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 no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/76806 / TESIS

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<p>Cryogenic transmission electron microscopy (cryoEM) has become an increasingly common tool for determining structures of proteins and protein complex at near atomic resolution. We seek to determine the structure of p97 by cryoEM using an affinity capture approach that employs a family of novel synthetic lipids bearing water soluble PEG units and known high affinity inhibitor molecules at the distal end of the polymer. A library of inhibitor modified affinity lipopolymers of 5000 KD PEG molecular weights were synthesized. The inhibitor modified lipid coated grids were used to capture p97. The reconstruction of p97 revealed the structure at dimeric state at 3.64 Å and monomeric state at 4.33 Å. A PEG unit composed of 20000 KD molecular weight based polyrotaxane containing NTA ligand as affinity tag has been synthesized, used to concentrate 6x-his tagged p97 on TEM which also enabled to see all 3D orientation of the target particles and an initial model of 10.64 Å resolution of p97 structure was resolved. </p>

Layered double hydroxides (LDHs) are clay-like minerals commonly referred to as anionic clays" with a wide range of physical and chemical properties. LDHs often find application in pharmaceuticals, as polymer additives, as additives in cosmetics, as nanomaterial's and in catalysis. This is due to having variable layer charge density, reactive interlayer space, ion exchange capabilities, a wide range of chemical compositions and rheological properties (Forano et al., 2006). Various techniques exist for the synthesis of layered double hydroxides. These include co-precipitation, the urea method, induced hydrolysis, sol-gel and hydrothermal methods. Many of these produce environmentally unfriendly effluents or by-products, are energy intensive, make use of metallic salts or require inert synthesis environments (Rives, 2001). Limitations associated with these existing processes make LDH synthesis at an industrial level expensive or difficult to achieve. The need for 'green', affordable and repeatable synthesis methods are therefore often sought after. Recently the use of mechanochemistry as an alternative synthesis technique has gained wide-spread attention. Mechanochemistry involves the breaking and forming of chemical bonds due to an induced mechanical force. Various mechanochemical techniques for the synthesis of LDH materials exist or have been explored. These include methods such as single-step, two-step and mechano-hydrothermal grinding techniques. Grinding methods can be conducted dry, wet or collectively (Qu, Zhang, et al., 2015a). Mechanochemistry has further been used in conjunction with micro-wave energy and ultrasonic irradiation. The use of mechanochemistry as a synthesis method has proven to be promising with successful and unique LDHs produced. Intercalation of unique or complex anions within the interlayer has further been proven possible. The versatility and robust nature of this synthesis method makes it ideal for industrial application. Although many studies exist it was noted that limited research has been conducted on single-step wet grinding for LDH synthesis and warrants further investigation (Qu, Zhang, et al., 2015a) (Iwasaki,Yoshii, et al., 2012). This was due to factors such as incomplete conversion, difficulties associated with grinding and morphological imperfections. Single step wet milling could be benifi cial as a synthesis procedure as it eliminates hazards associated with dry powder, contains less process steps and is therefore possibly more cost effective and can be conducted batch, semi-batch or continuously due to fluid flow. Throughout the literature research conducted it was further noted that not many different milling devices have been explored. Ball mills, mixer mills and manual grinding were the most common methods used to supply mechanical energy to a system. The study therefore aims to expand on single-step wet synthesis of LDH materials by making use of a different milling device, namely a Netzsch LME 1 horizontal bead mill. The selected mill is designed for wet grinding application and can easily be up-scaled to a commercial batch, semi-batch or continuous process. Raw materials selected were a combination of oxides, hydroxides and basic carbonates. This would eliminate hazardous salt by-products and effluent, promoting 'green' synthesis of LDH materials. It was noted that the synthesis of LDH with the use of these materials have previously proven to be challenging (Qu, Zhang, et al., 2015a). The study was divided up into two sections namely a 'parameter study' and a 'versatility study'. The 'parameter study' involved exploring the in influence of milling and experimental parameters, such as rotational speed, retention time, solids loading, bead size and jacket water temperature, on the synthesis of Mg-Al LDH. The raw materials selected were MgO and Al(OH)3 combined at a divalent to trivalent cationic ratio of 2:1. The parameters were individually investigated, with the exception of jacket water temperature as it was varied with a change in retention time and a change in rotational speed. Unless stated otherwise or under investigation, parameters were investigated at a set speed of 2000 rpm, jacket water temperature of 30 °C, solids loading of 10 %, retention time of 1 h and with 2 mm yttrium stabilised zirconia beads. Therefore when investigating a specific c parameter, the others remained as stated above. Comparatively the 'versatility' study further explores the synthesis of Mg-Al, Ca-Al, Cu-Al and Zn-Al LDH by adapting optimal synthesis conditions, derived from existing mechanochemical techniques and methods, to the selected process. These were related to the divalent to trivalent cationic ratio and selected starting materials. Ageing of the samples obtained through the 'versatility study' were further explored to determine if the potential for a two-step commercial process exists. The study was investigated at a set speed of 2000 rpm, jacket water temperature of 30 °C, solids loading of 10 %, retention time of 1 h and with 2 mm yttrium stabilised zirconia beads. Half of the sample collected was subjected to ageing at 80 °C for 24 h under atmospheric conditions. / Dissertation (MEng (Chemical Engineering))--University of Pretoria, 2020. / This research was funded by Techsparks (Pty) Ltd and the Technology and Human Resources for Industry Programme (THRIP) administered by the Department of Trade and Industry, South Africa, (grant number THRIP/133/31/03/2016) / Chemical Engineering / MEng (Chemical Engineering) / Unrestricted

In this work, a comparative electrochemical study has been performed to evaluate corrosion inhibition property of several film-forming corrosion inhibitors provide by Akzo Nobel on carbon steel in a chloride solution. For carbon steel exposed to 1 M NaCl solution with and without added inhibitor, electrochemical measurements including electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) at different exposure time intervals, and potentiodynamic polarization at the termination of the exposure, have been performed to investigate the film forming process and to evaluate corrosion inhibition efficiency of the inhibitors, as well as its evolution with time. The corrosion resistance data obtained from the EIS and LPR measurements are in good agreement. The results indicate different inhibition properties of the inhibitors tested. The inhibition effect of SSF CI-1 is negligible in the first hour of exposure, but it increases steadily with time for 1 day, and then remains the same level during the exposure up to one week. SSF CI-2 exhibits a good inhibition effect in the first hour, but the effect decreases with time to a low level after 8 hours, and then increases again with prolonged exposure. SSF CI-4 shows a low inhibition effect during the first day, and then increases to a maximum level after three days’ exposure. For SSF CI-5 and SSF CI-6, the inhibition effect within 8 hours is relative low but higher than that of SSF CI-4, and the effect increases with time during prolonged exposure. The SSF CI-5 seems to be better than SSF CI-6 because of a more stable inhibition effect. The EIS results indicate that most of the inhibitors form a resistive surface film on carbon steel, which becomes more resistive and protective after several days’ of exposure. However, in the initial stage of exposure, the SSF CI-6 does not show an effect of formation of a resistive film on the surface. The potentiodynamic polarization measurements suggest that, SSF CI-1 and SSF CI-2 are anodic type inhibitor, SSF CI-4 is cathodic type inhibitor, and SSF CI-5 and SSF CI-6 are mix type inhibitor. Moreover, the inhibitors tested show a similar corrosion inhibition effect as mussel adhesive protein (MAP) at the low dosage level.

<p> Cellulose-based materials have been attracting significant attention in recent years for their potential as renewable and biodegradable materials. Cellulose nanofibrils (CNFs) in particular are readily attainable from woody biomass in high purity and without harsh chemical processes. These CNFs can undergo chemical surface modifications after a simple workup, imbuing them with new attributes that differ from their naturally paper-like structure and properties. In this research, CNFs are modified with oleic acid—another common biomass found in high concentrations in some vegetable oils—which transforms the naturally hydrophilic cellulose into a superhydrophobic material. This transformation can be carried out using solventless mechanochemistry and worked up in ethanol, supporting a green process from start to finish.</p> <p><br></p> <p>Since cellulose contains many free, exposed hydroxyl groups, carboxylic acids can be condensed onto exposed hydroxyls to form esters. In this research, we focus specifically on the oleic acid moiety because its internal alkene has potential for further reactivity. Here we explore methods to introduce crosslinks into esterified CNF (eCNF) for structural and mechanical reinforcement between fibrils. Several methods are attempted, including methods involving thiolene chemistry and epoxide ring opening.</p> <p><br></p> <p>Additionally, efforts have been made to develop a method to disperse eCNF materials in ethyl acetate for deposition by spray coating. Dispersions of eCNF in ethyl acetate are sufficiently stable to enable deposition using simple airbrushing tools. The eCNF coatings are homogenous, superhydrophobic, and have good adhesion to a wide variety of surfaces. </p>

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Le développement d’une nouvelle génération de catalyseurs dits biohybrides est basé sur l’association d’un complexe métallique et d’une protéine. D’un côté, le complexe métallique est responsable de l’activité catalytique ; de l’autre côté, la protéine protège le complexe métallique vis-à-vis de la dégradation en milieu aqueux et fournit également un environnement chiral propice à une catalyse énantiosélective. Ces catalyseurs fonctionnant de manière sélective en milieu aqueux s’inscrivent tout à fait dans les préceptes de la chimie verte.Une nouvelle famille de protéines artificielles, nommée αRep, a été récemment décrite. Toutes les protéines de la bibliothèque αRep présentent le même repliement en solénoïde incurvé, mais diffèrent à la fois en taille (nombre de motifs répétés) et dans la nature de 5 acides aminés par motif répété. Une surface variable est ainsi générée sur la surface concave du solénoïde. Ces protéines sont extrêmement stables et modifiables. La modularité de ces protéines ouvre la voie à un panel varié d’ingénierie des protéines, notamment la conception de catalyseurs artificiels.Au sein de la bibliothèque αRep, le variant αRep-A3 est une protéine homodimérique pour laquelle les surfaces concaves de chaque monomère génèrent une crevasse. Les résidus formant cette crevasse peuvent être modifiés sans affecter la structure tridimensionnelle de la protéine. Le but de cette thèse a été d’évaluer la capacité de la protéine αRep-A3 à procurer une architecture rigide pour l’incorporation de complexes de métaux de transition. Pour cela, différents ligands de métaux de transition (phénanthroline, terpyridine, porphyrine) ont été couplés covalemment à des variants de αRep-A3 à différentes positions. Des résultats encourageants concernant la réaction de Diels-Alder entre azachalcone et cyclopentadiène suggèrent que ce type d’architecture pourrait fournir une base intéressante pour la création de nouvelles classes de métalloenzymes entièrement artificielles. Des pistes pour l’amélioration des catalyseurs basés sur les αRep par des méthodes d’évolution dirigée sont alors avancées sur la base de ces résultats. / The development of a new generation of so-called biohybrid catalysts is based on the association of a metal complex and a protein. On the one hand, the metal complex is responsible for the catalytic activity; On the other hand, the protein protects the metal complex from degradation in aqueous medium and also provides a chiral environment conducive to enantioselective catalysis. These catalysts, which function selectively in an aqueous medium, fit perfectly into the precepts of green chemistry.A new family of artificial proteins, called αRep, has recently been described. All proteins in the αRep library exhibit the same curved solenoid folding, but differ in size (number of repeating units) and in the nature of 5 amino acids per repeat unit. A variable surface is thus generated on the concave surface of the solenoid. These proteins are extremely stable and modifiable. The modularity of these proteins paves the way for a varied panel of protein engineering, including the design of artificial catalysts.Within the αRep library, the variant αRep-A3 is a homodimeric protein for which the concave surfaces of each monomer generate a crevice. The residues forming this crevice can be modified without affecting the three-dimensional structure of the protein. The aim of this thesis has been to evaluate the ability of the αRep-A3 protein to provide a rigid scaffold for the incorporation of transition metal complexes. To this end, various transition metal ligands (phenanthroline, terpyridine, porphyrin) have been covalently coupled to variants of αRep-A3 at different positions. Encouraging results regarding the Diels-Alder reaction between azachalcone and cyclopentadiene suggest that this type of scaffold could provide an interesting basis for the creation of new classes of fully artificial metalloenzymes. From these results, lines of improvement for αRep-based catalysts by means of directed evolution are then advanced.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第21178号 / 人博第850号 / 新制||人||203(附属図書館) / 29||人博||850(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 吉田 寿雄, 教授 内本 喜晴, 教授 田部 勢津久 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

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