Submitted by Franciele Moreira (francielemoreyra@gmail.com) on 2018-08-29T13:43:45Z No. of bitstreams: 2 Dissertação - Lucas Clementino Mourão - 2018.pdf: 2137358 bytes, checksum: fb0f843e55d7839ce63dfaae63046a2b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-29T14:13:25Z (GMT) No. of bitstreams: 2 Dissertação - Lucas Clementino Mourão - 2018.pdf: 2137358 bytes, checksum: fb0f843e55d7839ce63dfaae63046a2b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-29T14:13:25Z (GMT). No. of bitstreams: 2 Dissertação - Lucas Clementino Mourão - 2018.pdf: 2137358 bytes, checksum: fb0f843e55d7839ce63dfaae63046a2b (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-07-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The great environmental concern, coupled with the risk of depletion of non-renewable raw material, has driven the search for new sustainable technologies with major concern to the reduction of pollutant emissions. Hydrogen, a chemical of enormous importance to industrial plants, stands out as a clean and renewable energy source. This chemical is commonly produced from non-renewable sources, such as natural gas reforming. Due to specific reaction conditions, the supercritical water gasification of wet biomass is a promising way for the production of hydrogen and others high added value fuel gases. Ethanol is an attractive material because it is renewable, has low toxicity compared to other resources and has high hydrogen content in its molecule. In order to become this technology viable, a decisive point is the development of a catalyst aiming at cost reductions and high selectivity to the products of interest. In this work, ethanol gasification was carried out in supercritical water with heterogeneous catalysts. The tests were performed on an Inconel Alloy 625 tubular reactor under the following operating conditions: temperatures of 400, 450, 500, 550, 600 and 650 ºC, pressure of 250 bar, 5 g loading of heterogeneous catalyst, reactor feed: ethanol/water molar ratio of 1:10 and mass flow rate of 5 g/min. The catalysts were synthesized by wet impregnation method using aqueous solutions of Cu, Co and Zn nitrates as precursors for the active phase and spherical pellets of Al 2 O 3 as catalytic support. The catalysts and the catalytic support were characterized by Thermogravimetry and Differential Thermal Analysis (TG/DTA), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), textural analysis by Adsorption/Desorption Isotherms of N 2 at 77 K and X-Ray Diffraction (XRD). The gasification results indicated that H 2 production was mainly due to ethanol dehydrogenation. The catalysts showed higher conversions than observed for catalytic support only. The CuAl catalyst showed higher H 2 selectivity as well as higher H 2 molar flow at 650 °C. The CoZnAl catalyst showed a high tendency for C 2 H 4 formation at any reaction temperature, especially at 650 °C. / A grande preocupação ambiental, junto da possibilidade de insuficiência de matéria prima não renovável, tem estimulado a busca de novas tecnologias sustentáveis com maior atenção à emissão de poluentes. O hidrogênio, substância química de enorme importância nas industriais, destaca-se como uma fonte de energia limpa e renovável. Hidrogênio é comumente produzido a partir de fontes não renováveis, como na reforma à vapor do gás natural. Devido a características reacionais específicas, a gaseificação de biomassas úmidas em meio contendo água em condições supercrítica é um caminho promissor para a produção de hidrogênio e outros gases combustíveis com alto valor agregado. O etanol se mostra um material atraente pois é renovável, apresenta baixa toxicidade em comparação com outros recursos e possui alto teor de hidrogênio em sua molécula. Em busca de viabilizar tal tecnologia um ponto determinante é o desenvolvimento de catalisadores visando reduções de custo e aumento de seletividade aos produtos de interesse. Neste trabalho foram realizados testes de gaseificação de etanol em água supercrítica com catalisadores heterogêneos. Os testes foram executados em reator tubular feito de Inconel 625 sob as seguintes condições operacionais: temperaturas de 400, 450, 500, 550, 600 e 650 ºC, pressão de 250 bar, carga de 5 g de catalisador heterogêneo, alimentação do reator com razão molar de Etanol:Água de 1:10 e vazão mássica de alimentação de 5 g/min. Os catalisadores foram sintetizados a partir do método de impregnação de soluções aquosas dos nitratos precursores de Cu, Co e Zn com excesso de solvente e usando como suporte catalítico pellets esféricos de Al 2 O 3 . Os catalisadores e o suporte catalítico foram caracterizados por Termogravimetria e Análise Térmica Diferencial (TG/ATD), Fluorescência de Raios X (FRX), Microscopia Eletrônica de Varredura (MEV), análise textural por Isotermas de Adsorção/Dessorção de N 2 a 77 K e Difração de Raios X (DRX). Os resultados de gaseificação indicaram que a produção de H2 se deu principalmente a partir da desidrogenação de etanol. Os catalisadores demonstraram conversões maiores ao observado apenas para o suporte catalítico. O catalisador CuAl apresentou maior seletividade a H 2 bem como maior vazão molar de H 2 à temperatura de 650 ºC. O catalisador CoZnAl apresentou elevada tendência a formação de C 2 H 4 em qualquer temperatura de reação, especialmente à temperatura de 650 ºC.

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-04-07T20:19:45Z No. of bitstreams: 2 Dissertação - Letícia Gomes do Nascimento - 2017.pdf: 6868423 bytes, checksum: 7a54ea8b28095c4c81126f3998e87c13 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-10T11:16:14Z (GMT) No. of bitstreams: 2 Dissertação - Letícia Gomes do Nascimento - 2017.pdf: 6868423 bytes, checksum: 7a54ea8b28095c4c81126f3998e87c13 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-10T11:16:14Z (GMT). No. of bitstreams: 2 Dissertação - Letícia Gomes do Nascimento - 2017.pdf: 6868423 bytes, checksum: 7a54ea8b28095c4c81126f3998e87c13 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The Biginelli reaction involves the cyclocondensation of three reagents in the presence of an acid catalyst to obtain dihydropyrimidinones (DHPMs).This compound and its analogues are widely known to possess various pharmacological properties, such as antibacterial, antiinflammatory, antifungal, antiviral, anticancer and antihypertensive. This reaction is usually carried out via homogeneous catalysis, which presents, however, some difficulties, such as regeneration of the catalyst and difficult separation of the final product, thus becoming an obstacle for industrial use. In the present work, it was proposed the use of two classes of heterogeneous catalysts, which are: metal oxides and acid carbons in order to achieve attractive characteristics in the Biginelli reaction, as a reduction of reaction time and increase in yield. The acidic carbons were prepared by carbonization by impregnation of agroindustrial residues with sulfuric acid at a temperature of 200 °C in the mass ratio of 1:10 (precursor: H2SO4) for 6 h. The pure HY-340 and Nb2O5 were both tested and chemically treated with a solution of 30% sulfuric acid. The catalysts were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric (TG), differential thermal analysis (DTA), textural adsorption/desorption analysis of N2 at -196 °C and desorption of ammonia at programmed temperature (DTP-NH3), scanning electron microscopy (SEM) and X-ray Dispersive Energy Spectrometry (EDS). The contents of C, N, O and S present on the surface of the coals were quantified by Elementary Analysis (CHNS-O). Exploratory catalytic tests were carried out to define the best experimental conditions of solvent, temperature, molar ratio and amount of catalyst. The results obtained allowed to establish the best experimental conditions for the realization of the Biginelli reaction. Thus, the following parameters were adopted to evaluate the performance of the different catalysts. These are: 5% catalyst content (by mass), molar ratio of 1 Benzaldehyde: 1,5 Methyl acetoacetate: 1,5 Urea, without solvent and temperature of 130 °C. The best catalyst was Nb2O5 treated with sulfuric acid, whereby a yield of 94% of dihydropyrimidinones (DHPMs). / A reação de Biginelli envolve a ciclocondensação de três reagentes na presença de um catalisador ácido para a obtenção de Dihidropirimidinonas (DHPMs). Este composto e seus derivados são amplamente conhecidos por possuir diversas propriedades farmacológicas e terapêuticas. Esta reação é geralmente realizada via catálise homogênea, que apresentam, no entanto, algumas dificuldades, como regeneração do catalisador e difícil separação do produto final, tornando-se dessa forma um obstáculo para utilização industrial. O presente trabalho teve como objetivo geral avaliar diferentes catalisadores ácidos heterogêneos na produção de dihidropirimidinonas, como óxidos de nióbio sulfonados e carvões sulfonados produzidos a partir de resíduos agroindustriais (casca de arroz e bagaço de tomate). Os carvões ácidos foram preparados por carbonização, por meio da impregnação de resíduos agroindustriais com ácido sulfúrico a uma temperatura de 200 °C na proporção mássica de 1:10 (precursor: H2SO4), por 6 h. Testou-se, também, o ácido nióbico (HY-340) e Nb2O5 ambos puros e tratados quimicamente com uma solução de 30% de ácido sulfúrico. Os catalisadores foram caracterizados por Difração de Raios X (DRX), Espectroscopia no Infravermelho (IV), Termogravimetria (TG), Análise Térmica Diferencial (DTA), Análise Textural por Adsorção/Dessorção de N2 a -196 °C, Dessorção de Amônia a Temperatura Programada (DTP-NH3), Microscopia Eletrônica de Varredura (MEV) e Espectrometria de Energia Dispersiva de Raios X (EDS). Os teores de C, N, O e S presentes na superfície dos carvões foram quantificados por Análise Elementar (CHNS-O). Foram realizados testes catalíticos exploratórios para definir melhores condições experimentais de solvente, temperatura, razão molar e quantidade de catalisador. Os resultados obtidos permitiram estabelecer as melhores condições experimentais para a realização da reação de Biginelli. Desse modo, adotaram-se os seguintes parâmetros para avaliar o desempenho dos diferentes catalisadores. São estes: teor de 5% de catalisador (em massa), razão molar de 1 Benzaldeído: 1,5 Acetoacetato de metila: 1,5 Ureia, sem solvente e temperatura de 130 °C. O melhor catalisador foi o Nb2O5 tratado com ácido sulfúrico, em que obteve-se um rendimento de 94% de dihidropirimidinonas (DHPMs).

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-08-23T19:33:44Z No. of bitstreams: 1 chrishebertdejesusfranco.pdf: 4893679 bytes, checksum: 66f0f0a8b8adf726daadd7a28c127959 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T15:56:28Z (GMT) No. of bitstreams: 1 chrishebertdejesusfranco.pdf: 4893679 bytes, checksum: 66f0f0a8b8adf726daadd7a28c127959 (MD5) / Made available in DSpace on 2018-09-03T15:56:28Z (GMT). No. of bitstreams: 1 chrishebertdejesusfranco.pdf: 4893679 bytes, checksum: 66f0f0a8b8adf726daadd7a28c127959 (MD5) Previous issue date: 2018-07-23 / Este trabalho aborda a síntese e caracterização estrutural de três novos polímeros de coordenação derivados da combinação dos íons lantanídeos, neodímio(III) e lantânio(III), com o ácido 5-sulfoisoftálico nomeados como Nd-5sis-gel, La-5sis-gel e Nd-5sis, além da síntese de outros dois compostos derivados do ácido p-sulfobenzoico combinado com os íons lantanídeos nomeados como Nd-psb e La-psb. Os compostos foram sintetizados, principalmente, por meio de reações solvotérmicas que se mostraram mais eficientes e com maior reprodutibilidade e por meio de cristalização em gel, em que a metodologia apesar de favorecer a formação de cristais, não se mostrou adequada para garantir a reprodutibilidade das sínteses. Todos os compostos apresentados foram caracterizados por técnicas espectroscópicas de absorção na região do infravermelho e de espalhamento Raman e análise elementar de carbono, hidrogênio e nitrogênio. As estruturas cristalinas para os polímeros de coordenação Nd-5sis-gel, La-5sis-gel e Nd-5sis foram determinadas por difração de raios X por monocristal, em que uma correção de absorção de raios X no conjunto de reflexões coletadas se mostrou adequada para a determinação estrutural desses compostos. Análise termogravimétrica e difração de raios X por policristais com variação de temperatura para o polímero bidimensional, Nd-5sis, foram realizadas e os resultados mostram uma estabilidade térmica até 550 °C, com um ligeiro ganho de massa em atmosfera de oxigênio após o processo de desidratação após 150 °C referente à formação de fases cristalinas de carbonatos e óxido carbonato de neodímio na estrutura. Estudos em relação a efeitos de estrutura e superfície foram desenvolvidos para o composto Nd-5sis utilizando um modelo de reação com peroxido de hidrogênio, a formação do complexo neodímio-hidroperoxo na superfície permitiu a determinação da quantidade de sítios na superfície do polímero bidimensional. Foram ainda desenvolvidos dois testes catalíticos utilizando o composto Nd-5sis como catalisador heterogêneo nas reações de condensação cíclica de glicerol e ureia e na oxidação de linalol. As características do polímero de coordenação permitiram a obtenção de valores de conversão e seletividade para a reação de condensação cíclica comparáveis com vários catalisadores descritos na literatura e a partir dos dados experimentais foi possível determinar a taxa da reação e estimar a taxa de produção e consumo de glicerina e carbonato de glicerina em um processo catalítico. A estabilidade química e estrutural do polímero bidimensional foi avaliada até o quarto ciclo de reação e foi observado que o polímero apresenta uma boa atividade catalítica após um processo de recristalização adequado entre um ciclo e outro da reação. Os testes catalíticos para oxidação de linalol se mostraram viáveis apresentando bons valores de conversão e seletividade para a reação. Sendo que a formação do complexo neodímiohidroperoxo na superfície foi fundamental para garantir a atividade catalítica. Além disso, o caráter heterogêneo da reação foi avaliado e os resultados indicam que o composto Nd-5sis atua como catalisador heterogêneo da reação, uma vez que a remoção do polímero na reação de oxidação interrompe o processo de conversão. A estabilidade estrutural do composto Nd5sis foi avaliada, após o primeiro ciclo, e os resultados indicam uma estabilidade da estrutura cristalina ao final da reação. / This work deals with the synthesis and structural characterization of three new coordination polymers derived from lanthanum(III) and neodymium(III) ions with 5-sulfoisophthalic acid, named as Nd-5sis-gel, La-5sis-gel and Nd-5sis, in addition to the synthesis of two other compounds derived from p-sulfobenzoic acid combined with these lanthanide ions named as Nd-psb and La-psb. The compounds were synthesized mainly by solvothermic reactions, which were efficient and with greater reproducibility and by gel crystallization, in which the methodology, despite of favoring the formation of crystals, it was not suitable to security the reproducibility of the syntheses. All the compounds were investigated by spectroscopic techniques of infrared absorption and Raman scattering and elemental analysis of carbon, hydrogen and nitrogen. The crystalline structures for the coordination polymers Nd-5sis-gel, La-5sis-gel and Nd-5sis were determined by single crystal X-ray diffraction, in which a X-ray absorption correction applied to the collected reflections proved to be appropriate for the structural determination of these compounds. Thermogravimetric analysis and X-ray diffraction of polycrystalline materials with temperature variation for the two-dimensional polymer, Nd-5sis, were performed and the results show a thermal stability up to 550 °C, with a slightly increased in weight in oxygen atmosphere after the dehydration process after 150 °C, related to the formation of crystalline phases of neodymium carbonates and oxocarbonate in the structure. Studies on the structural and surface effects were carried out for the Nd-5sis by means of a reaction model with hydrogen peroxide. The formation of the neodymiumhydroperoxide complex on the surface allowed the determination of the amount of sites on the surface of the two-dimensional polymer. Two catalytic tests were also performed for the Nd-5sis as a heterogeneous catalyst in the cycloaddition reactions between glycerol and urea and for the oxidation of linalool. The properties of the coordination polymer allowed getting conversion and selectivity values for the cycloaddition reaction comparable with several catalysts described in the literature and from the experimental data it was possible to set the reaction rate and to estimate the production and consumption rate of glycerol and glycerol carbonate in a catalytic process. The chemical and structural stability of two-dimensional coordination polymer was evaluated up to the fourth cycle of reaction and it was observed that the polymer shows a good catalytic activity after a suitable recrystallization process between one cycle and another of the reaction. The catalytic tests for linalool oxidation show viably good conversion and selectivity values for the reaction. The formation of the neodymium-hydroperoxide complex on the surface was essential to ensure catalytic activity. In addition, the heterogeneity of the reaction was evaluated and the results show that the Nd-5sis acts as a heterogeneous catalyst in the reaction, since the removal of compound, in the oxidation reaction, stops the conversion process. The structural stability of Nd-5sis was evaluated after the first cycle and the results indicate that at the end of the reaction the crystalline structure is preserved.

Les réactions de catalyse hétérogène impliquant un gaz et un liquide sont mises en oeuvre dans des réacteurs à lit fixes. Ces réacteurs peuvent être assimilés à un milieu poreux. La nature complexe de ce milieu rend la compréhension des interactions entre phases difficile, et nécessite une étude exhaustive à l’échelle globale et locale afin d’identifier les paramètres clés de l’hydrodynamique, des transferts de chaleur et de matière. Nous avons donc développé une cellule miniaturisée bidimensionnelle transparente, qui permet l’observation directe des écoulements avec une très bonne résolution spatiale et temporelle. En faisant varier le débit total et le rapport des débits gaz/liquide, nous avons mis en évidence l’apparition des régimes ruisselant et pulsé, observés par ailleurs dans des systèmes tridimensionnels. Grâce à une méthode d’analyse d’image, nous sommes capables de quantifier et cartographier la saturation liquide locale apparente et la morphologie des phases. L’analyse des variances a permis d’étudier les transitions de régimes pour différentes propriétés de la phase liquide. Cette approche a permis de comparer avec la littérature, mais aussi de s’intéresser aux mécanismes de génération et propagation des instabilités lors des transitions. Il a été mis en évidence que l’apparition des instabilités responsables de la déstabilisation du régime ruisselant intervient pour un nombre deWeber liquide fixé, indiquant que le régime pulsé apparait suite à la déstabilisation des interfaces gaz /liquides par les forces inertielles. Enfin, une étude préliminaire des transferts thermiques dans la cellule a été réalisée. La cellule est utilisée pour réaliser la réaction exothermique d’hydrogénation de l’alpha-methylstyrène. Un modèle simple de transferts thermique a été utilisé pour caractériser l’augmentation de température dans la cellule. Bien que cette approche ne permette pas des mesures quantitatives, elle ouvre à la perspective de suivi de transferts thermiques par caméra infra-rouge. / Heterogeneously catalyzed reactions involving a gas and a liquid phase are frequently achieved in fixed bed reactors. These reactors can be described as a porous medium. The complex nature of this medium makes the understanding of the interplay between phases difficult, and requires a thorough study at the global andlocal scale to identify the key parameters of hydrodynamics, mass and heat transfers. Therefore, we have developed a miniaturized two-dimensional system that is transparent to allow the direct observation of the flow with very high spatial and temporal resolution. While varying the total flow rate and the gas/liquid flow rate ratio, we observe the appearance of the trickle and the pulse flow regime, which can be observed in threedimensional beds. Thanks to some image analysis techniques, we are able to quantify and to map the local apparent liquid saturation and the morphology of the phases. Variances analysis allowed the study of the transition for different liquid properties. This approach allowed the comparison with the existing state of art, but also the study of the onset and propagation mechanisms of the instabilities during the transition. We report that the onset of instabilities responsible for the destabilization of the trickle flow regime occurs at a fixed Weber number. This indicates that the pulsed regime is due to the destabilization of the gas/liquid interface by inertial forces. Finally, a preliminary study of thermal transfers in the device was realized. The device was used to perform the exothermic hydrogenation of alpha-methylstyrene. A simple model is used to characterize the temperature increase in the device. Although this approach does not allow quantitative measurements, it opens up the perspective of monitoring thermal transfers with an infra-red camera.

Le méthanethiol (MeSH) est un intermédiaire important dans la synthèse de la méthionine, un acide aminé largement utilisé dans l'industrie agro-alimentaire. Le marché étant en constante augmentation, il est indispensable d'optimiser la formation de MeSH à partir de méthanol (MeOH) et de sulfure d'hydrogène (H2S) en présence de K2WO4/Al2O3 (10,5 % massique). L'impact de paramètres clés, tels la conversion du méthanol, la température ou le rapport molaire H2S/MeOH a été étudié dans des conditions proches de celles du procédé. Un fort effet inhibiteur de l'eau, co-produit de la réaction, a été mis en évidence, aussi bien sur l'activité catalytique que sur les sélectivités des différents produits. En revanche, le dioxyde de carbone (CO2) et le monoxyde de carbone (CO), produits non valorisables, n'ont aucun impact sur les performances du catalyseur. Un schéma réactionnel complet a été établi rendant compte de la formation des différents produits de réaction. Un modèle cinétique faisant intervenir le formalisme de Langmuir-Hinshelwood, en accord avec les résultats expérimentaux, a été développé.La caractérisation du catalyseur K2WO4/Al2O3 a confirmé que le site actif est une paire acide-base, l'acidité étant apporté par le tungstène alors que le potassium génèrerait une basicité à la surface du matériau. A partir de ces observations, la mesure des performances catalytiques de solides à base de terres rares, présentant une acidité et une basicité plus fortes, montre que ceux-ci sont plus actifs que le catalyseur K2WO4/Al2O3, tout en conservant une sélectivité en MeSH similaire. / Methanethiol (MeSH) is a key intermediate involved in the synthesis of methionine, an essential amino acid widely used in food-processing industry. Given that methionine market is constantly growing, optimizing MeSH production from methanol (MeOH) and hydrogen sulfide (H2S) is of paramount importance. The impact of key parameters, such as MeOH conversion, temperature, or H2S/MeOH molar ratio has been studied in a range consistent with industrial conditions. A strong inhibiting effect of water (which is the co-product of the reaction) has been highlighted, both on catalytic activity and selectivities towards the different products. However, carbon dioxide (CO2) and carbon monoxide (CO), which are non-recoverable products, have no influence on catalytic performances. A complete reaction scheme accounting for the formation of the different reaction products has been proposed. A kinetic model using Langmuir-Hinshelwood formalism was developed, which affords precise estimation of experimental data.Characterization of K2WO4/Al2O3 catalyst confirmed that acid-base dual sites were the active sites responsible for MeSH formation. Acidity is mainly brought by tungsten species whereas potassium addition allows increasing the basicity of the catalyst. Based on these observations, the catalytic performances of rare-earth based oxides, which possess stronger acidity and basicity, have been measured. These materials exhibit significantly higher activity than K2WO4/Al2O3 catalyst, with similar MeSH selectivity.

Ce travail de doctorat s’inscrit dans le cadre de la recherche fondamentale inhérente à la réaction catalytique d’hydrogénation du CO, qui permet de produire du pétrole de synthèse à partir des autres ressources fossiles disponibles à l’état naturel (gaz naturel et charbon).<p>Les objectifs de ce travail s’articulent autour de deux méthodes originales, respectivement de préparation et de caractérisation des catalyseurs. La première permet la formation in situ de catalyseurs par voie oxalique, alors que la seconde est une méthode de cinétique transitoire chimique appliquée à la réaction CO + H2.<p><p>Dans un premier temps, la préparation de catalyseurs « modèles » de cobalt et de nickel a été réalisée en faisant intervenir un oxalate comme précurseur à la formation in situ du catalyseur. L’étude de cette méthode de préparation par « voie oxalique » nous a tout d’abord permis de discuter du mécanisme de formation de l’oxalate, que nous envisageons comme une polymérisation faisant intervenir des ligands oxalate tétradentates établissant des ponts entre les atomes métalliques.<p>La décomposition thermique de l’oxalate de cobalt a été étudiée dans un second temps. Nous nous somme penchés en particulier sur l’influence de l’atmosphère de la décomposition sur la nature du catalyseur obtenu in fine. Utiliser l’hydrogène comme gaz réducteur permet d’obtenir des catalyseurs purement métalliques développant une surface spécifique intéressante.<p><p>Ces catalyseurs ont été utilisés pour les études cinétiques transitoires chimiques de la réaction CO + H2. Les phénomènes transitoires observés ont permis de corréler les hypothèses formulées pour l’élaboration d’un mécanisme original initialement proposé par A. Frennet. En particulier, la dépendance des vitesses réactionnelles aux pressions partielles de CO et d’hydrogène permet d’envisager un mécanisme d’allongement de chaîne basé sur la réactivité d’un intermédiaire réactionnel avec les réactifs en phase gazeuse. Au vu des recouvrements de surface sous conditions réactionnelles ainsi que des phénomènes transitoires observés, cet intermédiaire est constitué de plusieurs atomes (carbone, oxygène et hydrogène), et est à l’origine de la formation des produits de la réaction (CH4 et alcanes à plus longues chaînes), dont la désorption en phase gazeuse suit un processus en deux étapes lors duquel l’influence de l’hydrogène est primordiale.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

En réponse aux divers accords internationaux pour réduire l’émission de gaz à effet de serre et limiter leur impact sur le réchauffement climatique, une transition énergétique visant à augmenter la part des énergies renouvelables est en cours. Le concept du Power-to-Gas l’une des solutions permettant un stockage/déstockage adapté à cette énergie intermittente. Cependant, la réaction de méthanation, fortement exothermique, nécessite un procédé performant pour l’évacuation de la chaleur générée au cours de la réaction. Au cours de cette thèse, un milli-réacteur structuré, rempli avec une mousse cellulaire recouverte par un catalyseur (Ni/Cérine-Zircone), a été développé pour répondre à cette problématique. Le réacteur a été caractérisé par une étude hydrodynamique et une étude thermique, la seconde permis de visualiser la formation de points chauds. L’ajout de nanofibres de carbone a permis une meilleure gestion de la chaleur générée, limitant ainsi la désactivation du catalyseur (frittage). Des tests catalytiques réalisés à plus grande échelle ont montré l’intérêt des lits structurés vis-à-vis des lits fixes, classiquement utilisés dans les procédés, avec une élévation de température modérée d’environ 25°C. / In response to the different international agreements to reduce the emission of greenhouse gases and limit their impact on global warming, an energy transition is in progress to increase the share of renewable energies. The Power-to-Gas concept is one of many solutions proposed to answer the need to charge and discharge this intermittent energy source. However, the methanation reaction, highly exothermal, needs a process able to efficiently evacuate the heat produced by the reaction. During this thesis, a structure milli-reactor, filled with an open cell foam coated with a catalyst (Ni/Ceria-Zirconia), was developed as an answer to this issue. The reactor was hydrodynamically and thermally characterized. The second one allowed us to evidence hot spots formation. The presence of nanofibres allowed better control of the heat generated, limiting the deactivation of the catalyst (sintering). Catalytic tests, performed on a small scale pilot, clearly showed the advantage of structured beds compared to fixed bed, classically used in processes, with a moderate heat elevation around 25°C.

L’hydrogénation sélective d’hydrocarbures polyinsaturés présente un fort intérêt pour l’industrie pétrolière. Cette réaction est catalysée par des particules métalliques ou des alliages et a lieu sous pression d’hydrogène. Dans ce travail nous étudions la réaction d’hydrogénation sélective du butadiène en 1-butene en présence des catalyseurs Pt(111) et Sn/Pt-Pt(111). Cette étude a été menée à l’aide du programme VASP (Vienna Abinitio Simulation Package) qui permet de simuler des systèmes solides et surfaciques dans le cadre de la théorie de la fonctionnelle de la densité (DFT). Le choix des catalyseurs a été dicté par les communautés expérimentale et industrielle qui utilisent le plus souvent le platine car très actif, ou des alliages de platine-étain, moins actifs mais beaucoup plus sélectifs. L’hydrogénation du butadiène a déjà été étudiée par le passé mais uniquement à T=0 K et sans prendre en compte les conditions réelles de pression des réactifs. Notre but étant de comprendre les pas élémentaires de cette réaction, nous avons choisi de l’étudier à des conditions de T et de P proches de celles utilisées expérimentalement, c’est-à-dire 300-400 K et 1-10 bar. A cette fin, nous avons mis en place un modèle thermodynamique pour évaluer, dans un premier temps, la composition de la surface lors de la réaction. Il est alors apparu que la configuration de surface la plus stable correspond à une couverture de une monocouche d’hydrogène ce qui suggère un mécanisme de type Eley-Rideal. Puis nous avons étudié l’aspect cinétique ce cette réaction et calculé les chemins réactionnels pour différents recouvrements en hydrogène. Nous avons conclu qu’il existe une forte compétitivité entre le mécanisme pressenti, appelé Langmuir-Hinshelwood et impliquant des espèces fortement adsorbées, et le mécanisme Eley-Rideal proposant une adsorption faible de l’un des réactifs. Les calculs ont été effectués avec les fonctionnelles PBE et optPBE pour apporter un point de comparaison des méthodes. / Petroleum industry has a strong interest in the selective hydrogenation of polyunsaturated hydrocarbons. This reaction is catalyzed by metallic particles or alloys and happens under pressure of hydrogen. In this work, we study the selective hydrogenation of butadiene into 1-butene, on two model catalysts which are Pt(111) and Sn/Pt-Pt(111). For this, we used the VASP code (Vienna Abinitio Simulation Package) that allows to perform periodic calculations in the framework of the Density Functional Theory (DFT). The choice of the catalysts was driven by the experimental and industrial communities who mostly use platinum because of its high activity, or alloys such as tin-platinum alloy, less active but more selective. Butadiene hydrogenation was already modeled in the past but only at T=0 K and without taking into account the real pressure conditions of the reactants. Our aim is to understand the impact of the reaction conditions which is why we ran this study at T and P conditions close to the one used experimentally, e.g. 300-400 K et 1-10 bar. For this, we setup a thermodynamic model to evaluate in a first step the surface composition when the reaction occurs. It came out that the most stable surface configuration corresponds to a coverage of 1 ML of hydrogen which suggests an Eley-Rideal type mechanism. Then we studied the kinetic aspect of this reaction and we calculated the hydrogenation pathways for different coverages of hydrogen. We concluded that there is a strong competition between the sensed mechanism, called Langmuir-Hinshelwood mechanism and implying strongly adsorbed species, and the Eley-Rideal mechanism, proposing a weak adsorption of one of the two reactants.

Click chemistry is a molecular synthesis strategy based on reliable, highly selective reactions with thermodynamic driving forces typically in excess of 20 kcal mol-1. The 1,3-dipolar cycloaddition of azides and alkynes developed by Rolf Huisgen saw dramatic rate acceleration using Cu(I) as a catalyst in 2002 reports by Barry Sharpless and Morten Meldal enabling its click chemistry eligibility. Since these seminal reports, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has become the quintessential click reaction finding diverse utility. The popularity of the CuAAC has naturally led to interest in new catalyst systems with improved efficiency, robustness, and reusability with particular focus on nanomaterial catalysts, a common trend across the field of catalysis. The high surface area of nanomaterials lends to their efficacy as colloidal and heterogeneous nanocatalysts, but the latter boasts the added benefit of easy separation and recyclability. With any heterogeneous catalyst, a common question arises as to whether the active catalyst species is truly heterogeneous or rather homogeneous through metal ion leaching. Differentiating these processes is critical, as the latter would result in reduced efficiency, higher cost, and inevitable environmental and heath side effects. This thesis explores the CuAAC from an interdisciplary approach. First as a synthetic tool, applying CuAAC-formed triazoles as functional, modular building blocks in the synthesis of optical cation sensors by combining azide and alkyne modified components to create a series of sensors selective for different metal cations. Next, single-molecule spectroscopy techniques are employed to observe the CuNP-catalyzed CuAAC in real time. Combining bench-top techniques with single-molecule microscopy to monitor single-catalytically generated products proves to be an effective method to establish catalysis occurs directly at the surface of copper nanoparticles, ruling out catalysis by ions leached into solution. This methodology is extended to mapping the catalytic activity of a commercial heterogeneous catalyst by applying super-localization analysis of single-catalytic events. The approach detailed herein is a general one that can be applied to any catalytic system through the development of appropriate probes. This thesis demonstrates single-molecule microscopy as an accessible, effective, and unparalleled tool for exploring the catalytic activity of nanomaterials by monitoring single-catalytic events as they occur.

Des réacteurs avec solide en suspension (« slurry »), très répandu dans l'industrie chimique, du laboratoire à la production, offrent des bonnes capacités en transfert de matière et de chaleur. Leur flexibilité facilite le changement de la phase solide et permet une régénération en continue des catalyseurs en cas de désactivation. Cependant, ils présentent un fort rétro-mélange, et donc un désavantage pour des réactions ayant des enjeux de sélectivité et/ou de conversion poussées. L'écoulement segmenté dit de Taylor est souvent mis en œuvre dans les réacteurs micro-structurés (RMS), grâce à ses propriétés intéressantes (capacités de transfert, écoulement, piston). Cependant, l'utilisation des solides catalytiques dans ces RMS est le plus souvent résolue par immobilisation du catalyseur nuisant la flexibilité. L'écoulement « slurry Taylor » (EST) qui utilise les recirculations internes dans les segments liquides pour transporter des particules en poudre, peut potentiellement répondre à cet enjeu. L'objet de cette étude est la conception et la caractérisation de ce nouveau mode de contact gaz-liquide-solide (G-L-S) dans des tubes millimétriques horizontaux et verticaux. Des études hydrodynamiques ont révélé différents régimes d'écoulement dépendant de la vitesse et de l'orientation de l'écoulement. Pour étudier le transfert de matière L-S, une résine échangeuse d'ion a été utilisée et une première corrélation pour le nombre de Sherwood est proposée / Slurry reactors, widely encountered in chemical industry (laboratory scale up to manufactaring), offer good mass and heat transfer capacities and their high flexibility ensures the simple changeover of solid phases enables a continuous online fresh catalyst feed for fast deactivating catalysts. However slurry reactors promote a high degree of backmixing which can be a drawback for reactions with selectivity issues or when very high conversions are required. In microreaction technology, Taylor flow is often employed providing excellent heat and mass transfer and almost ideal plug flow behavior. Solid handing in these small structures is often resolved by immobilizing the solid catalyst which impinges on the flexibility. One possible solution to combine beneficial properties of Taylor flow with the operational flexibility of conventional slurry reactors is a “slurry Taylor” flow (STF) where catalyst particles are suspended and kept in motion by the internal circulations present in the liquid slugs. The focus of this work is the design and characterization of this innovative gas-liquid-solid contactor. Particles were transported in millimetric horizontal and vertical tubing without the risk of clogging. Hydrodynamic studies revealed different flow patterns depending mainly on velocity and flow orientation. Ion exchange resin particles were used to study the liquid-solid mass transfer and first correlation for the Sherwood number in STF is proposed