La présente thèse s’intéresse à la conception et la caractérisation des procédés microstructurés mettant en œuvre des réseaux de microcanaux de différentes dimensions. L’analyse de tels réseaux multi-échelles, représentatifs d’une parallélisastion de microsystèmes élémentaires, a essentiellement servi à identifier les principaux paramètres géométriques et physiques contrôlant les performances de ces réseaux complexes. On a cherché à quantifier l’influence des paramètres géométriques comme le rapport de résistances hydrodynamiques internes, le nombre de canaux et d’échelles opérant ainsi que leur répartition sur le réseau, sur des critères hydrodynamiques comme la maldistribution du fluide et la perte de charge résistive. Il est révélé qu’en fonction des contraintes imposées, un arrangement optimal des canaux sur un nombre pair d’échelles permet de réduire considérablement la maldistribution interne des flux et les pertes de charge résultantes. L’analyse thermique associée à l’analyse hydrodynamique a montré que les performances thermiques des réseaux sont fortement liées à leurs structurations géométriques internes. En présence de réactions catalytiques consécutives, ces mêmes réseaux enregistrent des déviations du rendement du produit désiré. Ces déviations peuvent être levées par une structuration appropriée du réseau catalytique multi-canal. La même architecture de ces réseaux peut être adaptée pour permettre le déroulement des opérations de mélange et/ou des réactions multi-phasiques. Ainsi, pour ces réseaux complexes, où un nombre élevé de variables imbriquées est considéré, des lignes directrices sont ressorties pour aider à leur conception et dimensionnement / This PhD thesis focuses on the design and the characterization of microstructured processes including microchannel networks of various dimensions. The analysis of such multi-scale networks, representative of elementary microsystems parallelization, is mainly used to identify the main geometrical and physical parameters controlling the network performances. Influence of geometrical parameters, such as the internal hydrodynamic resistances ratio, the number of channels and scales and their arrangement in the network, on hydrodynamic criteria like fluid maldistribution and pressure drop is investigated. It is shown that according to some specific constraints, an optimal arrangement of the channels on an even number of scales, allows to reduce significantly the internal flow maldistribution and the consequential pressure losses. The thermal analysis coupled with the hydrodynamic analysis illustrates that the thermal performances of microchannel networks are strongly affected by their internal geometrical arrangement. Nevertheless, the various mixture points located in the network compensate the fluid maldistribution resulting from a non appropriate geometrical arrangement. When consecutive catalytic reactions are performed inside these networks, deviations of the desired product rate can be recorded. These deviations can be reduced by an optimal catalytic network arrangement. The same architecture of these networks is also adapted to allow multi-phase mixing and /or reactions. Thus, using these complex networks, where several variables are considered, guidelines are derived in order to improve their design and their dimensionless

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第12950号 / 論工博第4126号 / 新制||工||1628(附属図書館) / 32249 / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 長谷部 伸治, 教授 前 一廣, 教授 吉田 潤一 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Cette thèse porte sur le développement d’un procédé industriel propre constitué par un couplage absorption-distillation, destiné aux traitements d’effluents gazeux chargés par un Composé Organique Volatil (COV). L’absorption est effectuée dans un microabsorbeur à film tombant. La première étape de ce travail consiste à caractériser le transfert de matière dans cet appareil, lors de l’absorption gaz/liquide du Perchloroéthylène (PCE) par le Di(2-EthylHexyl)Adipate (DEHA). Les expériences ont montré la faisabilité et l’intérêt de cette opération dans un micro-contacteur. En effet, les efficacités d’épuration obtenues sont comparables à celles des procédés classiques (jusqu’à 97%) et les quantités de solvant d’absorption utilisées sont très faibles. Une étude paramétrique a révélé une intensification significative du transfert de matière, côté gaz, et un gain en compacité, à la suite de la minimisation de l’épaisseur de la veine de gaz (2mm) et du débit de la phase gazeuse. Cette étude a également montré la limite du microabsorbeur à traiter de grands débits de gaz avec de bonnes efficacités, causée par la faible influence qu’exerce la vitesse du gaz sur le coefficient de transfert de matière. Ce comportement a été expliqué, grâce à des simulations en 2D, par une dispersion importante des profils de concentration indiquant une limitation diffusionnelle. Cette dernière provient essentiellement du régime laminaire lisse et de la petite taille caractérisant ce type de micro-procédé. Pour s’affranchir de cette limitation, la turbulence doit être favorisée dans le gaz. La deuxième étape de ce travail concerne l’extrapolation du microabsorbeur de laboratoire à l’échelle industrielle des PME/PMI, basée sur le concept du numbering-up. A l’issu des calculs, un absorbeur microstructuré efficace (95%), et compact (surface occupée ˜ 0,5m2) a été développé. Pour rentabiliser son fonctionnement, un recyclage par distillation flash du solvant d’absorption a été étudié. Les résultats obtenus ouvrent la voie sur une technique d’épuration prometteuse, qui nécessite néanmoins une validation théorique et expérimentale du couplage absorbeur-distillateur / This project focuses on the development of an industrial process, in which a coupled absorption/distillation unit is developed to treat gaseous effluents contaminated by a Volatile Organic Compound (VOC). Absorption is performed in a falling film microabsorber. The first stage of this work consists in characterizing the mass transfer in this device. The gas/liquid absorption of Perchloroethylene (PCE) by Di (2-EthylHexyl) Adipate (DEHA) is used as test case. Experiments showed the feasibility and the benefit of this separation process operated in a micro-contactor. Indeed, the purification efficiencies obtained are comparable to those of conventional processes (97%). Moreover, the required absorption solvent quantities are very low. A parametric study revealed significant mass transfer intensification on gas side and a gain in compactness due to the minimization of gas cavity thickness (2mm) and gas flowrate. This study also showed the limits of microabsorbers to handle large gas flowrates with good efficiencies, due to a low influence of gas velocity on the mass transfer coefficient. This behaviour was explained, thanks to 2D simulations, by a significant dispersion of concentration profiles, which indicates a diffusion limitation. The latter comes mainly from smooth laminar flow and the small size, a typical characteristic of micro-processes. To overcome this limitation, turbulence should be promoted in the gas. The second stage of this work concerns the microabsorber extrapolation from laboratory scale to industrial SMEs, based on the numbering-up concept. Calculations predict high throughputs with a microstructured absorber of competitive efficiency (95%) and high compactness (area occupied ˜ 0.5 m2). For profitable operation, solvent absorption recycling by a flash distillation is studied. The results lead to a promising treatment technique, which still requires a theoretical and experimental validation of the coupled absorber-distiller unit

[pt] No presente trabalho foi investigada a microfabricação de reatores fotocatalíticos de polidimetilsiloxano (PDMS) para o estudo comparativo de aumento de escala entre micro- e mesorreatores, e lignocelulósicos de bambu para reação de cicloadição alcino-azida catalisada por cobre(I) (CuAAC) em fluxo contínuo. Nesse cenário, foi desenvolvida uma configuração experimental de scale-up e numbering-up de sistemas meso- e microfluídicos fotocatalíticos, respectivamente, para comparar a eficiência de fotodegradação de TiO2/P25 em rodamina B (RB) e azul de metileno (em inglês, Methylene Blue, MB) sob irradiação UV. Os resultados obtidos sugerem que o aumento do volume (scale-up) reduz os valores de D(por cento), enquanto que numbering-up mantém a eficiência fotocatalítica com redução significativa do tempo de reação. M6-60 (micro)L apresentou melhor desempenho entre os dispositivos, com degradação total do MB (1,2 x 10-5 mol L-1) em apenas 1h, e foto-oxidação total de fenol (1,2 x 10-4 mol L-1) em 4h. Além disto, M6-60 (micro)L apresentou menor consumo de energia elétrica por ordem (0,012 kWh m-3) e maior rendimento quântico (2,6 x 10-2) em comparação com os outros dispositivos. O desenvolvimento de suportes sólidos lignocelulósicos apresentou importantes características para os processos de funcionalização de TEMPO-TAL com íons Cu(II) e Zn(II) e CuNPs. Os suportes foram devidamente caracterizados por MEV/EDS e FT-IR. Os resultados para a reação de CuAAC mostraram rendimentos de 79-82 por cento com reciclabilidade de até 7 vezes e lixiviação média de cobre de 1,30 ppm, e foram importantes para o desenvolvimento do microrreator de bambu. A microfabricação do microrreator lignocelulósicos de bambu (L(micro)R) foi realizada a partir de etapas de cortes, sem utilização de técnicas caras e sala limpa. L(micro)R mostrou fácil prototipagem e rápida oxidação com N-oxil-2,2,6,6-tetrametilpiperidina (TEMPO) e funcionalização com íons cobre (Cu-L(micro)R) e nanopartículas de cobre (CuNPs-L(micro)R). O desempenho de CuAAC em fluxo contínuo do Cu-L(micro)R foi demonstrado através da realização de estudos de reciclabilidade e rendimentos em diferentes taxas de fluxo (0,1 a 0,8 mL min-1). Cu-L(micro)R apresentou rendimentos de 60 por cento a 96 por cento para 5 tipos de reações CuAAC, indicando promissora aplicação na área de catálise em dispositivos microfluídicos. Todas as reações foram realizadas em regime de fluxo com MeOH:H2O (2:1) e lixiviação de cobre inferior a 6,0 ppm, produzindo uma série de 5 derivados de 1,2,3-triazol 1,4-dissubstituídos com boa eficiência em um ambiente com poucos recursos. CuNPs-L(micro)R apresentou limitação para realização de CuAAC por não alcançar as condições ideais de aquecimento, exigidas para ocorrência da reação. / [en] The present work had two main objectives. The first refers to the development of polydimethylsiloxane photocatalytic microreactors (PDMS) for the comparative scale-up study between micro- and mesoreactors. The second focused on the development of bamboo lignocellulosic microreactors for copper(I) catalyzed alkine-azide cycloaddition reaction (CuAAC). In this scenario, an experimental scale-up and numbering-up configuration of photocatalytic meso- and microfluidic systems were developed, to compare, respectively, the photodegradation efficiency of TiO2-P25 in rhodamine B (RB) and methylene blue (MB) under UV irradiation. The obtained results suggest that the scale-up reduces the values of D (percent), while numbering-up maintains the photocatalytic efficiency with a significant reaction time reduction. The best photocatalytic microfluidic system was M6-60 (micro)L, which presented total MB degradation (1.2 x 10-5 mol L-1) in only 1h, and total phenol photo-oxidation (1,2 x 10-4 mol L-1) in 4h. Furthermore, M6-60 (micro)LM6 had lower electrical energy consumption (0,012 kWh m-3) and higher quantum yield (2,6 x 10-2) compared to others. The development of solid lignocellulosic supports showed important characteristics for the TEMPO-TAL functionalization processes with Cu(II), Zn(II) ions and CuNPs. The supports were properly characterized by SEM/ EDS and FT-IR. The results for the CuAAC reaction showed yields of 79-82 percent with recyclability of up to 7 times and average copper leaching of 1.30 ppm, and were important for the development of the bamboo microreactor. The microfabrication of the bamboo lignocellulosic microreactor (L(micro)R) was performed from cutting steps, without using expensive techniques and clean room. L(micro)R showed easy prototyping and rapid oxidation with N-oxyl-2,2,6,6-tetramethylpiperidine (TEMPO) and functionalization with copper ions (Cu-L(micro)R) and copper nanoparticles (CuNPs-L(micro)R). Cu-L(micro)R continuous flow CuAAC performance was demonstrated by conducting recyclability and yield studies at different flow rates (0.1 to 0.8 mL-1). Cu-L(micro)R presented 60 percent to 96 percent yields for 5 types of CuAAC reactions, indicating promising application in the area of catalysis in microfluidic devices. All reactions were performed under a MeOH:H2O (2:1) flow regime and copper leaching below 6.0 ppm, producing a series of 5 efficiently 1,4-disubstituted 1,2,3-triazols derivatives in a resource-poor environment. CuNPs-L(micro)R presented limitation for CuAAC because it did not reach the ideal heating conditions required for the reaction to occur.