To see the other types of publications on this topic, follow the link: Catalyst and solvent-free synthesis.
Dissertations / Theses on the topic 'Catalyst and solvent-free synthesis'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Catalyst and solvent-free synthesis.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Botti, Luca. "Mechanochemical solvent-free synthesis of Sn-β Zeolite and Ag2O/TiO2 catalysts". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11941/.
Full textAbstract:
Preparations of heterogeneous catalysts are usually complex processes that involve several procedures as precipitation, crystallization and hydrothermal treatments. This processes are really dependent by the operative conditions such as temperature, pH, concentration etc. Hence the resulting product is extremely affected by any possible variations in these parameters making this synthesis really fragile. With the aim to improve these operations has been decided to exploit a new possible strong environment-respectful process by mechanochemical treatment, which permits to carry out solvent free-solvent synthesis exploiting the Mixer Mill MM400 (Retsch) in order to have reproducible results. Two different systems have been studied in this kind of synthesis: a tin β -zeolite tested in a H-trasnfer reaction of cyclohexanone and a silver on titania catalyst used in the fluorination of 2,2 dimethyl glucaric acid. Each catalyst has been characterized by different techniques in order to understand the transformations involved in the mechanochemical treatment.
2
Brunner, Kyle Martin. "Novel Iron Catalyst and Fixed-Bed Reactor Model for the Fischer-Tropsch Synthesis." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3752.
Full textAbstract:
This work investigates a novel iron Fischer-Tropsch (FT) catalyst preparation and describes the development of a trickle fixed-bed recycle reactor model (TFBRRM) for the FT synthesis applicable to both iron and cobalt catalysts. The iron catalyst preparation was developed using a novel solvent deficient precipitation reaction. Fifteen Fe/Cu/K/SiO2 catalysts were prepared to investigate key preparation variables including timing of promoter addition, washing or not washing after precipitation, and drying temperature. Adding promoters to starting materials before precipitation (1S) gives more uniform promoter distributions which gives higher water-gas shift activity and lower methane selectivity. Unwashed catalysts have smaller average pore and crystallite diameters (3.9-10.8 nm versus 15.3-29.5 nm) and 30% smaller pore volumes, but 65% higher rates of reaction than washed catalysts. Catalysts dried first at 100 °C have up to 50% smaller average pore and crystallite diameters, but 10-20% higher rates of reaction than catalysts dried first at 60 °C. Overall, 1S catalysts, left unwashed, and dried first at 100 °C are best suited in activity, selectivity, and stability for wax production from hydrogen-deficient feed stocks such as coal, biomass, or municipal waste. The activity of the most active catalyst of this study is greater than or equal to the activities of two of three catalysts reported in the literature. This dissertation describes in detail the TFBRRM, reports its validation, and presents results of varying fundamental, theoretically-based parameters (e.g. effective diffusivity, Prandtl number, friction factor, etc.) as well as physical process parameters (i.e. recycle ratio, pressure, flow rate, tube diameter, cooling temperature, and pellet diameter and shape). For example, the model predicts that decreasing effective diffusivity from 7.1E-9 to 2.8E-9 m^2/s results in a lower maximum temperature (from 523 to 518 K) and a longer required bed length to achieve 60% conversion of CO (from 5.7 to 8.5 m). Using the Tallmadge equation to estimate friction losses as recommended by the author results in a pressure drop 40% smaller than using the Ergun equation. Validation of the model was accomplished by matching published full-scale plant data from the SASOL Arge reactors.
3
Duong-Viet, Cuong. "Synthesis and processing of nitrogen-doped carbon nanotubes as metal-free catalyst for H2S selective oxidation process." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF029/document.
Full textAbstract:
Les nanotubes de carbone (NTCs) dopés avec différents hétéroéléments tels que l'oxygène et l'azote connaissent un intérêt croissant dans le domaine de la catalyse hétérogène comme leur utilisation en tant que catalyseur sans métaux. L'objectif de cette thèse consiste à la synthèse et la caractérisation de matériaux catalytiques à base de NTC dopés à l'azote supportés sur du carbure de silicium SiC par voie in situ (CVD) et ex-situ méthodes. Une autre approche a été utilisée pour la fonctionnalisation de la surface des nanotubes de carbone et basées sur l'utilisation d'un agent oxydant (HNO3) en phase gazeuse. Ce procédé d'oxydation crée non seulement des défauts sur la surface des nanotubes de carbone mais également décore leur surface avec des groupes fonctionnels oxygénés. Les NTCs dopés à l'oxygène et à l'azote ainsi synthétisés ont été caractérisés par différentes techniques (XPS, MEB, MET, BET, ATG). Ces catalyseurs carbonés présentent des performances remarquables en termes d'activité et de sélectivité en soufre, et une très grande stabilité sous flux en fonction du temps dans la réaction d'oxydation partielle de l'H2S en soufre élémentaire, et ce, même à vitesse spatiale de gaz élevée (WHSV) et faible rapport O2/H2S. L'influence des différentes propriétés physico-chimiques et les défauts présents sur la surface des NTC sur les performances catalytiques ont été étudiée et discutée dans le cadre de ce travail<br>Carbon nanotubes (CNTs) containing different doping such as oxygen and nitrogen composites have received more and more scientific attention as metal-free catalyst in the field of heterogeneous catalysis. The aim of this thesis is related to the synthesis and characterization of nitrogen-doped CNTs decorated on SiC support using both in-situ (CVD with NH3) and ex-situ (N@C) methods. Other approach was employed for the surface functionalization of CNTs is based on the use of oxidative agent (HNO3) in gas phase. This oxidation process not only creates defects on the CNTs surface but also decorates their surface with oxygenated functional groups. The as-synthesized oxygen- and nitrogen-doped CNTs are characterized by different techniques (XPS, SEM, TEM, BET, TGA). The carbon based catalysts exhibit outstanding performances in term of activity and sulfur selectivity, and very high stability with time on stream in the partial oxidation of H2S into elemental sulfur even at high gas space velocity (WHSV) and low O2-to-H2S molar ratio. The influence of the physical-chemical properties and defects present on the CNTs surface on the catalytic performance was thoroughly investigated and discussed within the framework of this work
4
Huang, Baiyu. "Facile Synthesis and Improved Pore Structure Characterization of Mesoporous γ-Alumina Catalyst Supports with Tunable Pore Size". BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3553.
Full textAbstract:
Mesoporous γ-alumina is the most extensively used catalysts support in a wide range of catalytic processes. The usefulness of γ-alumina relies on its favorable combination of physical, textural, thermal, and chemical properties. Pore structure properties are among the most important properties, since high surface area and large pore volume enable higher loading of active catalytic phases, while design of pore size and pore size distribution is critical to optimize pore diffusional transport and product selectivity. In addition, accurate determination of surface area (SA), pore volume (PV) and pore size distribution (PSD) of porous supports, catalysts, and nanomaterials is vital to successful design and optimization of these materials and to the development of robust models of pore diffusional resistance and catalyst deactivation.In this dissertation, we report a simple, one-pot, solvent-deficient process to synthesize mesoporous γ-alumina without using external templates or surfactants. XRD, TEM, TGA and N2 adsorption techniques are used to characterize the morphologies and structures of the prepared alumina nanomaterials. By varying the aluminum salts or the water to aluminum molar ratio in the hydrolysis of aluminum alkoxides, γ-alumina with different morphologies and pore structures are synthesized. The obtained alumina nanomaterials have surface areas ranging from 210 m2/g to 340 m2/g, pore volumes ranging from 0.4 cm3/g to 1.7 cm3/g, and average pore widths from 4 to 18 nm. By varying the alcohols used in the rinsing and gelation of boehmite/bayerite precursors derived from a controlled hydrolysis of aluminum alkoxides, the average pore width of the γ-aluminas can be tuned from 7 to 37 nm. We also report improved calculations of PSD based on the Kelvin equation and a proposed Slit Pore Geometry model for slit-shaped mesopores of relatively large pore size (>10 nm). Two structural factors, α and β, are introduced to correct for non-ideal pore geometries. The volume density function for a log normal distribution is used to calculate the geometric mean pore diameter and standard deviation of the PSD. The Comparative Adsorption (αs) Method is also employed to independently assess mesopore surface area and volume.
5
Haddad, Ryma. "Synthèse frugale de catalyseurs hétérogènes par procédé éco-responsable de chimie sol-gel sans solvants." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS643.pdf.
Full textAbstract:
L'industrie doit s'orienter vers une économie durable, elle doit réduire l’utilisation de ressources, la production de déchets et consommer moins d'énergie. La catalyse, notamment par l'utilisation de catalyseurs, joue un rôle clé dans cette transition car elle améliore considérablement l'efficacité énergétique de certaines réactions chimiques tout en ciblant sélectivement les produits de la réaction. Ainsi, la demande de catalyseurs a considérablement augmenté en raison de préoccupations environnementales et énergétiques. Pour rester compétitive, l'optimisation des performances des catalyseurs, des processus catalytiques et des propriétés des matériaux est essentielle, tout en réduisant les coûts énergétiques et financiers de leur fabrication. La thèse vise à développer des approches éco-responsables pour la fabrication de catalyseurs hétérogènes à grande échelle en utilisant la chimie sol-gel sans solvants couplée à des procédés de mélanges mécaniques tels que l'extrusion réactive. Cette stratégie permet d'obtenir des matériaux catalytiques performants tout en réduisant leur impact environnemental. Nous présenterons une étude fondamentale qui a abouti à la description des mécanismes de la synthèse d’extrudés de boehmite via la chimie sol-gel sans solvant couplé au procédé d’extrusion réactive. L’influence des paramètres de vieillissement des matériaux sur les propriétés mécaniques des extrudés (nécessaires pour une application industrielle réelle) a également été exploré. Des expériences ont été menées avec succès pour créer des catalyseurs à base de ruthénium et de nickel supportés sur des oxy-hydoxyde d’aluminium et sur des alumines. L’étude montre que cette approche dite « frugale » est compétitive sur l’efficacité catalytique et bien plus respectueuse de l'environnement que les méthodes traditionnelles<br>Industry needs to move towards a sustainable economy, by reducing resources and energy consumptions and reducing waste production. Catalysis, especially through the use of catalysts, plays a key role in this transition. It significantly improves the energy efficiency of specific chemical reactions and selectively targeting their products. As a result, demand for catalysts has increased considerably due to environmental and energy concerns. To remain competitive, it is essential to optimise catalyst performance, catalytic processes and material properties, while reducing the energy and financial costs of their manufacture. This thesis aims to develop eco-responsible approaches for the large-scale manufacture of heterogeneous catalysts using solvent-free sol-gel chemistry coupled with mechanical mixing processes such as reactive extrusion. This strategy makes it possible to obtain high-performance catalytic materials while reducing their environmental impact. We will present a fundamental study that led to the description of the mechanisms involved in the synthesis of boehmite extrudates using solvent-free sol-gel chemistry coupled with the reactive extrusion process. The influence of material ageing parameters on the mechanical properties of the extrudates (necessary for a real industrial application) was also explored. Experiments were successfully carried out to create catalysts based on ruthenium and nickel supported on aluminium oxyhydoxide and alumina. The study shows that this "frugal" approach is competitive in terms of catalytic efficiency and much more sustainable than traditional methods
6
Lazuen-Garay, A. "Solvent-free synthesis of metal-organic frameworks." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546378.
Full text
7
Sengupta, Sujata. "1,2,3-(NH)-triazoles its metal-free synthesis and application as ligands in transition metal catalysis /." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10984.
Full textAbstract:
Thesis (Ph. D.)--West Virginia University, 2010.<br>Title from document title page. Document formatted into pages; contains xii, 328 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 81-91).
8
Bowen, C. J. "Self-Assembly and Solvent Free Synthesis with Phosphine Ligands." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527662.
Full text
9
Mossaraf, Hossain. "Solvent free synthesis of some heterocycles and their applications." Thesis, University of North Bengal, 2017. http://ir.nbu.ac.in/handle/123456789/2621.
Full text
10
Bah, Juho. "Metal-Free Catalysis for Efficient Synthesis." Doctoral thesis, KTH, Organisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144577.
Full textAbstract:
The strength of efficient metal-free catalysis will be examined in this thesis. Efforts towards more sustainable processes will be demonstrated through implementation of strategies that meet several of the 12 principles of Green Chemistry.In the first part, a stereoselective total synthesis of multiple alkaloids from the Corynantheine and Ipecac families together with their non-natural analogues will be disclosed. A highly efficient, common synthetic strategy is applied leading to high overall yields starting from easily available starting material. Overall operational simplicity and sustainability have been the main focus. Time-consuming and waste-generating isolations and purifications of intermediates have been minimized, as well as the introduction of protection-group chemistry. Moreover, the first example of the total synthesis of Hydroxydihydrocorynantheol together with its non-natural epimer has been accomplished in multi-gram scale without protection groups and without a single isolation or purification step in high overall yield and diastereoselectivity.In the second part, carbocations will be presented as highly effective and versatile non-metal Lewis acid catalysts. Lewis acidity-tuning of carbocations will be introduced and applied in several reactions to suppress competing reactions. Finally, the broad scope of carbocation catalyzed transformations will be exposed.At large, evident progress has been made towards more sustainable chemistry.<br><p>QC 20140425</p>
11
Kleyi, Phumelele Eldridge. "Solvent-free synthesis of bisferrocenylimines and their coordination to rhodium (I)." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1053.
Full textAbstract:
Solvent-free reactions possess advantages compared to the solvent route, such as shorter reaction times, less use of energy, better yields, etc. Herein, the synthesis and characterization of bisferrocenylimines and arylbisamines are described. Reduction of the above compounds with LAH resulted in the formation of bisferrocenylamines and arylbisamines, respectively. The coordination chemistry of all the above compounds to rhodium(I) is also discussed in the prepared complexes [Rh(COD)(NN)]ClO4, where NN = bisferrocenylimines, and [Rh(COD)(NN)]BF4, where NN = bisferrocenylamines and arylbisamines. X-ray crystal structures of the complexes [Rh(COD)(NN)]ClO4 ([3.2] and [3.3]) have been obtained. Complexes of the type [Rh(COD)(NN)]BF4 were characterized with IR and UV-vis spectroscopy, cyclic voltammetry and conductometry. The catalytic activity of the complexes was also investigated: [Rh(COD)(NN)]ClO4 for the polymerization of phenylacetylene and [Rh(COD)(NN)]BF4 for the hydroformylation of styrene.
12
Leveneur, Sébastien. "Catalytic synthesis and decomposition of peroxycarboxylic acids." Phd thesis, INSA de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00560883.
Full textAbstract:
L'objectif de cette thèse fut de développer un process pour la production d'acide peroxycarbolique à partir du peroxyde d'hydrogène et d'un acide carboxylique dans un réacteur continu. Dans un premier temps, la stabilité des espèces peroxydées fut étudiée en utilisant une méthode d'analyse en direct (spectromètre de masse). Un effort particulier a été apporté pour trouver un catalyseur hétérogène ne provoquant pas la décomposition des espèces peroxydées et ayant une activité catalytique similaire à l'acide sulfurique. Un réacteur en continu en lit fixe a été construit en utilisant des résines échangeuses de cation.
13
Keskin, Nagehan. "Synthesis And Characterization Of Solvent Free Alkyd Resin With Hyperbranched Melamine Core." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612996/index.pdf.
Full textAbstract:
The use of volatile organic compounds (VOC) in coating materials has adverse effects on both human health and the environment. Due to concern over these problems, coating industry has attempted to decrease the solvent contents of coating materials for the last three decades by developing water dispersed and powder paints. A recently developed method to make solvent free paint is to use highly branched polymers in high solid alkyd resins. Highly branched polymers help to achieve resins with viscosity much lower than its linear counterparts.
In this study, a new alkyd based resin was formulated using long oil alkyd and melamine based hyperbranched polymer having 24 functional groups on its structure. The long oil alkyd was synthesized by using an oil mixture (40% linseed + 60% sunflower). Melamine was preferred as core molecule due to its excellent properties such as greater hardness, alkali and solvent resistance with thermal stability. The resin produced has low viscosity because its hyperbranched structure<br>therefore, it needs no solvent for its application. The chemical characterization of the resins with different compositions was performed using Fourier Transform Infrared Spectroscopy and thermal properties were determined by Differential Scanning Calorimetry. Physical and mechanical tests were conducted to determine hardness, flexibility, impact resistance, abrasion resistance, adhesion power, and gloss property of the samples. The viscosity of the resins decreased from 148 Pa.s to 8.84 Pa.s as the hyperbranched polymer to long oil alkyd ratio was increased from 1:3 to 1:24. On the other hand, the hardness values of the resins decreased from 198 Persoz to 43 Persoz. All resins showed excellent flexibility, formability, adhesion, and gloss.
14
Leon, Robert. "Stereoselective Transition-Metal-Free Diboration of Alkenes." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106845.
Full textAbstract:
Thesis advisor: James Morken<br>Boronates are extremely useful in synthesis due to the ability of carbon-boron bonds to be transformed into carbon-oxygen, carbon-nitrogen, or carbon-carbon bonds stereospecifically. This makes the stereoselective construction of carbon-boron bonds especially useful. The development of transition-metal catalyzed diboration of alkenes gave synthetic organic chemists a way to quickly make not one, but two carbon-boron bonds in a stereoselective fashion. However, there are many drawbacks to transition-metal catalysis, such as high cost of catalysts and chiral ligands, and air and moisture sensitivity of catalysts. These issues, in addition to difficulties in removing trace amounts of metal contaminants from reaction products have prevented transition-metal-catalysis from being used on the industrial scale. Discussed in this thesis are two different methods for stereoselective, transition-metal-free diboration of alkenes developed by the Morken group. Also discussed is the pioneering work in the area of transition-metal-free diboration done by the Fernández group, which inspired these methodologies<br>Thesis (BS) — Boston College, 2016<br>Submitted to: Boston College. College of Arts and Sciences<br>Discipline: Departmental Honors<br>Discipline: Chemistry
15
Pattisson, Samuel David. "From support to carbocatalyst : the aerobic and solvent free epoxidation of dec-1-ene using graphitic oxide as a catalyst." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/78390/.
Full textAbstract:
The solvent-free selective epoxidation of dec-1-ene has been achieved under mild conditions and using atmospheric oxygen as the sole oxidant. Furthermore this has been conducted in the absence of radical initiators which is a first for such an oxidation to the best of our knowledge. The selective epoxidation of alkenes typically requires the use of supported active metals such as gold or silver. These have been studied for the epoxidation of dec-1-ene however they were found to be inactive in the absence of radical initiators. Alternatively, this transformation has been achieved using a graphitic oxide catalyst which harbours no active metal species. This is yet another remarkable example of the potential of carbocatalysis for green chemistry. The commonly raised issues when using carbocatalysts such as identification of active species and presence of impurities are addressed. A range of graphitic oxides have been produced using modified Hofmann and Hummers methods with attention given to the effect of amount of oxidant used compared to commonly employed literature standards. We conclude that the popular highly oxidised Hummers materials used in the bulk production of graphene may not be the optimum material for all applications and that specification of graphitic oxides may be required to suit each application. An investigation of activity in the epoxidation of dec-1-ene partnered with a full characterisation of the surface suggests that an optimum level of oxidation is required along with the need for a surface free of potential poisons such as sulphur. We also evaluate the current methods used in the preparation and separation of these materials and suggest that for applications such as epoxidation alternative techniques may be required in order to realise its potential as a carbocatalyst. This work provides the basis for the development of an efficient catalyst for the selective epoxidation of α-alkenes, eradicating the need for expensive stoichiometric reagents or toxic radical initiators.
16
Bréault, Raymond. "Synthese de l'ethanol a partir de gaz de synthese (co+h::(2)) sur des catalyseurs au rhodium modifies : etude mecanistique." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13034.
Full text
17
Elago, Elago R. T. "The solvent-free approach versus the use of ionic liquids in the synthesis of ferrocenes." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/853.
Full textAbstract:
The philosophy of green chemistry has seen much development in the past decade. The use of environmentally benign solvents is amongst the areas of green chemistry that have received the most attention. In this context, imidazolium ionic liquids have been widely reported to offer high product yields, fast reaction rates, excellent selectivity and generally mild working conditions, when used as reaction media. In addition, concerns about costs of solvents and the long-term environmental impact that can potentially result when solvents are discarded after their use have led to focused investigations into solvent-free procedures, as reported in recent literature. We have set out to explore the extent to which these advantages could be realized within our research. Non-volatile, non-flammable imidazolium ionic liquids [bmim][I], [bmim][BF4] and [bmim][PF6] were used as green solvents in ferrocene chemistry. Ferrocenoate esters were synthesised efficiently by the respective DCC/DMAP-promoted reactions of ferrocenecarboxylic acid and substituted benzoic acids or, alternatively, the DMAP-promoted reactions of ferrocenoyl fluoride with a range of substituted phenols in [bmim][BF4] and [bmim][PF6]. High yields and short reaction times were achieved. In addition, the ionic liquid was reused several times without a reduction in product yields. Under solvent-free conditions, DCC/DMAP-promoted reactions provided high yields within 3 min of reaction. The possible rearrangement of one of the intermediates in these reactions was modelled theoretically using density function theory (DFT) at the B3LYP/6-31G* level of approximation. Catalyst-free esterification was achieved by the application of microwave radiation to the reaction of ferrocenoyl fluoride and a range of substituted phenols. All the reactions were complete after 1 min of irradiation and products were isolated in high yield. DPAT, HfCl4, Sc(OTf)3 and Al(OTf)3 were screened as catalysts for esterification in [bmim][BF4] and under solvent-free conditions at various temperatures. All attempts at esterification of ferrocenecarboxylic acid with alcohols and phenols were unsuccessful. The Suzuki cross-coupling reaction was carried out in [bmim][BF4]. The isolated yields are, however, poor and suffer from poor reproducibility with different batches of [bmim][BF4] used.
18
Aziz, Sarya. "Enzymatic synthesis of phenolic lipids from krill oil in solvent-free media and their microencapsulation." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121162.
Full textAbstract:
The optimization of the synthesis of phenolic lipids (PLs), obtained by the enzymatic transesterification of krill oil (KO) with selected phenolic acids (PAs) in solvent-free media (SFM), as well as their separation, characterization and encapsulation were investigated. Using high-performance liquid chromatography (HPLC), the evaporative light-scattering detector (ELSD) was shown to be a more appropriate tool of detection of PLs. The structural analyses of the synthesized PLs by HPLC/mass spectrometry (MS) suggested the formation of two phenolic monoacylglycerols. Using two immobilized commercial enzymes, Novozym 435 and Lipozyme TL IM, the enzymatic synthesis of PLs from KO with two phenolic acids (PAs), including 3,4-dihydroxyphenylacetic acid (DHPA) and dihydrocaffeic acid (DHCA), was investigated. The use of Novozym 435 and DHPA resulted in the highest bioconversion yield (BY). The central composite rotatable design (CCRD) was used to evaluate the effects of PA concentration (PAC) and lipase concentration (LC) as well as the agitation speed (AS) on the BY of PLs. For the models with PAC, fixed at 10 and 20 mM, the results revealed that LC had a significant quadratic effect (P <0.05) on the BY, whereas a significant linear effect was only obtained with PAC, fixed at 20 mM. The AS had a significant quadratic effect (P <0.05) on the BY, only for the model, with a PAC fixed at 10 mM. At fixed PAC of 20 mM, the response surface model predicted a BY of 75%, using a LC of 62 mg/mL and an AS of 154 rpm. The antioxidant capacity (AOC) and the oxidative stability of PLs, obtained by the enzymatic transesterification of PAs with the selected edible oils (EOs), including flaxseed (FSO), fish liver (FO) and krill (KO) oils, were determined. The statistical analyses of Tukey's test at P <0.05 revealed that the difference in AOC between that of the esterified oils of flaxseed (EFSO) and krill (EKO) and that of EOs was significant (P <0.05). The experimental findings showed that all esterified oils containing PLs had higher oxidative stability when they were subjected to light, oxygen and agitation at 50ºC as compared to that of the EOs; nevertheless, only the esterified fish oil (EFO) showed a significant difference in its peroxide value (PV), when it was placed in the dark at 25ºC. The development of a process to yield gelatin (GE)-gum arabic (GA) multinuclear microcapsules of KO, via complex coacervation, was investigated. A three-level-by-three factor Box-Behnken design (BBD) was used to evaluate the effects of the ratio of the core material to the wall (RCW), with x1 of 1.25:1 to 1.75:1, the stirring speed (SP) with x2 of 2 to 4, over a scale of 10 and the pH with x3 of 3.8 to 4.2, on the encapsulation efficiency (EE). The experimental findings indicated that x3 had the most significant linear and quadratic effects on the EE of KO and a bilinear one with x1; however, x2 did not have any effect. The optimal predicted conditions for a 92% of EE were 1.75:1 for RCW, 3.8 for pH and 3 for SP. The microcapsules, formed by complex coacervation and without any cross-linking agent, were multinucleated, circular in shape and had sufficient stability to maintain their structure. The microencapsulation of the esterified krill oil (EKO), obtained by complex coacervation, was carried out. The experimental findings showed that the presence of DHPA and PLs, in the EKO, affected the stability of GE-EKO emulsion. The ultrasonic liquid processor was found to be a more appropriate device for the emulsification of the EKO into GE, as compared to the high-shear homogenizer. In addition, the capsules prepared with a GE at pH 8.0 showed higher storage stability, with significantly (P <0.05) lower primary oxidative products, as compared to those prepared with a GE at pH 6.5. The microencapsulation of the EKO was effective in delaying the development of primary and secondary oxidation products during a period of 25 days of storage at room temperature.<br>L'optimisation de la synthèse de lipides phénoliques (PLs), obtenus par la transésterification enzymatique de l'huile de krill (KO) avec des acides phénoliques sélectionnés en milieu réactionnel sans solvant (SFM) ainsi que de leur séparation, caractérisation et encapsulation ont été étudiées. En utilisant la chromatographie en phase liquide (HPLC), le détecteur évaporatif à diffusion de lumière (ELSD) a été sélectionné pour les analyses des composants de KO et ses PLs estérifiés. Les analyses structurales des PLs synthétisés par HPLC/spectrométrie de masse (HPLC/MS) ont suggéré la formation de deux lipides phénoliques monoacylglycéroles. En utilisant deux enzymes commerciales immobilisées, Novozym 435 et Lipozyme TL IM et deux acides phénoliques (PA) modèles y compris l'acide 3,4-dihydroxyphénylacétique (DHPA) et l'acide dihydrocaffeique, la synthèse enzymatique des PLs à partir de KO, a été investiguée. Le meilleur rendement de bioconversion (BY) a été obtenu avec la Novozym 435 et le DHPA. Le plan composite central à caractère rotatif (CCRD) a été utilisé pour évaluer les effets de la concentration de l'acide phénolique (PAC) et de celle de la lipase (LC) ainsi que de la vitesse d'agitation (AS) sur le BY des PLs. Pour les modèles avec PAC, fixée à 10 et 20 mM, les résultats ont montré que la LC a un effet quadratique significatif (P <0,05) sur le BY, alors qu'un effet linéaire a été seulement obtenu avec PAC fixée à 20 mM. L'AS avait un effet quadratique significatif (P <0,05) sur le BY, seulement pour le modèle, avec une PAC fixée à 10 mM. Á PAC fixée à 20 mM, la surface de réponse du modèle a prédit un BY de 75%, en utilisant la LC de 62 mg/mL et la AS de 154 rpm. La capacité antioxydante (AOC) et la stabilité oxydative des PLs dans les huiles de lin (FSO), de poisson (FO) et de krill, ont été déterminées. Les analyses statistiques du test Tukey à P <0,05 ont révélé que la différence en AOC entre celle des huiles estérifiées de lin (EFSO) et de krill (EKO) et celle des blancs a été significative (P <0,05). Les résultats ont montré que tous les huiles estérifiées avec PLs avaient une stabilité oxydative plus élevée quant ils étaient exposés à la lumière et en présence de l'oxygène mais aussi soumis à l'agitation et à 50ºC comparée à celle des EOs. Le développement d'un processus pour produire des microcapsules multinucléaires, en utilisant l'association de gélatine (GE)-gomme arabique (GA) par la coacervation complexe a été investigué. Le plan Box-Behnken (BBD) à trois-niveaux-par-trois facteurs a été utilisé pour évaluer les effets du ratio huile/polymères (RCW) avec x1 de 1,25:1 à 1,75:1, la vitesse de la turbine (SP) avec x2 de 2 à 4, sur une échelle de 10 et un pH avec x3 de 3,8 à 4,2, sur l'efficience d'encapsulation (EE). Les résultats expérimentaux ont indiqué que x3 avait les effets linéaires et quadriques les plus significatifs sur la EE de KO et un effet bilinéaire avec x1; Par contre, x2 n'avait aucun effet. Les conditions optimales prédites pour une EE de 92% étaient 1,75:1 pour RCW, 3,8 pour pH et 3 pour SP. Les microcapsules, formées par la coacervation complexe et sans aucun agent d'articulation, étaient multinucléées, circulaires et assez stables pour maintenir leurs structures. La microencapsulation de l'huile de krill estérifiée par la coacervation complexe a été effectuée. Les résultats ont montré que la présence du DHPA et des PLs, dans l'EKO, avait un effet sur la stabilité de l'émulsion de GE-EKO. L'ultrason utilisé pour traitement liquide a été plus approprié pour l'émulsification de l'EKO dans GE, par rapport à l'homogénéisateur à haut débit. Les capsules préparées avec un GE à pH 8,0 ont montré une stabilité d'entreposage plus élevée avec une PV significativement (P <0,05) moins élevée que celles pour les capsules préparées avec un GE à pH 6,5. La microencapsulation de EKO a été effective pour retarder le développement de produits d'oxydation primaires et secondaires.
19
Ratajczak, Fabien. "Synthèse et réactivité de nitroxydes chiraux." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10134.
Full textAbstract:
Les nitroxydes sont des radicaux libres qui sont reduits en hydroxylamine ou oxydes en sel d'oxoammonium par des processus monoelectroniques reversibles. Les sels d'oxoammonium formes in situ oxydent notamment les alcools primaires et secondaires dans des conditions douces, catalytiques, et sont chimio et regioselectifs. Pour tester leurs potentialites en synthese asymetriques, deux methodes de synthese de nitroxydes chiraux a axe de symetrie c#2 ont ete mises au point. La premiere methode, originale, met en jeu la formation de dienolates en ,' d'aminodiesters suivie de leur reaction avec des electrophiles. Le dedoublement des amines d,l obtenues suivie d'une oxydation mene aux nitroxydes chiraux cycliques (cinq et six chainons) enantiomeriquement enrichis. La seconde strategie comporte deux additions nucleophiles successives sur des nitrones. Les nitroxydes optiquement actifs sont obtenus via un dedoublement d'amines. Une version enantioselective de cette methode a ete developpee a partir de la nitrone issue de la (2r,5r)-dimethylpyrrolidine. La stabilite des sels d'oxoammonium resultant de l'oxydation des nitroxydes prepares a ete etudiee par electrochimie. Ils sont peu stables, mais formes in situ ils catalysent l'oxydation des alcools. Certains d'entre eux sont capables de reconnaissance chirale dans le cas du dedoublement cinetique d'un alcool racemique ou de l'oxydation asymetrique d'un diol meso. Les exces enantiomeriques sont actuellement modestes, mais quelques resultats sont prometteurs. Enfin le nouveau systeme d'oxydation d'alcools primaires par le couple ncs/tempo mis au point presente une chimioselectivite remarquable.
20
Caldeira, Vin?cius Patr?cio da Silva. "Avalia??o da s?ntese e caracteriza??o de ze?lita ZSM-5 ausente de direcionador org?nico estrutural." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17641.
Full textAbstract:
Made available in DSpace on 2014-12-17T15:41:53Z (GMT). No. of bitstreams: 1
ViniciusPSC_DISSERT.pdf: 2657914 bytes, checksum: beb97c8aaf506ef6b97930de865d3dd2 (MD5)
Previous issue date: 2011-02-25<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior<br>The catalytic processes play a vital role in the worldwide economy, a business that
handles about US$ 13 billion per year because the value of products depends on the catalytic
processes, including petroleum products, chemicals, pharmaceuticals, synthetic rubbers and
plastics, among others. The zeolite ZSM-5 is used as catalyst for various reactions in the area
petrochemical, petroleum refining and fine chemicals, especially the reactions of cracking,
isomerization, alkylation, aromatization of olefins, among others. Many researchers have
studied the hydrothermal synthesis of zeolite ZSM-5 free template and they obtained
satisfactory results, so this study aims to evaluate the hydrothermal synthesis and the
physicochemical properties of ZSM-5 with the presence and absence of template compared
with commercial ZSM-5. The methods for hydrothermal synthesis of zeolite ZSM-5 are of
scientific knowledge, providing the chemical composition required for the formation of
zeolitic structure in the presence and absence of template. Samples of both zeolites ZSM-5 in
protonic form were obtained by heat treatment and ion exchange, according to procedures
reported in the literature. The sample of commercial ZSM-5 was acquired by the company
Sentex Industrial Ltda. All samples were characterized by XRD, SEM, FTIR, TG / DTG /
DSC, N2 adsorption and desorption and study of acidity by thermo-desorption of probe
molecule (n-butylamine), in order to understand their physicochemical properties. The
efficiency of the methods applied in this work and reported in the literature has been proved
by well-defined structure of ZSM-5. According as the evaluation of physicochemical
properties, zeolite ZSM-5 free template becomes promising for application in the refining
processes or use as catalytic support, since its synthesis reduces environmental impacts and
production costs<br>Os processos catal?ticos desempenham um papel vital na economia mundial, um
neg?cio que movimenta aproximadamente US$13 bilh?es por ano, pois o valor dos produtos
depende dos processos catal?ticos, incluindo os produtos petrol?feros, qu?micos,
farmac?uticos, borrachas sint?ticas e pl?sticos, entre outros. A ze?lita ZSM-5 ? utilizada como
catalisador em rea??es nas ?reas petroqu?mica, petrol?fera e qu?mica fina, destacando-se as
rea??es de craqueamento, isomeriza??o, alquila??o, aromatiza??o de olefinas, entre outras.
Muitos pesquisadores t?m estudado a s?ntese hidrot?rmica da ze?lita ZSM-5 ausente de
direcionador org?nico estrutural e obtiveram resultados satisfat?rios, assim, este estudo visa
avaliar a s?ntese hidrot?rmica e as propriedades f?sico-qu?micas da ZSM-5 com a presen?a e
aus?ncia de direcionador org?nico estrutural, em compara??o com ZSM-5 comercial. Os
m?todos para a s?ntese hidrot?rmica da ze?lita ZSM-5 s?o de conhecimento cient?fico,
fornecendo a composi??o qu?mica necess?ria para a forma??o da estrutura zeol?tica em
presen?a e aus?ncia de direcionador org?nico estrutural. As amostras de ambas as ze?litas
ZSM-5 na forma prot?nica foram obtidas atrav?s de tratamentos t?rmicos e troca i?nica, de
acordo com procedimentos relatados na literatura. A amostra de ZSM-5 comercial foi
concedida pela empresa Sentex Industrial Ltda. Todas as amostras foram caracterizadas por
DRX, MEV, FTIR, TG/DTG/DSC, Adsor??o e dessor??o de N2 e estudo da acidez por
termodessor??o de mol?cula sonda (n-butilamina), a fim de compreender suas propriedades
f?sico-qu?micas. A efici?ncia dos m?todos aplicados no presente trabalho e relatados na
literatura foi comprovada pela estrutura bem definida da ze?lita ZSM-5. Conforme a
avalia??o das propriedades f?sico-qu?micas, a ze?lita ZSM-5 ausente de direcionador org?nico
torna-se promissora para aplica??o em processos de refino ou utiliza??o como suporte
catal?tico, visto que, sua s?ntese reduz os impactos ambientais e custos de produ??o
21
Obst, Martin [Verfasser], and Burkhard [Akademischer Betreuer] König. "Solvent-Free Visible-Light Photocatalysis and Synthesis in Deep-Eutectic Solvents / Martin Obst ; Betreuer: Burkhard König." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1185758119/34.
Full text
22
Wilson, Benn Charles. "Silica-Supported Organic Catalysts For The Synthesis Of Biodegradable Polymers." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4918.
Full textAbstract:
Aliphatic polyesters such as polycaprolactone and polylactide have received more attention in recent years for their use in biomedical applications because of their biodegradable nature. These polymers are often synthesized using homogeneous metal complexes. Unfortunately, using homogeneous metals as catalysts leads to metal contamination in the product polymer, a result which is highly undesirable in a polymer intended for biomedical use.
More recent work has shown that these polymers can be synthesized using homogeneous metal-free complexes. These catatlysts are generally less active than metal catalysts, and although they do not contaminate the polymer with metal residue, they are still difficult to recover and hence recycle for further use.
In this work, we attempted to create a metal-free, silica-supported catalyst for use in the synthesis of polycaprolactone or polylactide.
Ultimately, n-propylsulfonic acid-functionalized porous and nonporous silica materials are evaluated in the ring-opening polymerization of epsilon-caprolactone. All catalysts allow for the controlled polymerization of the monomer, producing polymers with controlled molecular weights and narrow polydispersities. Polymerization rates are low, with site-time-yields generally one to three orders of magnitude lower than metal-based systems. The catalysts are easily recovered from the polymerization solution after use and are shown to contain significant residual adsorbed polymer. Solvent extraction techniques are useful for removing most of the polymer, although the extracted solids are not effective catalysts in recycle experiments. These new materials represent a green alternative to traditional metal-based catalysts, as they are recoverable and leave no metal residues in the polymer.
23
Fabre, Indira. "Experimental and theoretical mechanistic studies of transition-metal free and copper-catalyzed reactions." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE033/document.
Full textAbstract:
Cette thèse présente des travaux de méthodologie de synthèse et des études mécanistiques. Une approche complémentaire est utilisée, avec des résultats expérimentaux et des résultats théoriques issus de calculs DFT. Trois réactions ont été étudiées. La première réaction est l’alpha-arylation de cétones énolisables en l’absence de métal de transition. Elle se déroule en présence de DMF et de tBuOK. L’étude mécanistique met en évidence la formation d’une espèce riche en électrons par déprotonation du solvant. La deuxième réaction étudiée est la N-arylation de pyrazoles via la formation d’aryldiazoniums in situ. Cette réaction est catalysée au cuivre. Une évaluation de la méthode DFT la plus adaptée est présentée. Un double cycle catalytique est proposé, faisant intervenir le complexe de cuivre et l’acide acétique. La dernière réaction étudiée est la formation stéréoselective d’alkényl thioethers fluorés trisubstitués par catalyse au cuivre. La méthodologie de synthèse est présentée, suivie d’une étude mécanistique. Celle-ci révèle un mécanisme radicalaire qui peut être généralisé à d’autres substrats<br>In this thesis, synthetic methodology development and mechanistic studies are presented. A complementary approach, using both experiments and theoretical outcomes from DFT, is used. Three reactions were studied. The first reaction is the transition-metal free alpha-arylation of enolizable ketones. It proceeds using DMF and tBuOK. The mechanistic study reveals the formation of an electron-rich species by deprotonation of the solvent. The second reaction studied is the copper-catalyzed N-arylation of pyrazoles with arenediazonium salts generated in situ. A benchmark is performed to evaluate the best DFT methodology. A double catalytic cycle is proposed, involving copper and acetic acid. The last reaction studied is the copper-catalyzed stereoselective access to trisubstituted fluorinated alkenyl thioethers. The development of the methodology is presented. Then a mechanistic study reveals a radical mechanism that can be generalized to other substrates
24
Sorour, Noha. "Lipase-catalyzed synthesis of phenolic lipids in solvent-free medium using selected edible oils and phenolic acids." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97003.
Full textAbstract:
The enzymatic synthesis of phenolic lipids (PLs) in solvent-free medium (SFM), by transesterification of flaxseed and fish liver oils with selected phenolic acids was investigated, using Candida antarctica lipase as the biocatalyst. The enzymatic synthesis of phenolic lipids from flaxseed oil was optimized in terms of water activity, agitation speed, enzyme and phenolic acid concentrations. Increasing the water activity of the flaxseed oil reaction mixture from 0.18 to 0.38 resulted in a significant increase in the bioconversion yield from 62 to 77%. The highest enzymatic activity (178 nmol of PLs/g solid enzyme/min) was obtained with the use of 40 mg of solid enzyme (400 PLU)/mL reaction volume at 150 rpm. Under the optimized conditions there was a significant increase in the proportion of linolenic acid (C18:3 n-3), which increased from 57% in the flaxseed oil to 75 and 64% in the produced phenolic mono- and diacylglycerols, respectively. The volumetric productivity (Pv) of the transesterification of flaxseed oil and 3,4-dihydroxyphenyl acetic acid (DHPA) in SFM was increased 11-fold as compared to that in organic solvent medium. On the other hand, a bioconversion yield of 61% was obtained for the transesterification of fish liver oil with dihydrocaffeic acid (DHCA). Optimization of the enzymatic synthesis of phenolic lipids in SFM from fish liver oil was carried out, using response surface methodology (RSM), based on a four-factor-five-level central composite rotatable design (CCRD). The optimal conditions for the enzymatic reaction were obtained at 50.0ºC, 20.9 mM phenolic acid, 51.2 mg of solid enzyme (512 PLU)/mL, 160 rpm agitation speed, water activity of 0.5 and 3.45 mg Silica gel/mL. The bioconversion yield obtained under these optimized conditions was 86.5%, which is very close to the predicted value of 84.5%. Hence, the predicted values showed good validation with the experimental ones. The overall results demonstrated that RSM can be applied effectively to optimize lipase-catalyzed synthesis of phenolic lipids in SFM, from fish liver oil and DHCA. Under the optimized conditions, there was a significant increase in the relative proportions of the two highly desirable essential fatty acids, where (EPA, C20:5 n-3) was increased from 11.5% in the unmodified fish liver oil to 21.2, 20.7, 20.8, 20.1 and 19.8% in dihydrocaffeoylated, 3,4-dihydroxyphenyl acetoylated, caffeoylated, feruloylated and sinapoylated lipids, respectively, whereas (DHA, C22:6 n-3) increased from 12.0% to 21.4, 19.4, 27.5, 22.1 and 22.0%, respectively. Atmospheric pressure chemical ionization-mass spectrophotometry (APCI-MS) analyses confirmed the formation of six 3,4-dihydroxyphenyl acetoylated and six dihydrocaffeoylated lipids from the transesterification of flaxseed and fish liver oils in SFM using DHPA and DHCA, respectively, as substrates. Although the synthesized phenolic lipids demonstrated radical scavenging activity, expressed as IC50 from 1.6 to 3.7-fold higher than that of its corresponding phenolic acid, it was compared to that of α-tocopherol.<br>La biosynthèse des lipides phénoliques sans solvent, par la transésterification de l'huile de graines de lin (HGL) et l'huile de foie de poisson (HFP) en utilisant comme substrats les acides phénoliques, a été étudiée en utilisant la lipase Candida antarctica comme biocatalyseur. L'optimisation de la biosynthèse des lipides phénoliques à partir de l'HGL a été investiguée en considérant l'activité thermodynamique de l'eau, la vitesse d'agitation, la concentration de l'enzyme et l'acide phénolique. Le rendement de la bioconversion a augmenté de 62 à 77% lorsque l'activité thermodynamique de l'eau du mélange réactionnel de l'HGL a augmenté de 0.18 à 0.38. L'activité enzymatique maximale (178 nmol de PLs/g solide enzyme/min) a été obtenue lors de l'utilisation de 40 mg d'enzyme solide (400 PLU/mL de volume réactionnel) à 150 rpm. En utilisant les conditions réactionnelles optimales, la proportion de l'acide linolénique (C18:3 n-3) a augmenté significativement de 57% dans l'HGL à 75 et 64% dans les produit mono- et diacylglycerols phénoliques, respectivement. La production volumétrique (Pv) de la transésterification de l'HGL et de l'acide dihydroxyphényl acétique (ADHP) en milieu non organique a été 11 fois supérieure à celle obtenue dans le milieu organique. Par ailleurs, le rendement de la bioconversion de 61% a été obtenu lors de la transésterification de l'HFP et de l'acide dihydrocafféique (ADHC). L'optimisation de la synthèse enzymatique des lipides phénoliques a été étudiée en utilisant la méthodologie des surfaces de réponse (MSR), basée sur le factorielle quatre à cinq niveaux sur un plan composite centrale rotatif. Les conditions optimales de la réaction enzymatique ont été déterminées comme suit: 50.0ºC, 20.9 mM d'acide phénolique, 51.2 mg d'enzyme solide (512 PLU)/mL, vitesse de l'agitation 160 rpm, 0.5 de l'activité thermodynamique de l'eau et 3.45 mg de gel Silicate/mL. Le rendement de bioconversion maximum obtenu expérimentalement de 86.5% est très proche de la valeur prédite de 84.5%. Ceci démontre une bonne validation du model. Les résultats, en général, démontrent que la MSR peut être appliquée effectivement pour l'optimisation de la biosynthèse des phénols lipidiques en l'absence de solvant à partir de l'HFP et l'ADHC en utilisant la lipase comme biocatalyseur. Dans les conditions optimales, il y a eu une augmentation significative des proportions relatives des deux acides gras essentiels désirés. L'EPA (C20:5 n-3) dans l'HFP modifié a augmenté de 11.5% à 21.2, 20.7, 20.8, 20.1 et 19.8% dans les lipides dihydrocaffeoylates, 3,4-dihydroxyphenyl acetoylates, caffeoylates, feruloylates et sinapoylates, respectivement, alors que (DHA, C22:6 n-3) a augmenté de 12.0% à 21.4, 19.4, 27.5, 22.1 et 22.0%, respectivement. Les analyses de l'ionisation chimique à pression atmosphérique-spectroscopie de masse (APCI-MS) confirment la formation de six 3,4-dihydroxyphényl acetoylates et de six lipides dihydrocaffeoylates, à partir de la transésterification de l'HGL et de l'HFP avec l'ADHP et l'ADHC, respectivement. Les lipides phenoliques synthetisés ont demontré un pouvoir radicalaire, exprimé par le IC50, de 1.6 à 3.7-fois supérieure à celui des acides phénoliques correspondants, mais il était comparable à celui de α-tocophérol.
25
Daoud, Attieh Mira. "Enzymatically initiated synthesis of biomimetic receptors based on molecularly imprinted polymers by free radical polymerization." Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2266/document.
Full textAbstract:
Depuis de nombreuses années, l’utilisation d’enzyme pour la synthèse de polymères naturels ou synthétiques a largement été développée en tant que procédé alternatif plus vert et plus respectueux de l’environnement. En effet, comparée aux méthodes conventionnelles de synthèse, les enzymes offrent une sélectivité élevée, une capacité à réagir dans des conditions de réaction douces, ainsi que la possibilité de recyclage du biocatalyseur. D’autre part, les polymères à empreintes moléculaires (MIPs) sont des matériaux synthétiques avec des propriétés de reconnaissance moléculaire spécifique envers une molécule cible. Récemment, les MIPs ont été utilisés dans les applications environnementales et biomédicales de part leur propriétés de reconnaissance moléculaire, leur spécificité et sélectivité. Cependant, leur application reste limitée en raison de leur faible biocompatibilité et de la présence de résidu de polymérisation potentiellement nocif. Ce travail de thèse a pour objectif de proposer une méthode alternative pour la synthèse de MIPs basée sur le concept de chimie verte. La peroxydase de raifort (HRP) est utilisée pour initier la co-polymérisation en milieux aqueux de monomères fonctionnels méthacrylates et d’agents réticulants en catalysant la génération des radicaux libres. Différents hydrogels ont été synthétisés et caractérisés, en particulier une cytotoxicité plus faible a été obtenue comparée à celle des polymères synthétisés traditionnellement. La synthèse a été optimisée afin de pouvoir contrôler la taille des particules et le rendement de polymérisation. Des MIPs sous forme de nanoparticules ont été préparés en milieu aqueux pour plusieurs molécules de faible poids moléculaire ainsi que pour des protéines par polymérisation radicalaire libre initiée par HRP. L’effet de la méthode d’initiation a été évalué en comparant les propriétés de ces MIPs à ceux préparées par les méthodes traditionnellement. L’immobilisation de l’HRP a été aussi effectuée pour synthétiser des hydrogels et des MIPs. L’enzyme immobilisée a pu être réutilisée pour synthétiser des MIPs avec les mêmes performances en termes de morphologie, rendement, spécificité et sélectivité. Ces nouveaux matériaux offrent de nombreuses perspectives pour des applications environnementales et biomédicales<br>Enzyme-catalyzed synthesis of natural and synthetic polymers has been developed since several decades, as an eco-friendly process. Compared to the conventional methods, enzymes offer high selectivity, ability to operate under mild conditions and to recycle the catalyst. On the other hand, molecularly imprinted polymers (MIPs) are synthetic materials with specific recognition properties for target molecules. They have recently attracted increasing attention in environmental and newly in biomedical applications for their specificity and selectivity. However, concerns about MIP toxicity for human and environment safety are of great importance. Herein, carrying forward the concept of green chemistry, an enzyme-mediated synthesis approach is described to prepare molecularly imprinted nanoparticles (MIP-NPs) in aqueous media. Horseradish peroxidase (HRP) is used to initiate the polymerization of methacrylate-based monomers and cross-linkers by catalyzing the generation of free radicals. Different hydrogels are synthesized and characterized. “Greener” hydrogels are obtained with lower cytotoxicity than that of polymers synthesized by traditional way. The hydrogels synthesis is optimized in order to control the particles sizes and polymerization yields. Moreover, water-compatible MIP nanoparticles for the recognition of different small molecules and proteins are prepared in aqueous media by HRP-initiated free radical polymerization and compared to MIPs prepared by the thermal or photopolymerization methods. HRP immobilization is also performed for hydrogels synthesis as well as MIP preparation. The reusability of immobilized enzyme is investigated for the preparation of several MIP batches with the same morphology, yield as well as good specificity and selectivity. We believe that this new synthesis method for MIPs will provide new opportunities to enlarge the use of molecular imprinting technology in biomedical and environmental applications
26
Suhartanto, Thomas. "Modified nickel catalysts for carbon free carbon dioxide reforming of methane to synthesis gas." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312296.
Full text
27
Reckling, Amy. "Synthetic and Mechanistic Studies in Ruthenium-catalyzed Olefin Metathesis." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23787.
Full textAbstract:
Ruthenium - catalyzed olefin metathesis is now an invaluable tool in organic synthesis. However, routes to the dominant metathesis catalysts, the second - generation Grubbs and Hoveyda catalysts (RuCl 2 (PCy 3 )(H 2 IMes)(=CHPh) and RuCl 2 (H 2 IMes)[= CH( o - O i Pr)C 6 H 4 ], respectively) are plagued with problems. The common reliance on in situ methods to generate the N - heterocyclic carbene H 2 IMes severely limits stoichiometric control, and results in contamination by byproducts, some of which are readily overlooked, and some of which are difficult to remove. Both can affect batch - to - batch reproducibility in catalysis. This thesis work demonstrated that widespread perceptions of the instability of free H 2 IMes are erroneous, and that the free carbene is readily handled under water - free conditions. Clean, convenient, near - quantitative routes were developed to these second - generation catalysts by ligand exchange of their first - gen eration counterparts RuCl 2 (PCy 3 ) 2 (=CHPh), RuCl 2 (PCy 3 )[= CH( o - O i Pr)C 6 H 4 ] with free H 2 IMes, with sequestration of the liberated phosphine by an ion - exchange resin. A second focus was examination of a much - debated hypothesis in olefin metathesis: that is, the extent to which the high productivity of the Hoveyda catalysts reflects re - uptake of the styrenyl ether functionality released in the initial cycle of metathesis. Current evidence for and against this "boomerang" hypothesis is critically examined, and new approaches to examining its operation are described. Specifically, the rate of decomposition, vs. re - uptake, is examined for the active species RuCl 2 (PCy 3 )(=CH 2 ), and background exchange of the parent catalyst with free styrenyl ether is measured by use of a 13 C - labelled styrenyl ether. These studies confirm the relevance of the boomerang mechanism for first - generation Hoveyda catalysts.
28
Krol, Michael Joseph Jr. "The Solvent-Free Synthesis of and N-Methyl-N-Alkylpiperidinium Salts and Their Anion Exchange Reactions with Dilithium Phthalocyanine." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1366905299.
Full text
29
Patrick, Scott R. "Synthesis and reactivity of novel (NHC)gold(I) complexes." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6302.
Full textAbstract:
The fields of N-heterocyclic carbenes and homogeneous gold catalysis have experienced tremendous growth within the last two decades. In addition, the combination of these fields to give NHC-gold complexes has delivered superior stability and reactivity, allowing the isolation of new reactive species and a better understanding of the fundamental chemistry. The work presented in this thesis attempts to synthesise novel NHC-gold complexes and document their reactivities. The main themes discussed in this work are: (a) the understanding and avoidance of silver additives in gold-mediated transformations; and (b) the study of different NHCs to provide optimal sterics and electronics for a given application. In Chapter 2, the reported “Gold(I)-Mediated C-H Activation of Arenes” is investigated. The role of each additive is assessed, and in particular the reliance on silver salts is considered. An NHC ligand was used to stabilise reactive intermediates, which provided new insights into the function of the silver additive. Gold(I) hydroxides are repeatedly shown to be invaluable synthetic equivalents, as well as key intermediates in silver-free protocols. Chapter 3 details numerous attempts to synthesise [Au(OH)(NHC)] complexes that are stable, pure and in high yields. Chapter 4 documents the synthesis of gold species featuring the ITent family of NHC ligands. Their highly flexible steric bulk is investigated by crystallographic studies, and is believed to contribute to their relatively high stabilities. Chapter 5 describes the use of the newly synthesised [Au(OH)(NHC)] complexes to generate mono- and bifluoride species. The reaction conditions were then optimised in order to maximise yields and regioselectivities. Finally, Chapter 6 examines the use of NHC selenium adducts to measure the π-accepting ability of these ligands. These are then coordinated to gold, whereupon different geometries are observed depending on the nature of the NHC.
30
Shearouse, William C. "Development and mechanistic understanding of ball milling as a sustainable alternative to traditional synthesis." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353089340.
Full text
31
Riemer, Daniel. "Transition Metal-Free Catalytic Systems for the Utilization of CO2 to Achieve Valuable Chemicals." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-14D4-5.
Full text
32
Strompen, Simon [Verfasser], and Andreas [Akademischer Betreuer] Liese. "Process development of a solvent-free, chemoenzymatic reaction sequence for the enantioselective synthesis of beta-amino acid esters / Simon Strompen. Betreuer: Andreas Liese." Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2012. http://d-nb.info/1048542920/34.
Full text
33
Pham, Van Tuyet. "The synthesis and reactions of chiral 1,3,2-oxazaphospholane derivations : kinetic and mechanistic studies of polyether omega-phase catalyzed reactions of potassium cyanide with benzyl bromide in non-polar, aprotic solvent toluene." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27416.
Full text
34
Rostamizadeh, S., N. Shadjou, and E. Isapoor. "MCM-41-nPrNH2 as a Recoverable Nanocatalyst for the Synthesis of New Phenylpyrido[4,3-d]pyrimidin-2-amine Derivatives." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35002.
Full textAbstract:
MCM-41 anchored n-propylamine (MCM-41-nPrNH2) was found to be a highly efficient and recoverable
nanocatalyst for the synthesis of new class of phenylpyrido[4,3-d]pyrimidin-2-amine derivatives under
solvent free conditions in high to quantitative yields. All the structures of title compounds 3a-j were
elucidated by comprehensive 1H NMR, 13C NMR, IR and Mass spectra
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35002
35
Lu, Wei. "Synthesis, characterisation and analysis of structurally imposing eight-membered ring heterocyclic carbenes : salts, free carbenes, metal complexes and catalysis." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/43548/.
Full textAbstract:
The work reported in this thesis is concerned with the preparation, metal coordination and catalytic applications of expanded eight-membered N-heterocyclic carbenes. This is divided into four chapters, which cover the following areas of research. Chapter One provides the historical and literature overview of synthesis, reactions and catalysis applications for the six- and seven-membered NHCs. Structure and electronic properties of the expanded ring NHC systems are also discussed and compared with their phosphine and five-membered NHC counterparts. Chapter Two focuses on the synthesis and characterisation of symmetrical, unsymmetrical and backbone functionalised eight-membered NHC halide salts and free carbenes. The precursor salts were all prepared by the amidine route while treatment with KHMDS forms the free NHCs. The 8-NHC ring adopts a boat conformation with the backbone folded over the central NHC carbon. Their N-CNHC-N angles are large, ranging between 129° and 131°, with the attendant CNHC-N-CN-substituent angles being very small. Chapter Three describes the synthesis and characterisation of a series of Ag(I), Rh(I), Ir(I) and Ni(I) complexes. Structural analysis of silver-(8-NHC) complexes reveal that these large rings cause the aromatic substituents on the ring nitrogens to bend around and essentially enclose the Ag centre. The percentage buried volume (%Vbur) of silver complexes increases considerably as the ring size expands from 5- to 8-membered NHC, reflecting the high steric demand imposed by the larger ring systems. It was also found that the 8-Mes ligand was too large to coordinate to the [Rh/IrCl(COD)]2 dimer, only the less sterically demanding 8-o-Tol was able to form stable [Rh/IrCl(8-o-Tol)(COD)] complexes. Comparison of CO stretching frequencies for [RhCl(NHC)(CO)2] complexes with 5-, 6-, 7- and 8-membered rings reveal that 8-o-Tol is the most basic of all the NHC ligands. A series of paramagnetic (8-NHC) Ni(I) complexes were prepared also, along with their characterization and EPR analysis. Chapter Four provides the results of catalytic performances for the 8-membered NHC rhodium and iridium complexes in the transfer hydrogenation of ketones. 8-NHC nickel complexes were also tested as catalysts in Suzuki and Kumada cross-coupling reactions.
36
Pirenne, Vincent. "New radical additions of alkylsulfonyl cyanides onto unactivated olefins : enantioselective approaches towards the total synthesis of leucophyllidine." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0438/document.
Full textAbstract:
Dans le cadre de la synthèse totale de la leucophyllidine, un alcaloïde bis-indolique, des réactions de carbo- et sulfonyl-cyanation radicalaires sans étain ont été développées. Les cyanures de sulfonyle RSO2CN, préparés à partir des thiocyanates correspondant par une nouvelle méthode d’oxydation, sont utilisés comme pièges radicalaires. Ces réactifs fragmentent en présence d’initiateur thermique (carbo-cyanation) ou par le biais de la catalyse photoredox (sulfonyl-cyanation). Dans ce dernier cas, une étude mécanistique approfondie sur le cycle photo-catalytique a été accomplie. Ces méthodologies introduisent un nitrile sur une chaîne carbonée insaturée par voie radicalaire, fournissant des intermédiaires avancés pour la synthèse totale d’alcaloïdes. Pour la synthèse asymétrique de l’eucophylline, le fragment sud de la leucophyllidine, la sulfonyl-cyanation de cyclobutènes énantioenrichis a montré d’excellentes diastéréosélectivités. Différentes stratégies d’ouverture de cycle ont ensuite été examinées<br>During our efforts directed toward the total synthesis of leucophyllidine, a bis-indole alkaloid, the tin-free radical carbo-cyanation and sulfonyl-cyanation of olefins were developed. The sulfonyl cyanides, acting as radical traps, were synthesized through a new oxidation of the corresponding thiocyanate. These reagents were found to fragment under thermal initiation (carbo-cyanation) or using the photoredox catalysis (sulfonyl-cyanation). A thorough mechanistic study was accomplished for the sulfonyl-cyanation. These methodologies install a nitrile onto an olefin backbone, furnishing advanced intermediates for the total synthesis of alkaloids. For the asymmetric synthesis of eucophylline, the south fragment of leucophyllidine, the sulfonyl-cyanation of optically pure cyclobutenes showed excellent diastereoselectivities. Different ring-opening reactions of the corresponding cyclobutane were then examined
37
Koyutürk, Burak [Verfasser], Hubert A. [Akademischer Betreuer] Gasteiger, Klaus [Gutachter] Köhler, and Hubert A. [Gutachter] Gasteiger. "Towards the Scalable Synthesis of PGM-free Catalysts for Oxygen Reduction Reaction / Burak Koyutürk ; Gutachter: Klaus Köhler, Hubert A. Gasteiger ; Betreuer: Hubert A. Gasteiger." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1228536120/34.
Full text
38
Keddie, Daniel Joseph. "The synthesis of novel profluorescent nitroxide probes." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/16702/1/Daniel_Keddie_Thesis.pdf.
Full textAbstract:
A number of novel isoindoline nitroxides have been synthesised using a variety of synthetic techniques. Several carbon-carbon bond forming methodologies, including the first examples of Heck and Sonogashira coupling applied to the isoindoline nitroxide class, were utilised to give novel robust aromatic frameworks. Palladium-catalysed Heck coupling of brominated nitroxides and ester-substituted olefins generates novel nitroxides possessing extended conjugation. Hydrolysis of the nitroxide esters gave the corresponding carboxylic acids, which showed enhanced water solubility. Sonogashira coupling of an iodo-isoindoline nitroxide gave several novel alkynesubstituted nitroxides in high yield. Subsequent coupling of a deprotected ethynyl nitroxide with aromatic iodides gave acetylene-linked nitroxides and an acetylene linked nitroxide dimer. A butadiyne linked dinitroxide was successfully synthesised via Eglinton oxidative coupling of two ethynyl nitroxides. The synthesis of a novel water-soluble dicarboxy nitroxide was achieved by base hydrolysis of a dinitrile. Functional group interconversion furnished anhydride and imide substituted nitroxides from the diacid. Subjecting the imide to the Hofmann rearrangement gave an unexpected brominated amino-carboxy nitroxide. The dicarboxy nitroxide and the brominated amino-carboxy nitroxide were both shown to have a protective effect on Ataxia-Telangiectasia cells, indicating a possible role as antioxidants in the treatment of this disease. A fluorescein nitroxide was successfully synthesised through the condensation of the anhydride substituted nitroxide and resorcinol. After limited success using a variety of other techniques, Buchwald-Hartwig amination was able to furnish a rhodamine nitroxide, via a triflate-fluorescein nitroxide. The extended aromatic nitroxides possess suppressed fluorescence and we have described these systems as profluorescent. The profluorescent nitroxides were found to have significantly lower quantum yields than the non-radical analogues and displayed a substantial increase in fluorescence intensity upon radical trapping, making them useful probes for free radical reactions.
39
Keddie, Daniel Joseph. "The synthesis of novel profluorescent nitroxide probes." Queensland University of Technology, 2008. http://eprints.qut.edu.au/16702/.
Full textAbstract:
A number of novel isoindoline nitroxides have been synthesised using a variety of synthetic techniques. Several carbon-carbon bond forming methodologies, including the first examples of Heck and Sonogashira coupling applied to the isoindoline nitroxide class, were utilised to give novel robust aromatic frameworks. Palladium-catalysed Heck coupling of brominated nitroxides and ester-substituted olefins generates novel nitroxides possessing extended conjugation. Hydrolysis of the nitroxide esters gave the corresponding carboxylic acids, which showed enhanced water solubility. Sonogashira coupling of an iodo-isoindoline nitroxide gave several novel alkynesubstituted nitroxides in high yield. Subsequent coupling of a deprotected ethynyl nitroxide with aromatic iodides gave acetylene-linked nitroxides and an acetylene linked nitroxide dimer. A butadiyne linked dinitroxide was successfully synthesised via Eglinton oxidative coupling of two ethynyl nitroxides. The synthesis of a novel water-soluble dicarboxy nitroxide was achieved by base hydrolysis of a dinitrile. Functional group interconversion furnished anhydride and imide substituted nitroxides from the diacid. Subjecting the imide to the Hofmann rearrangement gave an unexpected brominated amino-carboxy nitroxide. The dicarboxy nitroxide and the brominated amino-carboxy nitroxide were both shown to have a protective effect on Ataxia-Telangiectasia cells, indicating a possible role as antioxidants in the treatment of this disease. A fluorescein nitroxide was successfully synthesised through the condensation of the anhydride substituted nitroxide and resorcinol. After limited success using a variety of other techniques, Buchwald-Hartwig amination was able to furnish a rhodamine nitroxide, via a triflate-fluorescein nitroxide. The extended aromatic nitroxides possess suppressed fluorescence and we have described these systems as profluorescent. The profluorescent nitroxides were found to have significantly lower quantum yields than the non-radical analogues and displayed a substantial increase in fluorescence intensity upon radical trapping, making them useful probes for free radical reactions.
40
Ballentine, Michael Drake. "Imidazolium Ionic Liquids as Multifunctional Solvents, Ligands, and Reducing Agents for Noble Metal Deposition onto Well-Defined Heterostructures and the Effect of Synthetic History on Catalytic Performance." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2101.
Full textAbstract:
1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]Tf2N) was investigated as a multifunctional solvent, ligand, and reducing agent for platinum deposition onto well-defined CdSe@CdS nanorods. Platinum deposition was carried out thermally and photochemically using Pt(acac)2 as the metal precursor. Thermal deposition was investigated in [BMIM]Tf2N with and without addition of a sacrificial reducing agent, and product topology was compared with the products obtained from polyol reduction using 1,2-hexadecanediol, oleic acid, and oleylamine in diphenyl ether. Photochemically induced platinum deposition was carried out at room temperature in [BMIM]Tf2N, and product topology was compared with the photodeposition products obtained from a toluene dispersion. Thermal deposition of platinum in ionic liquid showed rods of broken morphology and small platinum nanoparticles speckled across the rods’ surface, while photodeposition of platinum exhibited particles decorated throughout the nanorod surface but larger in size than those exhibited by thermal means. Photocatalytic
reduction of methylene blue was studied using these Pt-CdSe@CdS heterostructured nanoparticles, and catalytic performance was correlated with topology and synthetic history. Initial findings of catalytic performance suggest that there in an advantage of depositing platinum nanoparticles onto the CdSe@CdS in the ionic liquid system. Methylene blue dye was degraded using each system and the results show and there is an increased performance of the nanorods synthesized in the ionic system.
41
Appy, Lucie. "Nouvelles approches de synthèses de nucléotides et de leurs conjugués." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS047.
Full textAbstract:
Cette thèse relève de la problématique globale de synthèse de molécules phosphorées et en particulier de nucléotides et de leurs analogues (dérivés polyphosphorylés, liponucléotides, glyconucléotides...). En effet, ces dérivés qu’ils soient endogènes ou synthétiques, sont largement utilisés comme outils biologiques. Certains de ces composés présentent également un fort potentiel thérapeutique en particulier dans le domaine des agents antiviraux ou antitumoraux. La préparation de ces composés polyphosphorylés demeure un challenge technologique du fait de rendements de synthèse faibles et des multiples étapes de purification longues et fastidieuses.L’objectif fondamental de ce manuscrit réside dans la mise au point de nouvelles méthodologies de synthèses efficaces et/ou éco-responsable de dérivés nucléotidiques. Le premier chapitre de ce manuscrit correspond à présentation non exhaustive des méthodes de synthèse décrites dans la littérature, en soulignant leurs atouts et inconvénients. Le deuxième chapitre concerne la mise au point d’une méthodologie de synthèse supportée de nucléotides et d’analogues nucléotidiques en série adénosine. Enfin, le dernier chapitre, une seconde méthodologie inédite et éco-responsable est rapportée faisant appelle à une stratégie de synthèse sans solvant<br>This thesis relates to the global problem of the synthesis of phosphorylated biomolecules, and in particular of nucleotides and their analogues (polyphosphorylated derivatives, liponucleotides, glyconucleotides…). Indeed, these derivatives, whether endogenous or synthetic, are widely used as biological tools. Some of these compounds also exhibit strong therapeutic potential, in particular in the field of antiviral or antitumor agents. The preparation of these polyphosphorylated derivatives however remains a technological challenge owing to the multiple tedious and expensive purification steps, often leading to modest to low yields.The primary objective of this work, lies in the development of new, efficient and/or eco-responsible synthetic methodologies of nucleotides derivatives. The first chapter of this manuscript corresponds to a non-exhaustive presentation of the methods described in the literature for the synthesis of various nucleotides, emphasizing their advantages and drawbacks. The second chapter concerns the development of a supported synthesis methodology of nucleotides and nucleotide analogues in the adenosine series. Finally, the last chapter describes a second new and eco-responsible methodology using a solvent-free approach
42
Wendel, Daniel Andreas Wolfgang [Verfasser], Bernhard [Akademischer Betreuer] Rieger, Shigeyoshi [Gutachter] Inoue, Wolfgang [Gutachter] Eisenreich, Herbert W. [Gutachter] Roesky, and Bernhard [Gutachter] Rieger. "Synthesis and Reactivity of Acyclic Silylenes: On the Way to Metal-free Catalysis / Daniel Andreas Wolfgang Wendel ; Gutachter: Shigeyoshi Inoue, Wolfgang Eisenreich, Herbert W. Roesky, Bernhard Rieger ; Betreuer: Bernhard Rieger." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1164156993/34.
Full text
43
Madkikar, Pankaj [Verfasser], Hubert A. [Akademischer Betreuer] Gasteiger, Klaus [Gutachter] Köhler, and Hubert A. [Gutachter] Gasteiger. "Synthesis and Characterisation of Noble-Metal-Free and Low-Loaded Platinum Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells / Pankaj Madkikar ; Gutachter: Klaus Köhler, Hubert A. Gasteiger ; Betreuer: Hubert A. Gasteiger." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1189316390/34.
Full text
44
Torregrosa, García Rubén. "Extracció reactiva de llavors oleaginoses per a la preparació de monoglicèrids." Doctoral thesis, Universitat de Lleida, 2016. http://hdl.handle.net/10803/385622.
Full textAbstract:
En aquest treball s’ha desenvolupat un mètode en dues etapes per a l’obtenció d’extractes rics en monoglicèrids a partir de llavors de soja i de sèsam. La primera etapa consisteix en una hidròlisi i esterificació directa amb glicidol i solketal dels triglicèrids continguts en les llavors, catalitzada amb miceli liofilitzat de Rhizopus oryzae en absència de solvent. La segona etapa ha estat la desprotecció del glicerol protegit en forma de 1,2-acetonid (solketal) amb catalitzadors àcids. El rendiment màxim d’obtenció de monoglicèrids a l’extracte final de reacció ha estat del 81 %, amb les següents condicions: Temps d’hidròlisi de 24 h i d’esterificació de 6 h emprant solketal, a una temperatura de reacció de de 50 °C per a la primera etapa i utilitzant com a solvent una barreja acetonitril:HCl 1M en proporció 4:1 (v/v), amb un temps de reacció de 6 h a temperatura ambient per a la segona etapa.<br>En este trabajo se ha desarrollado un método en dos etapas para la obtención de extractos ricos en monoglicéridos a partir de semillas de soja y de sésamo. La primera etapa consta de una hidrólisis y esterificación directa con glicidol y solketal de los triglicéridos de las semillas, catalizada con micelio liofilizado de Rhizopus oryzae en ausencia de solvente. La segunda etapa ha consistido en la desprotección del grupo 1,2-acetonido (solketal), empleando catalizadores ácidos. El rendimiento máximo de obtención de monoglicéridos en el extracto final de reacción ha sido del 81 %, empleando las siguientes condiciones: tiempo de hidrólisis de 24 h y de esterificación de 6 h utilizando solketal, a una temperatura de reacción de 50 °C para la primera etapa y utilizando como solvente una mezcla de acetonitrilo:HCl 1M en proporción 4:1 (v/v), con un tiempo de reacción de 6 h a temperatura ambiente para la segunda etapa.<br>In this work, a two-step method has been developed to prepare monoglyceride enriched extracts from soybean and sesame seeds. In the first step, direct extraction, hydrolysis and esterification of triglycerides from seeds is performed with glycidol and solketal. Reactions are catalyzed with lyophilized mycelium of Rhizopus oryzae in solvent-free conditions. The second step is the cleavage of solketal ring (1,2-acetonide structure) using acid catalysts. The maximum yield of monoglycerides in the two-step reaction process is 81 % using the following conditions: reaction time of 24 h for hydrolysis and 6 h for esterification using solketal, at a temperature of 50 °C in the first step and using a solvent mixture of acetonitrile:1 M HCl in 4:1 (v/v) with a reaction time of 6 h at room temperature in the second step.
45
Guillon, Morvan. "Développement de matériaux pour le couplage de la valorisation de CO2 avec l'électrolyse haute température (HTE) pour la production d'éthylène." Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAF026.
Full textAbstract:
La production de l’éthylène est un enjeu énergétique majeur du XXIème siècle. La réaction du couplage oxydant du méthane permet la production d’éthylène à partir de méthane et d’oxygène. Cette réaction présente ainsi un intérêt particulier puisqu’elle permet la production d’éthylène en s’affranchissant d’une dépendance aux matières premières pétrolières, principalement utilisées pour la production de l’éthylène. Dans cette étude l’objectif est de développer un matériau en vue d’une insertion à l’anode d’un électrolyseur haute température pour produire de l’éthylène décarboné à partir de CO2. Après une étape de réduction à la cathode de ce même électrolyseur, du méthane peut être produit avec la technologie et power-to-methane. Le méthane est ainsi injecté à l’anode de l’électrolyseur pour effectuer la réaction du couplage oxydant du méthane. Les matériaux développés dans ce travail doivent donc répondre aux caractéristiques associées à une bonne anode et doivent agir comme catalyseur de la réaction du couplage oxydant du méthane. Ainsi la synthèse et la caractérisation d’oxydes mixtes ont été réalisées. L’activité des catalyseurs a été évaluée à l’échelle du laboratoire en variant les paramètres opératoires pour déterminer les conditions optimales pour obtenir le meilleur rendement en éthylène. Des optimisations de synthèses, avec des ajustements des compositions et des dopages, ont été réalisées pour obtenir la meilleure performance catalytique dans le cadre du couplage oxydant du méthane<br>Ethylene production is a major energy challenge for the 21st century. The oxidative coupling of methane reaction enables ethylene to be produced from methane and oxygen. This reaction is therefore of particular interest as it enables ethylene production without dependence on petroleum feedstocks, which are mainly used for ethylene production. The aim of this study is to develop a material for insertion in the anode of a high-temperature electrolyzer to produce decarbonated ethylene from CO2. After a reduction step at the cathode of the same electrolyzer, methane can be produced using power-to-methane technology. Methane is injected at the anode of the electrolyzer to carry out the oxidative coupling of methane reaction. The materials developed in this work must therefore meet the characteristics associated with a good anode and act as a catalyst for the oxidative coupling of methane reaction. Mixed oxides were synthesized and characterized. The activity of the catalysts was evaluated on a laboratory scale, varying the operating parameters to determine the optimum conditions for delivering the best ethylene yield
46
Wang, Yun. "Catalyseurs d'oxydation en conditions de chimie verte : métaux non toxiques, eau oxygénée, transformation de la biomasse, recyclage par greffage." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30241.
Full textAbstract:
Afin de développer une chimie plus respectueuse de l'environnement, l'accès à de nouveaux procédés est nécessaire. Plus spécifiquement, dans le domaine de l'oxydation, l'utilisation d'oxydants toxiques doit être bannie, l'utilisation de solvants limitée et l'utilisation de catalyseurs recyclables développée. Dans ce contexte, deux approches " vertes " ont été explorées. La première d'entre elle consiste à éliminer ou remplacer l'acide acétique, additif qui, en présence de H2O2 et de complexes de Mn ou de Fe, favorise la formation exclusive d'époxydes lors d'oxydation d'alcènes. Pour cela, deux stratégies ont été testées. La première consiste à introduire dans la seconde sphère de coordination de complexes de Fe(III) et de Mn(II) des fonctions fluoroalcools devant faciliter l'activation d'H2O2. Comparés aux complexes analogues non modifiés, aucune amélioration de l'activité catalytique pour l'oxydation de cyclooctène n'est observée. Cependant, des complexes de Ni(II) et de Co(II) à ligands non modifiés ont démontré une activité catalytique élevée pour la photoproduction d'hydrogène. La seconde stratégie est basée sur le remplacement de l'acide acétique. Pour cela, en utilisant des billes de silice fonctionnalisées par des fonctions COOH (SiO2@COOH) comme co-réactif, une sélectivité significative en faveur de l'époxyde est observée lors de l'oxydation d'alcènes en présence de complexes de Mn(II) et de Fe(III) à ligand BPMEN. La seconde approche concerne des réactions d'(ép)oxydation sans solvant et utilisant des catalyseurs recyclables à base de polyoxométallates (POMs). Les catalyseurs SiO2@PMo et SiO2@PW, respectivement obtenus par greffage ionique de H3PMo12O40 ou H3PW12O40 sur des billes de silices fonctionnalisées par des fonctions pendantes NH2 (SiO2@NH2). Avec une faible charge catalytique, les deux catalyseurs sont efficaces lors de réactions d'oxydation avec une meilleure sélectivité que les POM libres. De plus, les deux catalyseurs réutilisés ont donné des conversions et des sélectivités similaires après deux recyclages<br>In order to develop a chemistry more respectful of the environment, access to sustainable processes is mandatory. More specifically, in the field of oxidation chemistry, use of toxic oxidants has to be banished, use of solvents limited and reusable catalysts developed. In this context, two types of greener approaches have been explored. The first approach concerns removal or replacement of acetic acid, an additive - in association with H2O2, favoring exclusive formation of epoxides with Mn and Fe metal complexes as catalysts. For this objective, two strategies have been explored. The first one consists in introducing fluoroalcohol functions in the second coordination sphere of metal complexes with pyridinophane-based ligand to easily activate H2O2. Those complexes did not enhance the catalytic activity for cyclooctene oxidation reactions in comparison to analogous Mn(II) and Fe(III) complexes with unmodified ligands. However, Ni(II) and Co(II) metal complexes with unmodified ligands display interesting catalytic activity for H2 photoproduction. The second strategy aimed to replace acetic acid. Using silica beads functionalized with COOH pendant arms (SiO2@COOH) as additive and H2O2 as oxidant, catalytic epoxidation reactions catalyzed by Mn(II) and Fe(III) metal complexes with BPMEN ligand displayed significant selectivity towards epoxide. The second approach concerns organic-solvent free (ep)oxidation processes with catalysts based on polyoxometalates (POMs). Catalysts SiO2@PMo and SiO2@PW, respectively obtained by ionic grafting of H3PMo12O40 or H3PW12O40 on silica beads functionalized with NH2 pending functions (SiO2@NH2), have been fully characterized. With low catalyst loading, both catalysts displayed efficient oxidation activity and better selectivity than the free POMs. Moreover, recovered beads gave similar conversion and selectivity after two recycling processes
47
Wang, Yi-Fu, та 王義富. "Three-component Reaction : Efficient and Facile Method for the One-pot Synthesis ofα-Aminophosphonates using new Catalyst under Solvent-free Condition". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/84580174679716917946.
Full textAbstract:
碩士<br>國立臺灣師範大學<br>化學系<br>94<br>α-Amino phosphonates can be synthesized by using carbonyl compounds (aldehyde or ketone)、aniline ,and triethylphosphite in the presence of the proper catalysts(Iodine,Trichloro-1,3,5-Triazine,Ceric Ammonium Nitrate,or Iron Chloride) under solvent-free condition at room temperature. The methodology can afford high yields of products and short reaction time compared to tranditional methods.
48
Panda, Partha Pratim. "Solvent free synthesis of Dibenzyl Sulfide using H2S rich Monoethanolamine under two phase transfer catalysis." Thesis, 2012. http://ethesis.nitrkl.ac.in/3241/1/partha.pdf.
Full textAbstract:
With the depletion of crude oil reserves, oil refineries are being forced to process sour crude which is high in sulfur content. Sulfur, if not removed from the system may corrode the system or may lead to unwanted side reactions which would entail consumption of reactants and energy. Usually the sulfur is removed by absorption in ammonia solution which is further processed in a Claus Unit to produce elemental sulfur which requires a high amount of energy. Also, the supply of elemental sulfur usually outstrips demand thereby eroding the profit margins. With a view to making more sophisticated fine chemicals which have higher usability and better market value, this project was undertaken to study the kinetics of the solvent-free synthesis of dibenzyl sulfide was carried out using H2S-rich monoethanolamine under two phase transfer catalysis with a phase transfer catalyst (PTC), polyethylene glycol (PEG). The effects of different parameters, such as speed of agitation, temperature, monoethanolamine concentration, catalyst concentration, initial sulfide concentration and concentration of benzyl chloride, on the conversion and reaction rate of benzyl chloride were studied to establish the mechanism of the reaction.
49
Chen, Chia-Ming, and 陳家銘. "Catalyst-Free Synthesis and Characterization of Aligned ZnO and ZnO:Ga nanorods." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/g6wmzs.
Full textAbstract:
碩士<br>國立臺北科技大學<br>光電工程系研究所<br>100<br>In this thesis, by using ZnO as buffer layer successfully via catalyst-free vapor transport, single crystal ZnO grows on c-plane sapphire board. We can detect growing time relative to its length under SEM when observing its surface. PL strength and crystal quality is good under the observation of X-ray diffraction of growth direction of nanorods.
Then using Ga2O3 as doping reaction, other setting numbers are the same as making the ZnO nanorods. Because the doping of Ga2O3, obvious shortening of the length of nanorods is observed under SEM. Analyzing under PL and X-ray diffraction and HRTEM, the quality of crystal is worse under limited effective doping numbers. Ga2O3 is sensitively influential to the quality of ZnO nanorods.
50
Fong, Jhong-Ping, and 馮仲平. "Catalyst-free thermal evaporation synthesis and optical properties of ZnO nanostructures." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/444pxy.
Full textAbstract:
碩士<br>國立臺北科技大學<br>光電工程系所<br>94<br>In this study, ZnO nanostructures have been synthesized on a-plane sapphire substrates without catalyst through a simple pressure-controlled thermal evaporation. Vertically aligned ZnO nanowires, with the mean diameter of about 23 nm and the length of 50 – 800 nm, were grown at 600oC in a flowing argon environment (pressure ~ 18 Torr) for 15 minutes. The photoluminescence (PL) and Raman measurements showed good crystalline and emission qualities of this sample. Then we investigated how the substrate temperature, pressure, and growth time affect the structural and optical properties of the ZnO nanostructures. Higher pressure would result in larger nanowire density but less alignment. The substrate temperature would affect the form of nanostructures via changing the preferred lattice growing direction. Furthermore, PL study revealed that the ultraviolet emission peak blueshifts slightly as the growth temperature increases. Longer growth time would lead to thicker nanowires. We found that the intensity of the UV emission increases with decreasing wire diameter. In addition, special ZnO nanostructures such as nanowalls, nanoflowers, and nanocombs have been grown under suitable conditions. We also successfully synthesized high-density well-aligned ZnO nanowire array on a pulsed laser deposition prepared ZnO nanorod film via thermal evaporation.