Carbon dioxide (CO2) is formed when fossil fuels such as oil, gas and coal are burned in power producing plants. CO2 is naturally found in the atmosphere as part of the carbon cycle, however it becomes a primary greenhouse gas when human activities disturb this natural balanced cycle by increasing levels in the atmosphere. In light of this fact, greenhouse gas mitigation strategies have garnered a lot of attention. Carbon capture, utilization and sequestration (CCUS) has emerged as a possible strategy to limit CO2 emissions into the atmosphere. The technology involves capturing CO2 at the point sources, using it for other markets or transporting to geological formations for safe storage. This thesis aims to understand and probe the chemistry of the reactions between CO2 and iron-bearing sediments to ensure secure storage for millennia. The dissertation work presented here focused on trapping CO2 as a carbonate mineral as a permanent and secure method of CO2 storage. The research also explored the use of iron-bearing minerals found in the geological subsurface as candidates for trapping CO2 and sulfide gas mixtures as siderite (FeCO3) and iron sulfides. Carbon dioxide sequestration via the use of sulfide reductants of the iron oxyhydroxide polymorphs lepidocrocite, goethite and akaganeite with supercritical CO2 (scCO2) was investigated using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The exposure of the different iron oxyhydroxides to aqueous sulfide in contact with scCO2 at ~70-100 ˚C resulted in the partial transformation of the minerals to siderite (FeCO3). The order of mineral reactivity with regard to siderite formation in the scCO2/sulfide environment was goethite < lepidocrocite ≤ akaganéite. Overall, the results suggested that the carbonation of lepidocrocite and akaganéite with a CO2 waste stream containing ~1-5% H2S would sequester both the carbon and sulfide efficiently. Hence, it might be possible to develop a process that could be associated with large CO2 point sources in locations without suitable sedimentary strata for subsurface sequestration. This thesis also investigates the effect of salinity on the reactions between a ferric-bearing oxide phase, aqueous sulfide, and scCO2. ATR-FTIR was again used as an in situ probe to follow product formation in the reaction environment. X-ray diffraction along with Rietveld refinement was used to determine the relative proportion of solid product phases. ATR-FTIR results showed the evolution of siderite (FeCO3) in solutions containing NaCl(aq) concentrations that varied from 0.10 to 4.0 M. The yield of siderite was greatest under solution ionic strength conditions associated with NaCl(aq) concentrations of 0.1-1 M (siderite yield 40% of solid product) and lowest at the highest ionic strength achieved with 4 M NaCl(aq) (20% of solid product). Based partly on thermochemical calculations, it is suggested that a decrease in the concentration of aqueous HCO3- and a corresponding increase in co-ion formation, (i.e., NaHCO3) with increasing NaCl(aq) concentration resulted in the decreasing yield of siderite product. At all the ionic strength conditions used in this study, the most abundant solid phase product present after reaction was hematite (Fe2O3) and pyrite (FeS2). The former product likely formed via dissolution/reprecipitation reactions, whereas the reductive dissolution of ferric iron by the aqueous sulfide likely preceded the formation of pyrite. These in situ experiments allowed the ability to follow the reaction chemistry between the iron oxyhr(oxide), aqueous sulfide and CO2 under conditions relevant to subsurface conditions. Furthermore, very important results from these small-scale experiments show this process can be a potentially superior and operable method for mitigating CO2 emissions. / Chemistry

A reactive transport model is proposed to simulate the reactivity of cement based material in contact with CO2-saturated brine and supercritical CO2 (scCO2) under CO2 geological storage conditions. This code is developed to solve simultaneously transport and chemistry by a global coupled approach, considering the effect of temperature and pressure. The variability of scCO2 properties with pressure and temperature, such as solubility in water, density and viscosity are taken into account. It is assumed that all chemical processes are in thermodynamical equilibrium. Dissolution and precipitation reactions for portlandite (CH) and calcite (CC) are described by mass action laws and threshold of ion activity products in order to account for complete dissolved minerals. A chemical kinetics for the dissolution and precipitation of CH and CC is introduced to facilitate numerical convergence. One properly chosen variable is able to capture the precipitation and dissolution of the relevant phase. A generalization of the mass action law is developed and applied to calcium silicate hydrates (C-S-H) to take into account the continuous variation (decrease) of the Ca/Si ratio during the dissolution reaction of C-S-H. The changes in porosity and microstructure induced by the precipitation and dissolution reactions are also taken into account. Couplings between transport equations and chemical reactions are treated thanks to five mass balance equations written for each atom (Ca, Si, C, K, Cl) as well as one equation for charge balance and one for the total mass. Ion transport is described by using the Nernst-Plank equation as well as advection, while gas and liquid mass flows are governed by advection. Effect of the microstructure and saturation change during carbonation to transport properties is also considered. The model is implemented within a finite-volume code, Bil. Principles of this method and modeling approach are discussed and illustrated with the help of a simple example. This model, with all the efforts above, is able to simulate the carbonation processes for cement based materials, at both saturated and unsaturated conditions, in a wide CO2 concentration, temperature and pressure range. Several sets of experiments, including sandstone-like conditions, limestone-like conditions, supercritical CO2 boundary and unsaturated conditions reported in the literature are simulated. Good predictions are provided by the code when compared with experimental observations. Some experimental observed phenomena are also explained by the model in terms of calcite precipitation front, CH dissolution front, porosity profile, etc

Cette thèse porte sur la mise en œuvre de procédés innovants d'extraction de composés naturels bioactifs de plantes. Nous avons considéré ici l'extraction d'un composé anti-oxydant, l'acide rosmarinique, à partir du végétal mélisse (Melissa officinalis L.), qui contient également d'autres composés d'intérêt (citral et caryophyllène). Différentes techniques d'extraction-purification, soit à haute pression (extraction au CO2 supercritique) ou à pression atmosphérique (extraction Soxhlet, extraction batch, nanofiltration etc.) ont été envisagées. L'objectif de ce travail a été d'étudier expérimentalement l'influence des paramètres opératoires (débit, composition et concentration du solvant, taille des particules, pression et température) sur la cinétique des processus afin de sélectionner les meilleures conditions pour chaque opération. Les résultats expérimentaux ont été ensuite comparés avec plusieurs modèles mathématiques décrivant les phénomènes de transfert de masse et l'écoulement au travers du milieu poreux constitué par la matière végétale broyée. Cette démarche, à partir de la détermination des paramètres physiques du modèle, a fourni les éléments pour une extrapolation potentielle à l'échelle industrielle. Du point de vue du procédé complet d'extraction-purification, l'originalité du travail a été de proposer plusieurs scénarii d'enchainement d'opérations, couplant en synergie des opérations conventionnelles à pression atmosphériques (macération, nano-filtration etc.) et des opérations de traitement au CO2 supercritique avec co-solvant. / This thesis deals with the extraction of natural bioactive compounds from plants (case study with Lemon Balm (Melissa officinalis L.)) by using different separation techniques at high (supercritical extraction) and atmospheric pressure (Soxhlet extraction, batch extraction, nanofiltration etc.). The influence of main operational parameters (solvent composition and flow rate, particle size of the raw material, pressure, temperature) on the process kinetics is studied experimentally with the aim to determine appropriate operational conditions for better extraction. The experimental results are confronted to a number of mathematical models in order to estimate the applicability of different theoretical concepts to the particular process and to select and apply appropriate models for determination of important parameters, characterizing the mass transfer process and necessary for scale-up and design purposes. Coupling between different separation methods is also considered and a number of integrated process schemes are proposed resulting in better yield of the targeted compounds.

Un modèle de transport réactif est proposé pour simuler la réactivité des matériaux à base de ciment en contact avec une saumure saturée en CO2 et/ou le CO2 supercritique (CO2sc) dans les conditions de stockage géologique du CO2. Un code a été développé pour résoudre simultanément le transport et la chimie par une approche globale couplée, compte tenu de l'effet de la température et de la pression. La variabilité des propriétés du CO2sc avec la pression et la température, telles que la solubilité dans l'eau, la densité et la viscosité sont pris en compte. On suppose que tous les processus chimiques sont en équilibre thermodynamique. Les réactions de dissolution et de précipitation de la portlandite (CH) et de calcite (CC) sont décrites par des lois d'action de masse et des seuils de produit d'activité ioniques. Une cinétique de dissolution de CH est introduite pour faciliter la convergence numérique. La définition d'une variable principale permet de capturer la précipitation et la dissolution des phases solides à base de calcium. Une généralisation de la loi d'action de masse est développée et appliquée aux silicates de calcium hydratés (CSH) pour tenir compte de la variation continue (diminution) du rapport Ca/Si au cours de la dissolution des CSH. Les variations de porosité et de la microstructure induites par les réactions de précipitation et de dissolution sont également prises en compte. Le couplage entre le transport et la chimie est modélisé par cinq équations de bilan de masse écrites pour chaque atome (Ca, Si, C, K, Cl), ainsi que par une équation de conservation de la masse totale et celle de la charge électrique. Les lois de Darcy et de Nernst-Planck sont utilisées pour décrire le transport de masse et d'ions. Les propriétés de transport dépendent du degré de saturation et de la porosité. Le modèle est implémenté dans le code de volumes finis, Bil. Les principes de cette méthode et l'approche de modélisation sont discutés et illustrés sur un exemple simple. Ce modèle est en mesure de simuler les processus de carbonatation des matériaux à base de ciment, dans des conditions à la fois saturés et insaturés, dans une large plage de concentration de CO2, de température et de pression. Plusieurs expériences, rapportées dans la littérature, sont simulées en utilisant divers types de conditions aux limites: (i) solutions saturées ou non en CO2 et carbonate de calcium, (ii) gas supercritique de CO2. Les prédictions sont comparées avec les observations expérimentales. Certains phénomènes observés expérimentalement peuvent être également expliqués par le modèle / A reactive transport model is proposed to simulate the reactivity of cement based material in contact with CO2-saturated brine and supercritical CO2 (scCO2) under CO2 geological storage conditions. This code is developed to solve simultaneously transport and chemistry by a global coupled approach, considering the effect of temperature and pressure. The variability of scCO2 properties with pressure and temperature, such as solubility in water, density and viscosity are taken into account. It is assumed that all chemical processes are in thermodynamical equilibrium. Dissolution and precipitation reactions for portlandite (CH) and calcite (CC) are described by mass action laws and threshold of ion activity products in order to account for complete dissolved minerals. A chemical kinetics for the dissolution and precipitation of CH and CC is introduced to facilitate numerical convergence. One properly chosen variable is able to capture the precipitation and dissolution of the relevant phase. A generalization of the mass action law is developed and applied to calcium silicate hydrates (C-S-H) to take into account the continuous variation (decrease) of the Ca/Si ratio during the dissolution reaction of C-S-H. The changes in porosity and microstructure induced by the precipitation and dissolution reactions are also taken into account. Couplings between transport equations and chemical reactions are treated thanks to five mass balance equations written for each atom (Ca, Si, C, K, Cl) as well as one equation for charge balance and one for the total mass. Ion transport is described by using the Nernst-Plank equation as well as advection, while gas and liquid mass flows are governed by advection. Effect of the microstructure and saturation change during carbonation to transport properties is also considered. The model is implemented within a finite-volume code, Bil. Principles of this method and modeling approach are discussed and illustrated with the help of a simple example. This model, with all the efforts above, is able to simulate the carbonation processes for cement based materials, at both saturated and unsaturated conditions, in a wide CO2 concentration, temperature and pressure range. Several sets of experiments, including sandstone-like conditions, limestone-like conditions, supercritical CO2 boundary and unsaturated conditions reported in the literature are simulated. Good predictions are provided by the code when compared with experimental observations. Some experimental observed phenomena are also explained by the model in terms of calcite precipitation front, CH dissolution front, porosity profile, etc

Este trabalho teve como objetivo o mapeamento da composição do óleo essencial (OE) de Corymbia citriodora produzido no Brasil pelas principais destilarias, Três Barras (FTB) e Meneghetti (FMG), e a extração do OE e oleoresina (OR) a partir das folhas utilizando a tecnologia de fluidos supercríticos. Foram estudados os efeitos das condições do processo, pressão (P) e temperatura (T), sobre a composição química e rendimento dos extratos, além da atividade antioxidante de alguns ensaios. As folhas picotadas apresentaram umidade de 7,33±1,1 e 8,66±0,5% para a FMG e FTB, respectivamente. As extrações, a partir das folhas com CO2 em condições sub e supercríticas, foram realizadas em duas etapas. Na primeira etapa, obteve-se o OE e, em seguida, as condições foram reajustadas para se fazer a extração da OR. As combinações das variáveis P e T foram determinadas conforme um delineamento composto central rotacional (DCCR), sendo feito um para cada etapa de extração. Para todos os extratos obtidos na primeira etapa, bem como dos OEs obtidos por arraste à vapor (AV) e hidrodestilação (HD), determinou-se o perfil de voláteis por cromatografia gasosa acoplado ao espectrofotômetro de massa (GC/MS). Os ensaios de maior rendimento em OE sem a coextração de pigmentos (100 bar e 60ºC, FTB=1,59% e FMG= 1,56%) e OR (220 bar e 70ºC, FTB=1,59% e FMG= 1,56%) tiveram sua atividade antioxidante determinada pelos métodos DPPH e branqueamento do β-caroteno. A OR também foi avaliada quanto ao seu teor de compostos fenólicos totais, pelos métodos Folin Ciocalteu e Azul da Prússia, e flavonoides totais. Para a amostra FTB, verificou-se a influencia positiva da P no rendimento de óleo essencial (p<0,05), enquanto que para a amostra FMG nenhuma variável teve influencia significativa (p>0,05). Na resposta rendimento da OR, as variáveis independentes P e T não tiveram influencia significativa. A concentração do citronelal (CC) teve influencia significativa da P para a amostra FTB e da interação P × T, para a FMG. Para a amostra FTB, na condição supercrítica de 100 bar e 60ºC, o rendimento em OE foi semelhante ao obtido por HD (1,59% e 1,6±0,15%, respectivamente), porém o teor de citronelal foi superior (de 87,6%) ao método convencional (79,5%). Nestas mesmas condições para a amostra FMG, os rendimentos foram de 1,53 e 1,16±0,15% e os teores de citronelal de 71,8% e 57,9% para os OE obtidos por SFE e HD, respectivamente. Os OEs obtidos por AV das amostras FTB e FMG apresentaram teores de citronelal de 79,8 e 76,6%, respectivamente. Nestes OEs foram identificados diversos compostos com atividade biológica comprovada; verificou-se variações tanto na quantidade quanto na qualidade dos compostos encontrados em cada amostra. As ORs obtidas das folhas FTB e FMG apresentaram alta capacidade antioxidante em ambos os métodos testados, branqueamento do β-caroteno e DPPH, com 81,6±3,0 e 81,7±1,6% de inibição e EC50 de 18,04±0,6 e 12,6±0,4 mg/mL, respectivamente. A capacidade redutora dos compostos da OR foi maior para o método do Azul da Prússia (FTB= 15,7±1,6 e FMG= 12,9±0,5 mg EAG/100g de folhas) em relação ao reagente Folin-Ciocalteu (FTB=74,2±4,0 e FMG= 84,8±2,4, em mg EC/100g de folhas). Os teores de flavonoides (FTB=26,7±3,9 e FMG=20,4±0,9, em mg EC/100g de folhas) foram superiores aos valores dos compostos fenólicos obtidos pelo método de Folin-Ciocalteu, provavelmente porque o extrato foi testado em sua forma bruta. Os resultados encontrados demonstram que através das condições adequadas de extração com CO2 supercrítico é possível a obtenção de um OE enriquecido em citronelal e de uma OR com alta atividade biológica. A técnica também permite um melhor aproveitamento da matéria-prima, através da extração sequencial e seletiva de OE e OR, em relação aos métodos convencionais. / The aim of this work was to evaluate the Corymbia citriodora essential oil (EO) composition produced by the main Brazilian distilleries; Meneghetti and Três Barras moreover evaluate the yield, composition and biological activity of (EO) and oleoresin (OR) obtained from leaves by using supercritical fluids technology. The effects of operational conditions, pressure (P) and temperature (T), on chemical composition and yield were studied. The cut leaves showed moisture content of 7,33±1,1 and 8,66±0,5% to FMG and FTB samples, respectively. The extractions using CO2 in sub and supercritical conditions were performed in two steps. In the first step the EO was obtained. After, the operational conditions were readjusted to make the OR extraction. The P and T values were determined using a complete factorial experimental design (CFED). It was used two experimental designs, one for each step. The volatile profile of all EO, obtained by steam distillation (AV), hydrodistillation (HD) and SFE were determined using a gas chromatography coupled with mass spectrometer (GC/MS) equipment. The experiments that provide the higher yields in EO without pigments coextraction (100 bar e 60ºC, FTB=1,59% e FMG= 1,56%) and OR (220 bar e 70ºC, FTB=1,59% e FMG= 1,56%) had their antioxidant activity determined by DPPH test and β-carotene bleaching assay. The OR was also evaluated for its content of total flavonoids and total phenolics by two different methods, Prussian Blue and Folin-Ciocalteu. In the FTB sample, SFE, to the sample FTB was observed the positive influence of P on essential oil yield (p<0,05), whereas to FMG the variables P and T or its interaction do not have significantly influence in this response. The citronellal concentration (CC) had a positive influence of P to FTB sample and P x T interaction to FMG sample. To FTB, at 100 bar and 60ºC, the EO yield was similar from that obtained by HD (1,59% e 1,6±0,15%, respectively). However the citronelal concentration was higher than ( 87,6%) that obtained by the convencional method (79,5%). At the same conditions, to the FMG sample at the same conditions, the yields were 1,53 e 1,16±0,15% and the citrionelal concentration were 71,8% e 57,9% to the EO obtained by SFE and HD, respectively. OE obtained by AV from FTB and FMG showed citronellal concentrations of 79,8 e 76,6%, respectively. In this EO were identified a variety of compounds with biological activity; it was verified variations in both quantity and the quality of the compounds in each sample. The ORs obtained from FTB and FMG showed a high antioxidant capacity in both, β-carotene bleaching assay and DPPH test, with inhibition of 81,6±3,0 e 81,7±1,6% and EC50 of 18,04±0,6 e 12,6±0,4 mg/mL, respectively. Reducing capacity of OR compounds was higher in Prussian Blue method (FTB= 15,7±1,6 e FMG= 12,9±0,5 mg EAG/100g of leaves) in relation to Folin-Ciocalteu reagent (FTB=74,2±4,0 e FMG= 84,8±2,4, em mg EC/100g de folhas). Total flavonoids (FTB=26,7±3,9 e FMG=20,4±0,9, em mg EC/100g of leaves) were higher than the value of phenolic compounds obtained in Folin-Ciocalteu reagent, probably because the extract was tested crude. The results obtained suggest that by using the SFE it is possible to obtain an EO with a high citronellal concentration. OR also showed a high antioxidant capacity. The SFE technique also improve the raw material utilization by the sequencial and selective extraction of EO and OR, in relation of conventional methods.

Ce travail de thèse rend compte de la mise en oeuvre d’un système de synthèse en continu dupoly(acide acrylique) en milieu CO2 supercritique (15 MPa et 75 °C). Nous avons conçu undispositif microfluidique résistant aux hautes pressions permettant l’écoulement de gouttes desolution aqueuse de monomère dans une phase continue constituée d’un mélangesupercritique d’éthanol dans du CO2 et contenant l’amorceur azobisisobutyronitrile (AIBN).Nous avons déterminé par spectroscopie IR la répartition des différentes espèces chimiquesdu mélange en fonction de la pression et la température, puis caractérisé la décompositionthermique de l’amorceur selon la composition du milieu réactionnel par spectroscopie UVVis.Enfin, nous avons montré que les gouttes sont comparables à des réservoirs demonomère alimentant sans cesse la phase continue. En raison de ce transfert rapide vis-à-visde la conversion de l’AA en chaîne polymère, la réaction de polymérisation s’effectuecontinûment avec un rapport molaire monomère sur amorceur constant durant tout le tempsde séjour dans le microcanal (jusqu’à 41 min). Une gamme large de masses molaires avec desindices de polymolécularité faibles a été obtenue : de 20 000 à 120 000 g.mol-1 pour 1,35 à1,70, en variant simplement les concentrations de monomère de la solution aqueuse initiale.Les paramètres expérimentaux influençant les propriétés du poly(acide acrylique) obtenu,ainsi que le lieu de la polymérisation ont été étudiés. / In this work, a continuous microfluidic device was developed to perform the synthesis ofpoly(acrylic acid) in supercritical CO2 (15 MPa and 75°C). This high pressure resistantdevice allows generating segmented flows in microcanal: an aqueous solution of monomerwas dispersed in a mixture of ethanol in CO2 containing initiator AIBN. The distribution ofdifferent components in this biphasic system has been determined by IR spectroscopyaccording to the pressure and the temperature. The thermal decomposition of AIBN indifferent reaction media has been investigated using UV-Vis spectroscopy. During thereaction, the droplets were used as reservoirs which insure the transfer of monomer to thecontinuous phase. Because of this rapid transfer compared to the reaction conversion, thepolymerization reaction was carried out continuously with a constant molar ratio betweenmonomer and initiator throughout the residence time (up to 41 min). It has been showed thata large range of molecular weights of poly(acrylic acid) (20 000 and 120 000 g.mol-1) withlow polydispersity index (1.35 à 1.70) can be obtained by just changing the initial monomerconcentration in the droplets. The effect of other parameters influencing the properties ofpoly(acrylic acid) as well as the locus of polymerization have been discussed.

La fonctionnalisation des surfaces de silice permet d’obtenir des matériaux compétitifs dans le cadre de l’extraction spécifique d’ions. Cependant, les solvants généralement utilisés pour fonctionnaliser la silice présentent des contraintes économiques comme environnementales. Le CO2 supercritique est une alternative verte à l’utilisation de solvants organiques. Les objectifs de cette thèse sont de caractériser la fonctionnalisation par voie CO2 supercritique des surfaces de silices par des alcoxysilanes, de déterminer le devenir de cette fonctionnalisation dans des milieux de quelques nanomètres et de préciser leur comportement en solution. Plusieurs systèmes modèles à base de silice ont été utilisés comme support au greffage : des surfaces planes de silice, des surfaces planes espacés de quelques nanomètres simulant des milieux confinés plans (nanocanaux) et de la silice à mésoporosité organisée (SBA-15). Afin de déterminer l’impact des groupements fonctionnels sur la fonctionnalisation, plusieurs ont été utilisés ou préparés : le 3-(mercaptopropyl)triméthoxysilane (MPTMS), 3-[amino(éthylamino)propyl]triméthoxysilane (AEAPTMS) et le 3-(iodopropyl)triéthoxysilane (IPTES). Les résultats obtenus sur les surfaces planes de silice ont permis de déterminer différentes morphologies et structures de couche selon le groupement fonctionnel de l’alcoxysilane. Pour le MPTMS, l’obtention d’une monocouche auto-assemblée est possible à 60ºC. Pour l’AEAPTMS, des couches polycondensées sont obtenues quelle que soit la température du procédé de greffage. Pour l’IPTES, une bicouche a été obtenue à 120°C. Ces mêmes morphologies ont permis d’expliquer le remplissage des nanocanaux de silice, avec la présence additionnelle de molécules physisorbées. Le transfert des procédés de greffage sur des silices mésoporeuses SBA-15 a montré que les morphologies des couches obtenues sur les surfaces planes de silice n’étaient pas strictement transposables. En effet, il a été montré que le MPTMS et l’IPTES se greffaient dans la microporosité. Alors que les molécules de MPTMS se greffent en monocouche à la surface des mésopores, le greffage d’IPTES sur leur surface n’a pas pu être mis en évidence. De plus, de la polycondensation a aussi été caractérisée dans une fraction des mésopores. Cette polycondensation n’est pas pilotée par les mêmes paramètres expérimentaux suivant la molécule.Par ailleurs la post-fonctionnalisation des groupements iodo en phosphonate par la réaction d’Arbuzov-Michaelis est avérée dans les surfaces planes comme dans les silices mésoporeuses. Dans le cas des silices SBA-15 post-fonctionnalisées, le matériau final correspond à une silice SBA-15 ayant des pores plus grands qu’avant la post-fonctionnalisation et présentant de groupements phosphonates dans ses murs. Les mesures de leur évolution en solution ont montré la stabilité du matériau à différents pH et que les solutions diffusaient plus ou moins vite dans les murs de la silice. Les coefficients de diffusion des solutions calculés ont prouvé que la fonctionnalisation, en bouchant la microporosité, ralentissait la diffusion des solutions dans les murs de silice. Dans le cas de solutions basiques, cette diffusion est plus élevée probablement à cause de l’affinité des cations avec les groupements phosphonates. Des études de sorption ainsi que des effets d'irradiations γ seraient des perspectives intéressantes de ce travail. / Surface functionalization of silica leads to the synthesis of materials with possible applications in the selective ion extraction. However, organic solvents classically used to functionalize the silica surface have economic and environmental issues. Supercritical carbon dioxide (SC CO2) seems a greener alternative to the use of these organic solvents. The aim of this PhD work is to characterize the SC CO2 functionalization of silica surfaces by alkoxysilanes, to determine the evolution of the grafting in nanometric media and to precise the behavior of the materials in aqueous solution. Different model systems based on silica have been used as grafting supports: plane silica surfaces, parallel and plane surfaces spaced of few nanometers (silica nanochannels) and organised mesoporous silica (SBA-15). In order to determine the impact of the alkoxysilane head groups on the supercritical CO2 functionalization, different alkoxysilanes have been used or prepared: 3-(mercaptopropyl)trimethoxysilane (MPTMS), 3-[amino(ethylamino)propyl]trimethoxysilane (AEAPTMS) and 3-(iodopropyl)triethoxysilane (IPTES). The results obtained in plane silica surfaces allowed the determination of different morphologies and structures of the grafted layers, depending on the alkoxysilane used. The same morphologies have been found on the grafting of silica nanochannels, with the addition of physisorbed molecules. The transfert of the SC CO2 grafting process SBA-15 silica showed that the process was not strictly transposable. AEAPTMS could not be grafted in mesoporous silicas SBA-15 having a pore size lower than 7,5 nm. MPTMS and IPTES molecules are both grafted on the microporosity and a fraction of mesopores is obtured. Moreover, MPTMS monolayers are grafted at the mesoporous surface. The driving parameters of the polycondensation change depending on the grafted molecule.Besides, the post-functionalization of the iodo groups in phosphonate by the Arbuzov-Michaelis reaction have been effectively performed in plane and in mesoporous silicas. In SBA-15 silica, the post-functionalization leads to materials with higher porosity and with phosphonate groups in the pore wall. The measure of the evolution in aqueous solution show that the material is stable at different pH values and that the solution diffuses in the pore walls. The calculated diffusion coefficients highlight that the functionalization, which obstructed the microporosity, slowed down the diffusion of the aqueous solutions in the silica walls. In the case of basics solutions, the diffusion is probably enhanced by the affinity of the cations with the phosphonate groups. Sorption studies and the effects of γ-irradiations in the grafted materials could be interesting outlooks of this work.

The separation of the expensive catalysts from the solvent and reaction products remains one of the major disadvantages of homogeneous catalytic reactions, which are otherwise advantageous because of their high activity, tuneable selectivity and ease of study. Ideally, the homogeneous reactions would be carried out in continuous flow mode with the catalyst remaining in the reactor at all times, whilst the substrates and products flow over the catalyst. The system we have been studying is one where the catalyst is dissolved in a thin film of an ionic liquid, and this is supported within the pores of a microporous silica. This supported ionic liquid phase (SILP) catalyst is then placed in a tubular flow reactor, similar to that used for heterogeneous reactions. The raw materials are then injected into the rig, pass through the reactor and the products and the raw materials that have not reacted are collected at the other end of the rig. Supercritical CO₂ is used to transport the raw materials and products along the catalyst bed, allowing a continuous flow mode with low leaching for both the catalyst and the ionic liquid. We have applied this procedure first to alkene metathesis catalysed by a ruthenium complex that has been especially designed to dissolve in 1-butyl-3-methyimidazolium triflamide (BMIM NTf₂), which was used as ionic liquid. Activity is observed for the ring closing metathesis of diethyl 2,2-diallylmalonate, but the catalyst is not stable, only allowing about 300 turnovers. This instability is attributed to the formation of Ru=CH₂ moieties, which dimerise to an inactive species. More success is achieved with internal alkenes such as 2-octene and especially methyl oleate. Self metathesis of methyl oleate continues for >10.000 turnovers over 10 h, with only small decreases in activity. The cross metathesis of methyl oleate with dimethyl maleate has also been studied. Cross metathesis dominates in the early stages of the reaction but the cross metathesis products diminish with time. Surprisingly, the catalyst does not deactivate since self metathesis of methyl oleate continues. The phase behaviour of the reaction was monitored and gave us an insight into the reasons for this change in selectivity. Methoxycarbonylation reactions in continuous flow proved to be a much more difficult process than the previous metathesis reactions. Higher catalyst loading was needed to reduce the reaction times. The first continuous flow reactions showed conversion predominantly, if not exclusive, of 1-octene isomerised products. The presence of ionic liquid (IL) in the SILP system was essential, otherwise the catalyst leached out of the reactor very quickly. Batch reactions showed that none of the studied parameters (absence of presence of either BMIM NTf₂, OMIM NTf₂, silica or CO₂) had any influence on the reaction, but when observing the results it was noticed that the reactions that gave the best results were performed in a close range of pressures between 55 and 70 bar, indicating that the reaction might be pressure dependent. Further continuous flow reactions in that range of pressures gave the best conversions to methoxycarbonylation products. Unfortunately, at these pressures and without CO₂ the reaction took place in a liquid phase and thus substantial IL and catalyst leaching was observed, causing a decrease in conversion and making the reaction not feasible under continuous flow conditions. Nevertheless, the catalyst system composed of Pd, 1,2-bis(di-tert-butylphosphinomethyl)benzene (DTBPMB) ligand and acid showed an excellent linear selectivity, usually higher than 90%, both in batch and continuous flow reactions. Hydrogenation reactions of dimethyl itaconate (DMI) and dibutyl itaconate (DBI) using Rh-MeDuPhos showed excellent activity and enantioselestivity in a batch mode. In a continuous flow mode IL leaching caused a decrease of the enantioselectivity. The best results were obtained when CO₂ was not present. On the other hand, the absence of CO₂ implied that the reaction was performed in a liquid phase and therefore abundant IL leaching was observed along with a decrease in the enantioselectivity. A study of the reaction behaviour when using CO₂ in its different phases (liquid, gas and supercritical) was carried out. Under supercritical conditions IL leaching was avoided but conversion was not observed. When using CO₂ in its liquid phase some conversion was observed and full conversion occurred in its gas phase, but abundant IL leaching caused a decrease in the enantioselectivity. Better results were obtained by immobilising a Rh-MeDuPhos catalyst onto alumina via heteropoly acids. The effect of pressure, H₂ flow and substrate flow were studied and the stability of the reaction in the long term was examined under optimal conditions. More than 12,900 TONs were achieved after 4 days of continuous reaction, with conversions higher than 90% during the 3 first days and e.e. higher than 99% during the 2 first days.

Ce travail concerne l'extraction de substances naturelles d'origine végétale en utilisant des procédés « verts » tels que l'extraction au CO2 supercritique (CO2-SC, de 90 à 1000 bar) et l'extraction à l'eau sub-critique (SWE). Ces procédés sont une alternative à l'hydrodistillation (HD) et l'extraction par solvant (SE) traditionnellement utilisés dans l'industrie des produits naturels. La majorité du travail a été réalisée sur l'espèce Tetraclinis articulata où les performances des procédés, CO2-SC , HD, SWE et SE, ont été optimisées puis comparées en termes de rendement, composition chimique, durée…, et en particulier activité antioxydante des extraits (évaluée par les tests ABTS+ and DPPH). La plus forte activité antioxydente a été mise en évidence pour les extraits CO2-SC, ceci étant très probablement dû à une moindre dégradation thermique, comme l'a indiqué la comparaison des compositions chimiques. La CO2-SC basse pression (90 bar) a permis d'obtenir un extrait de bonne qualité et, pour ce cas, une modélisation a été proposée pour comprendre et identifier le mécanisme limitant qui s'est avéré être l'équilibre solide-fluide. La modélisation de l'hydrodistillation a également été proposée, basée sur le modèle de Sovová . Ensuite, l'approche a été étendue à d'autres plantes : Eucalyptus cinerea, Eucalyptus Camaldulensis, Cypres sempervirens et callitris. / This work has dealt with extraction of natural substances from plants using « green » processes such as supercritical CO2 extraction (CO2-SC from 90 to 1000 bar) and extraction with subcritical water (SWE). These processes are an alternative to hydrodistillation (HD) and solvent extraction (SE) traditionally used in the natural products industry. Main part of the work was done on the species Tetraclinis articulata, and performance of the different processes, CO2-SC, HD,SWE and SE, were optimized and compared in terms of yield, chemical composition, duration ... and especially antioxidant activity of extracts (assessed by the ABTS+ and DPPH tests). CO2-SC extracts exhibited the strongest antioxidant activity and comparison of chemical compositions of the different extracts indicated that this is very probably due to lower thermal degradation of active molecules. For low pressure CO2-SC (90 bar), a model was proposed to understand and identify the limiting mechanism that proved to be solid-fluid equilibrium. For hydrodistillation, modelling, based on the Sovová 's model was also proposed. Then, the approach was extended to other plants: Eucalyptus cinerea and Eucalyptus camaldulensis, Cypres sempervirens and Callitris.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growth in the generation of electrical and electronic equipment waste (WEEE) has won global importance and cell phones are highlighted between these wastes because of short life cycle and its amounts of hazardous materials. In LCD screens, there is a mixture of indium tin oxide (ITO), typically tin oxide (10-20 %) and indium oxide (80-90 %). The indium (In) is a metal of relatively limited resources and has extensive use. Thus, this work aims to obtain an effective method for extraction of In from LCD screens of mobile phones. To this purpose, after manual separation of LCD screens followed by mechanical treatment, leaching at atmospheric pressure comparing the citric, malic and acetic acids, were carried out varying parameters like temperature, concentration of acid, solid:liquid ratio, volume peroxide hydrogen and reaction time. Therefore, the best conditions set out in the leaching at atmospheric pressure were used for extraction in supercritical CO2, where the employment of different temperatures and critical pressures were studied, in order to make the process faster and more efficient. The In concentration extracted in both cases was determined by atomic absorption (AAS). The extraction using 1M citric acid, 90 °C, 1:20 solid:liquid ratio with 5 % of the volume of H2O2 performed for 3 hours resulted in extraction of 76.5 % of In present in the LCD screens from obsolete cell phones. The leaching process using supercritical fluid in the presence of co-solvents, provided reduction in extraction time and higher percentage of metal extraction, reaching 90.2 % when were used 1 M citric acid, 80 °C, 1:20 ratio solid:liquid with 5 % v/v of H2O2, pressure of 150 bar and 30 minutes of process time. In order to transfer the obtained In in solution to a solid phase, the adsorption process was carried out with activated carbon and Spirulina as adsorbent, yielding removal 77.8 and 67.8 %, respectively. Thus, a new process for In recovery was developed, which in addition to reducing environmental pollution generated by the incorrect disposal of LCD screens of mobile phones and the employment of inorganic acids conventionally used, reduces the consumption of natural resources, making the promising process. / O crescimento na geração de resíduos de equipamentos elétricos e eletrônicos (REEE) tem ganhado importância mundial e, os telefones celulares ganham destaque entre esses resíduos pelo ciclo de vida curto e quantidade de materiais perigosos que possuem. Nas telas de LCD, presentes neste tipo de resíduo, há uma mistura de óxido de estanho (10-20 %) e índio (80-90 %), denominada ITO. O índio (In) é um metal de recursos relativamente limitados e que possui ampla utilização. Assim, o presente trabalho possui como objetivo a obtenção de um método eficaz para extração de In presente em telas de LCD de telefones celulares. Para tal, após a separação manual das telas de LCD seguido de processamento mecânico, foram realizadas lixiviações sob pressão atmosférica comparando os ácidos cítrico, málico e acético, variando parâmetros como temperatura, concentração de ácido, relação sólido:líquido, volume de peróxido de hidrogênio e tempo de reação. Logo, as melhores condições estabelecidas nas lixiviações sob pressão atmosférica foram utilizadas para extração de In com CO2 supercrítico, onde se estudou o emprego de diferentes temperaturas e pressões críticas, a fim de tornar o processo mais rápido e eficiente. A concentração de In extraída, em ambos os processos, foi determinada por absorção atômica (AAS). A extração a pressão atmosférica utilizando ácido cítrico a 1 M, 90 °C, razão sólido:líquido de 1:20, com 5 % do volume de H2O2 realizada durante 3 horas proporcionou a extração de 76,5 % de In das telas de LCD obtidas a partir de celulares obsoletos. O processo utilizando a lixiviação com fluido supercrítico, na presença de co-solventes, proporcionou redução no tempo de extração, além de maior percentual de extração do metal, chegando a 90,2 % de extração quando utilizado ácido cítrico a 1 M, 80 °C, razão sólido:líquido de 1:20, com 5 % do volume de H2O2, pressão de 150 bar e tempo de processo de 30 min. Visando a recuperação do In da fase aquosa obtida na lixiviação, realizou-se o processo de adsorção utilizando carvão ativado e Spirulina como adsorventes, obtendo-se remoção de 77,8 e 67,8 %, respectivamente. Assim, um novo processo de recuperação de In foi desenvolvido, que além de reduzir a poluição ambiental gerada pelo descarte incorreto de telas de LCD de telefones celulares e pelos ácidos inorgânicos convencionalmente utilizados, diminui o consumo de recursos naturais, tornando o processo promissor.