipitation-reduction method showed a significant synergistic effect, particularly when the ratio of the two metals was 1. Under the reaction conditions used (T = 60 °C or 80 °C, P = 5 bar air, t = 5 h), these catalysts selectivity to gluconic acid and their activity was found to be greater than that of monometallic counterparts, especially when the catalyst is supported on TiO2. XPS analysis showed that the Au+δ, Pd+2 and CuOH species played an important role in the base-free reaction. Bismuth as the second metal showed no beneficial effect, unlike palladium and copper. The Au-Pt catalysts supported on ZrO2 proved to be still active when the gold content was less than 0.3 wt.%. Ultimately, the nature of the support has a very important impact on the mechanism of the base-free reaction conducted on gold-based catalysts (formation of H2O2 in situ). The reason lies in the interactions of the support with the bimetallic phase thus favoring the formation of the active species

A oxidação seletiva de alcoóis é importante para a síntese de intermediários e produtos químicos utilizados na fabricação de inúmeros materiais. O interesse em novos métodos catalíticos para a oxidação de moléculas orgânicas tem aumentado juntamente com a busca por processos ecossustentáveis. Neste trabalho foram estudadas diferentes estratégias de deposição de nanopartículas bimetálicas de ouro e paládio sobre um suporte magnético, constituído por nanopartículas de magnetita revestidas por sílica. Dois métodos de síntese de nanopartículas bimetálicas de ouro e paládio foram estudados: (I) a síntese de nanopartículas bimetálicas formadas por ligas de ouro e paládio, seguida pela deposição dessas nanopartículas pré-formadas sobre o suporte catalítico e (II) a síntese de nanopartículas bimetálicas do tipo core-shell, por meio da redução sucessiva de ouro e paládio sobre o suporte catalítico. A morfologia dos catalisadores foi determinada por diferentes técnicas de microscopia eletrônica. O desempenho catalítico das nanopartículas bimetálicas foi estudado na reação modelo de oxidação de álcool benzílico com oxigênio. Os catalisadores mostraram-se ativos e seletivos para benzaldeído sem a necessidade do uso de solvente ou base e, após separação magnética, foram usados em sucessivas reações com desempenho satisfatório / The selective oxidation of alcohols is important for the synthesis of intermediates and chemical products used for the production of many materials. The interest in new catalytic methods for the oxidation of organic molecules has increased along with the search for eco-sustainable processes. In this thesis we studied different deposition strategies of gold and palladium bimetallic nanoparticles on a magnetic support, comprised by silica coated magnetite nanoparticles. Two synthetic methods for the preparation of supported gold and palladium bimetallic nanoparticles were investigated: (I) the synthesis of gold and palladium bimetallic nanoparticles, followed by deposition of the preformed nanoparticles on the catalytic support and (II) the synthesis of core-shell bimetallic nanoparticles, through the sequential reduction of gold and palladium on the catalytic support. The catalysts\' morphology was investigated by electronic microscopy techniques. The catalytic behavior of the bimetallic nanoparticles was investigated in the model reaction of the oxidation of benzyl alcohol with oxygen. The catalysts were active and selective for benzaldehyde without the use of solvent and base and, after magnetic separation, were able to be reused in successive runs and showed a good performance.

L’émergence de nouveaux matériaux structurés à l’échelle nanométrique, aux propriétés contrôlées, a ouvert de nouvelles perspectives vis-à-vis des matériaux qui nous entourent. C’est notamment le cas des métaux et de leurs alliages et il est crucial d’établir le lien entre leurs propriétés structurales et leurs propriétés chimique et physique pour en permettre une utilisation optimale. Cette thèse s’inscrit dans ce contexte et porte sur la synthèse et la caractérisation en microscopie électronique en transmission de nanoparticules d’alliage bimétallique Au-Cu. En s’appuyant sur le diagramme de phase décrit à l’échelle macroscopique, nous nous sommes particulièrement intéressés aux nanoparticules de compositions nominales Au3Cu, AuCu et AuCu3. Le premier axe de ce travail consiste en l’élaboration de nanoparticules d’alliage Au-Cu. Deux voies de synthèse sont explorées : la voie chimique reposant sur le procédé polyol et la voie physique par ablation par laser pulsé. Le premier mode d’élaboration permet l’obtention de nanoparticules parfaitement cubiques dont la composition est systématiquement riche en Au. Les nanoparticules produites par voie physique présentent en revanche une composition maitrisée et modifiable. D’un point de vue structural, un recuit de ces dernières particules mène à leur mise en ordre chimique et à l’observation de structures L10 et L12. Cependant, nous montrons que cette transition de phase est bloquée dans les nanostructures présentant des défauts structuraux. Enfin, l’évolution du paramètre de maille des nanoparticules synthétisées selon ces deux voies de synthèse, en fonction de leur composition, a été établie et suit exactement la loi de Vegard décrite pour le matériau massif.Dans un second temps, nous avons observé des nanoparticules obtenues par voie physique en microscopie électronique en transmission environnementale, c’est-à-dire dans des conditions proches des environnements d’utilisation habituellement appliqués en catalyse. Les expériences menées en température révèlent que le mécanisme de dissolution de nanoparticules d’Au et d’alliage Au-Cu portées à haute température se fait en deux étapes : il y a fusion des nanoparticules suivi de leur évaporation pour des tailles de nanoparticules centrées autour de 10 nm. Les expériences réalisées en couplant le chauffage des nanoparticules au passage d’un gaz (H2 ou O2), en flux et dans des conditions de pression bien supérieures à celles accessibles jusqu’à maintenant, ont permis d’étudier leur comportement thermodynamique en condition oxydantes et réductrices. Nous avons notamment montré que des cycles d’oxydo-réduction de nanoparticules de taille moyenne supérieure à 20 nm conduisent à un effet Kirkendall menant, de manière réversible, à la formation de nanoparticules creuses (doughnut). Cette thèse interdisciplinaire constitue travail pionnier dans la compréhension du système d’alliage bimétallique Au-Cu à l’échelle nanoscopique / The emergence of new materials, structured at the nanoscale, with controlled properties, has opened new prospects regarding materials around us. In particular for metals and alloys, it seems crucial to connect their structural properties to their chemical and physical properties in order to optimise their use.Within this context, this thesis is focused on the synthesis and the characterisation of Au-Cu bimetallic alloy nanoparticles by transmission electron microscopy. On the basis of the bulk phase diagram, we especially studied particles with nominal compositions Au3Cu, AuCu et AuCu3.The first part of this work is dedicated to the synthesis of nanoparticles in two different ways. The chemical way is based on the polyol process and leads to nanoparticles exhibiting a cubic shape, and a systematically rich Au content. On the other hand, nanoparticles obtained by Pulsed Laser Deposition (PLD), a physical method of synthesis, display a well-controlled and tuneable composition. From a structural point of view, the annealing of the particles leads to chemical order and the stabilisation of L10 and L12 structures. However, we reveal that this phase transition is blocked in nanostructures with crystal defects. Moreover, we establish the evolution of the lattice parameter of the particles as a function of the composition and we demonstrate that, as in the bulk case, it is in agreement with Vegard’s law.In the second part, the nanoparticles synthesised via the physical method are studied using environmental transmission electron microscopy, i.e. in conditions close to those usually applied in catalytic reactors. Experiments performed at high temperature highlight that the dissolution of Au and Au-Cu nanoparticles occurs in a two-step process: fusion occurs first and is followed by evaporation for nanoparticles with a mean diameter of 10 nm.Coupling heating with gas flow (H2 or O2) in higher pressure condition than those usually reached allows us to study the thermodynamic behaviour of the nanoparticles in oxidative or reductive conditions. Most Notably, we show that oxidation-reduction cycles performed on nanoparticles with a diameter larger than 20 nm leads to a Kirkendall effect and the reversible formation of hollow particles (doughnuts).This cross-disciplinary thesis is a pioneering work towards understanding the bimetallic Au-Cu alloy system at atomic scale

On March 23 - 26, 1898, Populists, Democrats, and Silver Republicans of Oregon held their state conventions in Portland and agreed upon a common platform and a common state ticket for the elections of June 6, 1898. None of the available works on Oregon history explains that this fusion was the culmination of a two-year effort to unite the reform forces the state. This thesis tries to fill the gap. Because of the lack of secondary works on the subject, the thesis is based mainly on two sources: newspapers on microfilm, especially The Oregonian; and the unpublished correspondence of party chairman Cooper (January, 1897 - February, 1898, in the Oregon Historical Society). It will be seen that the party was at first a local party, dealing especially with economic problems, and then broadened its scope to embrace Populist principles. The first chapter deals with the national background. It briefly reviews the currency legislation since 1834 and the economic situation, especially of farmers, in the wake of the panic of 1893. The National Silver Party is discussed, because the Union Bimetallic Party of Oregon may have been intended as a state branch of this national organization. The terms "free coinage of silver" and "bimetallism" are explained, and the demand for direct legislation, arising in the early 1890's, is alluded to with special reference to Oregon. In the second chapter the origin of the Union Bimetallic Party is traced to splits over the money question within the Republican Party of Yamhill County. After the new party had scored a complete victory in the county elections, it was expanded into other counties; the first state convention was held on July 9, 1896. The presidential election of November, 1896, and the ''hold-up''-legislature of 1897 are dealt with as far as members of the Union Bimetallic Party were involved. After months of inactivity the party was revitalized in the spring of 1897 and further expanded in the following months. Emphasis is laid upon the internal debate over union or fusion, e.g., whether the old party organizations should .be dissolved or maintained. This question was decided in January, 1898, in favor of the latter solution and the Union Bimetallic Party was thus reduced to a coordinating body and practically became superfluous. The fifth chapter deals with several forces which were detrimental to the Union cause: the return of prosperity since the spring of 1897; the chronic lack of funds; the rumors about alleged secret deals with Mitchell Republicans and Pennoyer Democrats; and the resistance of Mid-road Populists. The proceedings of the state conventions of 1898 are described. As far as the campaign is concerned, only the impact of the war with Spain is alluded to. On June 6, 1898, the Union forces suffered a severe defeat; some reasons for this defeat are given.

Catalisadores de ouro tem despertado bastante interesse nos últimos anos devido à elevada seletividade apresentada na hidrogenação de moléculas multifuncionais, proporcionando assim uma síntese química mais limpa. No entanto, esses catalisadores exibem uma atividade muito menor do que os metais do grupo VIII, devido à sua capacidade limitada de dissociar H2. O paládio tem sido frequentemente combinado ao ouro para atuar em reações de hidrogenações catalíticas, devido à sua elevada capacidade de adsorver e dissociar o hidrogênio molecular, resultando em catalisadores bimetálicos AuPd que muitas vezes apresentam desempenhos catalíticos superiores aos seus homólogos monometálicos. Neste trabalho, foi estudada a ativação de nanopartículas de ouro para reações de hidrogenação pela adição de paládio, considerando a influência de ligantes estabilizantes presentes na superfície do ouro. Os catalisadores monometálicos Auw/TiO2 e Au/TiO2 foram sintetizados através da imobilização de nanopartículas pré-formadas na ausência e presença de excesso de estabilizantes (oleilamina ou hexilamina) provenientes da síntese, respectivamente. Seguindo o mesmo princípio também foram obtidos monometálicos Pd/TiO2. Catalisadores bimetálicos Auw@Pdx/TiO2 e Au@Pdx/TiO2 foram obtidos através da adição de quantidades crescentes de Pd sobre os monometálicos de ouro. Os catalisadores monometálicos apresentaram desempenhos catalíticos inferiores aos respectivos bimetálicos. Estudos iniciais na reação de hidrogenação de ciclohexeno foram fundamentais para compreender a influência da composição e do estabilizantes nas diferentes reações de hidrogenação nas quais os materiais foram aplicados. Os catalisadores livres de ligantes se mostraram ativos nesta reação, Auw@Pdx/TiO2, sendo observado um aumento da atividade à medida que a quantidade de paládio se tornava crescente, alcançando um máximo com 20% de Pd (Auw@Pd0,2/TiO2), seguida de uma diminuição da atividade com a adição de porcentagens maiores. Assim, concluiu-se que a presença de sítios de Au e Pd, além da ausência de excesso de ligantes na superfície, são significativamente importantes para tornar ativos os catalisadores Auw@Pdx/TiO2. Os catalisadores bimetálicos com ligantes na superfície, que apresentaram pior desempenho na hidrogenação de alquenos, mostraram-se promissores na semi-hidrogenação de alquinos. O catalisador contendo 1% de Pd (Au@Pd0,01/TiO2), ao ser empregado na hidrogenação de fenilacetileno, apresentou 100% de conversão e seletividades a estireno > 90%. Ao serem adicionadas porcentagens de Pd ≥ 3%, a seletividade a estireno diminui significativamente. Esta também foi alterada ao variar a quantidade de ligante (alquilamina) na superfície do catalisador bimetálico e independe do tamanho da cadeia orgânica do ligante empregado. Finalmente, podemos concluir que sistemas catalíticos altamente ativos e seletivos podem ser obtidos controlando a quantidade de paládio adicionado ao ouro, mas a presença de ligantes estabilizantes também tem influência e não pode ser negligenciada. / Over the past few years, gold catalysts have aroused great interest among researchers due to an enhanced selectivity exhibited in the hydrogenation of multifunctional molecules, enabling greener chemical synthesis. Nevertheless, since gold has a very limited ability to dissociate molecular hydrogen, these catalysts show lower activity compared to group VIII metals. Palladium has been widely used in combination with gold in catalytic hydrogenations; due to its high ability to adsorb and dissociate molecular hydrogen, the resulting bimetallic AuPd systems often show superior performance over their monometallic counterparts. The present work embodies studies on the activation of gold nanoparticles for hydrogenation reactions by adding increasing amount of palladium, considering the influence of capping ligands on the activity and selectivity exhibited by the bimetallic Au@Pd catalysts. The monometallic Auw/TiO2 and Au/TiO2 catalysts were prepared via immobilization of preformed nanoparticles in the absence and presence of excess stabilizers (oleylamine and hexylamine) used in the synthesis, respectively. Monometallic Pd/TiO2 was also synthesized following the same principle. Bimetallic catalysts Auw@Pdx/TiO2 e Au@Pdx/TiO2 were obtained by the addition of increasing amounts of Pd on the gold monometallic catalyst. The monometallic catalysts presented lower catalytic performances than the respective bimetallics. Initial studies of cyclohexene hydrogenation were instrumental to understand the influence of the composition and the presence of stabilizers in different hydrogenation reactions where the material were applied. Ligand-free catalysts were active in this reaction, Auw@Pdx/ TiO2, and an increase in activity was observed as the amount of palladium increased, reaching a maximum at 20% Pd (Auw@Pd0.2/TiO2), followed by a decrease in activity with the addition of larger percentages. Thus, it was concluded that the presence of Au and Pd sites, in addition to the absence of excess capping ligands, are significantly important in making the catalysts active. Bimetallic catalysts containing capping ligands, which presented worse performance in the hydrogenation of alkenes, showed promising results in the semi-hydrogenation of alkynes. The catalyst containing 1 wt% Pd (Au@Pd0.01/TiO2), when used in the hydrogenation of phenylacetylene, reached 100% conversion and > 90% selectivity to styrene. When percentages of Pd ≥ 3 wt% were added, the selectivity to styrene decreases significantly. Selectivity was also altered by varying the amount of ligand (alkylamine) on the surface of the bimetallic catalyst and regardless the size of the organic chain. Finally, we can conclude that highly active and selective catalytic systems can be obtained by controlling the amount of added palladium on gold, but the presence of capping ligands is also importante and can not be neglected.

Catalytic combustion is an environmentally friendlytechnique to combust fuels in e.g. gas turbines. Introducing acatalyst into the combustion chamber of a gas turbine allowscombustion outside the normal flammability limits. Hence, theadiabatic flame temperature may be lowered below the thresholdtemperature for thermal NOXformation while maintaining a stable combustion.However, several challenges are connected to the application ofcatalytic combustion in gas turbines. The first part of thisthesis reviews the use of catalytic combustion in gas turbines.The influence of the fuel has been studied and compared overdifferent catalyst materials. The material section is divided into two parts. The firstconcerns bimetallic palladium catalysts. These catalysts showeda more stable activity compared to their pure palladiumcounterparts for methane combustion. This was verified both byusing an annular reactor at ambient pressure and a pilot-scalereactor at elevated pressures and flows closely resembling theones found in a gas turbine combustor. The second part concerns high-temperature materials, whichmay be used either as active or washcoat materials. A novelgroup of materials for catalysis, i.e. garnets, has beensynthesised and tested in combustion of methane, a low-heatingvalue gas and diesel fuel. The garnets showed some interestingabilities especially for combustion of low-heating value, LHV,gas. Two other materials were also studied, i.e. spinels andhexaaluminates, both showed very promising thermal stabilityand the substituted hexaaluminates also showed a good catalyticactivity. Finally, deactivation of the catalyst materials was studied.In this part the sulphur poisoning of palladium, platinum andthe above-mentioned complex metal oxides has been studied forcombustion of a LHV gas. Platinum and surprisingly the garnetwere least deactivated. Palladium was severely affected formethane combustion while the other washcoat materials were mostaffected for carbon monoxide and hydrogen. <b>Keywords:</b>catalytic combustion, catalyst materials,palladium, platinum, bimetallic, garnet, spinel, hexaaluminate,deactivation, sulphur, poisoning, diesel, methane,hydrocarbons

Oxide thin films and bimetallic model catalysts have been studied using metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), low energy ion scattering spectroscopy (LEISS), X – ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), infrared reflection absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) under ultra high vacuum (UHV) conditions. Of particular interest in this investigation was the characterization of the surface morphology and electronic/geometric structure of the following catalysts: SiO2/Mo(112), Ag/SiO2/Mo(112), Au–Pd/Mo(110), Au–Pd/SiO2/Mo(110), and Pd– Sn/Rh(100). Specifically, different types of oxide surface defects were directly identified by MIES. The interaction of metal clusters (Ag) with defects was examined by work function measurements. On various Pd related bimetallic alloy surfaces, CO chemisorption behavior was addressed by IRAS and TPD. Observed changes in the surface chemical properties during the CO adsorption-desorption processes were explained in terms of ensemble and ligand effects. The prospects of translating this molecular-level information into fundamental understanding of ‘real world’ catalysts are discussed.

The main objective of this study was to evaluate the feasibility of using nanoscale zero-valent iron (nZVI) as the source of hydrogen to enhance in situ anaerobic biodegradation of trichloroethylene (TCE). In the first part of this study, microcosms were constructed to evaluate the effects of different controlling factors [e.g., different redox conditions (aerobic and anaerobic conditions), different microorganisms (in situ microorganisms, activated sludge, and anaerobic sludge), and different sources of substrates and electron donors (phenol, cane molasses, hydrogen, and nZVI)] on TCE biodegradation. In the second part of this study, batch experiments were conducted to evaluate the feasibility of hydrogen production by nZVI and bimetallic particles. Results from the microcosm study indicate that in-situ microorganisms were capable of degrading TCE under aerobic and anaerobic conditions. Results also show that TCE removal was more effective by activated sludge and anaerobic sludge. Aerobic biodegradation of TCE was enhanced by the addition of phenol and cane molasses. Under anaerobic conditions, TCE removal could be improved when cane molasses and hydrogen were supplied. In addition, anaerobic TCE degradation was more effective with the presence of hydrogen. Results of microcosms conducted with the addition of nZVI reveal that TCE was degraded completely in both live and autoclaved microcosms. This indicates that chemical reductive dechlorination seemed to dominate the removal of TCE in microcosms. Therefore, further studies with higher TCE concentrations or lower nZVI doses need to be conducted to determine the effects of the produced hydrogen on TCE biodegradation. Results from the hydrogen production experiments indicate that efficiency of hydrogen production by nZVI ranged from 30% to 76%. Higher dose of nZVI addition resulted in higher amount of hydrogen production. The total amounts of hydrogen production were correlated with the doses of nZVI. In addition, rates and efficiency of hydrogen production by bimetallic particles were better than those of nZVI. Results of the batch experiments reveal that nZVI and bimetallic particles had good efficiency on hydrogen production. This indicates that nZVI and bimetallic particles have high potential to be used as hydrogen producers. In this study, a simple system consisted of only water and nZVI or bimetallic particles was applied to produce hydrogen. Although TCE in microcosms with nZVI addition was totally consumed by nZVI, results of microcosms with hydrogen addition demonstrated that hydrogen was able to improve the efficiency of anaerobic TCE biodegradation. Thus, it may be feasible to use nZVI as the source of hydrogen to enhance in situ anaerobic biodegradation of TCE. The advantages of using nZVI as the source of hydrogen include: (1) rapid removal of significant contaminant concentrations in the early stage of nZVI injection; (2) creation of a more reducing environment; (3) safer than liquid hydrogen, which is stored in steel containers; and (4) direct hydrogen supply without transfer of biological mechanisms compared to commercial hydrogen release compounds and other organic substrates. Results of this study suggest that biological reductive dechlorination of TCE can be enhanced if proper doses of nZVI are supplied in situ. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site.