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Tesi sul tema "Catalysts"
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1
Beckler, Robert Kendall. "Polynuclear metal complexes as model mixed oxide catalysts". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11897.
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2
Liu, Hongying. "Syntheses, structures, and catalysis of polynuclear metal complexes". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/30561.
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3
Paliga, James Francis. "Developing Earth-abundant metal-catalysts for hydrofunctionalisation". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31115.
Testo completoAbstract (sommario):
The iron-catalysed hydromagnesiation of styrene derivatives has been developed further from previous publications, expanding the electrophile scope to enable the regioselective formation of new carbon-carbon and carbon-heteroatom bonds (Scheme A1). A commercially available pre-catalyst and ligand were used to give an operationally simple procedure that did not require prior synthesis of a catalyst. This work also investigated the hydromagnesiation of dienes, using a screen of ligands commonly used in transition metal catalysis. An investigation into the magnesium-catalysed hydroboration of olefins was also carried out. Although mostly unsuccessful, it was demonstrated that in the presence of a magnesium catalyst, a small amount of vinyl boronic ester could be formed from an alkyne (Scheme A2). Simple magnesium salts were also investigated for the reduction of carbonyls. Lastly, this work explored the titanium-catalysed hydrosilylation of olefins, using a novel activation method developed within the group (Scheme A3). The results were compared to those published previously using traditional organometallic activation methods and attempts at identifying conditions to improve chemoselectivity were carried out.
4
Clarke, Richard John. "Mesopore immobilised bis(oxazoline) catalysts for enantioselective catalysis". Thesis, University of Birmingham, 2003. http://etheses.bham.ac.uk//id/eprint/3578/.
Testo completoAbstract (sommario):
Mesoporous silica materials have the potential to replace many conventional silicas for uses such as supports for heterogeneous catalysis and absorbents. The large pore size and high surface area make them ideal for supporting bulky organometallic catalysts for enantioselective reactions. We have immobilised chiral bis(oxazoline) metal complexes onto the surfaces of some of these versatile supports (MCM-41 and MCM-48) via different tethering strategies. The resulting heterogeneous catalysts were shown to be highly active in the enantioselective cyclopropanation of styrene with ethyl diazoacetate.
5
Rosenthal, Daniel Jay. "Estimating the acid site density of silica-alumina by infrared spectroscopy using a selective reactant poison". Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10222.
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6
Trant, Aoife Geraldine. "Structural and catalytic studies of novel Au/Ni enantioselective catalysts". Thesis, St Andrews, 2008. http://hdl.handle.net/10023/854.
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7
Reddy, P. K. "Exploration of catalysts and catalysis under near working conditions". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4577.
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Gill, Christopher Stephen. "Novel hybrid organic/inorganic single-sited catalysts and supports for fine chemical and pharmaceutical intermediate synthesis". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28218.
Testo completoAbstract (sommario):
Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jones, Christopher; Committee Member: Agrawal, Pradeep; Committee Member: Teja, Amyn; Committee Member: Weck, Marcus; Committee Member: Zhang, John.
9
Nguyen, Joseph Vu. "Design, synthesis, and optimization of recoverable and recyclable silica-immobilized atom transfer radical polymerization catalysts". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6860.
Testo completoAbstract (sommario):
Despite the growing interest in heterogeneous polymerization catalysis, the majority of the polymerization catalysts used industrially are single-use entities that are left in the polymer product. Recoverable and recyclable polymerization catalysts have not reached the industrial utility of single-use catalysts because the catalyst and product separation have not become economical. The successful development of recyclable transition metal polymerization catalysts must take a rational design approach, hence academic and industrial researchers need to further expand the fundamental science and engineering of recyclable polymerization catalysis to gain an understanding of critical parameters that allow for the design of economically viable, recoverable solid polymerization catalysts.
Unfortunately, the rapid development of Atom Transfer Radical Polymerization over the past 10 years has not resulted in its wide spread industrial practice. Numerous reports regarding the immobilization of transition metal ATRP catalysts, in attempts to increase its applicability, have extended the fundamentals of recyclable polymerization catalysis. However, for industrial viability, more research is required in the area of how the catalyst complex immobilization methodology and support structure affect the catalyst polymerization performance, regeneration, and recyclability. A comprehensive rational catalyst design approach of silica-immobilized ATRP catalyst was undertaken to answer these questions and are discussed here.
10
Meyer, Simon [Verfasser]. "Carbide Materials as Catalysts and Catalyst Supports for Applications in Water Electrolysis and in Heterogeneous Catalysis / Simon Meyer". München : Verlag Dr. Hut, 2014. http://d-nb.info/1058284967/34.
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11
Harms, Stefan Mathias. "The oligomerisation of propene over nickel oxide silica alumina". Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/22157.
Testo completoAbstract (sommario):
Bibliography: pages 129-132.A synthesis techniQue was developed for the preparation of a nickel oxide sil ica alumina catalyst. The propene oligomerisation activity and the selectivity of the catalysts prepared by homogeneous decomposition deposition (HDD) were investigated and compared with nickel oxide silica alumina catalysts prepared by the techniQues of impregnation (IMP) and co-precipitation (SG). Amongst others. the effect of the nickel content. reacti6n temperature and pressure, and water content of the feed, on the activity and selectivity. were investigated. Also investigated were the lifetime of the various catalysts and, in the case of HDD type catalysts. the ability to oligomerise high molecular weight hydrocarbons (Cb). Nickel oxide silica alumina prepared by the HDD method is more active for the propene oligomerisation than catalysts prepared by the IMP and SG methods. The product spectrum in the case of IMP and HDD type catalysts are similar, with a propene dimer (Cb) being the main product. In the case of SG type catalysts. however. a shift to heavier products was observed, i.e., propene dimer (Cb) and trimer (Cq) were formed in eQual Quantities. It is proposed that the increase in activity of HDD type catalysts was due to a large extent of metal dispersion and distribution and a stronger interaction between the metal and the support. It is also proposed that the metal is readily accessible to the reactant molecules. The activity and selectivity of catalysts prepared by the HDD method were independent of the nickel content. This was not the case for IMP and SG type catalysts. both of which showed decreasing activity with increasing nickel content when the nickel content was increased beyond 5 wt%. The lifetimes of the various catalysts were also examined. From the results obtained. over the first 10 h. the lifetime of HOD type catalysts was superior to that of the other catalysts studied. The activity and selectivity of the various catalysts were sensitive to the reaction conditions. Thus moving into the vapour phase. by either increasing the temperature at a fixed pressure or decreasing the pressure at a fixed temperature. was in each case acCompanied by a shift to heavier products and a decrease in activity.
12
Sonqishe, Thantaswa Millecent. "Treatment of brines using commercial zeolites and zeolites synthesized from fly ash derivative". Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_6127_1297842299.
Testo completoAbstract (sommario):
The objectives of this project was to ameroliate two waste materials, namely Acid Mine Drainage and Fly Ash and recover the solid residues for conversion into an adsorbent to treat brine. The solid residues were then converted into zeolite P through low temperature hydrothermal treatment. The adsorption capacity of the solid residues, zeolite P derived from the solid residues was compared to the commercial zeolite Y and fresh Arnot fly ash. The quality of the resulting water was assessed using different analytical methods before the reaction with adsorbents and after the reaction and a comparison was done based on the removal efficiency of elements Zeolite P from solid residues was successfully synthesized as confirmed by XRD, BET and FTIR. Brine treatment with fly ash, solid residues, zeolite P and commercial zeolite Y adsorbents was done concentration on the following major elements Na, K, Mg, Ca and Si. Zeolite P had higher or similar removal efficiency that the commercial zeolite Y for the following elements K, Ca and Mg. Fly ash is the only adsorbent that managed to reduce the concentration of Na in brine and also had a good removal efficiency of Mg. Si leached out of all the adsorbents which could be ascribed to Si being the major component of these adsorbents which could indicate some dissolution of these adsorbents under the conditions tested. Overall, zeolite P did not completely remove the major elements, especially for Na, but did result in a cleaner waste stream which would improve brine processing.
13
Venable, Margaret Hamm. "Syntheses, structures and support interactions of potential metal oxide catalyst precursors". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/26940.
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Linganiso, Linda Zikhona. "Adsorption studies on supported gold catalysts using temperature programmed desorption (TPD)". Thesis, Wits University, 2007. http://hdl.handle.net/10539/20167.
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Baumgart, Jerry William. "Characterization of a CoMo/Al[subscript]2O[subscript]3 catalyst exposed to a coke inducing environment". Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11714.
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Beach, Nicholas James. "Metathesis Catalysts in Tandem Catalysis: Methods and Mechanisms for Transformation". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22731.
Testo completoAbstract (sommario):
The ever-worsening environmental crisis has stimulated development of less wasteful “green” technologies. To this end, tandem catalysis enables multiple catalytic cycles to be performed within a single reaction vessel, thereby eliminating intermediate processing steps and reducing solvent waste. Assisted tandem catalysis employs suitable chemical triggers to transform the initial catalyst into new species, thereby providing a mechanism for “switching on” secondary catalytic activity.
This thesis demonstrates the importance of highly productive secondary catalysts through a comparative hydrogenation study involving prominent hydrogenation catalysts of tandem ring-opening metathesis polymerization (ROMP)-hydrogenation, of which hydridocarbonyl species were proved superior. This thesis illuminates optimal routes to hydridocarbonyls under conditions relevant to our ROMP-hydrogenation protocol, using Grubbs benzylidenes as isolable proxies for ROMP-propagating alkylidene species. Analogous studies of ruthenium methylidenes and ethoxylidenes illuminate optimal routes to hydridocarbonyls following ring-closing metathesis (RCM) and metathesis quenching, respectively. The formation of unexpected side products using aggressive chemical triggers is also discussed, and emphasizes the need for cautious design of the post-metathesis trigger phase.
17
Smallwood, Keith. "Catalysis and photocatalysis by platinized titanium dioxide and other catalysts". Thesis, University of Nottingham, 1993. http://eprints.nottingham.ac.uk/12591/.
Testo completoAbstract (sommario):
The gas-phase, thermal hydrogenations of propene and cyclopropane over various titania-supported metal catalysts have been investigated. Catalysts were prepared either by a photodeposition or a thermal reduction method. Absolute initial hydrogenation rates were calculated from total gas pressure vs time measurements. The activities of all catalysts were found to be very dependent upon catalyst state, as modified by reductive or oxidative pretreatments. These results are discussed in terms of reversible strong metal-support interactions, initiated via hydrogen spillover. For 0.5 %mass Pt on Ti02, the order of reaction with respect. to hydrocarbon was 0.5. An adsorption mechanism involving the alkylidene species is proposed as one possible explanation of this result. A negative order of reaction with respect to hydrogen was recorded. A Langmuir-Hinshelwood mechanism, involving competitive adsorption of hydrocarbon and hydrogen at supported metal sites, is proposed. Differences in behaviour between catalysts prepared by photodeposition and the thermally-prepared catalyst were observed during the hydrogenation studies. These include different apparent activation energies, maximum reaction rates at differing propene: hydrogen ratios and irreversible degradation of all photodeposited catalysts during cyclopropane hydrogenation. These differences are taken as being strongly indicative of differences in supported metal morphologies, arising as a consequence of the preparative routes employed. Temperature programmed desorption and scanning electron microscopy studies were undertaken in an attempt to establish and characterise these potential morphological differences. Although the results of these studies were, at best, inconclusive, the possible nature of such supported metal morphological differences is discussed on the basis of available evidence generated within this and other, similar, studies. The liquid-phase photocatalytic dehydrogenation of propan-2-ol, using the same catalysts, was also briefly investigated. Variations in measured activation energies suggest that photodeposited catalysts in the 'as prepared' state are contaminated with variable levels of impurity residues, particularly chloride ions.
18
Carter, Christabel Anne. "Asymmetric phase transfer catalysis : towards catalysts with a chiral anion". Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399654.
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Monti, Chiara. "Development of new catalysts for asymmetric catalysis via combinatorial chemistry". Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398589.
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20
Neate, Peter Gregory Nigel. "Pathways to sustainable catalysis : from novel catalysts to mechanistic understanding". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25441.
Testo completoAbstract (sommario):
Catalysis allows for the controlled formation of new bonds, whilst reducing both time and energy expenditure in the process. Catalysis has traditionally been the realm of precious metals, which have been used to carry out a bewildering array of reactions. However, there is an ever-increasing drive for the development of catalytic methodology employing sustainable and environmentally benign catalysts. Two such candidates are organocatalysis, omitting the need for metals where possible, or the use of iron catalysis. Two key areas to the advancement of the of field catalysis are the identification and development of new catalysts as well as an understanding of the mechanisms of established catalytic processes. Novel catalysts can provide many benefits such as enhanced or even novel reactivity, access to new classes of substrates or simply be more readily accessible compared with previously developed catalysts. To this end, the first example of Lewis-base-catalysis using the recently developed cyclopropenimine motif is reported. This was exploited in the trifluoromethylation of aldehydes and ketones using the Rupert-Prakash reagent (Scheme A-1). Scheme A-1 Cyclopropenimine-catalysed trifluoromethylation of aldehydes and ketones Developing an understanding of catalytic methodologies in the terms of their mechanism and active species is also a key area in catalysis. Insight into these can direct the expansion of these systems in terms of both more effective catalysts and tailoring reaction conditions as examples. The iron-catalysed hydromagnesiation of styrene derivatives was studied in detail. This culminated in a proposed mechanism, involving a novel hydride transfer process (Scheme A-2). Studies were carried out using a combination of kinetic analysis and in situ Mössbauer spectroscopy, as well as successfully isolating and studying the reactivity of a catalytically-relevant, formal iron(0)-species.
21
Konrad, Tina Maria. "Chiral phanephos derived catalysts and their application in asymmetric catalysis". Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4499.
Testo completoAbstract (sommario):
The research presented in this thesis is a project funded by the EU-network of the Marie Curie project NANO-HOST in collaboration with partner institutes. The aims of this network are to develop innovative methods for the preparation, recovery and reuse of single-site, nanostructured catalytic materials, and further on apply them in combination with specifically engineered reactors for a sustainable production process for making high value fine chemicals. One part of this project was to prepare chiral diphosphine ligands and their complexes for currently challenging reactions, such as asymmetric carbonylations (homogeneous catalysis). Catalytic studies of these chiral diphosphine ligands were carried out in asymmetric hydroxy-and alkoxy-carbonylations and hydrogenation reactions. The second part of this project was the heterogenisation of these chiral homogeneous complexes through collaborations with the network partners and furthermore their catalytic behavior was studied.
22
Paterson, A. James. "Exploitation of synergy in oxidation catalysis with bimetallic aluminophosphate catalysts". Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/192867/.
Testo completoAbstract (sommario):
A series of novel bimetallic aluminophosphate catalysts were prepared with the simultaneous isomorphous substitution of cobalt (III) and manganese (III) for aluminium (III) and titanium (IV) replacing phosphorus (V). By substituting simultaneously for both Al (III) and P (V) in the ordered microporous aluminophosphate AlPO-5, the potential for catalytic application as either a solidacid or redox catalyst is produced. The bimetallic hydrothermal synthesis produced a phase pure and highly crystalline microporous catalyst which displayed properties not seen in monometallic AlPO-5 materials. These catalysts were fully characterized by physical, diffraction, spectroscopic and electrochemical techniques including powder X-ray diffraction, diffuse reflectance UV/Visible spectroscopy, cyclic voltammetry, extended X-ray absorption fine structure, X-ray absorption near edge spectra, scanning electron microscopy and surface/elemental (BET and ICP) methods. A significant change was observed when two metals were combined in the same structural framework, leading to an enhancement in the catalyst performance over the monometallic analogues. EXAFS indicated a change in the relative bond lengths, thought to be as a result of compensation in the structural distortion, similarly UV/Visible spectroscopy highlighted a change in the tetrahedral environment around the titanium centre when in combination with a redox metal. These catalysts were tested for the ammoximation of cyclohexanone using benign reagents to produce cyclohexanone oxime, a vital precursor in the production of nylon-6. Currently produced through hazardous processes, the ammoximation of cyclohexanone with metal substituted catalysts provides a more environmentally favourable solution. The use of a redox metal such as cobalt (III) in combination with titanium (IV) was shown to facilitate higher catalytic conversions compared with the monometallic AlPO-5 analogues while maintaining the high oxime selectivity. Similarly the epoxidation of cyclohexene with the solid oxidant acetylperoxyborate (APB) indicated a significantly higher conversion with the CoIIITiIVAlPO-5 catalyst. The substitution of two metals to replace both aluminium and phosphorus sites clearly influences and modifies the nature of the active site and provides an enhanced catalytic performance for ammoximation and epoxidation reactions. This synergy exerted through bimetallic substitution provides an important alternative approach to academic and industrial application of metal substitution within heterogeneous catalysis
23
Müller, Ruben S. Ramon. "Homogeneous gold catalysts : development of applications for gold(I) catalysts bearing N-heterocyclic carbene ligands". Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2531.
Testo completoAbstract (sommario):
Recently established as an excellent activator for π-systems, efforts made in gold chemistry have increased enormously, resulting in a new ‘Gold Rush’ in chemistry. This thesis is a small contribution to it. There are two main aspects dominating the following chapters: gold catalysts bearing N-heterocyclic carbenes (NHCs) as supporting ligand, and H₂O assisted catalysis. The initial motivation for the presented work was to specifically demonstrate the potential of [(NHC)AuCl] as suitable catalysts for both known and new organic transformations and to establish these commercially available catalysts in gold chemistry, a field currently dominated by phosphine bearing gold complexes. Water mediated catalysis became the next repeatingly occurring aspect of this thesis by pursuing this initial aim and finding water as a useful solvent or agent, respectively. Various useful applications for gold-NHC complexes are presented, starting with the Meyer-Schuster rearrangement of propargylic alcohols as a continuation of the work realized with propargylic acetates by the Nolan group in early investigations on gold catalysts. Next, a study on alkyne hydration is presented with focus on low catalysts loadings to establish gold catalysts as a powerful choice for such a highly relevant reaction. The catalytic system is then advantageously adapted to a silver-free variation, still active at low catalyst loadings and with further mechanistic insight. Inspired by gold activation of alkynes, a gap of reactivity in gold catalysis is closed by a successful demonstration of nitrile hydration, a functionality previously thought to be inert towards gold activation. In this context, formation and role of dinuclear hydroxy-bridged gold complexes is investigated highlighting these complexes as a possible resting state of gold complexes in the presence of water. Next, the formation of furanones via alkoxylation/lactonization of propargylic propiolates is presented, an observation initially made when exploring the scope of the Meyer-Schuster rearrangement. The dissertation finally closes with the gold-catalyzed formation of amides, this time however achieved from aldoximes reacting via dehydration/hydration mechanism.
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Posada, Pérez Sergio. "Heterogeneous catalysis of green chemistry reactions on molybdenum carbide based catalysts". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/552405.
Testo completoAbstract (sommario):
Our society has a problem with the use of fossil fuels, due to the vast and exceeding emissions derived from human activities. Two ways could be consider to mitigate these harmful effects. On the one hand, the capture, activation, and conversion of these hazardous gases towards valuable compounds, and on the other hand, the substitution of fossil fuels for renewable energies. This thesis encompasses the study of two different green chemistry reactions to convert the most abundant greenhouse gas in Earth's atmosphere and the production of a new environmental friendly fuel, the hydrogen.
In the current search for new catalysts, Transition Metal Carbides (TMCs) have arisen as an appealing alternative, because their exhibit broad and amazing physical and chemical properties and their low cost. In particular, titanium carbide (001) was proposed from experimental and theoretical points of view as active catalyst and support of small metal particles for CO2 hydrogenation to methanol and water gas shift reaction. However, given that titanium carbide is a cumbersome support to be used in applications due to the difficulty of obtaining nanoparticles on working conditions, we have carried out these reactions on cubic δ-MoC (001) and orthorhombic β-Mo2C (001) surfaces.
The adsorption and activation of a CO2 molecule on cubic δ-MoC (001) and orthorhombic β-Mo2C (001) surfaces have been investigated by means of periodic density functional theory based calculations using the Perdew-Burke-Ernzerhof exchange-correlation functional showing that both surface are promising catalyst for CO2 conversion because they are able to activate and bend the CO2 molecule. The β- Mo2C (001) surface is able to dissociate the CO2 molecule easily, with a low energy barrier, whereas δ-MoC (001) surface activates CO2 but it does not promote its direct dissociation. Experiments accomplished by the group of Dr. Jose Rodriguez revealed that CO and methane are the main products of the CO2 hydrogenation using β-Mo2C
(001) as catalyst, and the amount of methanol is lower. On the other hand, only CO and methanol are produced using δ-MoC (001).
Experiments revealed that the deposition of small copper particles on the carbide surfaces increase drastically the catalysts' activity and selectivity, which was demonstrated by theoretical calculations. On β-Mo2C, the amount of CO and methanol
increase whilst the amount of methane decrease, since copper blocks reactive sites on surface. This is a positive fact since copper avoid the excessive oxygen deposition, which deactivated the catalysts. On the other hand, the deposition of copper on δ-MoC
(001) increases a lot the amount of CO and methanol. In summary, our combining DFT- experimental study proposed the Cu/δ-MoC as promising catalyst for CO2 hydrogenation due to its activity (the amount of products is superior than other TMCS, metals, and the model of commercial catalysts), selectivity (only CO and methanol are produced), and stability ( this catalysts is not deactivated by the oxygen deposition).
The results obtained in the first part of the thesis were used to study the water gas shift reaction. Given that the excellent features, experiments proposed Au supported on δ-MoC (001) as catalysts. Our theoretical calculations demonstrated that clean δ-MoC (001) is not a good catalysts for WGS, due to the fact that the reverse reactions are favorable respect the direct ones, which implies that the amount of products is lower. Nevertheless, the deposition of Au clusters change the reaction mechanism, favoring the direct barriers instead of reverse ones, and increasing the amount of produced H2.
In summary, this thesis has displayed the prominent role of molybdenum carbides as support of small metal particles to catalyze green chemistry reactions.En aquesta tesi es mostra un treball computacional sobre l'ús de catalitzadors econòmics per a la conversió de CO2, un perillós gas d'efecte hivernacle i també per a la producció d'hidrogen, el combustible del futur. En la recerca actual de nous catalitzadors, els carburs de metalls de transició (TMC) han sorgit com una alternativa atractiva pel el seu baix cost i per exhibir excel·lents propietats físiques i químiques. En aquest treball utilitzarem com a catalitzadors les superfícies cúbica δ-MoC (001) i ortoròmbica β-Mo2C (001). L'adsorció de la molècula de CO2 mostra que ambdues superfícies són capaces d'activar i doblegar la molècula. La superfície β-Mo2C (001) és capaç de dissociar fàcilment la molècula de CO2, mentre que la superfície δ-MoC (001) activa CO2 però no la dissocia. Els experiments realitzats pel grup del Dr. Jose Rodriguez van revelar que el CO i el metà són els principals productes de la hidrogenació de CO2 utilitzant β-Mo2C (001) com a catalitzador, i la quantitat de metanol és menor. D'altra banda, només es produeixen CO i metanol utilitzant δ-MoC (001). La deposició de partícules de coure a les superfícies del carbur augmenta dràsticament l'activitat dels catalitzadors, cosa que es va demostrar mitjançant càlculs teòrics. A la superfície β-Mo2C, la quantitat de CO i metanol augmenten mentre que la quantitat de metà disminueix. D'altra banda, la deposició de coure a δ-MoC (001) augmenta molt la quantitat de CO i metanol. En resum, el nostre estudi proposa el Cu/δ-MoC com a prometedor catalitzador de la hidrogenació de CO2 a causa de la seva activitat (la quantitat de productes és superior a la resta de TMCS, metalls i el model de catalitzadors comercials), selectivitat (només el CO i el metanol es produeixen) i l'estabilitat (aquests catalitzadors no es desactiven per la deposició d'oxigen). Tenint en compte els resultats previs, es va proposar la deposició d'or en la superfície δ-MoC per a la producció d'hidrogen. Els càlculs teòrics demostren que la superfície δ-MoC (001) no és un bon catalitzador per WGS, però la deposició dels clústers d'or canvia el mecanisme de reacció i augmenta la quantitat d'H2 produïda.
25
Fjellander, Ester. "Self-adaptable catalysts : Importance of flexibility and applications in asymmetric catalysis". Doctoral thesis, KTH, Organisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12852.
Testo completoAbstract (sommario):
The topic of this thesis is the design and synthesis of biaryl-based self adaptableligands for asymmetric metal catalysis. The results discussed in papers I-III are covered, together with some unpublished results concerning substrate-adaptable catalysts. A general survey of self-adaptable catalysts is presented first. The second chapter of this thesis starts with a survey of inversion barriers in biphenyl-based ligands and catalysts. Thereafter, the determination of barriers to conformational adaptation in dibenzoazepines and dibenzophosphepines is described. Palladium complexes with a diphosphine ligand or a diamine ligand, as well as the free diamine ligand, were studied. Entropies and enthalpies of activation were determined with variable temperature NMR spectroscopy. The mechanism of conformational change in the metal complexes was elucidated. The third chapter describes the synthesis of semiflexible and rigid phosphinite ligands, as well as their application in rhodium-catalysed asymmetric hydrogenation. Modest enantioselectivities (up to 63% ee) were obtained. The semiflexible ligand was found to behave like the most active rigid diastereomer. The fourth chapter describes the behaviour of amine and phosphoramidite ligands in model complexes relevant to the palladium-catalysed asymmetricallylic alkylation of benchmark substrates. Diphosphoramidite and aminephosphoramiditeligands were designed and synthesised. Pd(olefin) complexesof diamine and diphosphoramidite ligands were studied, and their symmetry determined. It was found that both types of ligands are able to adapt their conformation to the substrate.QC20100630
26
Ou, Xiaoxia. "Developing hierarchically structured catalysts on cellular foams for continuous flow catalysis". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/developing-hierarchically-structured-catalysts-on-cellular-foams-for-continuous-flow-catalysis(e3fb780b-5212-4428-894d-288d4b819c6c).html.
Testo completoAbstract (sommario):
The development of modern chemical and environmental industry requires novel reactor concepts to enable the transfer of catalysts developed in laboratories into the industrial context. The applications of structured reactors/catalysts such as cellular foams are one of the most promising technologies that can facilitate this crucial step. Open-cell foams with stochastically interconnected cells and high porosities (>60%) can promote the low pressure drop during operation and improve the transport phenomena, overtaking the conventional fixed beds for continuous flow catalysis. In this PhD project, silicon carbide (SiC) cellular foams were investigated to evaluate the potential for developing heterogeneous catalysis using foam-based catalysts in continuous flow regime, due to the good compatibility with framework catalyst coatings and features of the cellular structure. The work was carried out by (i) studying morphological and structural features of SiC foams using X-ray computed tomography technique in relation to their implications for applications in chemical engineering; (ii) developing a microwave-assisted method based on the microwave absorbing feature of SiC for fast yet selective synthesis of zeolite (ZSM- 5) coatings on SiC foams; (iii) developing Fe-ZSM-5/SiC structured catalysts using a chemical vapour deposition method and subsequently studying their application as the foam bed reactor in the catalytic wet peroxide oxidation (CWPO) reaction (using phenol as the model compound); and (iv) developing intra-framework Fe-ZSM-5 catalyst on SiC foams (ferrisilicate/SiC) to address the Fe leaching issue from the Fe-ZSM-5/SiC catalyst. Satisfactory results were obtained through the systematic study of the SiC foam based catalysts, showing the potential of using SiC foams to develop structured catalysts for continuous flow environmental catalysis.
27
Cunje, Alwin. "Noble gases and catalysis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0012/NQ59125.pdf.
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Durgun, Gülay Artok Levent. "Short-time suzuki reactions of arly halides catalyzed by palladium-loaded NaY zeolite under aerobic conditions/". [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/kimya/T000528.pdf.
Testo completoAbstract (sommario):
Thesis (Master)--İzmir Institute of Technology, İzmir, 2006.Keywords:Suzuki reactions, palladium, NaYzeolite, heterogeneous catalyst, C-C coupling. Includes bibliographical references (leaves. 71-81).
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Lev, Daniel Abraham. "Group 8 and 9 half sandwich complexes of N-heterocyclic phosphines : synthesis, reactivity, and catalysis /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3158465.
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Oh, Seokjoon. "Graphite-conjugated catalysts : bridging heterogeneous and homogeneous catalysts". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122714.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2019Cataloged from PDF version of thesis. Page 156 blank.
Includes bibliographical references.
This interconversion occurs via complex multistep, multielectron reactions, which can be carried out by either metallic heterogeneous or molecular homogeneous electrocatalysts. Metallic heterogeneous catalysts have a continuum of electronic states that distribute the redox burden of multielectron reactions, allowing for efficient catalysis. However, heterogeneous catalysts display a variety of active sites and local electronic structures, and are difficult to fine-tune at a molecular level. On the other hand, homogeneous catalysts allow a great degree of synthetic control over the catalytic active site. Moreover, the relative ease in spectroscopic characterization allows a mechanistic understanding of molecular catalysis at a level that is unattainable for heterogeneous catalysis. To bridge the advantages of both types of catalysts, we have developed a surface functionalization strategy for conjugating molecularly well-defined active sites to graphitic carbon surfaces.
First, I will discuss the preparation and characterization of two new types of conjugating N-heterocyclic linkages to graphitic carbon surfaces. This work presents a general method for characterizing modified carbon surfaces with molecular-level structural detail. Then, I will present the electrocatalytic carbon dioxide reduction activity of a graphite-conjugated rhenium catalyst, and compare its catalytic behavior to that of a molecular analog. Electrochemical and spectroscopic data show that graphite-conjugated catalysts do not behave identically to their molecular analogs, but rather show properties similar to that of metallic heterogeneous catalysts, providing a unique bridge between the worlds of heterogeneous and homogeneous catalysis.
Finally, in the appendix, I will present a chapter on the stability of graphite-conjugated linkages under electrochemical polarization, followed by a chapter on catalyzing the reduction of molecular pyridinium species using a graphite-conjugated rhodium catalyst.
by Seokjoon Oh.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry
31
Craig, Kim Meyer. "New concepts in catalyst design: homogeneous organometallic catalysts with tunable architectures". Thesis, University of Auckland, 2010. http://hdl.handle.net/2292/6114.
Testo completoAbstract (sommario):
This theses describes the development of homogeneous catalysts containing receptor elements which are capable of participating in reversible bonding interactions with groups bearing complementary functionality. This approach is amenable to combinatorial chemistry, and could facilitate catalyst development processes which are conventionally expensive and time-intensive. To date, the implication of reversible supra molecular interactions in anthropogenic organometallic catalysis are not widely understood.
32
Mansor, N. B. "Development of catalysts and catalyst supports for polymer electrolyte fuel cells". Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1460064/.
Testo completoAbstract (sommario):
Polymer Electrolyte Membrane fuel cells (PEMFC) are clean and efficient electrochemical energy converters that can be adapted to a wide range of domestic and automotive applications. However, large-scale commercialisation is hindered by issues of cost and durability relating to the catalyst layer. This work aims to address the need for cheaper and durable catalysts through the development of novel catalyst and catalyst support. The initial aim of this work is to investigate the potential application of Pd-based alloy catalyst in PEMFC. Pd is about 42% cheaper than Pt and 50 times more abundant on earth. Previous studies have shown that there is a correlation between electronic structure and catalytic activity of Pd binary alloys, and therefore it is possible to design a highly efficient Pd-based alloy catalyst. In this work, Pd-based catalyst was synthesised and characterized electrochemically in ex-situ and in-situ configurations to determine their activity and durability. It was found that Pd-based catalyst could potentially replace Pt as a low-cost anode catalyst. The second part of this work investigated the potential application of graphitic carbon nitride materials as catalyst support. Carbon black is the most widely used catalyst support for state-of-the-art PEMFCs even though it is known to undergo carbon corrosion during operation. Graphitic carbon nitride could offer enhanced durability and activity due to their graphitic structure and intrinsic catalytic properties. In addition, graphitic carbon nitride is low-cost, fairly simple to synthesise and highly tunable. In this work, various graphitic carbon nitride materials were prepared and characterised using accelerated carbon corrosion protocol. They were found to be more electrochemically stable compared to conventional carbon black. Superior methanol oxidation activity is also observed for graphitic carbon nitride supported Pt catalysts on the basis of the catalyst electrochemical surface area. However further work is needed to optimise the deposition and utilisation of metal catalyst on graphitic carbon nitride materials.
33
Damian, Karen Serena. "Pd catalysed synthesis of phosphines for homogeneous catalysis". Thesis, St Andrews, 2009. http://hdl.handle.net/10023/907.
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Shiels, Rebecca Anne. "Synthesis, characterization, and evaluation of silica and polymer supported catalysts for the production of fine chemicals". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29629.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Christopher Jones; Committee Member: Dr. Dennis Hess; Committee Member: Dr. Hang Lu; Committee Member: Dr. Marcus Weck; Committee Member: Dr. Pradeep Agrawal. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Widyaningrum, Rosalia Nugraheni. "Mesoporous silica-supported catalysts to enhance hydrogen production during cellulose pyrolysis". Thesis, The University of Sydney, 2011. https://hdl.handle.net/2123/28917.
Testo completoAbstract (sommario):
Pyrolysis of biomass has been studied worldwide as a potential path to produce hydrogen from renewable sources. Major problem in a non-catalytic biomass pyrolysis is tar formation, which causes complication in the utilization of product gas. Elimination of tar requires a high temperature, and it leads to low energy efficiency since tar itself contains high potential energy.
The utilization of metal catalysts is considered an effective method to reduce tar content and subsequently increase the hydrogen production. Nickel catalyst has been previously investigated for its tar cracking activity and identified as one of the best catalysts, but it has a drawback when used at high temperature because sintering of metal particle and carbon deposition occur. To address this challenge, a suitable catalyst support and promoter are required to minimize sintering and enhance the activity of nickel catalyst.
This project approached the issue by studying the potential catalyst supports and the effect of promoter in the catalytic activity of nickel catalyst. Three catalyst supports: mesoporous silica SBA-15 (Santa Barbara Amorphous), MCF (Mesocellular Foam), and commercial y-Alz03 were investigated, and palladium was chosen as a promoter. Mesoporous silica SBA-15 and MCF were synthesized using sol-gel method with Pluronic P123 as a structure directing agent, tetraethyl orthosilicate (TEOS) as a silica source, and 1,3,5-trimethylbenzene as a swelling agent for MCF synthesis. Nickel and palladium were deposited into the supports by wet impregnation techniques. The catalysts were characterized using N2 adsorption-desorption (BET and BJH methods), xray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray fluorescence (XRF). The activity of the catalyst was tested in cellulose pyrolysis using thermogravimetric analyzer coupled to a mass spectroscopy (TGA-MS).
This work studied the role of nickel catalysts in the pyrolysis of cellulose, the role of catalyst supports, and the effect of Pd promoter in increasing the catalytic activity to enhance hydrogen production. The results of this study suggest that mesoporous silica MCF was a good catalyst support because the MCF-supported Ni catalyst gave the highest H2 yield. The H2 yield was 73.5 mL/ g cellulose, which was 1.7 times H2 yield from SBA-15-supported Ni-catalyst, and 3.3 times H2 yield produced by y-Alz03-supported Ni-catalyst. The addition of 0.5 wt% Pd promoter also increased the H2 yield by 14%.
36
Chen, Gang. "Synthesis of fluorinated BINOL ligands and asymmetric catalysis with its derived catalysts". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58758.pdf.
Testo completo
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Yamamoto, Takashi. "Studies on the Catalysis by New Solid Acid Catalysts and the Characterization". Kyoto University, 1999. http://hdl.handle.net/2433/77922.
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Richardson, John Michael. "Distinguishing between surface and solution catalysis for palladium catalyzed C-C coupling reactions: use of selective poisons". Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22704.
Testo completoAbstract (sommario):
This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts.
This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed.
39
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.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains xii, 328 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 81-91).
40
Dorfling, Sasha-Lee. "Enantioselective transformations using tetrol as a chiral mediator". Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/d1021195.
Testo completoAbstract (sommario):
(+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives were reacted with varying molar ratios of titanium isopropoxide (2:1, 1:1 and 1:2 tetraol:titanium isopropoxide) in an attempt to prepare potential titanium-based tetraol catalysts for enantioselective transformations. In each case, infrared and HNMR spectra suggested that the product was formed. We tentatively proposed that the structure of the catalyst was a spiro-type, but we could not determine conclusively what its exact structure was, despite using numerous techniques at our disposal (molecular modelling calculations, H NMR and IR spectroscopy, thermal analyses, powder diffraction, and single crystal X-ray diffraction). The catalyst and derivatives thereof were able to act catalytically for the enantioselective additions of diethylzinc compounds to aldehydes. The effects of temperature and solvent were investigated, and toluene and -78 °C were selected as optimal from the results obtained. (The reaction could, however, not be maintained at this low temperature for extended periods due to the fact that we did not have, at our disposal, the correct equipment. Each 16 h reaction was thus allowed to reach room temperature in each case.) The selectivity for the product 1-phenylpropan-1-ol (when benzaldehyde was the starting aldehyde) varied depending on the nature of the aryl substituents of the titanium-based catalyst. Using 0.2 molar equivalents of the chiral titanates, the highest selectivity was 42 percent (e.e.), but only when excess Ti(O-i-Pr)4 had been added to the reaction mixture. This was achieved with the tetra(ortho-methoxyphenyl)-TETROLate derivative. TETROL and its derivatives were also successful in metal-free catalysis where higher conversions and selectivities were observed, compared to when these were complexed to titanium. The highest selectivity was 70 percent (e.e.), achieved with the tetra(ortho-methylphenyl)TETROL derivative.
41
Barakat, Khaldoon A. Cundari Thomas R. "Computational studies of selected ruthenium catalysis reactions". [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5203.
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Guo, Jiawen, e 郭嘉雯. "Chiral spirodiphosphine dioxides organocatalysis and hydrogen transfer reduction". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196023.
Testo completoAbstract (sommario):
Recently, during the past10 years, with the intensified attention paid to the environment and industrial development, there has been growing interest in organocatalysis. One important area of the organocatalysis is the development of new designs of chiral catalysts for the synthesis of optically pure products. Another important area is to develop methods to simplify the purification of multi-component reactions.
A chiral spirobiindane-based bisphosphine oxide catalyst was synthesized and employed in various reactions including Abramov-type phosphonylation reactions, reductive aldol reactions, direct aldol reactions, allylations, reductive cyclizations and C=N reduction reactions. The rigid and axially chiral spirobiindane skeleton of the bisphosphine oxide introduces steric hindrance and results in moderate to good enantioselectivity in Abramov phosphonylation and reductive cyclization reactions. However, the great steric hindrance of the catalyst also imposes negative effects on catalyst activity and yields of reactions. The observed slow reaction rates may possibly have led to the undesired, non-selective background reactions and therefore a lowered enantioselectivity.
Secondly, the success of polymer-supported reagents in facilitating product purification prompted our attempt to prepare and examine two different types of polymer-supported benzothiazolines for hydrogen transfer reduction. An in situ generated self-supported polybenzothiazoline proved to be a rapidly formed polymer under mild conditions and could be applied to hydrogenation transfer reduction reactions with active alkenes. A rasta resin-supported benzothiazoline was also synthesized and examined in similar transformations. Both of the two polymer reagents afforded the desired reduction products, but further optimizations may be required to suppress the formation of byproducts and to improve their reactivity.published_or_final_version
Chemistry
Master
Master of Philosophy
43
Bismuto, Alessandro. "Main group species for catalytic hydroboration". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31537.
Testo completoAbstract (sommario):
Modern synthetic chemistry is unimaginable without transition metal catalysis. Yet the often high cost, toxicity and scarcity of many transition metals is driving attempts to find sustainable alternatives. Thus, the development of catalytic processes using main-group catalysts is now of broad interest. This thesis reports the development of a facile protocol for the aluminium-catalysed hydroboration of alkynes, alkenes and polar bonds using commercially-available catalysts. The catalytic hydroboration is proposed to occur by hydroalumination followed by product release through σ-bond metathesis with pinacol borane. An alternative route to alkenyl boranes is the 1,1-carboboration of alkynes using stoichiometric B(C6F5)3. A zwitterionic intermediate in the Piers' borane-catalysed hydroboration and 1,1-carboboration of alkynes with B(C6F5)3 has been characterised and its divergent reactivity identified. This has led to the development of a B(C6F5)3 - catalysed hydroboration of alkynes using HBpin.
44
Blancas, Blancas Javier. "Síntesis y Caracterización de catalizadores CoMoW soportados en Al-Mg-Li potencialmente aplicables en la obtención de combustibles limpios". Tesis de maestría, Universidad Autónoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/99583.
Testo completoAbstract (sommario):
Esta tesis se desarrollo en el laboratorio de nanotecnologia del CCIQS, y se usaron colaboraciones interinstitucionales con el ININ, IMP principalmenteEn este trabajo de tesis se estudió el efecto de la incorporación de tungsteno (W) en formulaciones catalíticas de baja acidez CoMo/Al2O3-MgO-Li2O, caracterizando las propiedades físicas y químicas, así como la actividad catalítica en la hidrodesulfuración de DBT y la selectividad catalítica hacia la ruta de desulfuración directa (DSD). El trabajo quedo estructurado como a continuación se detalla: Capítulo 1: Introducción, antecedentes, hipótesis, objetivo general y objetivos particulares, con los cuales se pretende dar a conocer una idea general del problema de la contaminación ambiental en el aire producida por los gases de efecto invernadero, además del proceso de hidrodesulfuración de combustibles como medida para reducir las emisiones de SOX por vehículos automotores. Capítulo 2: Fundamentos teóricos de las técnicas de caracterización empleadas para estudiar las formulaciones catalíticas obtenidas. Capítulo 3: Desarrollo experimental, metodología seguida para la obtención y caracterización de estos catalizadores proponiendo la adición de tungsteno (W) en la fase activa para la obtención del catalizador trimetálico CoMoW soportado en Al2O3, Al2O3-MgO y Al2O3-MgO-Li2O, para analizar el comportamiento catalítico que estos catalizadores tienen en la remoción del de azufre (S), se usó el dibenzotiofeno (DBT) como molécula modelo representativa de una de las fracciones del petróleo. Capítulo IV: Resultados y la Discusión de la caracterización física y química realizada a estos catalizadores para explicar su comportamiento catalítico como la conversión y sobre todo la selectividad, empleando diferentes técnicas de caracterización para determinar las propiedades estructurales y texturales, se emplearon técnicas como la fisisorción de N2, Espectroscopia infrarroja (FTIR), Espectroscopia Raman, difracción de rayos x (DRX) y Espectroscopia Ultravioleta-Visible (UV/Vis), se determinó la cantidad y fuerza de los sitios ácidos con la termodesorción de amoniaco (TPD de NH3), se evaluó la actividad catalítica para determinar el desempeño de la formulación catalítica en cuanto a la remoción de azufre en el DBT. Capítulo V: Conclusiones generales de la tesis. Por último, referencias bibliográficas y anexos
UAEM-SIEA Proyecto 4488 y CB-168827
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Green, Riho Thomas Seljamae. "Supramolecular assemblies of bioinorganic complexes formed via reaction of (S)-proline with nickel clusters on Au(111)". Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/11956.
Testo completoAbstract (sommario):
Considerable research over several decades has been directed at the development of heterogeneous enantioselective hydrogenation catalysts via the chiral modification of Ni catalysts by chiral molecules such as α-hydroxy acids and α-amino acids. Some of these systems have proved to be very successful yielding catalysts achieving very high enantioselectivity. However, the modified surfaces display relatively poor stability under catalytic conditions, so there is a demand to produce more robust chiral architectures for application in this area of catalysis. The formation of metal organic coordination networks on surfaces has been the subject of intensive study in the last decade. This thesis reports the formation of metal organic structures via the reaction of (S)-proline with nanoscale Ni islands grown on Au(111). Initially, (S)-proline was studied Au(111) using low temperature scanning tunnelling microscopy (LT-STM), XPS and high resolution electron energy loss spectroscopy (HREELS). Adsorpton of (S)-proline at 300 K resulted in the formation of a mixture of the zwitterionic and anionic forms of proline. The former species condensed into ordered arrangements at 77 K giving a structure very similar to one crystal plane of solid proline. Proline species were relatively weakly bound and the vast majority of adsorbed proline desorbed by 370 K. (S)-proline adsorption was examined on Ni/Au(111) over a range of Ni coverages from 0.05 ML up to >1.0 ML STM, XPS, HREELS and DFT calculations. (S)-proline was found to oxidise Ni from the edges of the Ni islands producing nickel prolinate species. Five distinct classes of supramolecular assemblies were produced depending on Ni coverage and annealing temperature. The nature of each of these structures is described. It is concluded that one assembly is built up from Ni(prolinate)₂ (square planar) complexes, three of the assemblies have a fundamental building block consisting of a Ni(prolinate)₃ octahedral complex and the final structure, observed at high annealing temperatures, is constructed from oligomerized proline species. The interaction of the prochiral reagent, methyl acetoacetate, with some of these supramolecular assemblies is reported.
46
Liang, Jack S. (Jack Shih-Chieh) 1972. "Development and applications of enantioselective organometallic catalysts : I. Organotin catalysts; and, II. Planar-chiral nitrogen heterocyclic catalysts". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85292.
Testo completo
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Lamb, Gareth William. "Phosphine modified rhodium catalysts for the carbonylation of methanol /". St Andrews, 2008. http://hdl.handle.net/10023/574.
Testo completo
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Sabbagh, Ingrid Theresa. "Metathesis catalysts : an integrated computational, mechanistic and synthetic study". Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1006208.
Testo completoAbstract (sommario):
An integrated approach to the design of potential rutheniun-based metathesis catalysts is described, in which closely defined synthetic forays provide the focus and rationale for detailed computational and mechanistic studies. The ground-state geometry of a 1st-generation Grubbs catalyst has been explored at the molecular mechanics, semi-empirical and DFT levels, and the resulting structures have been shown to compare favourably with literature data and with the structure of a known crystalline analogue. The DMol³ DFT code has also been shown to represent accurately both the geometry of the corresponding co-ordinatively unsaturated monophosphine derivative, and the ligand dissociation energy associated with its formation. A DFT free-energy profile of the degenerate metathesis of ethylene has been generated, using a truncated model of the 1st-generation Grubbs catalyst, permitting location, for the first time, of the three expected transition states and providing new information regarding the rate-determining step. DFT methods have been used to facilitate the design of a tridentate camphor-derived ligand for use in the construction of a novel Grubbs-type catalyst. The phosphine ligand dissociation energy of the putative catalyst and the ethylene metathesis energy profile of a truncated model have also been studies at the DFT level. The attempted synthesis of the proposed ligand proceeded via a novel 8-bromocamphoric anhydride intermediate and afforded several unexpected and novel products, including a cisfused γ-Iactone, and a bromo camphoric acid derivative. Single crystal X-ray analysis of the latter reveals a chiral, polymeric H-bonded packing arrangement, rendering it suitable for chiral inclusion studies. Computational methods, including the GAUSSIAN-based GIAO NMR prediction technique, were used to support the structural characterisation of the novel camphor derivatives. DFT-Ievel computational analysis of the C-8- and C-9 bromination of camphor has afforded theoretical insights which permit the reconciliation of two earlier empirical explanations regarding the regioselectivity of these transformations; moreover, the theoretical results suggest that a third, previously disregarded factor, plays a significant role. A coset analysis, in conjunction with DFT-Ievel energy profiling, has also been used to resolve conflicting opinions regarding the origin of the major byproduct. Computed electronic parameters (CEP's) have been calculated for the anionic ligands involved in a series of 2nd-generation Grubbs-Hoveyda-type catalysts, and used to explain some apparently anomalous trends in catalyst activity. A linear relationship between ligand CEP's and selected ¹H NMR chemical shifts has also been demonstrated and used to identify a transient ruthenium complex in solution. The ability of the malonate di-anion to bind to ruthenium in a bidentate manner has been explored and demonstrated, under suitable conditions. DFT methods have been used to design and assess the ruthenium-chelating potential of a novel tridentate malonate derivative. A synthetic pathway to this ligand has been designed and several novel heterocyclic intermediates have been isolated and characterised. An NMR-based kinetic study of the Grubbs-catalysed self-metathesis of l-octene has been completed, and the effects of temperature, concentration and solvent variations on the kinetic parameters have been studied. Application of the Guggenheim method and a simplified mechanistic model has permitted the accurate calculation of pseudorate constants for the initiation and, for the first time, the propagation phase of the reaction. Theoretical studies of this reaction at the DFT and molecular mechanics levels have been shown to support previous assumptions regarding the selectivity and temperature-dependence of metallacycle formation.
49
Lamb, Gareth W. "Phosphine modified rhodium catalysts for the carbonylation of methanol". Thesis, University of St Andrews, 2008. http://hdl.handle.net/10023/574.
Testo completoAbstract (sommario):
The carbonylation of methanol to acetic acid is one of the most important applications in homogeneous catalysis. The first chapter comprises a review on the mechanistic studies into the catalytic cycle of the ‘Monsanto process’ and includes some of the most prominent studies into the use of phosphines in the rhodium-catalysed carbonylation of methanol. The second chapter of this thesis reports on an investigation into the application of rhodium complexes containing several C4 bridged diphosphines, namely BINAP, dppb, dppx and dcpb as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes. In the third chapter I report on an investigation into how electronic properties and coordination mode affect the elimination of phosphonium salts from rhodium complexes. The stability of a range of monodentate, bidentate and tridentate rhodium-phosphine complexes was tested. I also report on the formation of a novel bidentate complex containing a partially quaternised TRIPHOS ligand and investigate the mechanism of formation using 13CH3I. Strong evidence is also presented supporting a dissociative mechanism as the means of phosphine loss from the rhodium centre. In the final chapters I report an investigation into the stability of rhodium-aminophosphine ligand complexes and into increasing the solubility of potential rhodium pre-catalysts through the use of amine-containing phosphine ligands.
50
Solmi, Matilde Valeria. "Synthèse d'acides carboxyliques à partir de substrats oxygénés, de CO2 et de H2". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1287/document.
Testo completoAbstract (sommario):
Les acides carboxyliques aliphatiques sont utilisés dans de nombreux secteurs industriels et leur importance économique augmente. Ils sont actuellement produits en grande quantité, grâce à des procédés utilisant le C0 qui est principalement non- renouvelable. L'anhydride carbonique est une molécule potentiellement écologique, renouvelable et abondante. Cette thèse décrit l'étude et l'optimisation d'un système catalytique homogène de Rh, utilisé pour produire des acides carboxyliques aliphatiques à partir de substrats oxygénés, C02 et H2. Le système consiste en un précurseur de Rh, un additif à base d'iodure et un ligand PPh3, fonctionnant dans un réacteur discontinu sous une pression de C02 et de H2. Les conditions de réaction ont été optimisées pour chaque classe de substrats étudiés: alcools primaires et secondaires, cétones, aldéhydes et époxydes. 30 molécules différentes ont été converties en acides carboxyliques, conduisant à des rendements jusqu'à 80%. En plus, le système a été étudié avec une approche de « Design of Experiment », ce qui a permis d'obtenir des informations supplémentaires concernant les paramètres étudiés. Le mécanisme de réaction et les espèces catalytiques actives ont été étudiés par différentes manipulations comme des réactions compétitives, des expériences de RMN et l'utilisation de molécules marquées. La réaction est composée de transformations non catalytiques et de deux étapes catalytiques. La réaction se déroule à travers une réaction de reverse Water Gas Shift (rWGSR) transformant le C02 et l'H2 en C0 et H20, qui sont consommés dans l'hydrocarboxylation suivante de l'alcène formé in situ pour livrer l'acide carboxylique. Le système catalytique est similaire aux catalyseurs traditionnels à base du Rh pour les réactions de carbonylation et de Water Gas Shift. Le PPh3 est nécessaire pour fournir des ligands supplémentaires, permettant au catalyseur de fonctionner avec une quantité minimale de ligand toxique de C0. En plus, un système catalytique hétérogène a été étudié pour la même réaction. « Single Atom Catalysts » (SACs) reçoit beaucoup plus d'attention que les solutions catalytiques, car il présente à la fois les avantages des catalyseurs homogènes (sélectivité, haute activité) et des catalyseurs hétérogènes (séparation et recyclage faciles). Des atomes de rhodium simples dispersés sur du graphène dopé avec l'N ont été synthétisés et caractérisés, obtenant des informations concernant la structure chimique et physique du matériau. Finalement, ils ont été testés ainsi que les catalyseurs pour l'activation du C02, la production d'acides carboxyliques, les réactions d'hydrogénation et d'hydrogénolyseAliphatic carboxylic acids are used in many industrial sectors and their importance from an economical point of view is increasing. They are currently produced in large quantities, through processes exploiting the mostly non-renewable C0 as C1 synthon. Carbon dioxide is a potential environmentally friendly, renewable and abundant C1 building block. The aim of this work is to provide a catalytic protocol converting C02, H2 and oxygenated substrates to obtain useful chemicals, like carboxylic acids.To this end a homogeneous catalytic Rh system, used to produce aliphatic carboxylic acids starting from oxygenated substrates, C02 and H2 was investigated and optimized. The system consists of a Rh precursor, iodide additive and PPh3 ligand working in a batch reactor under C02 and H2 pressure. The reaction conditions were optimized for each class of investigated substrates: primary alcohols, secondary alcohols, ketones, aldehydes and epoxides. The reaction scope was investigated and 30 different molecules were converted into carboxylic acids, leading to yields of up to 80%. ln addition, the system was studied using a Design of Experiment approach, obtaining additional information regarding the studied parameters.The reaction mechanism and the catalytically active species were studied, by different experiments like competitive reactions, NMR and labelling experiments. This investigation resulted in a deeper knowledge of the reaction pathway, composed of some non-catalytic transformations and two catalytic steps. The reaction proceeds through a reverse Water Gas Shift Reaction (rWGSR) transforming C02 and H2 into C0 and H20, which are consumed in the following hydrocarboxylation of the in-situ formed alkene to give the final carboxylic acid product. The catalytic system is similar to traditional Rh carbonylation and Water Gas Shift catalysts. The PPh3 is needed to supply additional ligands allowing the catalyst to work in reaction conditions with a minimal amount of toxic C0 ligand. ln addition, a heterogeneous catalytic system was investigated for the same reaction. Single atom catalysts (SACs) are receiving much attention as catalytic solution, since they have both the advantages of homogeneous (selectivity, high activity) and heterogeneous (easy separation and recycling) catalysts. Single Rh atoms dispersed on N-doped graphene were synthesized and characterized, obtaining information regarding the chemical and physical structure of the material. Eventually, they were tested as catalysts for C02 activation, carboxylic acid production, hydrogenation and hydrogenolysis reactions
Aliphatische Carbonsauren werden in vielen industriellen Bereichen verwendet und ihre wirtschaftliche Bedeutung nimmt zu. Sie werden derzeit in gror.en Mengen hergestellt, indem das meistens nicht erneuerbare Kohlenmonoxid als C1-Synthon genutzt wird. Kohlendioxid ist ein potenziell umweltfreundlicher, erneuerbarer und abundanter C1-Baustein. Das Ziel dieser Arbeit ist die Entwicklung eines Protokolls zur katalytischen Umwandlung von C02, H2 und sauerstoffhaltigen Substraten, um nützliche Chemikalien, wie Carbonsauren zu erhalten. Zu diesem Zweck wird ein homogenes Rh-Katalysatorsystems zur Herstellung aliphatischer Carbonsauren aus sauerstoffhaltigen Substraten, C02 und H2 untersucht und optimiert. Das System besteht aus Rh-Prakursor, lodid-Additiv und PPh3 als Ligand, die in einem Batchreaktor unter C02 und H2 eingesetzt werden. Die Reaktionsbedingungen wurden für folgende Substratklassen optimiert: primare Alkohole, sekundare Alkohole, Ketone, Aldehyde und Epoxide. Es wurden insgesamt 30 verschiedene Substrate mit Ausbeuten bis zu 80% zu Carbonsauren umgesetzt. Darüber hinaus wurde das System mit einem ,,Statistische Versuchsplanung"-Ansatz untersucht, um zusatzliche lnformationen zu den untersuchten Parametern zu erhalten. Mechanismus und katalytisch aktive Spezies wurden durch verschiedene Experimente wie Konkurrenzreaktionen, NMR- und Markierungsexperimenten untersucht. Dies erschloss den Reaktionsweg, der aus mehreren nicht-katalytischen Transformationen und zwei katalytischen Schritten besteht. Die Reaktion verlauft durch eine ,,reverse Wassergas-Shift-Reaktion" (rWGSR), die C02 und H2 in C0 und H20 umwandelt. Diese werden wiederum bei der nachfolgenden Hydrocarboxylierung des in-situ gebildeten Alkens unter Bildung der Carbonsaure verbraucht. Das katalytische System ahnelt herkômmlichen Rh-Carbonylierungs- und WGSR-Katalysatoren. PPh3 fungiert als zusatzlicher Ligand, der es dem Katalysator ermôglicht unter den gleichen Reaktionsbedingungen mit minimaler Menge toxischen C0 als Liganden zu arbeiten. Zusatzlich wurde ein heterogenes katalytisches System für die gleiche Reaktion untersucht. ,,Single atom catalysts" (SACs) erhalten gror.e Aufmerksamkeit als neue Katalysatorklasse. Sie kombinieren die Selektivitat und hohe Aktivitat homogener und die einfache Abtrennung und Recycling heterogener Katalysatoren Verschiedene Katalysatoren aus auf N-dotiertem Graphen dispergierten Rh-Atomen, wurden synthetisiert und charakterisiert. Dadurch wurden lnformationen über die chemische und physikalische Struktur des Materials gewonnen und als Katalysatoren für C02-Aktivierung, Carbonsauresythese, Hydrierung und Hydrogenolyse getestet