La lignine est une macromolécule, constituant de la biomasse lignocellulosique, qui est composée d’unités propylphénoliques. Cette matière est produite par l’industrie papetière en tant que coproduit de la cellulose. Actuellement, sa valorisation se limite en grande partie à des applications énergétiques. Or, la lignine peut être une source alternative de phénols si elle est dépolymérisée efficacement. Ce travail porte sur la transformation de la lignine en synthons aromatiques dans l’eau et en mélange eau-alcools en conditions sous-critique (225°C et 40-80 bar). Dans un premier temps, des études de conversion sont réalisées en réacteur fermé en utilisant l’eau comme solvant sur une lignine Kraft en présence de catalyseurs (Pt, Pd, Ru sur Al2O3,TiO2, ZrO2), le catalyseur Pd/ZrO2 nous a permis d’obtenir un rendement en phénols identifiés de 2%en 3 heures. Afin d’améliorer la conversion de la lignine en minimisant les réactions de condensations entre unités phénoliques, l’eau est remplacée par un mélange eau/alcool (éthanol, méthanol, isopropanol). La combinaison eau/isopropanol sans catalyseur nous permet d’augmenter le rendement en phénols identifiés de 5%. Nous avons ensuite essayé d’appliquer notre approche en réacteur continu. Même si le mélange eau/isopropanol était le meilleur solvant en réacteur fermé, le passage en réacteur continu s’est avéré complexe par la formation de produits solides. L’utilisation d’un mélange eau/éthanol a permis d’éviter ce problème et un rendement en gaiacol jusqu’à 1% est obtenu. L’éthanol permet de stabiliser des synthons instables dans le milieu par alkylation et estérification / Lignin is a macromolecule comprising lignocellulosic biomass, and is composed of propylphenyl units. Lignin is produced in large amounts by the paper industry when cellulose is isolated from biomass. Currently, its value is largely limited to source of energy and heat in recovery boilers. Nonetheless lignin can be an alternative source of aromatics if depolymerized effectively. The present work focuses on the transformation of lignin into aromatic building blocks using sub-critical water and mixtures of water/alcohols (225°C and 40-80 bar). Preliminary studies were carried out in a batch reactor; water was used as a solvent for the conversion of a Kraft lignin in the presence of catalysts (Pt, Pd, Ru on Al2O3, TiO2, ZrO2). The Pd/ZrO2 catalyst gave the highest yield of identified phenols with 2% in 3 hours. To improve the conversion of the lignin by minimizing condensation reactions between phenolic units, the water was replaced with a mixture water/alcohol (ethanol, methanol, isopropanol). The combination water/isopropanol without catalyst allowed us to increase the yield of identified phenols to 5%. The results obtained in batch reactor were extrapolated to a trickle-bed reactor. Even though the water/isopropanol mixture gave the best results in batch reactor, the implementation on a continuous reactor proved to be complex (formation of solids clogging the reactor). The use of a water/ethanol mixture prevented this problem and a yield in guaiacol of up to 1 % was obtained. Ethanol helps stabilize unstable building blocks by alkylation and esterification. This is evidenced by the NMR and chromatographic analysis

No description available.

No description available.

Chemical recycling stands as a method for managing plastic waste, by transforming it into monetary value through a circular recycling process. Addressing the demand for a solution on sustainable polymers made from renewable sources, this project aimed to design a polymer that facilitates the process of chemical recycling. Three linear oxalate polymers and two elastomers were synthesized through step-growth polymerization techniques. The thermal and mechanical properties were evaluated via thermal gravimetric analysis, differential scanning calorimetry, size exclusion chromatography, and tensile testing. The thermal properties of the oxalate polymers could be determined. Dimethyl polyoxalate had the highest molecular weight, but due to insufficient molecular weight the mechanical properties could not be evaluated for any of the linear polymers. Introducing a crosslinker,pentaerythritol, to the dimethyl polyoxalate increased the molecular weight, creating an etworked and flexible elastomer with mechanical properties that could be evaluated. Two elastomers were synthesized with different amounts of crosslinker. A successful chemical recycling process was conducted on the linear dimethyl polyoxalate and the elastomer with a higher amount of crosslinker. This was achieved through ring closing depolymerization to obtain sublimated monomer crystals and later resynthesized through ring opening polymerization. The elastomers also demonstrated mechanical recyclability through reprocessing. / Kemisk återvinning står som en metod för att hantera plastavfall, genom att omvandla det till monetärt värde genom en cirkulär återvinningsprocess. För att möta behovet på en lösning av hållbara polymerer gjorda från förnybara källor, syftade detta projekt till att designa en polymer som underlättar processen för kemisk återvinning. Tre linjära oxalatpolymerer och två elastomerer syntetiserades genom stegvisa polymerisationstekniker. De termiska och mekaniska egenskaperna utvärderades via termogravimetrisk analys, differentiell svepkalorimetri, storlek-uteslutning kromatografi och dragprovning. De termiska egenskaperna hos oxalatpolymererna kunde bestämmas. Dimetylpolyoxalat hade den högsta molekylvikten, men på grund av otillräcklig molekylvikt kunde de mekaniska egenskaperna inte utvärderas för någon av de linjära polymererna. Införandet av en tvärbindare, pentaerythritol, till dimetylpolyoxalatet ökade molekylvikten, vilket skapade en nätverksbunden och flexibel elastomer med mekaniska egenskaper som kunde utvärderas. Två elastomerer syntetiserades med olika mängder tvärbindningsmedel. En framgångsrik kemisk återvinningsprocess genomfördes på den linjära dimetylpolyoxalatet och elastomeren med en högre mängd tvärbindare. Detta uppnåddes genom ringslutande depolymerisation för att erhålla sublimerade monomerkristaller som senare återsyntetiserades genom ringöppningspolymerisation. Elastomerna visade också mekanisk återvinningsbarhet genom upparbetning.

O uso desenfreado dos recursos naturais durante as últimas décadas têm impactado drasticamente o meio ambiente, direcionando a humanidade a investir no desenvolvimento de tecnologias para produção sustentável e ecológica de novas fontes de energia renovável e de produtos verdes. Nesse âmbito, o uso de resíduos derivados da biomassa vegetal tem sido apresentado como uma promissora alternativa à substituição de combustíveis, componentes químicos e polímeros de origem fóssil. Esse material é barato, abundante e não compete direta ou indiretamente com a segurança alimentar. Hoje, mais de 200 compostos químicos e biopolímeros de valor agregado podem ser obtidos a partir do processamento de material lignocelulósico. Todavia, essa tecnologia ainda não é plenamente desenvolvida, afetando sua competitividade econômica, sendo que o maior custo atribui-se à despolimerização enzimática dos polissacarídeos que formam a parede celular vegetal (PCV). Essa etapa requer preparados enzimáticos compostos por diversas enzimas, que agem sinergicamente sobre a complexa estrutura da PCV. Dentre essas enzimas, as pectinases e xilanases desempenham um importante papel na desconstrução dos polímeros pécticos e da hemicelulose. O presente trabalho objetivou o estudo funcional e estrutural de diferentes classes de pectinases e xilanases com potencial biotecnológico, no intuito de contribuir para o desenvolvimento pleno da despolimerização enzimática da PCV. Dentro dessa perspectiva, foram estudadas: uma pectina metilesterase (Sl-PME) e uma endo-poligalacturonase (Sl-EndoPG) do inseto Sphenophorus levis; uma exo-poligalacturonase (Bl-ExoPG) de Bacillus licheniformis; uma xilanase GH10 (MT-Xyn10) e duas GH11 (MT-Xyn11a e MT-Xyn11b) identificadas no metatranscriptoma de um consórcio microbiótico derivado de compostagem de bagaço de cana-de-açúcar. A estrutura cristalográfica da Sl-PME evidenciou alta semelhança com outra PME de inseto. Também foi concluído que as PMEs de inseto são mais similares às bacterianas, quando comparadas às fúngicas e vegetais, principalmente em relação ao sulco catalítico. Além disso, PMEs de inseto, exclusivamente, apresentam uma permutação circular, possívelmente realcionada a um evento de transferência horizontal. A Bl-ExoPG apresentou-se monomérica em solução, com atividade ótima em pH neutro a 60°C, sendo estável em uma ampla faixa de pH (5-10) e com considerável termoestabilidade em elevadas temperaturas. Essa enzima, também, apresentou especificidade por pectina não-metilada, liberando unicamente monômeros de ácido galacturônico. As três xilanases estudadas apresentaram-se monoméricas em solução, com maior atividade entre 30 e 45°C e pHs de 6 a 9, retendo atividade acima de 50% nos pHs 5 e 10. Além disso, todas elas apresentam especificidade por xilano, sendo que a MT-Xyn10 apresentou, também, alta atividade sobre arabinoxilano. A MT-Xyn10 apresentou um conjunto de propriedades enzimáticas bastante atrativas às aplicações industriais, uma vez que é altamente estável em uma ampla faixa de pH (4-10), termoestável em temperaturas de até 50°C e sua ação catalítica produz diversos xilo-oligossacarídeos de alto valor agregado. A análise da estrutura cristalográfica da MT-Xyn11a revela três particularidades estruturais, compartilhadas com a MT-Xyn11b, mas não descritas para outras GH11. Dentre essas particularidades, um loop parece limitar o acesso do substrato ao sítio catalítico, contribuindo diretamente para a baixa afinidade ao substrato apresentada por essas duas enzimas. / Decades of unbridled use of natural resources have drastically affected the global environment, driving humanity to invest in the development of novel technologies for production of sustainable and ecofriendly renewable energy sources and green products. In this context, plant biomass residues have been presented as a promising alternative to fuels, chemicals and polymers derived from fossil reserves. This feedstock is abundant, cheap and does not compete directly or indirectly with food security. Today, more than 200 value-added chemicals and biopolymers can be generated by processing lignocellulosic material. However, this technology is not fully developed yet; its major costs stem from the enzymatic depolymerization of the polysaccharides that constitute the plant cell wall (PCW). This step requires enzymatic cocktails composed of several enzymes that synergistically deconstruct the complex PCW. Among these enzymes, pectinases and xylanases play an important role in the depolymerization of pectic polymers and hemicellulose. The present work is a functional and structural study of different classes of pectinase and xylanases with biotechnological potential. It intends to contribute to the full development of PCW enzymatic depolymerization. With this perspective, we studied a pectin methylesterase (Sl-PME) and an endo-polygalacturonase (Sl-EndoPG) from the insect Sphenophorus levis; an exo-polygalacturonase (Bl-ExoPG) from Bacillus licheniformis; a GH10 xylanase (MT-Xyn10); and two GH11 xylanases (MT-Xyn11a and MT-Xyn11b) from the metatranscriptome of sugarcane bagasse compost-derived microbial consortia. The Sl-PME crystallographic structure showed high similarity with other insect PME. It was also concluded that insect PMEs are more similar to bacterial PMEs than fungi or plant PMEs, especially in relation to the catalytic groove. Moreover, insect PMEs exclusively presented a circular permutation that is possibly related to an event of horizontal gene transfer. Bl-ExoPG is monomeric in solution, with optimal activity on neutral pH and 60°C, being stable in a wide pH range (5-10) and with considerable thermostability at high temperatures. This enzyme, also presented specificity for non-methylated pectin substrates, releasing only monomers of galacturonic acid as catalytic product. All three xylanases studied here are monomeric in solution, with optimal activity between 30°C and 45°C and between pHs 6 and 9, retaining more than 50% of original activity in the pHs 5 and 10. Besides, they all showed specificity for xylan, and MT-Xyn10 also showed high activity on arabinoxylan. MT-Xyn10 revealed a set of enzymatic properties attractive for industrial applications, such as high stability in a wide pH range (4-10), thermostability up to 50°C and released products that are high value-added xilo-oligosaccharides. The MT-Xyn11a crystallographic structure revealed three structural particularities shared with MT-Xyn11b, but not previously described in other GH11. Among these particularities, a loop seems to limit the substrate access to the catalytic site, contributing to the low enzyme affinity presented by both MT-Xyn11a and MT-Xyn11b.

Made available in DSpace on 2015-04-22T22:02:02Z (GMT). No. of bitstreams: 1 Dissertacao Vera Lucia Imbiriba Bentes.pdf: 2492256 bytes, checksum: 6177030a4e14eea635a818dbbb2b0e91 (MD5) Previous issue date: 2008-11-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing use and application of plastic materials have raised the index of residues of these materials in the great cities, mainly poli(ethylene tereftalate) (PET). Amongst the recycling techniques proposals to minimize the accumulation of these polymeric residues, the chemical recycling, has intensified the interest, on the part of the scientific community, a time that products of a high aggregate value can be achieved, that they can be used in new industrial processes. Of this form, the present work had as objective, to investigate the solubility of the PET postconsumer in different chemical agents, to promote the depolymerization chemical of the PET by hydrolysis basic and to carry preliminary study of the degradation of monomers post-hydrolysis through heterogeneous Fenton reaction using pure and Co- and Mn-doped magnetites catalysts, as source of Fe2+ in H2O2 having as molecule of reference for the study, the methylene blue (MB). The hydrolysis reaction was carried in reflux system under temperature of 110 oC for three hours using NaOH 7.5 mol L-1 as catalytic and the gotten products had been characterized by spectroscopic method in the region of the IV. The reactions of heterogeneous Fenton had been monitored by UV-visible measurements. Between the gotten results, it could be verified (i) PET solubility in phenol concentrated solution of about 40 oC; (ii) the chemical recycling of the PET presented yield of 99.72 % with recovery of monomers terephthalic acid (AT) and ethylene glycol (EG) monomers which were characterized by IV; (iii) the study of degradation of the methylene blue (MB) 20 mg L-1 was monitored by UV-visible measurements in λmax = 663 nm thus the kinetic model that better described the process was of the pseudo first-order, disclosing bigger capacity of degradation for the doped magnetite catalysers with Co and Mn, respectively; (iv) degradation of AT, was observed in λmax = 283 nm and had a similar behavior to the reference molecule; (v) the loss of the organic load of the solution afterhydrolysis of the PET was bottle was analyzed qualitatively by comparison of the spectrums obtained by FT-IV/ATR before and after of the heterogeneous Fenton reaction. Thus the results gotten in this work are considered satisfactory and promising for news studies future. / O crescente uso e aplicação de materiais plásticos tem elevado os índices de resíduos desses materiais nos lixões das grandes cidades, principalmente, o poli(tereftalato de etileno) (PET). Dentre as técnicas de reciclagem propostas para minimizar o acúmulo desses resíduos poliméricos, a reciclagem química, tem despertado maior interesse por parte da comunidade científica, uma vez que se podem obter produtos de elevado valor agregado, que podem ser utilizados em novos processos industriais. Dessa forma, o presente trabalho teve como objetivos, investigar a solubilidade do PET pós-consumo em diferentes agentes químicos, promover a despolimerização química do PET via hidrólise básica e realizar estudo preliminar da degradação dos monômeros pós-hidrólise através de reação de Fenton heterogênea utilizando catalisadores de magnetitas pura e dopadas com Co e Mn, como fonte de Fe2+em presença de H2O2, tendo como molécula de referência para o estudo, o corante azul de metileno (MB). A reação de hidrólise foi conduzida em sistema de refluxo sob temperatura de 110oC por três horas, utilizando NaOH 7,5 molL-1 como catalisador da reação e os produtos finais foram caracterizados por método espectroscópico na região de absorção do IV. As reações de Fenton heterogênea foram monitoradas através de medidas espectrofotométricas na região do UV-visível. Entre os resultados obtidos, pôde-se verificar (i) a solubilidade do PET em solução concentrada de fenol ∼ 40 oC; (ii) a reciclagem química do PET apresentou rendimento de 99,72 % com recuperação dos monômeros do ácido tereftálico (AT) e de etileno glicol (EG) que foram caracterizados por IV; (iii) o estudo da degradação da molécula de referência, MB 20 mg L -1, foi monitorado em λ = 663 nm, de maneira que o modelo cinético que melhor descreveu o processo foi o de pseudo primeira-ordem, revelando maior capacidade de degradação para os catalisadores de magnetitas dopadas com Co e Mn, respectivamente; (iv) a degradação do AT, foi observado em λ = 283 nm e teve comportamento semelhante ao da molécula de referência; (v) a perda de carga orgânica da solução pós-hidrólise do PET foi feita qualitativamente por comparação dos espectros IV/ATR das amostras de solução pós-hidrólise antes e depois de submetida á reação de Fenton. De maneira geral os resultados obtidos neste trabalho são considerados satisfatórios e promissores para outros futuros estudos.

O uso desenfreado dos recursos naturais durante as últimas décadas têm impactado drasticamente o meio ambiente, direcionando a humanidade a investir no desenvolvimento de tecnologias para produção sustentável e ecológica de novas fontes de energia renovável e de produtos verdes. Nesse âmbito, o uso de resíduos derivados da biomassa vegetal tem sido apresentado como uma promissora alternativa à substituição de combustíveis, componentes químicos e polímeros de origem fóssil. Esse material é barato, abundante e não compete direta ou indiretamente com a segurança alimentar. Hoje, mais de 200 compostos químicos e biopolímeros de valor agregado podem ser obtidos a partir do processamento de material lignocelulósico. Todavia, essa tecnologia ainda não é plenamente desenvolvida, afetando sua competitividade econômica, sendo que o maior custo atribui-se à despolimerização enzimática dos polissacarídeos que formam a parede celular vegetal (PCV). Essa etapa requer preparados enzimáticos compostos por diversas enzimas, que agem sinergicamente sobre a complexa estrutura da PCV. Dentre essas enzimas, as pectinases e xilanases desempenham um importante papel na desconstrução dos polímeros pécticos e da hemicelulose. O presente trabalho objetivou o estudo funcional e estrutural de diferentes classes de pectinases e xilanases com potencial biotecnológico, no intuito de contribuir para o desenvolvimento pleno da despolimerização enzimática da PCV. Dentro dessa perspectiva, foram estudadas: uma pectina metilesterase (Sl-PME) e uma endo-poligalacturonase (Sl-EndoPG) do inseto Sphenophorus levis; uma exo-poligalacturonase (Bl-ExoPG) de Bacillus licheniformis; uma xilanase GH10 (MT-Xyn10) e duas GH11 (MT-Xyn11a e MT-Xyn11b) identificadas no metatranscriptoma de um consórcio microbiótico derivado de compostagem de bagaço de cana-de-açúcar. A estrutura cristalográfica da Sl-PME evidenciou alta semelhança com outra PME de inseto. Também foi concluído que as PMEs de inseto são mais similares às bacterianas, quando comparadas às fúngicas e vegetais, principalmente em relação ao sulco catalítico. Além disso, PMEs de inseto, exclusivamente, apresentam uma permutação circular, possívelmente realcionada a um evento de transferência horizontal. A Bl-ExoPG apresentou-se monomérica em solução, com atividade ótima em pH neutro a 60°C, sendo estável em uma ampla faixa de pH (5-10) e com considerável termoestabilidade em elevadas temperaturas. Essa enzima, também, apresentou especificidade por pectina não-metilada, liberando unicamente monômeros de ácido galacturônico. As três xilanases estudadas apresentaram-se monoméricas em solução, com maior atividade entre 30 e 45°C e pHs de 6 a 9, retendo atividade acima de 50% nos pHs 5 e 10. Além disso, todas elas apresentam especificidade por xilano, sendo que a MT-Xyn10 apresentou, também, alta atividade sobre arabinoxilano. A MT-Xyn10 apresentou um conjunto de propriedades enzimáticas bastante atrativas às aplicações industriais, uma vez que é altamente estável em uma ampla faixa de pH (4-10), termoestável em temperaturas de até 50°C e sua ação catalítica produz diversos xilo-oligossacarídeos de alto valor agregado. A análise da estrutura cristalográfica da MT-Xyn11a revela três particularidades estruturais, compartilhadas com a MT-Xyn11b, mas não descritas para outras GH11. Dentre essas particularidades, um loop parece limitar o acesso do substrato ao sítio catalítico, contribuindo diretamente para a baixa afinidade ao substrato apresentada por essas duas enzimas. / Decades of unbridled use of natural resources have drastically affected the global environment, driving humanity to invest in the development of novel technologies for production of sustainable and ecofriendly renewable energy sources and green products. In this context, plant biomass residues have been presented as a promising alternative to fuels, chemicals and polymers derived from fossil reserves. This feedstock is abundant, cheap and does not compete directly or indirectly with food security. Today, more than 200 value-added chemicals and biopolymers can be generated by processing lignocellulosic material. However, this technology is not fully developed yet; its major costs stem from the enzymatic depolymerization of the polysaccharides that constitute the plant cell wall (PCW). This step requires enzymatic cocktails composed of several enzymes that synergistically deconstruct the complex PCW. Among these enzymes, pectinases and xylanases play an important role in the depolymerization of pectic polymers and hemicellulose. The present work is a functional and structural study of different classes of pectinase and xylanases with biotechnological potential. It intends to contribute to the full development of PCW enzymatic depolymerization. With this perspective, we studied a pectin methylesterase (Sl-PME) and an endo-polygalacturonase (Sl-EndoPG) from the insect Sphenophorus levis; an exo-polygalacturonase (Bl-ExoPG) from Bacillus licheniformis; a GH10 xylanase (MT-Xyn10); and two GH11 xylanases (MT-Xyn11a and MT-Xyn11b) from the metatranscriptome of sugarcane bagasse compost-derived microbial consortia. The Sl-PME crystallographic structure showed high similarity with other insect PME. It was also concluded that insect PMEs are more similar to bacterial PMEs than fungi or plant PMEs, especially in relation to the catalytic groove. Moreover, insect PMEs exclusively presented a circular permutation that is possibly related to an event of horizontal gene transfer. Bl-ExoPG is monomeric in solution, with optimal activity on neutral pH and 60°C, being stable in a wide pH range (5-10) and with considerable thermostability at high temperatures. This enzyme, also presented specificity for non-methylated pectin substrates, releasing only monomers of galacturonic acid as catalytic product. All three xylanases studied here are monomeric in solution, with optimal activity between 30°C and 45°C and between pHs 6 and 9, retaining more than 50% of original activity in the pHs 5 and 10. Besides, they all showed specificity for xylan, and MT-Xyn10 also showed high activity on arabinoxylan. MT-Xyn10 revealed a set of enzymatic properties attractive for industrial applications, such as high stability in a wide pH range (4-10), thermostability up to 50°C and released products that are high value-added xilo-oligosaccharides. The MT-Xyn11a crystallographic structure revealed three structural particularities shared with MT-Xyn11b, but not previously described in other GH11. Among these particularities, a loop seems to limit the substrate access to the catalytic site, contributing to the low enzyme affinity presented by both MT-Xyn11a and MT-Xyn11b.

The catalytic depolymerization/pyrolysis of nylon 6 and 66 were investigated with the prospect of helping to curb the amount of carpet landfilled. Thermogravimetric analysis was used to determine which catalysts (and their nylon/catalyst ratio) were most suited for the depolymerization. By adding bases, the onset of degradation for some bases was 100 aC lower than that of the pure nylons. Potassium hydroxide and sodium hydroxide were found to be the most effective catalysts at a catalyst ratio of 100:1 of nylon 6 and nylon 66 to catalyst, respectively. After determining the most efficient catalyst, kinetic models/parameters from the TGA data were determined. These parameters were used in a reactive extrusion model for depolymerizing nylon 6 in carpet. Data from the model was then used to do cost analysis for the process. It was found that to get a Present Value Ratio greater than 1, the flow rate has to be greater than or equal to 500 lb/hr. At even higher flow rates up to the model¡¦s limit (1500 lb/hr), the Net Present Value shows that this process is economically viable. Extrusion of a 100:1 ratio of pure N6 and KOH was done in a 30 mm counter-rotating non-intermeshing twin screw extruder. The material collected from the vents of the extruder was tested with a gas chromatograph- mass spectrum (GC-MS) in tandem. There was only one significant peak from the GC and the primary molecular weight on the MS was 113, the molecular weight of caprolactam. This shows that the process could be profitable and require little purification if done industrially.

Le développement des bioraffineries repose sur une conception optimisée d’installations industrielles en synergie comportant un grand nombre de flux de matière et d’opérations unitaires. Le recours à des simulateurs de procédés présente un intérêt certain dans la conception, l’analyse et l’optimisation de tels procédés. Souhaitant initier le développement d’un outil de simulation adapté à ce secteur, nous nous sommes appuyés sur l’exemple d’un procédé d’oxydation de biopolymères par extrusion réactive. Les procédés d’extrusion réactive sont caractérisés par un couplage intime entre écoulement, thermique et cinétiques réactionnelles. Les modalités de ce couplage dépendent des réactions visées. Souhaitant proposer un modèle flexible, intégrable dans un simulateur statique de procédés, et permettant d’atteindre un bon compromis entre la prédictivité et la quantité d’essais nécessaires pour ajuster les paramètres du modèle, nous avons opté pour une approche de modélisation mixte reposant à la fois sur une représentation de l’écoulement à l’aide de réacteurs idéaux et sur des lois de la mécanique des fluides. L’écoulement est modélisé par une cascade de réacteurs continus parfaitement agités (RCPA) avec reflux. Chaque RCPA est caractérisé par un taux de remplissage qui dépend des conditions opératoires. Le calcul du taux de remplissage des RCPA, de la pression matière et des débits circulant entre les RCPA en régime permanent est effectué en réalisant un bilan matière sur chaque RCPA. La température matière dans chacun des RCPA est calculée grâce à un bilan thermique. La modification chimique du matériau est décrite à l’aide de trois réactions : l’oxydation dépolymérisante, la formation de groupements fonctionnels (carbonyles et carboxyles) et la dégradation thermomécanique du biopolymère sous l’effet de la chaleur et des contraintes de cisaillement. L’établissement des équations de bilan de population auxquelles on applique la méthode des moments, permet de calculer simultanément les masses molaires moyennes en nombre et en poids du polymère ainsi que la teneur en agent oxydant dans chacun des RCPA. La viscosité est reliée à masse molaire moyenne. Un algorithme de calcul itératif permet de coupler le bilan matière, le bilan thermique et le calcul réactionnel. Les données expérimentales nécessaires à la validation du modèle ont été fournies par la plate-forme expérimentale mise au point au CVG (Centre de Valorisation des Glucides, Amiens) dans le cadre du programme Synthons. Une méthode d’ajustement des paramètres du modèle à partir d’un nombre minimal de données expérimentales a été proposée, permettant d’évaluer le caractère prédictif du modèle. Le modèle d’extrusion réactive ainsi ajusté a permis de reproduire les résultats expérimentaux obtenus pour différents matériaux, débits, vitesses de rotation, et sur deux extrudeuses detaille et de configuration différentes. L’intégration du modèle d’extrusion réactive dans un simulateur de procédés - le logiciel USIM PAC - a permis de simplifier sa mise en œuvre,offre des perspectives en optimisation et dimensionnement d’équipement et rend possible la simulation de l’opération d’extrusion réactive au sein d’une chaîne de transformation complète. / The development of biorefineries requires integrating and optimizing plants and handling a large number of material flows and unit operations. The development of a process simulator dedicated to this field would thus be of great interest. This is what we intended to initiate by relying on the example of the oxidation of biopolymers by reactive extrusion. Reactive extrusion is characterized by a strong coupling between flow, heat transfer and reaction kinetics. This coupling depends on the desired reactions. We here intended to elaborate aflexible model, being easily integrated into a static process simulator, and enabling to reach agood compromise between the predictive character of the model and the amount of experiments required to adjust model parameters. Therefore, we adopted a hybrid modelling approach combining a flow description based on ideal reactors and continuum mechanics laws. Flow is modeled as a cascade of continuous stirred tank reactors (CSTR) with possible backflow. Flow rates between CSTRs are calculated using physical laws taking into account the operating conditions and geometric parameters of the equipment. Each CSTR is characterized by a filling ratio, which depends on the operating conditions. The calculation of steady-state filling ratio, pressure and flow rates between the CSTRs is achieved by performing a material balance in each CSTR. Material temperature in each CSTR is calculated through a thermal balance. The chemical modification of the material is described using three reactions: the oxidative depolymerization, the formation of functional groups(carbonyl and carboxyl) and the thermomechanical degradation of the biopolymer induced by heating and shearing. The number-averaged and weight-averaged molecular weight of the biopolymer and the oxidant content in each CSTR are computed simultaneously by applying the moment operation to population balance equations. Viscosity is linked to the mean molecular weight. An iterative algorithm enables to couple material balance, thermal balance and reaction kinetics. The experimental data required for model validation were provided by the experimental platform developed at the CVG (Centre de Valorisation des Glucides,Amiens, France) in the frame of the Synthons program. A method was proposed in order to adjust model parameters with a minimal number of experimental data, enabling to assess the predictive character of the model. Once the parameters were adjusted, the reactive extrusion model enabled to reproduce the experimental results obtained with different raw materials,flow rates, screw rotation speeds, and using two extruders with different size and screw configuration. The integration of the reactive extrusion model into a process simulator - the USIM PAC software - enabled to simplify its implementation. This constitutes a promising step in a perspective of process optimization and scale-up, and enables to simulate a reactive extrusion operation within a global plant simulator.

With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions. Alternatively, selective benzylic oxidation strategies have recently been explored for lignin and lignin models. In this work, heterogeneous catalytic methods using supported base metals and layered-double hydroxides were evaluated for the oxidation of lignin models both before and after benzylic oxidation. Additionally, by studying putative reaction intermediates, insights were gained into the mechanisms of oxidative fragmentation of the model compounds. Generally, it was found that after benzylic oxidation models were more susceptible to oxidative fragmentation. Indeed, several heterogeneous oxidation systems were found to convert lignin models to oxygenated aryl monomers (mainly benzoic acids and phenols) using inexpensive primary oxidants (i.e., hydrogen peroxide and molecular oxygen). Reactions were conducted at relatively mild temperatures and at low oxygen concentrations for the purpose of an easy transition to large-scale experiments. Finally, the catalytic systems that resulted in significant cleavage of lignin models were applied to a Kraft lignin. Oxidation of Kraft lignin resulted a mixture of products for which analytical data and increased solubility are consistent with interunit cleavage within the lignin macromolecule.