<p>Adhesives  are  found  in  almost  every  aspect  of  the  modern  world.  They  are  found  in plywood used in buildings, electronics, shoes, plumbing and in almost every facet of your daily life. Nature also has an abundance of these adhesives that are used fora multitude of applications. Some  animals, like  the  blue  mussel, use  their  adhesive  for  protection  against  ocean  waves  and predators  while other animals, such  as  the  spider, use  it  to  trap  prey. Investigation  of  theses adhesives has led to the identification of several different proteins that allow for these animals to make  their  adhesive.  Some  of  them  are  composed of rare  amino  acids that  while  other  animals use  a combination  of  inorganic  and  organic  components.  Understanding  of  these  unique adhesives  can be  a  boon  for designof future  adhesives  that  do  not  have  the disadvantagesof current day commercialized glues.</p> <p>Increasing interest  in  the  restoration  of  natural  oyster  reefs  and  the  cement  that  holds them  together  has  resulted  in  the  identification  of  the  Shelk2  protein  that  is  found  both  in  the mantle  of  the  oyster’s  shell  as  well  as  the  cement  that  holds  the  reefs  together. Gaining  an understanding  of  how  this  protein  functions  and  its  part  in  the  oyster  reef  could  be  quite beneficial  for  projects  investing  in  reef  restorations  as  well  as  underwater  adhesion.  Gathering protein  from  the  animal  for  experimentation  and  characterization  can  be  labor  intensive  and extremely challenging. Luckily, cloning technology has become a useful tool for the expression of large quantities of proteins that can be difficult or impossible to gather from the native animal. Using <em>E. coli</em>, it  is  possible  to design  and express  this protein  in  hopes  of  gaining  a  better understanding of its impact on oyster settlement and adhesion.</p> <p>Sustainability is a major downside to current day adhesives that current technologies have not  been  able  to  solve. Most adhesives  that  are  on  the  market  today  are  primarily  derived  from petroleum. Current  research  has  begun  investigating  alternatives  to  the  large   epoxy   and formaldehyde  adhesive  market,  but  the  barrier  of  entry  is  hard  to  overcome.  To  replace  these glues  the  new  material  must  be  affordable,  non-petroleum  derived,  and  available  on  a  massive scale.  These  requirements  are  hard  to  meet  for  many  materials  and  due  to  that  the  current  bio-adhesive are generally very low strength.</p> <p>The work presented here will detail the characterization, and expression of some of these natural  adhesives that  have  been  found  in  the  Eastern  oyster. Another  aspect of  this  work includes the synthesis of a new bio-based adhesive system. Utilizing biomimetic chemistry along with  sustainably  sourced  materials  a  new  adhesive  has  been  formulated that  has  comparable adhesive strength to current day commercial adhesives.</p>

This dissertation focuses on the assessment and development of heterogeneous catalysts for the deperoxidation of cyclohexyl hydroperoxide and oxidation of cyclohexane, which will be based in metal oxides and gold nanoparticles. For this endeavour a multidisciplinary approach will be used combining theoretical chemistry, kinetic studies and synthesis and characterisation of materials. The starting choice for the catalyst to carry out the process is supported gold nanoparticles. The approach of this dissertation is to first model the mecha- nism of cyclohexyl hydroperoxide decomposition and oxidation of cyclohexane on gold nanoparticles by theoretical calculations, and use these findings to synthesise efficient heterogeneous catalysts which will be subsequently tested and optimised experimentally. But as it will be seen, some metal oxides are active rather than acting as mere supports, which will also be studied both theoretical and experimentally. Each chapter has a specific focus and constitutes a strand of the overall goal: Chapter 1 provides an introductory background on the topics that this dissertation lies upon: oxidation of cyclohexane, heterogeneous catalysis and catalysis by gold and metal oxides. Chapter 2 outlines the objectives of the thesis, formulating the relevant hypotheses of this research and the subsequent validation tests. Chapter 3 exposes the methodology with a brief conceptual background that has been used to carry out this work. Chapter 4 is the first chapter dealing with results. It consists in a theoretical study using density functional theory of the reaction mechanism over different models of gold nanoparticles, in order to study the influence of several parameters on their catalytic activity: the particle size, atom coordination, and presence of additional species like oxygen atoms and water. Chapter 5 uses the findings found in chapter 4 to drive the synthesis of supported gold nanoparticles. It consists in a experimental study of gold-based catalysts, which is combined with a theoretical study which takes into account an additional variable: the support. Chapter 6 exploits one of the findings of chapter 5. One of the supports used for anchoring the gold nanoparticles is active by itself, namely cerium oxide. This chapter comprises an experimental work about its activity, studying parameters like particle size, morphology and the effect of doping. Chapter 7 continues with the catalytic activity of cerium oxide-based materials, but now from a theoretical point of view. It first presents a systematic study of the parameters relevant for the proper quantum mechanical description of cerium oxide, which is followed by a mechanistic study on different models. Chapter 8 outlines the conclusions obtained in this dissertation, present- ing them in a summarised way. Even though each chapter presents its corresponding conclusions at its end, this chapter groups them all in a structured way for the reader's convenience, so a global view of the project can be swiftly grasped. The results herein further the knowledge of heterogeneous catalysis for the oxidation of cyclohexane, one of the most important industrial reactions, and which continues to be a challenge. Although the ultimate goal is to develop an industrial catalyst, the dissertation also aims to show how computational chemistry can drive the design of novel materials, and how it can help to understand catalytic reactions at the atomic level. / El presente trabajo se centra en el estudio y desarrollo de catalizadores heterogéneos para la desperoxidación de ciclohexil hidroperóxido y la oxidación de ciclohexano, basados en óxidos metálicos y nanopartículas de Au. Para lograr tal objetivo se ha usado un enfoque multidisciplinar, que combina química teórica y estudios cinéticos, a la vez que síntesis y caracterización de materiales. El candidato inicial para llevar a cabo el proceso consiste en partículas de Au soportadas. El camino a seguir pasa primero por modelizar el mecanismo de descomposición de ciclohexil hidroperóxido y oxidación de ciclohexano mediante cálculos teóricos, y utilizar el conocimiento generado por este estudio para dictar la síntesis de catalizadores heterogéneos, comprobando y optimizando posteriormente su actividad de forma experimental. Sin embargo, como será visto a lo largo de este trabajo, algunos óxidos metálicos dejan de lado su papel como mero soporte físico para las partículas de Au y son activos por sí mismos. Tal hecho será estudiado tanto teórica como experimentalmente. Cada capítulo tiene un objetivo específico, y es a su vez una parte del objetivo global de esta investigación: El capítulo 1 provee al lector de una breve introducción a los temas sobre los que yace este trabajo: oxidación de ciclohexano, catálisis heterogénea y catálisis mediante Au y óxidos metálicos. El capítulo 2 expone de una forma breve y concisa los objetivos de esta investigación, formulando la hipótesis de partida y los correspondientes experimentos para su validación. El capítulo 3 describe la metodología utilizada junto a una explicación de los fundamentos en los que se basa cada técnica. El capítulo 4 es el primer capítulo que discute los resultados obtenidos en esta investigación. Se trata de un estudio usando la teoria del funcional de densidad para investigar el mecanismo de reacción del proceso sobre diferentes modelos teóricos de Au, con el objetivo de comprender la influencia de diversos factores en la actividad catalítica, tales como el tamaño de partícula, la coordinación de los á'tomos de Au y la presencia de especies adicionales como átomos de O y agua. El capítulo 5 hace uso de los resultados obtenidos en el estudio anterior, y los utiliza para dirigir la síntesis de nanopartículas soportadas de Au. Se trata de un estudio experimental en el que se investigan diversos factores que pueden afectar a su actividad catalítica. Este estudio se combina a su vez con uno de tipo teórico en el que se tiene en cuenta la influencia del soporte en la actividad catalítica de las particulas de Au. El capítulo 6 se basa en uno de los resultados obtenidos en el capítulo 5. Uno de los soportes utilizados para anclar las partículas de Au resulta de por sí activo: el CeO2. Su notable actividad para catalizar este proceso exige un estudio en mayor profundidad, el cual se lleva a cabo en este capítulo. Parámetros como el tamaño de particula, la morfología de superficie y el dopaje entre otros se investigan en este punto. El capítulo 7 sigue la estela del trabajo anterior sobre CeO2, pero ahora desde el punto de vista de la química teórica. Presenta primero un estudio sistemático de parámetros relacionados con la mecánica cuá'ntica que afectan al CeO2, con el objetivo de alcanzar una descripción satisfactoria de los modelos teóricos para este óxido. Tras esto, se lleva a cabo un estudio del mecanismo de reacción en dichos modelos de CeO2, a fin de comprender el origen de su actividad catalítica. El capítulo 8 presenta de forma estructurada y concisa todas las conclusiones que se han sacado a raíz de los resultados obtenidos. Aún a pesar de que cada capítulo presenta sus correspondientes conclusiones al final, aquí se presentan de una forma agrupada a comodidad del lector, para que pueda obtener de forma ágil una visión global de los resultados de esta investigación. / Aquest treball es centra en l'estudi i desenvolupament de catalitzadors hetero- genis per a la desperoxidació de ciclohexil hidroperòxid i la oxidació de ciclohexà, basats en òxids metàl·lics i nanopartícules de Au. Per aconseguir aquest objectiu s'ha utilitzat un enfocament multidisciplinari, en el qual es combinen química teòrica i estudis cinètics amb síntesi i caracterització de materials. El candidat inicial per dur a terme el procés consisteix en partícules de Au suportades. El camí a seguir passa primer per modelitzar el mecanisme de descomposició del ciclohexil hidroperòxid i la oxidació de ciclohexà mitjançant càlculs teòrics, i utilitzar el coneixement generat per aquest estudi per dirigir la síntesi de catalitzadors heterogenis, comprovant i optimitzant posteriorment la seua activitat de forma experimental. No obstant això, com es veurà al llarg d'aquest treball, alguns òxids metàl·lics deixen de costat el seu paper com a suport físic de les partícules de Au y són actius per si mateixos. Aquest fet s'ha estudiat tant teòrica com experimentalment. Cada capítol té un objectiu específic i és al mateix temps una part de l'objectiu global d'aquesta recerca: El capítol 1 proporciona al lector una breu introducció als temes tractats en aquest treball: oxidació de ciclohexà, catàlisi heterogènia i catàlisi mitjançant Au i òxids metàl·lics. El capítol 2 exposa d'una forma breu i concisa els objectius d'aquesta investigació, formulant la hipòtesi inicial i els corresponents experiments per a la seua validació. El capítol 3 descriu la metodologia utilitzada conjuntament amb una explicació dels fonaments en els quals es basa cada tècnica. El capítol 4 és el primer capítol que discuteix els resultats obtinguts en aquesta investigació. Es tracta d'un estudi usant la teoria del funcional de densitat per investigar el mecanisme de reacció del procés en diferents models teòrics de Au, amb l'objectiu de comprendre la influència en l'activitat catalítica de diversos factors, com ara la grandària de partícula, la coordinació dels àtoms de Au i la presencia d'espècies addicionals, com àtoms de O i aigua. El capítol 5 fa ús dels resultats obtinguts en l'estudi anterior, i els utilitza per dirigir la síntesi de nanopartícules suportades de Au. Es tracta d'un estudi experimental en el qual s'investiguen diversos factors que poden afectar a la seua activitat catalítica. Aquest estudi es combina amb un altre de caràcter teòric en el qual es té en compte la influència del suport en la activitat catalítica de les partícules de Au. El capítol 6 es basa en un dels resultats obtinguts en el capítol 5. Un dels suports utilitzats per fixar les partícules de Au resulta de per si actiu: el CeO2. La seua notable activitat per catalitzar aquest procés demana un estudi de major profunditat, el qual es duu a terme en aquest capítol. Paràmetres com la grandària de partícula, la morfologia de superfície i el dopatge, entre altres, s'investiguen en aquest punt. El capítol 7 continua l'estudi anterior sobre el CeO2, però ara des del punt de vista de la química teòrica. Presenta en primer lloc un es- tudi sistemàtic de paràmetres relacionats amb la mecànica quàntica que afecten al CeO2, amb l'objectiu d'aconseguir una descripció satisfactòria pels models teòrics d'aquest òxid. Després, es duu a terme un estudi del mecanisme de reacció en aquests models de CeO2, a fi de com- prendre l'origen de la seua activitat catalítica. El capítol 8 presenta de forma estructurada i concisa totes les conclusions que s'han extret arran dels resultats obtinguts. Encara que cada capí- tol presenta les seues corresponents conclusions al final, ací es presenten d'una forma agrupada per a la comoditat del lector, per què puga obtindre de forma àgil una visió global dels result d'una forma agrupada per a la comoditat del lector, per què puga obtindre de forma à / López Auséns, JT. (2016). From Quantum Mechanics to Catalysis: Studies on the oxidation of alkanes by gold and metal oxides [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/76806

<p dir="ltr">Reported herein is a brief summary regarding the previous syntheses of borane-amines, newly developed protocols to synthesize borane-amines, and the material and synthetic applications utilizing borane-amines. Methods to generate borane-amines typically relied on a metathesis-dehydrogenation reaction between ammonium salts and metal borohydrides in organic solvent, typically hazardous tetrahydrofuran (THF). However, due to the poor solubility of inorganic salts in organic solvent, stirring of the reaction mixture becomes difficult and, in turn, scalability is made challenging. We report two new methods to generate borane-amines that both rely on the hydroboration of sodium borohydride and a carbonyl activator, followed by the S_N2-type reaction with the amine to form the requisite borane-amine. The activator for our procedures are either 1) gaseous carbon dioxide or 2) water/ethyl acetate system. The CO₂ mediated protocol was applied to a variety of 1°-, 2°-, 3°-, and heteroaromatic amines as well as phosphines to form the corresponding borane adducts (73-99%). Water was also found to be a green, compatible activator. Interestingly, we had swapped environmentally and health hazardous THF with ethyl acetate (EtOAc) and found the reaction had still proceeded with competitive conversion of amines to the borane-amines (72-97%). The robustness of this reaction was demonstrated with a 1.1 mol scale synthesis of borane pyridine with 87% yield. With increased accessibility of borane-amines established, we sought to investigate their potential applications, including testing their hypergolic properties. Additionally, we utilized borane-ammonia for a sequential reduction/Friedel-Crafts alkylation of benzyl carbonyls. Traditionally an alkyl halide, the scope of the electrophilic aromatic substitution reaction has widened to include alcohols and carbonyls as potential Friedel-Crafts reactants. Few reports exist for the arylation of aldehydes and ketones, while no precedence exists for the arylation of carboxylic acids and esters. Our group previously reported that TiCl₄ is capable of eliminating oxygen from benzyl alcohols, forming a carbocation intermediate. Theoretically, the carbocation formed from TiCl₄ and benzyl alcohols would be vulnerable from attacks from other nucleophiles, including pi bonds from arenes. This was indeed proven to be the case when benzyl alcohol was reacted in 1 equiv. TiCl₄with benzene as the solvent and diphenylmethane was obtained as the sole product. By including borane-ammonia as a hydride source, various aryl carbonyls and aryl carbinols were also reduced to the corresponding alcohol <i>in situ</i>, enabling these substrates to participate in Friedel-Crafts alkylation.</p>

<p dir="ltr">Aromatic phosphonates and phosphine oxides are highly desirable synthetic targets used in pharmaceuticals, natural products, agrichemicals, catalysis, and materials science. While a variety of aromatic precursors have been used to access these motifs, aryl halides remain one of the most desirable coupling partners owing to their low cost, commercial availability, and regioselective reactivity. Traditional phosphonation often requires the use of harsh reductants in the presence of liquid ammonia, which are caustic and pose incredible environmental concerns. Milder, transition metal-catalyzed approaches have been developed, but can be limited by air sensitivity, cost, low reaction selectivity, and low functional group compatibility. Photoredox catalysis has been significantly advanced in the past decade in the pursuit of greener, more sustainable avenues to facilitate desirable reaction transformations under mild conditions. These methods most commonly use a dual catalytic strategy in which a metal is paired with an organocatalyst. While these approaches enable facile phosphonation of a variety of aromatic precursors, the metals and organocatalysts used are often expensive and toxic. Indeed, there remains unexplored chemical space for transition metal-free photoredox-catalyzed aryl C-P bond formations. Herein, we present a series of transition metal-free, photoredox-catalyzed approaches to the phosphonation of aryl halides. The approaches and mechanistic works will be discussed in the following order: </p><p dir="ltr">First, the discovery that 10<i>H</i>-phenothiazine (PTZ) enables the transition metal-free phosphonation of aryl halides using trialkyl phosphites will be presented. PTZ serves as a photocatalyst capable of reducing the aryl halide to access aryl radicals, which readily couple with phosphite esters. This transformation exhibits broad functional group tolerance in good to excellent yields. Then, photoredox catalysis by PTZ enables the formation of unsymmetrical aromatic phosphine oxides using triphenylphosphine (PPh₃) and aryl halides. This is the first work in which PPh₃ has been used as the starting material, and the reaction proceeds via the alkaline hydrolysis of quaternary phosphonium salts. The final work exhibits novel photocatalytic activity of <i>N</i>-heterocyclic carbenes (NHC) to activate aryl halides, form aryl radicals, and enable phosphonation. This method displays broad functional group tolerance under mild conditions and highlights its untapped synthetic utility as a photocatalyst.</p>

The effects of climate change have made the need to develop sustainable production practices for biofuels and other chemicals imminent. The development of the green economy has also led to many industries voluntarily improving the sustainability of the products they produce. The microbial production of fatty acid-derived chemicals allows for the opportunity to reduce petroleum-based chemicals in the marketplace. However, for microbial produced chemicals to be industrially competitive, significant work is needed to improve the production capacity of industrial strains. There are a number of bottlenecks and challenges related to the production of various fatty acid derivatives that need to be addressed. One of these key challenges relates to the source of the fermentation feedstock. While sources such as corn or sugar cane are currently common, these feedstocks compete with food supply and require nutrient-rich soils. The use of lignocellulosic feedstocks is preferred to combat this issue, however these feedstocks present their own unique challenges. Pretreatment is required to release fermentable sugars, and this process also results in various fermentation inhibitors released into the solution. A better understanding of how engineered strains utilize these fermentable sugars as well as improving resistance to the inhibitors will help to improve the chemical production capacity of these chemical products. This work will focus on describing key bottlenecks related to fatty acid-derived products, while also evaluating proposed solutions to these bottlenecks. / Master of Science / Currently, many common household products and plastics are developed using petroleum-based components. From plastic bottles to common cosmetics, these contain ingredients that are derived from petroleum. In order to combat our reliance on petroleum for these every day products, it is essential to develop alternate sources for these materials. A potential source involve using plant material and by-products to produce these same compounds that we are able to produce from petroleum. While there has been significant research to produce useful products such as bioethanol from corn, this is not an ideal crop. Corn requires more water and space than other crops such as grasses. In addition, these grasses can grow in soil that food crops are unable to grow in, so we don’t utilize valuable land to develop common household products. However, these grasses are much more difficult to treat and process in order to form these basic chemical ingredients. In order to use grass-based crops, it is possible to engineer organisms such as yeast to process the raw material into valuable chemical precursor. This work aims to genetically engineer yeast in order to produce some of these chemical precursors from a grass-like feedstock. In addition, this work also analyzes how physical characteristics of yeast affect the final product formation. Finally, a model was developed to show how yeast ferments corn-like and grass-like feedstocks differently.

Computational chemistry employs mathematical algorithms, statistics, and large databases to integrate chemical theory with experimental observations. Computational modeling allows us to make predictions concerning molecular properties and reactivity that ultimately lead to accurate assessment of the most important fundamental properties of chemical systems. Advances in theoretical techniques and computer power have dramatically increased the usefulness and importance of computational chemistry as a complement to experimental studies. This is especially relevant to catalytic reactions of industrial importance as well as the analysis of structural properties and the resulting spectroscopic phenomena in what are often otherwise counterintuitive models. This dissertation is a representation of the research I performed during my years as a graduate student in the Chemistry Department at the University of North Texas. My research has examined novel carbenes as efficient organocatalysts, structure-based design and optimization of small molecule drugs, and surveying methods to accurately describe structure and bonding and catalytic abilities of inorganic and organometallic systems. The works presented herein have been published or are awaiting submission to peer-reviewed scientific journals. A variety of computational techniques were employed in studying metal-mediated catalysis and organocatalysis as well as the structural and photophysical properties of systems containing closed-shell transition metal ions.

Im Rahmen der vorliegenden Dissertation wurden drei neue Zugangswege zu kettenverlängerten Kohlenhydraten aus ungeschützten Aldosen entwickelt. Dabei ermöglichen diese Protokolle die Synthese verschiedener Klassen von kettenverlängerten Strukturen. Neben der selektiven Darstellung von 2-Ketoaldonsäurederivaten konnten effiziente Zugangsstrategien zu hoch funktionalisierten bizyklischen C-Glycosiden und polyhydroxylierten Pseudopeptiden präsentiert werden. Dabei konnte gezeigt werden, dass ein breites Spektrum dieser verschiedenen Arten kettenverlängerter Kohlenhydrate aus ungeschützten natürlichen Hexose- und Pentose-Substraten zugänglich ist. Durch den Einbezug der natürlich vorhandenen Hydroxylgruppen der Aldosen ermöglichen die präsentierten Kaskadenreaktionen einen sehr effektiven Zugang zu hoch funktionalisierten Produkten, welche in Sequenzen unter Verwendung von Schützungsstrategien nur in aufwendigen, mehrstufigen Reaktionen zugänglich wären. Zudem konnte gezeigt werden, dass die natürlich vorkommende Chiralität in den verwendeten Substraten für ein stereoselektives Dirigieren der neu installierten Stereozentren nutzbar ist. Damit konnte eine bedeutende Erweiterung des bestehenden Repertoires von Methoden für die Verlängerung ungeschützter Kohlenhydrate erreicht werden.. Die entwickelten Transformationen bestechen durch ihre hohe Atomökonomie, wie auch durch ihre sehr gute ökologische und ökonomische Bilanz und erfüllen damit die Anforderungen an nachhaltige Synthesemethoden. / The scope of the presented work was the investigation of new organocatalysed synthesis strategies of carbon chain elongated carbohydrates. Here three new accesses to three different structure motifs of these biologically highly important and manifold compounds from unprotected carbohydrates were developed. Using naturally occurring, unprotected pentoses and hexoses, a wide variety of keto aldonic acids, bicyclic C-glycosides and glycosylated pseudopeptides are accessible in three different cascade reactions. All of the presented strategies enable the C-chain elongation by employment of the naturally occurring aldehyde motive without tedious protection ad deprotection protocols or synthetic modifications of the substrates. By utilisation of the chiral hydroxyl moieties of the carbohydrate chain, diastereoselective control of the installation of the stereocenters formed in the cascade reactions is achieved. The high regio- and diastereoselectivities, high yields as well as the convenient synthesis conditions of the presented protocols make the presented cascade reactions valuable tools among the already described accesses to the biological important compounds of chain elongated carbohydrates. The presented cascades enable the diastereoselective synthesis of a high variety of these motifs in only one synthetic step from readily available unprotected carbohydrates without additional modification steps. These advantages give rise to a very high atom economy of the transformations, which therefore fulfil the requirements to green chemistry and sustainable synthesis methods.

Un nouveau procédé d'extraction des huiles essentielles a été développé, mis au point et optimisé nommé «Vapo-diffusion Assistée par Micro-ondes (MSDf)». Le procédé MSDf à été appliqué à l'extraction des huiles essentielles des peaux d'oranges et de fleurs de lavande. Ce procédé est basé sur la combinaison d'une technique d'extraction classique : l'hydro-diffusion et le chauffage micro-ondes comme technologie d'intensification. Une deuxième nouvelle approche pour l'extraction des huiles essentielles à partir de matrices aromatiques sèches et sans ajout de vapeur ni d'eau nommé «Diffusion à sec générée par micro-ondes (MDG)». Le procédé MDG à été appliqué à l'extraction des huiles essentielles des graines de carvi. Le MSDf et le MDG apparaissent comme des procédures «douces» permettant un gain de temps et d'énergie considérable et la diminution des rejets de CO2 dans l'atmosphère / Microwave steam diffusion (MSDf) was developed as a cleaner and new process design and operation for isolation of essentials oils and was compared to conventional steam diffusion (SDf). This green process has been applied and tested using two aromatic matrixes: fresh orange peels and dry lavender flowers. This process is based on the combination of a traditional technique of extraction: hydro-diffusion and the microwave irradiation energy. Without adding any steam or water, we proposed also a novel and green approach for extraction of secondary metabolites from dried plant materials. This “steam and water free” approach based on a simple principle involves the application of microwave irradiation and earth gravity to extract the essential oil from dried caraway seeds. MSDf and MDG were better than SDf in terms of energy saving, cleanliness and reduced waste water

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.

Ce mémoire porte sur la synthèse de matériaux composites nanostructurés à base de polyoxométallates pour la conversion de l’énergie et des applications à des problèmes environnementaux. Pour atteindre ces objectifs, de nombreux composés nouveaux de cette famille d’oxydes moléculaires ont été synthétisés puis ont été associés à différentes matrices éco-compatibles dans le respect des principaux critères de la Chimie Verte. Les principales techniques d’étude sont l’électrochimie, la photochimie et la spectroscopie UV-visible. Dans le domaine de l’énergie, les catalyseurs obtenus se sont révélés très efficaces dans des réactions très importantes mais difficiles à réaliser, comme la production de l’hydrogène, la réduction de l’oxygène et l’oxydation de l’eau. De même, parmi les applications aux problèmes de dépollution, ces nanomatériaux ont montré une forte activité électrocatalytique et photocatalytique pour la réduction des oxydes d’azote, des bromates et la photodégradation d’un colorant textile toxique, l’Acide Orange 7. Les performances de ces nouveaux catalyseurs sont comparables à celles des meilleurs systèmes connus. / This thesis focuses on the synthesis of nanostructured composite materials based on polyoxometalates for energy conversion and applications to environmental problems. To achieve these goals, many new compounds of this family of molecular oxides were synthesized and were associated with different nature friendly matrices, in agreement with the main criteria of Green Chemistry. In the field of energy, the new catalysts have proved very effective in important but difficult to achieve reactions, such as producing hydrogen, oxygen reduction or water oxidation. Similarly, among applications to pollution problems, these nanomaterials have shown a strong electrocatalytic and photocatalytic activity for the reduction of nitrogen oxides, bromate and for the photodegradation of a toxic textile dye, Acid Orange 7. The performances of these new catalysts are comparable to those of the best known systems.