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ABSTRACT MODELING OF CARBON DIOXIDE SEQUESTRATION IN A DEEP SALINE AQUIFER BASBUg, BaSar M.S., Department of Petroleum and Natural Gas Engineering Supervisor : Prof. Dr. Fevzi G&uuml / mrah July 2005, 245 pages CO2 is one of the hazardous greenhouse gases causing significant changes in the environment. The sequestering CO2 in a suitable geological medium can be a feasible method to avoid the negative effects of CO2 emissions in the atmosphere. CO2 sequestration is the capture of, separation, and long-term storage of CO2 in underground geological environments. A case study was simulated regarding the CO2 sequestration in a deep saline aquifer. The compositional numerical model (GEM) of the CMG software was used to study the ability of the selected aquifer to accept and retain the large quantities of injected CO2 at supercritical state for long periods of time (200 years). A field-scale model with two injectors and six water producers and a single-well aquifer model cases were studied. In a single-well aquifer model, the effects of parameters such as vertical to horizontal permeability ratio, aquifer pressure, injection rate, and salinity on the sequestration process were examined and the sensitivity analyses were performed after simulating the field-scale model. The supercritical CO2, one-state fluid which exhibits both gas and liquid-like properties, and gaseous CO2 were sequestered in the forms of free CO2 bubble, dissolved CO2 in brine and precipitated CO2 with calcite mineral in a deep saline aquifer. The isothermal condition was assumed during injection and sequestration processes. The change in porosity and permeability values that might have occurred due to mineralization and CO2 adsorption on rock were not considered in this study. Vertical to horizontal permeability ratio and initial pressure conditions were the most dominating parameters affecting the CO2 saturation in each layer of the aquifer whereas CO2 injection rate influenced CO2 saturation in middle and bottom layers since CO2 was injected through bottom layer.

This thesis presents the results of the investigation on developing and evaluating a low temperature (<150oC) non - catalytic process using a hydrogen transfer agent (instead of molecu-lar hydrogen) for coal dissolution in supercritical CO2. The main idea behind the thesis was that one hydrogen atom from water and one hydrogen atom from the hydrogen transfer agent (HTA) were used to hydrogenate the coal. The products of coal dissolution were non-polar and polar while the supercritical CO2, which enhanced the rates of hydrogenation and dissolution of the non-polar molecules and removal from the reaction site, was non-polar. The polar modifier (PM) for CO2 was added to the freed to aid in the dissolution and removal of the polar components. The addition of a phase transfer agent (PTA) allowed a seamless transport of the ions and by-product between the aqueous and organic phases. DDAB, used as the PTA, is an effective phase transfer catalyst and showed enhancement to the coal dissolution process. COAL + DH- +H2O  COAL.H2 + DHO-- This process has a great feature due to the fact that the chemicals were obtained without requir-ing to first convert coal to CO and H2 units as in indirect coal liquefaction. The experiments were conducted in a unique reactor set up that can be connected through two lines. one line to feed the reactor with supercritical CO2 and the other connected to gas chromatograph. The use of the supercritical CO2 enhanced the solvent option due to the chemical extraction, in addition to the low environmental impact and energy cost. In this thesis the experiment were conducted at five different temperatures from atmos-pheric to 140°C, 3000 - 6000 psi with five component of feed mixture, namely water, HTA, PTA, coal, and PM in semi batch vessels reactor system with a volume of 100 mL. The results show that the chemicals were obtained without requiring to first convert coal to CO and H2 units as in indirect coal liquefaction. The results show that the conversion was found to be 91.8% at opti-mum feed mixtures values of 3, 1.0 and 5.4 for water: PM, HTA: coal, water: coal respectively. With the oil price increase and growing in energy demand, the coal liquefaction remain afforda-ble and available energy alternative.

La séparation de deux énantiomères est un procédé d’intérêt pour l’industrie pharmaceutique. En effet, souvent un seul des énantiomères exerce l'activité biologique requise. Cette problématique est abordée ici par l'utilisation d'enzymes énantiosélectives qui est une alternative intéressante aux méthodes conventionnelles (chromatographie chirale, synthèse asymétrique ou cristallisation). Cette approche a été mise en oeuvre pour les molécules de la famille des profènes (l’Ibuprofène, le Kétoprofène ou le Naproxène par exemple) qui sont des acides 2- arylpropioniques et constituent une classe importante de médicaments anti-inflammatoires non stéroïdiens. Tout d’abord, un travail de recherche dans le domaine de la catalyse enzymatique et de l’ingénierie d’enzymes a été effectué. Des enzymes aux potentialités prometteuses, issues de la levure Yarrowia lipolytica, pour la résolution de ces trois anti-inflammatoires ont été identifiées. S’appuyant sur la modélisation moléculaire, l’ingénierie moléculaire a été utilisée pour accéder à des enzymes performantes tant du point de vue de la sélectivité que de l’activité. Les réactions ont été réalisées conventionnellement dans un système diphasique phase aqueuse/décane car les profènes et les esters associés sont des substrats hydrophobes et très faiblement solubles dans l'eau, la réaction doit donc être effectuée dans un solvant apolaire en contact avec une phase aqueuse où l'enzyme libre est dissoute. Ce mode opératoire permet d'éviter une immobilisation de l'enzyme. Une enzyme pour chaque substrat avec une énantiosélectivité suffisante a pu être développée, à savoir Lip2p V232A pour l’ibuprofène, V235S pour le naproxène et V232F pour le kétoprofène. Les lipases de Candida rugosa se sont également avérées intéressantes pour la résolution des profènes mais moins que les lipases précédemment évoquées. Le deuxième aspect de cette thèse s’est intéressé à la mise oeuvre de cette technique de résolution enzymatique dans un procédé innovant de Chimie Verte où le dioxyde de carbone supercritique (CO2SC) remplace le décane. En effet, les solvants organiques tels que le décane peuvent être toxiques mais aussi difficiles à éliminer, à la fin du processus, ce qui conduit à des étapes fastidieuses et coûteuses de purification. Dans un premier temps l’étude a porté sur la résolution de l’acide 2-bromo phényl acétique par l’hydrolyse de son ester octylique (ester + eau <=> acide (profène) + alcool). L'acidification de la phase aqueuse en contact avec CO2SC (formation d'acide carbonique) s’est montrée préjudiciable pour obtenir des conversions élevées. Cet inconvénient a été atténué en utilisant des concentrations assez élevées de sels (Na2HPO4 et KH2PO4) pour tamponner la phase aqueuse. Une étude spécifique en cellule haute pression utilisant des sondes solvatochromiques a permis d’établir que l’utilisation de concentrations élevées de sels (de l’ordre de 1000 mmol/L) permettait de maintenir un pH de l‘ordre de 6. Dans ces conditions, des conversions élevées ont pu être obtenues pour des temps de réactions de l’ordre de 100 h. Cependant la cinétique s’est avérée plus lente par rapport à celle observée avec le décane. L’explication de cette différence n’est pas encore totalement élucidée mais deux pistes ont été privilégiées : la formation de carbamates dues aux interactions entre le CO2SC et les acides aminés composant l’enzyme ou une mauvaise ouverture du volet moléculaire qui recouvre le site actif de l’enzyme liée à la moindre hydrophobicité du CO2SC hydraté. Cette résolution énantiomérique a également été mise en oeuvre dans un système sans phase aqueuse en utilisant l‘enzyme sous sa forme immobilisée sur support solide en utilisant la réaction réverse, l’estérification. Utilisant les mêmes approches, la résolution énantiomérique de l’ibuprofène a également été réalisée. Les meilleurs résultats obtenus en système diphasique phase aqueuse/CO2SC permettent en 75 heures une résolution quasi-totale. / The separation of the two enantiomers (or enantiomeric resolution) is a process of interest to the pharmaceutical industry. Indeed, very often, only one of the enantiomers has the required biological activity. This issue is addressed here by the use of enantioselective enzymes which is an interesting alternative to conventional methods (chiral chromatography, asymmetric synthesis, crystallization). This approach has been implemented for separation of molecules of the profens family (Ibuprofen, Naproxen or Ketoprofen for example) that are 2-arylpropionic acids and are an important class of anti-inflammatory drugs (NSAIDs). One first aspect of this work was to use molecular modeling and molecular engineering to identify enzymes, from the yeast Yarrovia lipolytica, with promising potential from the point of view of selectivity and activity. Reactions were carried out conventionally in a biphasic aqueous phase/decane system since the profens and related esters are hydrophobic substrates and very sparingly soluble in water so that the reaction must be carried out in an apolar solvent in contact with an aqueous phase where the enzyme is dissolved. This procedure avoids immobilization of the enzyme. An enzyme with good enantioselectivity for each substrate was developed, namely Lip2p V232A for ibuprofen, V235S for naproxen and V232F for ketoprofen. Lipases of Candida rugosa also proved useful for the resolution of ibuprofen, naproxen and ketoprofen but were less efficient than the lipases mentioned above. The second aspect of this thesis focused to the implementation of this enzymatic resolution technology in an innovative process for Green Chemistry where decane was replaced by supercritical carbon dioxide (scCO2).Indeed, organic solvents such as decane may be toxic but also difficult to remove at the end of the process, which leads to cumbersome and costly purification steps. Initially the study focused on enzymatic resolution of 2- bromo phenyl acetic acid by hydrolysis of its octyl ester (ester + water <=> acid (profen) + alcohol). Acidification of the aqueous phase in contact with scCO2 (formation of carbonic acid) proved to be detrimental to obtain high conversions. This disadvantage was mitigated by using relatively high concentrations of salts (1000 mmol/L) to buffer the aqueous phase. A specific study in a high pressure cell using solvatochromic probes showed that the use of high concentrations of salts allowed maintaining a pH of about 6. In these conditions, high conversions could be obtained for reaction times of 100 hours. However kinetics proved to be slower compared to those observed using decane as the organic phase. The explanation for this difference is not yet fully understood but two hypotheses can be evoked: formation of carbamates due to interactions between the scCO2 and amino acids or a bad opening of the "lid" that covers the active site related to a lower hydrophobicity of hydrated scCO2. This enantiomeric resolution was also implemented in a non-aqueous phase system using the enzyme in its immobilized form on a solid support, using the reverse reaction: esterification of profen. Using the same approach, the enantiomeric resolution of ibuprofen was also carried out. Best results using aqueous phase/scCO2 system allowed total resolution within 75 hours.

L'industrie nucléaire publique et militaire génère une quantité importante d'effluents liquides radioactifs qu'il faut traiter avant leur rejet dans l'environnement. Des procédés de décontamination alternatifs aux techniques industrielles (évaporation, traitement chimique) sont en cours de développement, comme par exemple le traitement en colonne ou le couplage filtration/sorption. Une partie des recherches associées à ces techniques de décontamination porte sur l'élaboration et la mise en forme de sorbants spécifiques. Dans ce contexte, les objectifs de cette thèse étaient d'une part d'étudier la synthèse en milieu CO2 supercritique (SC) de films de TiO2 déposés sur des supports macroporeux et d'autre part d'évaluer leur potentiel d'extraction dans ces procédés alternatifs. Une méthode de synthèse reproductible a été mise au point, basée sur la décomposition thermique de l'isopropoxyde de titane en milieu CO2 SC entre 150°C et 350°C. Dès 150°C, cette méthode permet la réalisation de films de TiO2 nanostructurés et adhérents sur des supports macroporeux en céramique (mousses, supports tubulaires en alumine α). L'effet de la température de synthèse de ces matériaux sur leurs caractéristiques physico-chimiques et leurs propriétés de sorption a été étudié sur des poudres de TiO2 élaborées dans les mêmes conditions que les films supportés. Les meilleures performances de sorption ont été observées pour la poudre obtenue à 150°C, du fait de sa plus grande densité de sites de surface par rapport aux poudres élaborée à 250°C et 350°C. Cette température de synthèse (150°C) a donc été sélectionnée pour l'étude détaillée des sorbants composites (TiO2/supports) afin d'évaluer leurs performances de sorption dans les procédés de traitement en continu. Les essais de sorption en colonne ont montré qu'une mousse en alumine macroporeuse (Φpore=400µm) revêtue de TiO2 est adaptée pour traiter des effluents en mode dynamique à fort débit. La taille des macropores et la hauteur de colonne sont des paramètres importants à maitriser. Pour le traitement par filtration/sorption, les membranes de TiO2 présentent une bonne résistance mécanique et sont capables d'extraire le strontium en mode dynamique. D'autre part dans le cas du strontium, les sorbants composites (TiO2/mousse ou TiO2/support tubulaire) sont régénérables à 100% à l'aide d'une solution aqueuse acidifiée (pH=3). / Public and military nuclear industry generates a significant amount of radioactive liquid waste which must be treated before being released into the environment. Decontamination methods alternative to the industrial techniques (evaporation, chemical treatment) are being developed, such as column treatments or coupled filtration/sorption processes. Current researches mainly focus on the development and shaping of specific sorbents. In this context, the objectives of this thesis were first to study the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 and then to evaluate their potential for radionuclide extraction in these alternative processes. A robust synthesis method has been developed, based on the thermal decomposition of titanium isopropoxide in SC CO2 in the temperature range between 150°C and 350°C. Nanostructured TiO2 films were formed on the macroporous supports (ceramic foams, tubular α-alumina supports) with good adhesion, already at 150°C. The effect of the synthesis temperature on sorbents physico-chemical characteristics and sorption properties has been studied with TiO2 powders prepared under the same conditions as the supported films. The best sorption performance were observed for the powder prepared at 150°C, owing to its higher density of surface sites in comparison with powders prepared at either 250°C or 350°C. Consequently, this synthesis temperature (150°C) was selected for a detailed study of the composite sorbents (TiO2/support), in order to assess their sorption performance in continuous treatment processes. The sorption experiments have shown that a column of alumina macroporous foam (Φpore = 400μm) coated with TiO2 was suitable for processing effluents in dynamic mode with high throughputs. Both macropore sizes and column height were revealed as important parameters to be controlled. For the coupled filtration/sorption treatment, TiO2 membranes exhibit good mechanical strength and are able to extract strontium. On the other hand in the case of strontium, composite sorbents (TiO2/foam or TiO2/tubular support) can be fully regenerated by using an acidic aqueous solution (pH = 3).

La recherche de nouveaux procédés propres et durables pour extraire l’uranium des minerais en alternative à l’extraction liquide-liquide conduit à s’intéresser aux procédés d’extraction en milieu CO2 supercritique. L’objectif de ce travail est donc d’étudier la faisabilité de l’extraction de l’uranium des minerais en milieu CO2 supercritique, à l’aide de molécules extractantes adaptées. Dans un premier temps, des mesures de solubilité des ligands sélectionnés pour cette étude préliminaire, trioctylamine et PC88A (acide 2-éthylhexyl 2-éthylhexyl phosphonique), et des complexes métalliques que ces molécules forment avec le molybdène utilisé comme simulant inactif de l’uranium et l’uranium, ont été effectuées en milieu CO2 supercritique. L’étude du procédé d’extraction dynamique en milieu CO2 supercritique a ensuite été réalisée en inactif, d’abord sur une solution aqueuse sulfurique de molybdène puis sur des poudres d’oxydes de molybdène. Les étapes de solubilisation du complexe ligand-Mo en CO2 supercritique et d’attaque du solide par le système extractant (ligand/acide/oxydant) sont les étapes limitantes à contrôler. Le choix d’un système extractant adapté devient alors primordial. En tenant compte des résultats obtenus en inactif (Mo), des essais d’extraction sur minerai d’uranium à partir de PC88A en milieu CO2 supercritique ont finalement été réalisés en présence d’acide sulfurique et d’oxyde de manganèse. Le procédé a ainsi pu être validé, plus de 60 % de l’uranium du minerai a été collecté en sortie de montage. Toutefois, l’effet de certains paramètres opératoires reste à étudier ainsi que la synthèse/sélection de nouvelles molécules extractantes ciblées. / The research of clean and sustainable new processes to extract uranium from ores as an alternative to solvent extraction leads one to consider extraction processes using supercritical carbon dioxide. The aim of this work is to study the extraction feasibility of uranium ores by supercritical CO2, using suitable ligands. First, solubility measurements of selected ligands, trioctylamine and PC88A (2-ethylhexyl 2-ethylhexylphosphonic acid), and metal complexes formed between these ligands and molybdenum (uranium surrogate) or uranium, are performed in supercritical CO2. Supercritical CO2 extractions are then carried out on sulfuric aqueous solutions containing molybdenum and on molybdenum oxides powder. Solubilization of the extractant system (ligand/acid/oxidant) and solid leaching are the key steps which need to be controlled. Well-suited extractant system selection is therefore fundamental. The hypothetical mechanisms, describing supercritical carbon dioxide extraction, seem to be quite different from those usually observed in solvent extraction, especially in terms of selectivity and formed complex structure. Based on the results obtained with molybdenum, extraction trials on uranium ores were then conducted using PC88A in supercritical carbon dioxide with sulfuric acid and manganese oxide. More than 60% of uranium was recovered, which confirmed this new process feasibility. However, the influence of some operating parameters and the synthesis/selection of new suitable ligands remain to be further studied.

Este trabalho teve como objetivo a utilização da tecnologia que emprega CO2 em estado supercrítico para estudar a formação de micropartículas de óleos essenciais encapsulados em polissacarídeos. O referido tema tem caráter inovador e inédito, já que a tecnologia supercrítica tem sido utilizada na formação e impregnação de partículas, principalmente de solutos sólidos, mas não tem sido aplicada na encapsulação de óleos essenciais. Os processos estudados, RESS (Rápida Expansão de uma Solução Supercrítica) ou o PGSS (Partículas de Soluções ou Suspensões em Gás Saturado) envolvem baixas temperaturas, possibilitando a não degradação de compostos voláteis e termossensíveis, tornando-os mais estáveis. Foram utilizados nesta pesquisa, polímeros que são, normalmente, utilizados no processo convencional de \"aroma em pó\". Mesmo sendo insolúveis ou parcialmente solúveis em CO2 supercrítico houve o intuito de aproveitar estudos comprovados de estabilidade de óleos essenciais encapsulados nestes materiais e ainda manter o custo do produto já que polissacarídeos tem, relativamente, baixo valor comercial, quando comparado aos polímeros que são empregados nos estudos que usam estes processos. Ensaios preliminares foram realizados com diferentes polímeros: Amido modificado, dextrina, maltodextrina e Purity Gum Ultra&reg;, (gentilmente cedidos pela Corn Products, atual Ingredion Incorporated, Mogi Guaçu, SP, BR) no intuito de selecionar o material de parede mais apropriado para a microencapsulação do óleo essencial, representado pelo limoneno. Os resultados preliminares comprovaram que houve impregnação e possível microencapsulação do limoneno, observados e constatados através de análises de microscopia (óptica, eletrônica e de fluorescência confocal a laser) especialmente para Purity Gum Ultra&reg;, a qual apresentou comportamento desejável como estabilidade da dispersão preliminar e morfologia, em comparação com os outros polissacarídeos testados (dextrina, amido modificado e maltodextrina). Os ensaios subsequentes (dimensionamento das partículas, microscopia eletrônica de varredura, microscopia confocal na presença de fluoresceína, estabilidade térmica e quantificação do teor de limoneno microencapsulado) determinaram definitivamente a eficiência da Purity Gum Ultra&reg; como polímero mais apropriado como agente encapsulante, e com isso foi demonstrada a eficiência da técnica proposta para esta finalidade. Ainda, a técnica de microencapsulação empregada (PGSS) apresentou valores significativos na retenção do limoneno com até 86% quando a suspensão foi preparada utilizando etanol (EtOH) e lecitina de soja como surfactante, sendo um relevante indicativo de que o processo de microencapsulação via PGSS proporcionou eficiente retenção do limoneno, além de apresentar outras vantagens sobre os processos de microencapsulação convencionais utilizados na indústria de alimentos. O processo de microencapsulação que utiliza CO2 supercrítico é considerado como \"tecnologia limpa\", aliado a este solvente ser considerado abundante, barato e ambientalmente seguro. Neste estudo constatou-se que, além do emprego de baixa temperatura no processo (50 - 60º C), não houve necessidade do emprego de água na suspensão. / This study aimed to use the technology that employs CO2 in supercritical state to study the formation of microparticles encapsulated essential oils in polysaccharides. The supercritical technology has been used in impregnating particles, mostly of solid solutes, but has not been applied to the encapsulation of essential oils. The studied processes RESS (Rapid Expansion of a Supercritical Solution) or PGSS (Particles Solutions or Suspensions in Saturated Gas) involving low temperatures, not allowing degradation of volatile and polymers that are normally used in the conventional process of \"aroma powder\" were used in this study. Even though it is insoluble or partially soluble in supercritical CO2 proven in order to take advantage of the stability studies of encapsulated essential oils in these materials and still keep the cost of the product as polysaccharides have relatively low value when compared to the polymers that are employed in studies using these processes. Preliminary tests were performed with different polymers : modified starch, dextrin, maltodextrin and Purity Gum Ultra &reg;, ( kindly provided by Corn Products, Current Ingredion Incorporated, Mogi, SP, BR ) in order to select the most appropriate material for wall microencapsulation of essential oil, represented by limonene. Preliminary results showed that there was possible impregnation and microencapsulation of limonene, observed and recorded through analysis of microscopy (optical, electron and confocal) especially for Purity Gum Ultra &reg;, which showed desirable behavior such as dispersion and stability of primary morphology compared to other polysaccharides tested (dextrin, modified starch and maltodextrin). Subsequent tests (particle sizing, scanning electron microscopy, confocal microscopy in the presence of fluorescein, thermic stability and quantification of the limonene content microencapsulated definitely determined the efficiency of Purity Gum Ultra &reg; as the most appropriate polymer as agent encapsulating and it has been demonstrated the efficiency of the proposed technique for this purpose. The technique employed for microencapsulation (PGSS) showed significant amounts of limonene retention of up to 86% when the suspension was prepared using ethanol (EtOH) and soy lecithin as surfactant. Being indicative of a material that microencapsulation by PGSS provided efficient retention of limonene, besides other advantages over conventional microencapsulation processes used in the food industry. The microencapsulation process that uses CO2 supercritical is considered \"clean technology \" due to the low toxicity of CO2 besides this solvent is considered abundant, inexpensive and environmentally safe. In this study it was found that, in addition to using low temperature process ( 50 - 60º C ), there was no need for the use of water in suspension.

Since their discovery in the 1930s, polymeric foams have been widely used in the industry for a variety of applications such as acoustical and thermal insulation, filters, absorbents etc. The reason for this ascending trend can be attributed to factors such as cost, ease of processing and a high strength to weight ratio compared to non-foamed polymers. The purpose of this project was to develop an “indestructible” material made of polycarbonate (PC) for industrial applications. Due to the high price of polycarbonate, two foaming methods were investigated to reduce the amount of material used. Samples were foamed physically in supercritical CO2 or chemically with 5-phenyl-1H-tetrazole. After thermal characterization of the foams in differential scanning calorimetry (DSC), we saw that none of the foaming methods had an influence on the glass transition of polycarbonate. Micrographs taken in scanning electron microscopy (SEM) showed that foams obtained in physical and chemical foaming had different structures. Indeed, samples foamed in supercritical CO2 exhibited a microcellular opened-cell structure with a high cell density and a homogeneous cell distribution. On the other hand, samples foamed with 5-phenyl-1H-tetrazole had a macrocellular closed-cell structure with a much smaller cell density and a random cell distribution. Compression testing showed that polycarbonate foamed physically had a compression modulus a lot greater. Then, XLPE mesh 35 or 50 and wollastonite were added to the polymeric matrices to enhance the foaming process and the mechanical properties. DSC experiments showed that the addition of fillers changed the thermal properties of polycarbonate for both foaming methods by inducing a shift in glass transition. SEM revealed that fillers lowered the average cell diameter and increased the cell density. This phenomenon increased the compression modulus for polycarbonate foamed in supercritical CO2. However, mechanical properties decreased for samples foamed with 5-phenyl-1H-tetrazole due to their relative brittleness and the propagation of microcracks.

Le développement d'un procédé intégré et simplifié de bioraffinerie capable de produire une large gamme de molécules d'intérêt est crucial pour la commercialisation des microalgues. L'objectif de cette étude était de simplifier le processus de valorisation des microalgues en optimisant la sélectivité de l'extraction tout en respectant les principes de l'écoconception. Dans un premier temps, les travaux se sont focalisés sur la récupération sélective de lipides neutres sans désintégration préalable des cellules par extraction au CO2 supercritique de microalgueslyophilisées. Les résultats ont montré que près de 97% des lipides neutres de Chlorella vulgaris ont été extraits. Pour Nannochloropsis oculata, les lipides neutres représentaient la majorité de l’extrait (83%), tandis que la proportion de glycolipides et de phospholipides ne dépassait pas 12,1% et 5,3% respectivement. Après la récupération de la fraction lipophile par extraction supercritique, 67% des protéines totales ont été libérées par une double extraction aqueuse. En outre, plus que 84% des protéines, exemptes de pigments ont été obtenues, en utilisantl’ultrafiltration semi-frontale. Ensuite, en utilisant des microalgues humides, un procédé d'extraction assistée par ultrasons à basse fréquence a été étudié pour la récupération des protéines. Les résultats sur Chlorella vulgaris ont montré que presque toute la teneur en protéines (97%) était libérée dans la phase aqueuse, permettant une extraction hautement sélective tout en conservant l’intégrité cellulaire. En revanche, la totalité des protéines a été co-extraite avec des impuretés à partir de cellules de Spirulina sp. entièrement désintégrées. Ainsi, pour la clarification des protéines, un procédé d'ultrafiltration semi-frontale a conduit à 67% des protéines totales obtenues dans le perméat. En outre, jusqu'à 95% de phycocyanine ont été retenus avec d'autres impuretés comme les résidus et les pigments. Les essais montrent l’intérêt de l’extraction sélective des molécules, mais que l’efficacité du procédé dépend de la structure des cellules. Des travaux complémentaires devraient encore être réalisés pour mieux comprendre les mécanismes impliqués dans la libération des molécules. / The development of an integrated and simplified biorefinery process able to produce a wide range of multiple molecules of interest is crucial for the commercialization of microalgae. The objective of this study was to simplify the downstream processes of microalgae valorization by optimizing the selectivity of extraction while respecting the principles of ecodesign. On the one hand, using dry microalgae, supercritical CO2 extraction was carried out for selective recovery of neutral lipids without cell disruption pretreatment. Results showed that up to 97% of neutral lipids from Chlorella vulgaris were extracted. Neutral lipids from Nannochloropsis oculata represented most of the extracts (83%), whereas the proportion of glycolipids and phospholipids did not exceed 12.1% and 5.3%, respectively. Following the lipophilic recovery via supercritical extraction, 67 % of total proteins were released using double stage aqueous extraction. Moreover, up to 84% of the extracted proteins free from pigments were obtained using semi-frontal ultrafiltration. On the other hand, a green ultrasound assisted extraction process using water as solvent was performed on wet microalgae for protein recovery at low frequency (12 kHz). Results of Chlorella vulgaris showed that almost all the protein content (97%) was released in the aqueous medium allowing a highly selective extraction while microalgae cells remained intact. In contrary, total protein content were co-extracted with impurities from totally disintegrated Spirulina sp. Thus, for protein clarification, quasi-frontal ultrafiltration process was carried out leading to 67% of total proteins obtained in the permeate. Furthermore, up to 95% of phycocyanine were retained with other impurities like residues and pigments. Since selective extraction of all the molecules of interest in microalgae biomass remains a challenge, additional research must be conducted to alleviate the downstreamprocess.

Ce manuscrit présente une étude du procédé Supercritique Anti-Solvant (SAS) en combinant un travail expérimental et une étude de modélisation moléculaire. En comparaison aux méthodes traditionnelles de cristallisation en solution, le procédé SAS permet une baisse significative des quantités de solvants utilisées, un meilleur contrôle des caractéristiques des poudres générées ainsi qu’une plus grande sélectivité polymorphique. De nombreuses études expérimentales ou de modélisation numérique ont permis une meilleure compréhension de ce procédé, mais certains aspects, liés aux mécanismes de cristallisation sous pression, demeurent moins discutés. Par une investigation de ces mécanismes, l’objectif de ce travail a été de développer et de valider des méthodes permettant un meilleur contrôle du faciès des poudres générées et de la forme du polymorphe. De ces caractéristiques dépendent certaines propriétés des cristaux, telles que leur cinétique de dissolution ou encore leur stabilité physique et chimique, particulièrement importante pour le domaine pharmaceutique / This manuscript presents a study of the Supercritical Anti-Solvent (SAS) process by combining an experimental work and a molecular modeling study. Compared with conventional crystallization methods in liquid solutions, the SAS process allows a significant decrease in the amounts of solvents used, a better control of generated powder characteristics as well as a greater polymorphic selectivity. Many experimental studies or numerical modeling have allowed a better understanding of this process, but some aspects, related to crystallization mechanisms under pressure, remain less discussed. Through an investigation of these mechanisms, the objective of this work was to develop and validate methods allowing a better control of the crystal habit and of the polymorphic form of generated powders. Certain crystal properties depend on these characteristics, such as their dissolution kinetics or their physical and chemical stability, which are particularly important in the pharmaceutical field