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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

D-glucosamine as "green" substrate in synthesis of ligands for asymetric catalysis

Wojcik, Karolina 22 October 2012 (has links) (PDF)
Several ligands derived from D-glucosamine, designed for different catalytic reactions havebeen synthesized. The ligands for homogeneous catalysis based on 1,2-glucodiamine wereprepared, and used in reactions of allylic alkylation, hydrogenation and Michael addition.Supported Aqueous Phase Catalyst (SAPC) system was prepared from D-glucosamine anduse with very good results in Suzuki Miyaura cross coupling reactions. Catalyst was alsorecycled. Attempt to prepare ligands grafted on SBA-silica matrix were made as well asligands containing poly(ethylene) glycol moiety.
212

Application of a chiral metal–organic framework in enantioselective separation

Padmanaban, Mohan, Müller, Philipp, Lieder, Christian, Gedrich, Kristina, Grünker, Ronny, Bon, Volodymyr, Senkovska, Irena, Baumgärtner, Sandra, Opelt, Sabine, Paasch, Silvia, Brunner, Eike, Glorius, Frank, Klemm, Elias, Kaskel, Stefan 31 March 2014 (has links) (PDF)
A modular approach for the synthesis of highly ordered porous and chiral auxiliary (Evans auxiliary) decorated metal–organic frameworks is developed. Our synthesis strategy, which uses known porous structures as model materials for incorporation of chirality via linker modification, can provide access to a wide range of porous materials suitable for enantioselective separation and catalysis. Chiral analogues of UMCM-1 have been synthesized and investigated for the enantioseparation of chiral compounds in the liquid phase and first promising results are reported. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
213

Interactions of biomass derived oxygenates with heterogeneous catalysts in aqueous and vacuum environments

Copeland, John Robert 13 January 2014 (has links)
Biomass is one of the most promising replacements for fossil fuels as a feedstock for chemical and transportation fuel production. The combination of low vapor pressure and high polarity of most biomass derived molecules makes water the ideal solvent for biomass upgrading reaction schemes. Metal oxide and metal oxide supported catalysts are heavily used in oil refining and petrochemical production, and are capable of upgrading biomass molecules as well. However, the surface chemistries that dictate the behavior of aqueous phase biomass upgrading reactions over metal oxide catalysts are not nearly as well understood as in the case of gas phase hydrocarbon refining systems. This dissertation aims to investigate the surface chemistries of biomass derived oxygenate molecules on metal oxide and metal oxide supported metal catalysts. There are three main objectives in this dissertation: to understand how two and three carbon polyols interact with metal oxide surfaces, to elucidate the role of various surface sites on polyol-metal oxide interactions, and to discover the surface species of kinetic importance in aqueous phase reforming reactions of biomass molecules. Transmission infrared spectroscopy and density functional theory modeling were the major techniques used to demonstrate that polyols with alcohol groups on the first and third carbons, 1,3-propanediol and glycerol, form a multidentate surface species with a bridging alkoxide bond and an acid/base interaction through their two primary alcohol groups with Lewis acid sites of g-Al₂O₃. These interactions occur in the presence of bulk water. Polyols with alcohol groups only on the first and second carbons, ethylene glycol and 1,2-propanediol, only formed alkoxy bonds with the g-Al₂O₃ surface when bulk water was not coadsorbed, and these bonds were removed by re-adsorbing water. Glycerol also forms the same surface species on other metal oxides with strong Lewis acidic character: TiO₂ anatase, ZrO₂, and CeO₂. Glycerol only forms hydrogen bonds with MgO, which lacks strongly Lewis acidic sites. Basic surface hydroxyls and surface oxygen atoms of the metal oxides only played a minor role in interacting with the adsorbed glycerol. In-situ attenuated total reflectance infrared spectroscopy demonstrated that the aqueous phase reforming of glycerol over a 5 wt% Pt on g-Al₂O₃ catalyst is hindered by residual platinum bound hydrogen or oxygen atoms from commonly utilized catalyst reduction or cleaning procedures, respectively. A pretreatment consisting of multiple iterations of dissolved oxygen, dissolved hydrogen, and dissolved helium in water flow periods provides the cleanest Pt surface for monitoring carbon monoxide formation dynamics, and allows for observing the rate limiting step of the aqueous phase reforming reactions water-gas shift removal of Pt bound carbon monoxide. The bridging bound carbon monoxide is preferentially removed over the linearly bound species via water gas shift reactions even at room temperature.
214

Production of biodiesel from used cooking oil (UCO) using ion exchange resins as catalysts

Zainal-Abidin-Murad, Sumaiya January 2012 (has links)
This study focuses on the development of novel two-stage esterification-transesterification synthesis of biodiesel from used cooking oil (UCO) using novel heterogeneous catalysts. The esterification of the UCO was investigated using three types of ion exchange resins catalysts including Purolite D5081, Purolite D5082 and Amberlyst 15. Of all the catalysts investigated, Purolite D5081 resin showed the best catalytic performance and was selected for further optimisation studies. From the optimisation study, it was found that the external and internal mass transfer resistance has negligible effect on the esterification reaction. At the optimum reaction conditions, Purolite D5081 achieved 92% conversion of FFA. During reusability study, the conversion of FFA dropped by 10% after each cycle and it was found that progressive pore blockage and sulphur leaching were dominant factors that decreased the catalytic performance of the Purolite D5081 catalyst. A kinetic modelling for FFA esterification was carried out using Purolite D5081 as a catalyst. Three types of kinetic models were investigated i.e. pseudo homogeneous (PH), Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW). Experimental data obtained from the batch kinetic studies was successfully represented by the PH model and a good agreement between experimental and calculated values was obtained. The activation energy for esterification and hydrolysis reaction was found to be 53 and 107 kJ/moL. The transesterification of pre-treated cooking oil (P-UCO) was investigated using various types of heterogeneous catalysts including Purolite CT-122, Purolite CT-169, Purolite CT-175, Purolite CT-275, Purolite D5081, Diaion PA306s and Cs-supported heteropolyacids catalysts. Of all the catalysts investigated, Diaion PA306s catalyst showed the highest conversion of triglycerides and was selected for further optimisation studies. At the optimum reaction conditions, Diaion PA306s achieved ca. 75% of triglycerides conversion. During the reusability study, Diaion PA306s catalyst gave a similar conversion of triglycerides after being reused once. Therefore, it was concluded that the resin can be used several times without losing catalytic activity. Several purification methods have been investigated and dry washing method was chosen as the best alternative for biodiesel purification.
215

Struktur und Aktivität von Al2O3-geträgerten Eisenoxid-Katalysatoren zur Reinigung von Dieselabgas

Roppertz, Andreas 11 January 2017 (has links) (PDF)
In der vorliegenden Arbeit werden Al2O3-geträgerte Eisenoxid-Katalysatoren auf ihre Eignung in der Nachbehandlung von Dieselabgasen getestet. Hierbei werden die Oxidationsreaktionen von Kohlenmonoxid, Propen, Stickstoffmonoxid sowie Ammoniak getestet. Weiterhin wird die Katalysatoraktivität bei der Stickoxidminderung nach dem SCR-Verfahren untersucht. Basierend auf einer detaillierten Charakterisierung wird eine Struktur-Aktivitäts-Korrelation entwickelt, auf deren Basis ein Verständnis für die Art der aktiven Zentren solcher Katalysatoren generiert wird. Zudem wird ein Modell entwickelt, mit Hilfe dessen die spezifische Aktivität der verschiedenen Typen an aktiven Zentren bewertet werden kann. Darüber hinaus wird in dieser Arbeit auf die Stickoxidminderung nach dem SCR-Verfahren fokussiert, was die Untersuchungen des Reaktionsmechanismus sowie die Struktur-Aktivitäts-Korrelation an hydrothermal gealterten Katalysatoren beinhaltet.
216

Transformation du glycérol par catalyse hétérogène : aspects théoriques et expérimentaux / Chemical transformation of glycerol by heterogeneous catalysis : theoretical and experimental aspects

Auneau, Florian 17 October 2011 (has links)
Cette thèse s’intéresse à la conversion du glycérol en acide lactique (AL) et 1,2-propanediol (1,2-PDO) par catalyse hétérogène. Le mécanisme de la réaction fait débat, particulièrement au sujet de la première étape, qui peut être une déshydratation ou une déshydrogénation. Il est attendu que ces étapes élémentaires soient influencées par le pH et la nature de l’atmosphère. Ces paramètres ont donc été étudiés expérimentalement, en présence d’un catalyseur au rhodium supporté sur charbon. D’autre part, il y avait un manque de connaissances sur le comportement du glycérol à la surface métallique du catalyseur. Une approche théorique sur une surface modèle a donc été mise en oeuvre dans le champ de la théorie de la fonctionnelle de la densité (DFT), pour examiner les étapes élémentaires et calculer les états de transition correspondants. La combinaison de ces études a montré que la déshydrogénation du glycérol en glycéraldéhyde est la première étape de la réaction sur le catalyseur Rh/C en milieu basique sous atmosphère d’hélium et d’hydrogène. Cette étude a ensuite été étendue à un catalyseur iridium supporté sur charbon, qui a mené à de meilleurs rendements en 1,2-PDO et AL. L’utilisation de ce métal supporté sur carbonate de calcium a permis d’améliorer le rendement en AL, mais l’activité est plus faible. Cependant, ce catalyseur s’est révélé relativement actif dans l’eau à pH neutre, ce qui pourrait conduire à une synthèse plus verte de l’AL. Enfin, les aspects prédictifs de la chimie théorique ont été examinés, pour voir si la réactivité de ce polyol complexe (du point de vue de la chimie théorique) pouvait être modélisée par celle d’un monoalcool sur la surface. / This thesis reports a study of the heterogeneously catalysed conversion of glycerol into 1,2-propanediol (1,2-PDO) and lactic acid (LA). The mechanism and the first step of the reaction are especially debated, as it can be either dehydration or dehydrogenation. It is expected that these elementary steps can be influenced by pH variations and by the nature of the gas phase. These parameters were consequently investigated experimentally in the presence of a carbon supported rhodium catalyst. On the other hand, there was a lack of knowledge in the behaviour of glycerol at the surface of the metallic catalyst. A theoretical approach on a model Rh(111) surface was thus implemented in the framework of Density Functional Theory (DFT) to look over the alementary reactions and to calculate the corresponding transition states. The combination of experimental and theoretical results has shown that dehydrogenation into lyceraldehyde is the first step of the reaction on the Rh/C catalyst in basic media under He or H2 atmosphere. The study was then extended to carbon supported iridium catalyst that lead to the best 1,2-PDO and LA yields. The use of iridium catalyst supported on calcium carbonate allowed obtaining higher yields in LA, but catalytic performances were lower. This latter catalyst was surprisingly quite active when performing the reaction in neutral water, which provides opportunities for a greener synthesis of LA. Last, the predictive aspects of the theoretical chemistry were investigated to determine whether the reactivity of this polyalcohol can be modelized by the reactivity of a simpler monoalcohol on the surface.
217

La catalyse hétérogène au palladium en chimie fine : une étude sur la synthèse « one-pot » de stilbènes et bibenzyles : application à la synthèse de styrènes et aryl-indoles / Heterogeneous palladium catalysis in fine chemistry : a study on “one-pot” synthesis of stilbenes and bibenzyls : application to the synthesis of styrenes and arylindoles

Cusati, Giuseppe 15 October 2009 (has links)
Les synthèses « one pot » multi-étapes efficaces et éco-compatibles ont été envisagées pour la synthèse de molécules potentiellement bioactives tels que les systèmes bis(bibenzyliques) et leurs précurseurs stilbéniques ou bibenzyliques par catalyse hétérogène au palladium. Une synthèse « one-pot » impliquant une réaction de couplage de Heck suivie d’une hydrogénation des stilbènes ainsi formés a été mise au point en présence de Pd/C. Cette stratégie c’est révélée être limitée lors de l’application à des substrats désactivés et stériquement encombrées. Couplée au manque de disponibilité commerciale d’oléfines aromatiques intéressantes pour nos objectifs, nous avons mis au point une synthèse de styrènes par catalyse hétérogène à partir d’halogénures d’aryles et du vinyltrifluoroborate de potassium impliquant un couplage de Suzuki-Miyaura. Cette vinylation hétérogène a été ensuite appliquée à la synthèse « one-pot » de stilbènes. Des études d’optimisation de ce procédé sont encore en cours. Les stilbènes ainsi obtenus ont été utilisée pour la synthèse de bis(bibenzyles) ouverts et fermés. Pour ce faire différentes stratégies « one-pot » ont été évaluées au cours de ces travaux et des bis(stilbènes) ont été obtenus avec des rendements compris entre 30% et 50%. Les bis(stilbènes) ainsi obtenus ont été l’objet d’études en hydrogénation. A ce jour aucune de nos tentatives n’a permis l’obtention de bis(bibenzyles) quelles que soient les conditions employées. Des études sont en cours pour comprendre les raisons de ces résultats et obtenir les bis(bibenzyles) cibles de nos travaux / “One-pot” strategy, powerful tools for the creation of molecular complexity, has been applied in the synthesis of possible bioactive molecules such bis(bibenzyls) systems and their precursors stilbenes and bibenzyles using heterogeneous palladium catalysts. In this work a “one-pot” synthesis concerning a Heck coupling reaction followed by in situ hydrogenation with Pd/C has been studied for the synthesis of bibenzyl derivates. We have observed limitations for deactivated and hindered substrates. Moreover due to the low commercially availability of aromatic styrenes we focused our attention on the development of new heterogeneous vinylation reaction starting from aromatic halides and potassium vinyltrifluoroborate through a Suzuki coupling reaction. This strategy was then applied to “one-pot” stilbenes synthesis. The study is still under investigation in our laboratory. The synthesized stilbenes have been used as precursors in the synthesis of cyclic or acyclic bis(bibenzyls) derivates. Many different “one-pot” strategies have been developed that allowed to reach yields of bis(stilbenes) between 30% and 50% in only one step. Bis(stilbenes) have been objects of investigation as what concerned the hydrogenation. However every effort has not yet been successful under our reaction conditions. Studies are still in progress to understand the reasons of these results and to obtain bis(bibenzyls) systems, target of our research
218

La catalyse au palladium pour l'obtention d'indoles fonctionnalisés : application à une synthèse monotope d'indoloquinones par catalyse hétérogène / Palladium catalysis for functionalised indoles syntheses : application to a onepost synthesis of indoloquinone through heterogeneous catalysis

Batail, Nelly 08 October 2010 (has links)
Depuis le début des années 1990, l'hétéroannélation de Larock est apparue comme une méthode de choix pour obtenir, en une seule étape, des indoles 2,3-disubstitués. Cependant, bien qu'efficace, certains inconvénients restaient associés à cette stratégie comme l'utilisation d'un système catalytique homogène associé à l'emploi de sels. Pour cette raison, nous avons développé une nouvelle méthodologie sans sels ou additifs par catalyse hétérogène. Différents catalyseurs commerciaux ou faciles d'accès (Pd/C ou [Pd]/NaY) ainsi que de nouveaux complexes au palladium immobilisés sur SBA-15 ont été testés. De façon surprenante, ces nouvelles conditions ont permis une activation de 2-bromoanilines et ce, sans l'emploi d'additifs. Une autre méthode d'obtention de ces hétérocycles a émergé ces dernières années et se pose comme une alternative aux couplages traditionnels : l'arylation d'indoles. Malgré de nombreuses améliorations, aucun travail ne décrivait une procédure permettant une arylation complémentaire C2 ou C3 d'indoles libres avec un système catalytique unique. Nous avons développé un tel système, basé sur une pallado-catalyse dans l'eau. Cette stratégie permet d'atteindre des sélectivités C2/C3 ou C3/C2 élevées avec de bons rendements isolés par un simple contrôle du couple (base/halogénure d’aryle).Enfin, dans le cadre de nos travaux visant la synthèse par catalyse hétérogène de produits à haute valeur ajoutée, nous avons initié des études sur l'obtention de pyrroloiminoquinones. La méthode consistant en une catalyse hétérogène monotope en seulement deux grandes étapes devrait permettre un accès rapide à de nombreux dérivés bioactifs isolés d'organismes marins. / Since the beginning of the 90's, the Larock heteroannulation became a method of choice to afford, in a single step, 2,3-disubstituted indoles. While effective, this methodology suffered of drawbacks lied to the use of salts, additives and homogeneous catalyst. Thus, we developed the first ligand and salt free heterogeneous Larock heteroannulation. Different commercially available, home made catalysts (Pd/C or [Pd]/NaY) or new palladium complexes immobilised onto mesoporous silica SBA-15 were evaluated. Surprisingly, this methodology allowed an activation of the 2-bromoanilines without using additives. Another procedure to obtain indole nucleus emerged over the past few years as an outstanding alternative to traditional cross-coupling reactions: namely the “direct arylation”. Despite major improvements, no report focuses on complementary C2 and C3-arylation procedures by means of a unique catalytic system. Herein, we describe an innovative “on water” palladium-catalyzed C–H arylation of (NH)-indoles that is site-selective through a base/halide-controlled using cheap reagents. This methodology allows the preparation of either C2- or C3-arylindoles with high isolated yields. Finally, as part of our project related to syntheses of high added value products by heterogeneous catalysis, we investigated studies in order to obtain pyrroloiminoquinones. This new methodology using only two steps will permit an access to numerous bioactive analogues.
219

Development of catalytic enantioselective C-C bond-forming and cascade transformations by merging homogeneous or heterogeneous transition metal catalysis with asymmetric aminocatalysis

Afewerki, Samson January 2014 (has links)
Chiral molecules play a central role in our daily life and in nature, for instance the different enantiomers or diastereomers of a chiral molecule may show completely different biological activity. For this reason, it is a vital goal for synthetic chemists to design selective and efficient methodologies that allow the synthesis of the desired enantiomer. In this context, it is highly important that the concept of green chemistry is considered while designing new approaches that eventually will provide more environmental and sustainable chemical synthesis.The aim of this thesis is to develop the concept of combining transition metal catalysis and aminocatalysis in one process (dual catalysis). This strategy would give access to powerful tools to promote reactions that were not successful with either transition metal catalyst or the organocatalyst alone. The protocols presented in this thesis based on organocatalytic transformations via enamine or iminium intermediates or both, in combination with transition metal catalysis, describes new enantioselective organocatalytic procedures that afford valuable compounds with high chemo- and enantioselectivity from inexpensive commercial available starting materials. In paper I, we present a successful example of dual catalysis: the combination of transition metal activation of an electrophile and aminocatalyst activation of a nucleophile via enamine intermediate. In paper II, the opposite scenario is presented, here the transition metal activates the nucleophile and the aminocatalyst activates the electrophile via an iminium intermediate. In paper III,we present a domino Michael/carbocyclisation reaction that is catalysed by a chiral amine (via iminium/enamine activation) in combination with a transition metal catalysts activation of an electrophile. In paper IV, the concept of dual catalysis was further extended and applied for the highly enantioselective synthesis of valuable structural scaffolds, namely poly-substituted spirocyclic oxindoles. Finally, in paper V the concept of dual catalysis was expanded, by investigating more challenging and environmentally benign processes, such as the successful combination of a heterogeneous palladium and amine catalysts for the highly enantioselective synthesis of functionalised cyclopentenes, containing an all carbonquaternary stereocenter, dihydrofurans and dihydropyrrolidines.
220

Hydrogénation de l'acide succinique en phase aqueuse pour l'obtention sélective de 1,4-butanediol / Selective aqueous phase hydrogenation of succinic acid to 1,4-butanediol

Ly, Bao Khanh 16 April 2013 (has links)
Le but du projet est d’hydrogéner l’acide succinique en phase aqueuse à 160°C, sous 150 bar d’hydrogène pour obtenir sélectivement le 1,4-butanediol (BDO) en utilisant des catalyseurs x%Re-2%Pd/TiO2. Les catalyseurs monométalliques au palladium permettent d’obtenir sélectivement le produit intermédiaire : la γ-butyrolactone et très peu de BDO est obtenu. Leur activité catalytique est fonction de la dispersion de la phase métallique. L’addition de rhénium aux catalyseurs monométalliques au palladium permet de poursuivre la réaction jusqu’à l’obtention du BDO. Nous avons d’abord essayé deux méthodes d’addition ex situ de rhénium : réduction catalytique (RC) et imprégnation successive (IS). La meilleure sélectivité en BDO obtenue jusqu’à maintenant est de 90% en présence du solide 3,4%Re-2%Pd/TiO2 préparé par IS. Quelle que soit la méthode de dépôt (RC ou IS), le rhénium dans ces solides bimétalliques est réoxydé et lixivié dans la phase aqueuse sous l’atmosphère non réductrice. Malgré la lixiviation et le redépôt du rhénium sous hydrogène, le comportement des catalyseurs bimétalliques Re-Pd/TiO2 préparés ces deux méthodes reste différent. Le dépôt in situ de Re conduit à des catalyseurs bimétalliques prometteurs : SBDO = 73% avec 2% de rhénium déposé / The aim of our research project is the hydrogenation of the succinic acid in aqueous phase at 160°C, under 150 bar hydrogen to obtain selectively 1,4-butanediol (BDO) by using x%Re- 2%Pd/TiO2 catalyst. Palladium monometallic catalysts allow us to obtain selectively the intermediate product γ-butyrolactone and very little BDO. Their catalytic activity depends on the dispersion of the metallic phase. The reaction can be extended until obtaining BDO by adding the rhenium to palladium based monometallic catalysts. Firstly, we have tried two ex situ methods to add the rhenium: catalytic reduction (CR) and successive impregnation (SI). The best selectivity to BDO is 90% with the presence of 3,4%Re-2%Pd/TiO2 prepared by IS method. Moreover, for both deposition methods, the rhenium in the bimetallic catalysts is reoxidized with air and then leached into the aqueous phase. Despite leaching and redeposition of rhenium under hydrogen pressure, the behavior of bimetallic catalysts prepared by the two methods (CR and SI) is different. In situ deposition of the rhenium leads to promising bimetallic catalysts: SBDO = 73% with 2% of rhenium

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