La substitution des métaux nobles par des métaux de transition abondants et bon marché est un challenge majeur de ce siècle en chimie de synthèse. Récemment, les métaux abondants tels que le fer et le manganèse (1er et 3ème en abondance dans l'écorce terrestre) ont connu un essor remarquable en catalyse homogène, notamment en réduction. Les travaux de thèse ont portés sur le développement de nouveaux catalyseurs bien-définis efficaces du fer et du manganèse pour effectuer des réactions d'hydrogénation de dérivés carboxyliques, de réduction par prêt d'hydrogène et de déshydratation d'amides. / The substitution of noble metals by abundant and cheap transition metals is a major challenge of this century in synthetic chemistry. Recently, abundant metals such as iron and manganese (1st and 3rd in abundance in the Earth's crust) have seen remarkable growth in homogeneous catalysis, especially in reduction. The thesis work focused on the development of new well-defined efficient catalysts of iron and manganese to carry out reactions of hydrogenation of carboxylic derivatives, reduction by hydrogen and dehydration of amides.

In an attempt to overcome the high maintenance and costs associated with traditional physico-chemical methods, much work is being done on the application of enzymes for the recovery of valuable metals from solutions and industrial effluents. One of the most widely studied enzymatic metal recovery systems uses hydrogenase enzymes, particularly from sulphate reducing bacteria (SRB). While it is known that hydrogenases from SRB mediate the reductive precipitation of metals, the mechanism of enzymatic reduction, however, is not yet fully understood. The main aim of the present study was to investigate the role of a hydrogenase enzyme in the removal of rhodium from both aqueous solution and industrial effluent. A quantitative analysis of the rate of removal of rhodium(III) by a resting SRB consortium under different initial rhodium and biomass concentrations, pH, temperature, presence and absence of SRB cells and electron donor, was studied. Rhodium speciation was found to be the main factor controlling the rate of removal of rhodium from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached. Consequently, a pH-dependant rate of rhodium removal from solution was observed. The maximum SRB uptake capacity for rhodium was found to be 66 mg rhodium per g of resting SRB biomass. Electron microscopy studies revealed a time-dependant localization and distribution of rhodium precipitates, initially intracellularly and then extracellularly, suggesting the involvement of an enzymatic reductive precipitation process. A hydrogenase enzyme capable of reducing rhodium(III) from solution was isolated and purified by PEG, DEAE-Sephacel anion exchanger and Sephadex G200 gel exclusion. A distinct protein band with a molecular weight of 62kDa was obtained when the hydrogenase containing fractions were subjected to a 10% SDS-PAGE. Characterization studies indicated that the purified hydrogenase had an optimum pH and temperature of 8 and 40°C, respectively. A maximum of 88% of the initial rhodium in solution was removed when the purified hydrogenase was incubated under hydrogen. Due to the low pH of the industrial effluent (1.31), the enzymatic reduction of rhodium by the purified hydrogenase was greatly retarded. It was apparent that industrial effluent pretreatment was necessary before the application an enzymatic treatment method. In the present study, however, it has been established that SRB are good candidates for the enzymatic recovery of rhodium from both solution and effluent.

The enzymatic reduction of a high-valence form of metals to a low-valence reduced form has been proposed as a strategy to treat water contaminated with a range of metals and radionuclides. Metal reduction by sulphate reducing bacteria (SRB) is carried out either chemically (involving reduction by hydrogen sulphide) or enzymatically (involving redox enzymes such as the hydrogenases). While reduction of metal ions by hydrogen sulphide is well known, the enzymatic mechanism for metal reduction is poorly understood. The aims of this study were to investigate the role of SRB in facilitating platinum removal, and to investigate the role of a hydrogenase in platinum reduction in vitro. In order to avoid precipitation of platinum as platinum sulphide, a resting (non-growing) mixed SRB culture was used. The maximum initial concentration of platinum (IV), which SRB can effectively remove from solution was shown to be 50 mg.l⁻¹. Electron donor studies showed high platinum (IV) uptake in the presence of hydrogen, suggesting that platinum (IV) uptake from solution by SRB requires careful optimization with respect to the correct electron donor. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis indicated that platinum was being precipitated in the periplasm, a major area of hydrogenase activity in SRB. Purification of the hydrogenase by ammonium sulphate precipitation (65%), Toyopearl-Super Q 650S ion exchange and Sephacry 1 S-100 size exclusion chromatography revealed that the hydrogenase was monomeric with a molecular weight of 58 KDa, when analyzed by 12% SDS-PAGE. The purified hydrogenase showed optimal temperature and pH at 35°C and 7.5 respectively, and a poor thermal stability. In vitro investigation of platinum reduction by purified hydrogenase from mixed SRB culture showed that hydrogenase reduces platinum only in the presence of hydrogen. Major platinum (IV) reduction was observed when hydrogenase was incubated with cytochrome C₃ (physiological electron carrier in vivo) under hydrogen. The same observations were also noted with industrial effluent. Collectively these findings suggest that in vitro platinum reduction is mediated by hydrogenase with a concerted action of cytochrome C₃ required to shuttle the electron from hydrogenase.

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Les nanoparticules de métaux de transition ont suscité une attention considérable au cours des dernières années en raison de leur activité catalytique et sélectivité. Elles sont à la frontière entre la catalyse homogène et hétérogène et combinent les avantages des deux. Pour cette raison, les nanoparticules ont émergé en tant que catalyseurs pour différentes réactions telles que l'hydrogénation d'arènes. L'objectif final de cette thèse est la synthèse et la caractérisation de nanoparticules de ruthénium et l’exploration de leur performance catalytique en réactions d'hydrogénation d’arènes et polyarènes.Le Chapitre 1 contient une introduction générale à la synthèse, la caractérisation et l'application des nanoparticules en catalyse. Le Chapitre 2 définit les objectifs généraux de cette thèse.Le Chapitre 3 décrit la synthèse et la caractérisation de nanoparticules de ruthénium et de rhodium stabilisées par des ligands de type phosphine et leur application dans une étude comparative concernant la réduction d'une large gamme de phényles substitués, benzyle et de phénéthyle cétones. Dans le cas des cétones d'aryle, des nanoparticules de ruthénium ont démontré être plus sélectives pour l'hydrogénation du groupe aryle que celles de rhodium. Par contre, les nanoparticules de rhodium fournissent des produits d'hydrogénolyse. En ce qui concerne les arylcétones non conjuguées, les deux métaux sont très sélectifs envers l'hydrogénation du groupe aryle.Le Chapitre 4 décrit l'utilisation de nanoparticules de ruthénium stabilisées par la triphénylphosphine pour l'hydrogénation de substrats polycycliques aromatiques dans des conditions réactionnelles douces. Les systèmes contenant deux, trois ou plusieurs cycles aromatiques condensés sont réduites et montrent une haute sélectivité pour l’hydrogénation partielle. Le produit d'hydrogénation totale est uniquement obtenu pour les substrats moins encombrés, tels que le naphtalène et l'anthracène. L'influence d’un substituant (réductible ou non) sur l'hydrogénation du naphtalène est également étudiée.La recherche dans le Chapitre 5 explore la synthèse d'un nouveau ligand de type phosphine chirale, qui est obtenue avec un bon rendement et avec une pureté optique de 97%. Ensuite, cette phosphine et la cinchonidine commerciale (Figure 2) sont utilisées comme agents de stabilisation pour la synthèse de nanoparticules chirales.Ces nanoparticules ont été testées dans l'hydrogénation asymétrique de différents arènes disubstitués mais en terme d’énantiosélectivité, les résultats n’ont pas été bons. Une étude de deutération a été effectuée pour élucider la coordination des différents substrats à la surface de nanoparticules. Le Chapitre 6 présente les observations finales et les conclusions de cette thèse. / Transition metal nanoparticles have generated considerable attention in recent years as a result of their potential catalytic activity and selectivity. They are at the frontier between homogeneous and heterogeneous catalysis and combine the advantages of both. For this reason, nanoparticles emerged as promising catalyst for different reactions such as for the hydrogenation of arenes. The final goal of this thesis is the synthesis and characterization of ruthenium nanoparticles to explore their performance in arene and polyarene hydrogenation reactions. Chapter 1 contains a general introduction to the synthesis, characterization and application of nanoparticles in catalysis. Chapter 2 sets out the general objectives of this thesis. The research in Chapter 3 describes the synthesis and characterization of ruthenium and rhodium nanoparticles stabilized by phosphine donor ligands and their application in a comparative study in the reduction of a wide range of substituted phenyl, benzyl and phenethyl ketones. In the case of arylketones, ruthenium nanoparticles were found to be more selective than the rhodium ones towards the hydrogenation of the aryl group. Interestingly, only rhodium nanoparticles provided hydrogenolysis products. Concerning the non-conjugated aryl ketones, both metals were found to be really selective towards arene hydrogenation.The research in Chapter 4 describes the use of ruthenium nanoparticles stabilised by triphenylphosphine in the hydrogenation of polyaromatic substrates under mild reaction conditions. Systems containing 2, 3 or more fused benzene rings are reduced obtaining high selectivities towards the partial hydrogenation. The recovering of the total hydrogenated product is only achieved for the less hindered substrates like naphthalene and anthracene. Moreover, the influence on the hydrogenation of naphthalenes containing a substituent (reducible or not) is also studied. The research in Chapter 5 explores the synthesis of a new chiral phosphine ligand, which is obtained in good yield and with 97% optical purity. Then, this phosphine and commercial cinchonidine (Figure 1) are used as stabilizing agents for the synthesis of chiral nanoparticles. These nanoparticles are tested in the asymmetric hydrogenation of different substituted arenes but unsuccessful results in terms of enantioselectivity are obtained. Moreover, deuteration studies to elucidate the coordination of the different substrates to the nanoparticles surface are performed.Chapter 6 presents the final remarks and conclusions extracted from the results obtained in this thesis.

Anomalous Hall behavior of HgCdTe refers to a "double cross-over" feature of the Hall coefficient in p-type material, or a peak in the Hall mobility or Hall coefficient in n-type material. A magnetoconductivity tensor approach was utilized to identify presence of two electrons contributing to the conduction as well as transport properties of each electron in the material. The two electron model for the mobility shows that the anomalous Hall behavior results from the competition of two electrons, one in the energy gap graded region near the CdZnTe/HgCdTe interface with large band gap and the other in the bulk of the LPE film with narrow band gap. Hg0.78Cd0.22Te samples grown by LPE on CdZnTe(111B)-oriented substrates were exposed to various doses of thermal neutrons (~1.7 x 1016 - 1.25 x 1017 /cm2) and subsequently annealed at ~220oC for ~24h in Hg saturated vapor to recover damage and reduce the presence of Hg vacancies. Extensive Magnetotransport measurements were performed on these samples. SIMS profile for impurities produced by neutron irradiation was also obtained. The purpose for this study is to investigate the influence of neutron irradiation on this material as a basis for further study on HgCdTe74Se. The result shows that total mobility is observed to decrease with increased neutron dose and can be fitted by including a mobility inverse proportional to neutron dose. Electron introduction rate of thermal neutron is much smaller than that of fission neutrons. Total recovering of the material is suggested to have longer time annealing. Using Kane's model, we also fitted carrier concentration change at low temperature by introducing a donor level with activation energy changing with temperature. Results on Se diffusion in liquid phase epitaxy (LPE) grown HgCdTe epilayers is reported. The LPE Hg0.78Cd0.22Te samples were implanted with Se of 2.0×1014/cm2 at 100keV and annealed at 350-450oC in mercury saturated vapor. Secondary ions mass spectrometry (SIMS) profiles were obtained for each sample. From a Gaussian fit we find that the Se diffusion coefficient DSe is about one to two orders of magnitude smaller than that of arsenic. The as-implanted Se distribution is taken into account in case of small diffusion length in Gaussian fitting. Assuming a Te vacancy based mechanism, the Arrhenius relationship yields an activation energy 1.84eV. Dislocations introduced in HgCdTe materials result in two energy levels, where one is a donor and one is an acceptor. Hydrogenation treatment can effectively neutralize these dislocation defect levels. Both experimental results and theoretical calculation show that the mobility due to dislocation scattering remains constant in the low temperature range (<77K), and increases with temperature between 77K and 150K. Dislocation scattering has little effect on electrical transport properties of HgCdTe with an EPD lower than 107/cm2. Dislocations may have little effect on carrier concentration for semiconductor material with zinc blende structure due to self compensation.

Orientador: Antonio José Gomez Cobo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T13:34:13Z (GMT). No. of bitstreams: 1 Suppino_RaphaelSoeiro_D.pdf: 5206972 bytes, checksum: 371cc5a8b519d6d7c42de22340b60b7f (MD5) Previous issue date: 2014 / Resumo: A hidrogenação de compostos aromáticos é uma reação química de grande interesse industrial. Diante das crescentes restrições à presença desses compostos em combustíveis, a hidrodesaromatização catalítica é um dos processos mais importantes nas refinarias. Nesse contexto, o presente trabalho tem por objetivo estudar a hidrogenação de compostos aromáticos em fase líquida, empregando catalisadores à base de metais básicos (Fe, Co, Ni) e nobres (Ru, Pd, Pt) suportados em Al2O3 via impregnação úmida. Especificamente, buscou-se avaliar a influência da composição química, da redução sob H2 e do reuso de tais catalisadores sobre o desempenho catalítico. Catalisadores mono e bimetálicos foram preparados a partir de precursores clorados, através de coimpregnação úmida conduzida a 353 K (80 oC) e pH igual a 10. Durante a impregnação úmida, os sólidos foram reduzidos em fase líquida com formaldeído, sendo posteriormente reduzidos ex situ ou in situ sob H2. Os sólidos preparados foram caracterizados através das técnicas de titulação potenciométrica, adsorção de N2, espectroscopia de fotoelétrons excitados por raios X, microscopia eletrônica (varredura e transmissão) e redução à temperatura programada. O desempenho dos catalisadores foi avaliado na hidrogenação do tolueno e de uma mistura de aromáticos. As reações foram realizadas num reator Parr do tipo slurry, sob pressão de H2 de 5 MPa (50 atm) e à temperatura de 373 K (100 oC), com a adição de água e de solventes ao meio reacional. Na hidrogenação do tolueno, os catalisadores à base de Ru são muito mais ativos e seletivos ao produto da hidrogenação parcial (metilcicloexeno). O efeito da redução sob H2 sobre a atividade catalítica se mostra dependente da natureza do metal básico, enquanto os catalisadores à base de metais nobres têm a atividade diminuída. A adição de metal básico ao catalisador de Ru/Al2O3 também leva a uma diminuição da atividade, mas um efeito sinergético é obtido com a associação Ru-Pt. Para a mistura de aromáticos, a taxa de hidrogenação com o catalisador de Ru-Pt/Al2O3 segue a ordem: benzeno > tolueno > o-xileno > p-xileno. Nesse caso, a adição de solventes ao meio reacional e o reuso do catalisador diminuem a taxa de hidrogenação do benzeno e do tolueno, favorecendo a hidrogenação dos xilenos / Abstract: The hydrogenation of aromatic compounds is a chemical reaction of major industrial interest. Given the increasing restrictions on the presence of these compounds in fuels, the catalytic hydrodearomatization is one of the most important processes in refineries. In this context, the present work aims to study the hydrogenation of aromatic compounds in liquid phase employing catalysts based on base metals (Fe, Co, Ni) and noble metals (Ru, Pd, Pt) supported on Al2O3 by wet impregnation. Specifically, one has sought to evaluate the influence of the chemical composition, H2 reduction and reuse of the solids on its catalytic performances. Mono and bimetallic catalysts were prepared from chlorinated precursors by wet co-impregnation conducted at 353 K (80 °C) and pH of 10. During the wet impregnation, the solids were reduced with formaldehyde in liquid phase and subsequently reduced in situ or ex situ under H2. The prepared solids were characterized by potentiometric titration, N2 adsorption, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and temperature programmed reduction. Catalysts performances were evaluated for toluene and aromatics mixture hydrogenations. The reactions were performed in a "slurry" Parr reactor under H2 pressure of 5 MPa (50 atm) and at a temperature of 373 K (100 °C) with the addition of water and solvents to the multiphase reaction medium. For toluene hydrogenation, Ru-based catalysts are much more active and selective to the product of the partial hydrogenation (methylcyclohexene). The effect of H2 reduction on the catalytic activity is shown dependent on the nature of the base metal, while the noble metal catalysts have decreases its activities. The addition of base metal to the Ru/Al2O3 catalysts also leads to a decrease in activity, but a synergetic effect is obtained with the Pt-Ru association. For the aromatics mixture hydrogenation, the reaction rate to Ru-Pt/Al2O3 catalyst follows the order: benzene > toluene > o-xylene > p-xylene. In this case, the addition of solvents to the reaction medium, as well as the reuse of the catalyst decreases the benzene and toluene hydrogenation rates, favoring the xylenes hydrogenation / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

This diploma thesis is a study of the potential of heat transfer enhancement in the process of hydrogenation refining of oil. The simulation of the process and the heat-hydraulic analysis of the heat exchanger network are performed using the software tools. Based on the obtained results and the results of the optimization study, a new heat exchanger is placed in the process and its parameters are subject to further calculations. The aim is to study the possibilities of heat transfer enhancement for the newly used heat exchanger and to discuss aspects connected with the use of selected software.

Ce travail traite de la synthèse énantiosélective de composés trifluorométhylés via l’étude de la réaction d’isomérisation rédox d’alcools allyliques trifluorométhylés catalysée par des complexes de ruthénium. Nous avons mis au point la réaction d’isomérisation rédox d’alcools allyliques secondaires β-trifluorométhylés. Une étude du mécanistique réactionnel a mis en évidence que l’étape cinétiquement déterminante de cette réaction pour les substrats β-trifluorométhylés est différente de celle décrite pour les substrats non fluorés, il s’agit de l’étape d’insertion. Cette observation nous a permis de mettre au point une réaction d’isomérisation rédox énantiospécifique permettant un transfert intramoléculaire de chiralité via un processus suprafacial. Cette méthode a été appliquée à la synthèse du (S)-CF3-citronellol. En parallèle, nous avons étudié la réaction tandem : isomérisation rédox – transfert d’hydrogène en partant d’alcools allyliques ou d’énones β-trifluorométhylées permettant l’accès aux alcools saturés correspondants. / This work deals with the enantioselective synthesis of trifluoromethylated compounds via the study of the ruthenium catalyzed redox isomerization reaction of trifluoromethylated allylic alcohols. We have developed optmized conditions for the redox isomerization of β-trifluoromethylated secondary allylic alcohols. A mechanistic study of the reaction revealed that the rate determining step for β-trifluoromethylated substrates is different from that described for the non-fluorinated substrates. This observation allowed us todevelop an enantiospecific redox isomerization reaction with a total transfer of chirality via a suprafacialintramolecular process. This methodology has been applied to thesynthesis of (S)-CF3-citronellol. In parallel, we have studied the tandem reaction : redox isomerization - transfer hydrogenation starting from β-trifluoromethylated allylic alcohols orenones, allowing access to the corresponding saturated alcohols.