Dissertations / Theses on the topic 'Palladium-based'
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Amandusson, Helena. "Hydrogen extraction with palladium based membranes /." Linköping : Univ, 2000. http://www.bibl.liu.se/liupubl/disp/disp2000/tek651s.htm.
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Elhage, Ayda. "Palladium-based Catalyst for Heterogeneous Photocatalysis." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39388.
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Over the past decade, heterogeneous photocatalysis have gained lots of interest and attention among the organic chemistry community due to its applicability as an alternative to its homogeneous counterpart. Heterogeneous catalysis offers the advantages of easy separation and reusability of the catalyst. Several studies showed that under optimized conditions, efficient and highly selective catalytic systems could be developed using supported metal/metal oxide nanoparticles. In this dissertation, we summarize the progress in the development of supported palladium nanoparticles for different types of organic reactions.
Palladium-decorated TiO2 is a moisture, air-tolerant, and versatile catalyst. The direct excitation of Pd nanoparticles selectively isomerized the benzyl-substituted alkenes to phenyl-substituted alkenes (E-isomer) with complete conversion over Pd@TiO2 under H2-free conditions. Likewise, light excited Pd nanoparticles catalyzed Sonogashira coupling, a C-C coupling reaction between different aryl iodides and acetylenes under very mild conditions in short reaction times. On the other hand, UV irradiation of Pd@TiO2 in alcoholic solutions promotes alkenes hydrogenation at room temperature under Argon. Thus, The photocatalytic activity of Pd@TiO2 can be easily tuned by changing the irradiation wavelength. Nevertheless, some of these systems suffer from catalyst deactivation, one of the main challenges faced in heterogeneous catalysis that decreases the reusability potential of the materials. In order to overcome this problem, we developed an innovative method called “Catalytic Farming”. Our reactivation strategy is based on the crop rotation system used in agriculture. Thus, alternating different catalytic reactions using the same catalyst can reactivate the catalyst surface by restoring its oxidation states and extend the catalyst lifetime along with its selectivity and efficiency. In this work, the rotation strategy is illustrated by Sonogashira coupling –problem reaction that depletes the catalyst– and Ullmann homocoupling –plausible recovery reaction that restores the oxidation state of the catalyst (Pd@TiO2). The selection of the reactions in this approach is based on mechanistic studies that include the role of the solvent and evaluation of the palladium oxidation state after each reaction.
In a more exploratory analysis, we successfully demonstrated that Pd nanoparticles could be supported in a wide range of materials, including inert ones such as nanodiamonds or glass fibers. The study of the action spectrum shows that direct excitation of the Pd nanoparticles is a requisite for Sonogashira coupling reactions. The main advantages of heterogeneous catalysis compared to its homogeneous counterpart are easy separation and reusability of the catalyst.
Finally in order to facilitate catalyst separation from batch reaction and develop a suitable catalytic system for continuous flow chemistry, we employed glass fibers as catalyst support for a wide variety of thermal and photochemical organic reactions including C-C coupling, dehalogenation and cycloaddition. Different metal/metal oxide nanoparticles, namely Pd, Co, Cu, Au, and Ru were deposited on glass wool and fully characterized. As a proof of concept, Pd decorated glass fibers were employed in heterogeneous flow photocatalysis for Sonogashira coupling and reductive de-halogenation of aryl iodides.
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Kumar, Dheeraj. "Synthesis of vinyl acetate on palladium-based catalysts." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1747.
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Li, Guangqin. "Studies on Hydrogen-Storage Properties of Palladium Based Nanomaterials." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/193566.
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Brazeau, Nicolas. "Palladium-Based Catalysts for Ethanol Electrooxidation in Alkaline Media." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32201.
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Direct ethanol fuel cells have been shown to be a good alternative to internal combustion engines in order to reduce the CO2 emissions. In this study, Pd and Pd-based nanocatalysts were deposited on various supports (carbon black, graphene, SnO2, CeO2, TiO2, TiO2 nanotubes and SnO2/TiO2 nanotubes) and their effects on the catalytic properties of the deposited metal for ethanol oxidation in alkaline media are studied. These modifications to the catalytic systems have shown to cause an increase in the reaction rate at the surface of the catalyst and to reduce the overpotential of the ethanol oxidation reaction. Two different promotion mechanisms have been identified. Firstly, the supply of OH- ions at the metal-support interface facilitates the oxidation of adsorbed molecules on neighbouring Pd sites. Secondly, an increase in electron density of Pd nanoparticles with increasing support reducibility modifies the adsorption strength of ethanol and its oxidation intermediates.
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Shao, Zhecheng. "Novel conducting aniline-based materials using advanced palladium catalysts." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540875.
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Galkin, Maxim. "Palladium-catalyzed lignin valorization : Towards a lignin-based biorefinery." Doctoral thesis, Uppsala universitet, Syntetisk organisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265315.
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The work described in this thesis focuses on the cleavage of the β-O-4′ bond, which is the most abundant interunit linkage in the lignin polymer. In the first part, three methods based on palladium catalysis have been developed and their applicability has been verified using lignin model compounds. A transfer hydrogenolysis of the β-O-4′ bond using formic acid as a mild hydrogen donor together with a base. An aerobic oxidation of the benzylic alcohol motif in the β-O-4′ linkage to generate a key intermediate in the cleavage reaction was performed. A redox neutral cleavage of the β-O-4′ bond was accomplished in which no stoichiometric reducing or oxidizing agents were added. In the second part of the thesis, a mechanistic study is presented. The corresponding ketone from a dehydrogenation reaction of the benzylic alcohol motif was identified to be the key intermediate. This ketone and its enol tautomer was found to be responsible for the β-O-4′ bond cleavage reaction under the employed reaction conditions. In the final part of this thesis, the methodologies have been applied to native lignin. The depolymerization reaction was combined with organosolv pulping. This approach was successful, and together with cellulose and hemicellulose, propenyl aryls were generated in excellent yields directly from wood. In this transformation, the lignin derived molecules have been reduced by an endogenous hydrogen donor from the wood.
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Wang, Lixin. "Ferrocene-based molecular electronics and nanomanufacturing of palladium nanowires." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7757.
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Thesis (Ph. D.)--University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Awano, Tomotsugu. "Boron-Based Organic Synthesis via New Palladium-Catalyzed Coupling Reactions." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142247.
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Sun, Desheng. "On the corrosion behavior and biocompatibility of palladium-based dental alloys." Columbus, Ohio : Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1085789516.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xix, 155 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: William A. Brantley, College of Dentistry. Includes bibliographical references (p. 148-155).
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Ling, Chen. "First-principles study of palladium-based metal alloys as hydrogen purification membranes." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31798.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Sholl, David; Committee Member: Agrawal, Pradeep; Committee Member: Alamgir, Faisal; Committee Member: Fuller, Tom; Committee Member: Jones, Christopher. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Cao, Yang 1959. "Influence of structure of palladium and nickel based membranes on hydrogen permeation." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82838.
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The effects of Ni, Pd and Pd77Ag23 alloy membrane microstructures on hydrogen permeation have been investigated using the electrochemical permeation method. Deformation, annealing and electrodeposition have been used to modify the membrane microstructure.The delay for hydrogen permeation in palladium is increased when the degree of deformation increases. The annealing of deformed palladium and Pd 77Ag23 at 250ºC or 850ºC accelerates hydrogen diffusion. The annealed metals release hydrogen more rapidly than the deformed metals. The Pd77Ag23 alloy needs more time to release hydrogen. The solubility increases in both palladium and Pd77Ag23 when deformation increases. A hydrogen-trapping model has been developed, which allows the prediction of trends in the experimental data.
The nickel electrodeposits exhibit fiber texture with two components (100) and (110). Low current densities yield a dominant (100) texture. High current densities develop a strong (110) fiber texture. There is a texture transition region between 30 and 50A/dM2. After annealing at 800ºC for lh, the (100) texture is transformed to (111) texture. Diffusion coefficients increase as texture is transformed from (001) to (011) and (111). The diffusion coefficient of a sample without a dominant texture is lower than the values measured for the samples with (001), (110) and (111) textures. Diffusion coefficients of (001) and (011) polycrystalline membranes are higher than (001) and (011) single crystal membranes. However, in both cases the (011) diffusion coefficient is greater than the (001). By using absorption energies of (001), (011) and (111), the three basic planes in nickel, adsorption energies for other orientations have been estimated using the weighted average method. Absorption energies for different orientations have been shown in the form of an inverse pole figure.
The diffusivity of hydrogen increases six times from single crystal membranes to polycrystalline membranes, and increases six times again from polycrystalline membranes to nanocrystalline membranes. When nanocrystalline nickel membranes have been annealed between 200ºC and 900ºC, they yield a texture change in the nickel membrane from (100) fiber texture to a mixture of (100) fiber texture and (111) texture, and then only one recrystallization (111) texture component is observed. During annealing from 200ºC to 900ºC, a slight increase in the number of high angle (45º--65º) grain boundaries occurs and a percentage of the low (0º--15º) and middle angle (30º--45º) grain boundaries decreases slightly. After annealing at 800ºC and 900ºC, changes in the grain size do not affect the rate of diffusion of hydrogen.
There are four major microstructural factors: deformation defects, grain size, texture and grain misorientation, which affect hydrogen permeation in metals. In the polycrystalline materials studied, the importance of crystal defects, grain size, texture and grain misorientation on hydrogen permeation has been established.
In the developed multilayer membranes when hydrogen charging is from the nano-Ni side of the nano-Ni and poly-Ni composite membrane, the permeation current rises rapidly. When hydrogen charging is from the poly-Ni side of the same composite membrane, the permeation current gradually rises and it takes longer to reach a steady state. The permeability of the nano-poly-Ni membranes charging from the nano-Ni side is eight times higher than that of the same composite membrane charging from the poly-Ni side. The diffusivity of the nano-poly-Ni membranes charging from the nano-Ni side is two times higher than that of the same composite membrane charging from the poly-Ni side. The nano-poly-Ni membranes charging from the nano-Ni side release hydrogen faster than the same composite membrane charging from the opposite side. The diffusivity and permeability of the nano-poly-Ni membrane are smaller than those for a single nano-Ni membrane, but larger than those for a single poly-Ni membrane. The hydrogen permeation model for a bilayer membrane is built to simulate diffusion in the nano-Ni layer and the poly-Ni layer. The model can generate concentration profiles of hydrogen. The experimental data are in good qualitative agreement with the model.
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Saiman, Mohd Izham Bin. "Heterogeneous gold and palladium based catalysts for solvent-free oxidation of toluene." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/35776/.
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Catalyzed oxidation of aromatic hydrocarbons with molecular oxygen has been studied for several decades. For example, toluene can be converted into oxidation products such as benzyl alcohol, benzaldehyde, benzoic acid and benzyl benzoate. At present, the principal industrial production of benzoic acid via the oxidation of toluene involves the use of homogeneous cobalt catalysts in an air pressurized aqueous acetic acid mixture in the presence of Mn ions. However, the use of solvent causes difficulties in the separation of catalysts and products, equipment corrosion, and due to the environmental hazards associated with the use of liquid acids as solvent. Developing solvent free toluene oxidation having great activity has attracted special attention as a promising environmentally friendly reaction. Recently, gold based supported catalyst have been found to be highly effective oxidation catalyst where a number of important discoveries have been made such as in hydrogen peroxide synthesis and selective oxidation of alcohols to aldehydes. As a proof of concept for the following studies, oxidation of toluene and other aromatic hydrocarbons were carried out in round bottom flask with TBHP as oxidant. At mild condition (80 ºC), it was evident that Au-Pd supported catalyst is capable of oxidising aromatics C-H bonds on toluene and derivatives and TBHP as oxidant also have been discovered well in this thesis. The catalyst preparation method was shown to be very important in the formation of active site catalysts. The sol-immobilisation catalyst with a narrow distribution of small particles, was more active than Au-Pd alloy having Au-core palladium shell with PdO dominance on the surface via impregnation catalyst. In addition to that, the choice of support is crucial and this study discovered carbon as a preferred support give enhance on performance activity of toluene. At the same time, the distribution of products can be altered with the choice of preparation methods and support. The synergistic effect of Au and Pd was confirmed by superior catalytic activity compared to monometallic catalyst. Investigations of reaction conditions such as reaction time, reusability, pre-treatment conditions, metal ratio, and mass of catalyst were fully investigated. It was found that the activity and selectivity of the catalyst was highly dependent on these variables. Reaction mechanism was proposed and it was based on catalytic evaluation data. Even though, the proposed mechanism was contradicted by the EPR data study, it was believed that the reactive oxygen species (ROS) was involved in the surface of catalyst and give effect of the catalytic activity. Overall, the oxidation of toluene was successfully studied by using Au-Pd supported catalyst and can not be denied that the importance of TBHP as oxidant involve in this process has been proven.
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Cabaj, Maciej. "Preparation, characterisation and catalytic activity of palladium, silver and silver-based nanoparticles." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648133.
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Fernandez, Alvarez Georgina. "Palladium based catalysts for oxygen reduction in polymer electrolyte membrane fuel cells." Thesis, University of Newcastle upon Tyne, 2011. http://hdl.handle.net/10443/2213.
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An important issue in low temperature polymer electrolyte membrane fuel cells (PEMFC) is the lack of alternative catalysts to platinum for the oxygen reduction reaction (ORR). The high cost and potential limited availability of platinum restricts its long term use for large scale applications in PEMFC. Consequently, there is a great interest in alternative catalysts to platinum for PEMFC. In this research a systematic study of the synthesis and optimization of carbon-supported palladium and palladium alloy nanoparticle electrocatalysts is reported. The catalysts investigated were Pd, Pd-Au, Pd- Co, Pd-Fe and Pd-Ti supported on carbon black (Vulcan XC-72R). At least two different atomic metal to metal ratios for bimetallic catalysts were investigated. All catalysts were initially evaluated for the ORR by voltammetry in a three-electrode cell. Different reducing agents, including hydrogen, ethylene glycol (EG), formaldehyde and sodium borohydride were used for the synthesis of Pd nanoparticles. The use of EG led to Pd nanoparticles with the highest ORR activity; this synthetic method was optimised by adjusting the pH of the system. Pd nanoparticles of approximately 6 nm diameter dispersed on carbon black with exchange current densities for the ORR of ca. 1.0 x 10-11 A cm-2 were obtained. Two synthetic procedures were chosen for the preparation of bimetallic catalysts: simultaneous co-deposition of both metals on the carbon support and deposition of the second metal on carbon-supported Pd. Pd-Co alloy with atomic ratio Pd:Co 4:1 exhibited improved ORR activity compared to Pd/C after being heat treated at 300 ºC under H flow. The effect of heat treatment under H flow on 22 the ORR activity and physicochemical properties was also studied. Pure Pd particles exhibited sintering after heat treatment; the presence of Au, Co and Fe decreased the degree of sintering and the presence of Ti did not affect Pd particle growth. Pd and Pd-Co were evaluated in low temperature hydrogen PEMFC, and Pd was tested as cathode catalysts in hydrogen polybenzimidazole (PBI) based high temperature PEMFC, and in direct methanol fuel cells (DMFC). Optimized Pd and Pd-Co catalysts were tested in a hydrogen low temperature PEMFC and the results were compared to those of the state of the art commercial Pt catalyst. With approximately 1.7 times higher metal loading than Pt (still significantly lower cost) the fuel cell with the Pd cathode gave better performance than that with Pt operating with air at 40 ºC. A comparative study of Pd and Pt was carried out in DMFC using different methanol concentrations and under different operating conditions. At methanol concentrations of 5 M and higher, the Pd cathode based cell performed better than that with Pt at 60 ºC with air. A pseudo one dimensional model for Nafion® -based low temperature hydrogen PEMFC was developed to simulate the influence of cathode catalyst, metal loading, electrode thickness and different operating conditions on the cell voltage and current density output. The model considered mass transport through a thin film electrolyte and through porous media but not gas flow along the channels of the cell. The model closely predicted experimental results at 20 and 40 ºC. Above 40 ºC cell performance did not improve experimentally as was predicted by the model; this lack of improvement was attributed to the decrease of oxygen permeability through Nafion® caused by the lower humidity at higher temperatures. Predicted results showed that enhanced fuel cell performance in the whole current density range could be achieved by increasing metal loading in the cathode whilst maintaining the catalyst layer thickness, which could be practically achieved by increasing the metal content of the carbon-supported catalyst.
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Ab, Rahim Mohd Hasbi. "Heterogeneous gold, palladium and copper based catalysts for liquid phase oxidation of methane." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/55125/.
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The oxidation of lower alkanes especially methane to methanol under mild reaction conditions is one of the most challenging task for industry and academia. At present, indirect utilisation via synthesis gas is the only commercially viable process for methanol production. Therefore, this study intends to investigate the direct oxidation of methane to methanol using a novel low temperature approach. Recently, gold based supported catalysts have been found to be highly effective oxidation catalysts where a number of important discoveries have been made such as in hydrogen peroxide synthesis and selective oxidation of alcohols to aldehydes. Due to these recent advances, further work into the oxidation of carbon-hydrogen bonds especially methane by gold and gold-palladium alloyed nanoparticles was the central topic of this study. As a proof of concept for the following studies, oxidation of primary C-H bonds in toluene and toluene derivatives were carried out in a high pressure stirred autoclave with molecular oxygen as oxidant. It was evident that Au-Pd supported catalyst is capable in oxidising primary C-H bonds on toluene and toluene derivatives at lower temperature with high catalytic activity based on turnover number (TON) compared to available heterogeneous catalysts reported in literature. However, these catalysts are ineffective in the oxidation of methane with oxygen under mild conditions with water as solvent and temperature below 90 °C. In view of this, hydrogen peroxide has been used as oxidant and it was shown that Au-Pd supported nanoparticles are active for the oxidation of methane giving high selectivity to methanol especially in the reactions carried out with hydrogen peroxide generated using an in-situ approach. Methane oxidation reactions were carried out in aqueous medium. The main products were methanol, methyl hydroperoxide and only carbon dioxide as overoxidation product. Investigations of reaction conditions such as concentration of oxidant, reaction time, reaction temperature and pressure of methane were investigated. It was found that the activity and selectivity of the catalyst was highly dependant on these variables. Oxygenate productivity was found to increase by increasing the H2O 2 or H2/O2 concentration and methane pressure. Longer reaction times were detrimental to the methanol selectivity where overoxidation reaction occurred. Interestingly, the Au-Pd catalytic system was able to oxidise methane to methanol at temperatures as low as 2 °C. The applicability of the developed catalytic system was tested on ethane oxidation reaction and it successfully produced ethanol as the major product. The oxygenate productivity was higher as compared to methane due to the solubility factor and the difference in the strength of carbon-hydrogen bonds. The catalyst preparation method and pretreatment were shown to be very important in the formation of active catalysts. The Au-Pd alloy having Au core-palladium shell structure with PdO dominance on the surface and bigger particle size was preferred than analogue catalyst consists of Au and Pd in metallic state with smaller particle size. In addition to that, the choice of support is crucial and this study discovered TiO: as a preferred support where it could assist in stabilising the active hydroperoxy species. The Au:Pd ratio was also found to be an important variable, and equal weight ratio between Au and Pd was shown to be the optimised ratio for methane oxidation either using addition of H2O2 or in-situ H2O2 approach. The synergistic effect of Au and Pd was confirmed by superior catalytic activity compared to monometallic catalysts. Reaction mechanism was proposed and it was based on catalytic evaluation data, stability of the products and oxidation with radical scavengers. The proposed mechanism was in line with the theoretical modelling studies on similar catalytic systems. Optimisation of Au based supported catalyst with copper as co-metal supported on TiO2 was shown to improve the oxygenate productivity and methanol selectivity as well as enhanced the H2O 2 utilisation. In particular, trimetallic 5wt%AuPdl.0wt%Cu/TiO 2 synthesised via impregnation method and calcined in static air gave more than double turn over frequency (TOF = 1.404) with methanol selectivity around 83% as compared to bimetallic 5wt%Au-Pd/TiO2 catalyst (TOF = 0.692, methanol selectivity = 49%). It was suggested in this study that copper is responsible in enhancing the formation of intermediate methyl hydroperoxide species and in some extent to block the non-selective sites for hydrogen peroxide decomposition and hydrogenation by disrupting the surface structure of Au-Pd alloy whilst at the same time maintaining the active sites (Au-Pd alloy) responsible for selective formation of methanol. The oxidation state of copper was shown to be the main factor in controlling the catalytic activity and selectivity. Copper in a combination of multiple oxidation states was preferred than single oxidation state.
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Betham, Michael. "A comparative study of homogeneous and heterogeneous phosphine and carbene based palladium catalysts." Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407617.
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Jones, Simon Philip. "Influence of modifiers on Palladium based nanoparticles for room temperature formic acid decomposition." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:873277f2-c4f7-45b7-a16d-bba064e24bee.
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Heterogeneous catalysts form a highly important part of everyday life, ranging from the production of fertiliser enabling the growth of crops that sustain much of the world's population to the production of synthetic fuels. They constitute a key part of the chemical industry and contribute towards substantial economic and environmental benefits. Heterogeneous catalysts are also believed to have an important role to play in a future hydrogen economy, reducing our requirements for fossil fuels. To this end, formic acid has been proposed as a potential hydrogen storage material for small portable devices. Additionally, formic acid has historically been used as a probe molecule to study catalyst materials and recent developments in the knowledge of its decomposition pathways and the preferred sites of these reactions, establish a good foundation for further study. This work explores a range of novel modification techniques that alter the activity of Pd nanoparticles to decompose formic acid to H2 and CO2. The methods used are the addition of polymers, attaching various functional groups to the surface of the catalyst support and decoration of nanoparticles with sub-monolayer coverages of another metal. Using a range of characterisation methods including FTIR of an adsorbed CO probe, XRD and XPS coupled with computational modelling, it is found that these methods result in some significant electronic and/or geometric alterations to the Pd nanoparticles. For polymer modification, the nature of the pendent group is highly important in determining the effects of the polymer on the Pd particles, with all the tested polymers resulting in varying degrees of electronic donation to the Pd surface. The geometric modifications caused by the polymers also varied with pendent groups; with amine containing pendent groups found to selectively block low coordinate sites, preventing the undesired dehydration of formic acid which results in poisoning of the Pd catalyst by the resulting CO. Attachment of amine groups to the surface of metal oxide catalyst supports, is demonstrated to result in dramatic electronic promotional effects to the supported Pd nanoparticles, and when an amine polymer is attached to the support surface the geometric modification is again observed. Finally decoration of Pd nanoparticles with a sub-monolayer coverage of a second metal is examined, resulting in some similar electronic and geometric effects on Pd nanoparticle surfaces to those observed with polymer modification with corresponding changes in formic acid decomposition activity. Overall, a number of methods are displayed to tune the catalytic activity and selectivity of Pd nanoparticles for formic acid decomposition, resulting in catalysts with some of the highest reported TOF's at room temperature. These modification methods are believed to be potentially applicable to a wide range of other catalytic reactions that operate under mild conditions.
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Nitze, Florian. "Synthesis and characterization of palladium based carbon nanostructure-composites and their clean-energy application." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-68852.
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Carbon nanostructures are a wide field with many applications. The use of carbon nanostructures as support in heterogeneous catalysis is a key development that led together with the use of nanoparticles to a significant cost reduction of catalysts. Catalysts designed in this way are widely applied in fuel cell technologies. For portable devices especially low temperature fuel cells are desirable with low hazards for the user. One technology which fulfills these requirements is the direct formic acid fuel cell (DFAFC). DFAFC have many promising characteristics, such as high electromotive force and easy fuel handling. However, they still suffer from too low power output and lifetime for commercialization. This thesis focusses on two main aspects: the synthesis of carbon nanostructures by chemical vapor deposition (CVD) and their application as catalyst support. The materials are investigated by many different techniques ranging from transmission electron microscopy (TEM) to fuel cell tests. Different carbon nanostructures could be synthesized by catalytic CVD on palladium (Pd) nanoparticles. Multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs) and helical carbon nanofibers (HCNFs) were grown, selectively, dependent on temperature, using acetylene as carbon precursor. Especially HCNF raised further interest due to their unique structure. A growth model for HCNFs was developed based on an anisotropic extrusion model. The synthesis conditions for HCNFs were optimized until an almost 100 % purity with very high efficiency was obtained. The unique helical but fiber-like structure made the material very interesting as support for heterogeneous catalysis. Several catalysts based on Pd nanoparticle decorated HCNFs were developed. The synthesis methods ranged from standard methods like the polyol method to phase-transfer methods. The catalysts showed very promising results for the electro-oxidation of methanol, ethanol and formic acid. This makes them highly attractive for fuel cell applications. The catalysts were tested in DFAFC. The superiority of HCNF-based catalysts is attributed to the good attachment of nanoparticles to the defect-rich and easy to functionalize surface of HCNFs in combination with adequate film forming properties during electrode preparation.Nanostrukturerat kol är ett mycket brett fält med ett stort antal tillämpningar. Användning av kolnanostrukturer som support för heterogena katalysmaterial har tillsammans med utvecklingen av nanopartiklar lett till en avsevärd minskning av kostnaden för katalysatorer. Katalysatorer designade på detta sätt används frekvent i bränsleceller. För portabla tillämpningar är utvecklingen av säkra och miljövänliga lågtemperaturceller mycket viktig. En teknologi som uppfyller dessa kriterier är bränsleceller som drivs med myrsyra (DFAFC). Sådana bränsleceller har många önskvärda egenskaper, såsom en hög elektromotorisk kraft och en enkel hantering av bränslet. Trots dessa goda egenskaper har de också en del nackdelar som hindrar en full kommersialisering. De två mest problematiska är en för låg genererad effekt samt en för kort livslängd på katalysatorerna. Denna avhandling fokuserar på två huvudpunkter som adresserar dessa problem; tillverkning och karaktärisering av kolnanostrukturer producerade med CVD, och deras tillämpningar som support för katalysatorer. Materialen karaktäriseras med en rad olika tekniker, allt från transmission-elektronmikroskopi till bränslecellstester. Olika kolnanostrukturer har syntetiserats med katalytisk CVD på palladium (Pd) nanopartiklar. Produktionen av flerväggiga kolnanorör, kolfibrer och heliska kolnanofibrer har tillverkats med acetylen som kolkälla och genom att variera temperaturen kunde innehållet av olika typer av nanostrukturerat kol kontrolleras. Särskilt stort intresse har de heliska kolnanofibrerna rönt på grund av deras unika struktur. Vi beskriver en tillväxtmekanism baserad på en anisotrop diffusionsmodell. Genom att justera produktionsparametrarna visar vi att heliska kolnanofibrer kunde tillverkas med nära 100 %-ig renhet och hög effektivitet. Den unika heliska och fiberlika strukturen är mycket intressant for tillämpningar som support för heterogena katalysatorer. Ett flertal kompositer för katalytiska tillämpningar har utvecklats baserade på heliska kolnanofibrer, dekorerade med heterogena katalysatorer genom en rad olika kemiska/fysikaliska tekniker. De syntetiserade materialen visar mycket goda katalytiska egenskaper för att oxidera metanol, etanol och myrsyra. Därigenom blir de mycket attraktiva för användning i bränsleceller. Vi korrelerar de goda katalytiska egenskaperna med en bra vidhäftning av nanopartiklarna på de heliska kolnanofibrerna defekter, deras goda ledningsförmåga, bra egenskaper för att förbereda elektroder, samt deras stora yta i förhållande till deras volym och vikt.
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喜教, 鈴間. "Asymmetric addition reaction of organoboronic acid catalyzed by palladium with ferrocene-based phosphine ligand." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10352112/?lang=0, 2010. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10352112/?lang=0.
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Schmid, Thibault E. "Synergism between N-heterocyclic carbene and phosphorus-based ligands in ruthenium and palladium catalytic systems." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3452.
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N-heterocyclic carbenes (NHCs) have become a very popular class of ligands, which has found uses in numerous catalytic applications. The use of such compounds in combination with phosphorus-based ligands within metal complexes has enabled the design of very active yet robust catalytic systems. The following chapters will describe the design of novel well-defined palladium- and ruthenium-based pre-catalysts featuring a NHC and a phosphorus-based ligand, referred at as mixed ligand systems. Such species were employed in catalysis where their properties appeared highly beneficial, uses at low catalysts loading and under harsh conditions were then envisioned. The preparation of a series of well-defined palladium mixed NHC/phosphine species is presented in chapter 2. Their catalytic activity in the aqueous Suzuki-Miyaura reaction of aryl chlorides and boronic acids, using low catalyst loadings, is described. The observation of catalytic activity of the latter systems in the hydration of nitriles prompted us to further investigate this reactivity. This reaction appeared to be operative in the absence of palladium species and could be performed under base-catalysed conditions, which was studied in detail and depicted in chapter 3. The combination of a NHC and a phosphite ligand in ruthenium olefin metathesis pre-catalysts has been underexplored. Preliminary results showed that such species could be readily prepared and presented an unusual geometry and a high catalytic activity. Variations in phosphite-containing ruthenium olefin metathesis pre-catalysts are presented. Chapter 4 describes the investigation of various Schrock carbene moieties in such architectures, as well as their implications in structure and catalysis. Chapter 5 depicts attempts to design olefin metathesis Z-selective pre-catalysts by inserting a chelating NHC moiety within phosphite-containing ruthenium species. This dissertation concludes on the potential of such mixed species in catalysis, and armed with the new knowledge provided by this work, proposes potential developments of such chemistry in the design of always more robust and active catalytic systems.
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Baldoni, Chiara. "Study and development of hydrogen gas sensors based on a conductive polymer functionalized with palladium." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25682/.
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This thesis is focused on the research area of hydrogen gas detection and was developed in collaboration with the company Enereco S.p.A. Hydrogen is considered a promising green energy vector and so a key element for the future global clean energy transition. Despite this, it is an explosive gas with a wide flammability range of [ 4 – 77] % in air that makes mandatory the presence of efficient hydrogen detectors in any location in which the gas is used. This work aims to study and develop a new hydrogen gas sensor based on the conductive polymer poly (3,4 – ethylenedioxythiophene): polystyrene sulfonate, PEDOT:PSS, functionalized with palladium, an efficient hydrogen sensitive material.
Two functionalization processes of the polymer active layer, dip coating and electrodeposition, have been studied and the sensors’ performances upon hydrogen exposure have been evaluated in a two and three – terminal configuration (as Organic Electrochemical Transistors, OECTs) in liquid and gaseous environments. Moreover, the sensors’ performances dependence on the thickness of the PEDOT:PSS film have been analyzed by testing thicknesses of 2 μm, 230 nm and 150 nm. Sensors have been measured following exposure to hydrogen concentrations of 0.36%, 1%, 2%, 3%, 4% and 5% in nitrogen environment. An interpretation of the hydrogen sensing mechanism and a study of the physical and electrical properties of the functionalization process have been realized.
The thinner dip coated PEDOT:PSS two – terminal device in gaseous environment shows the best performances as hydrogen sensor in terms of current variation percentage, ≈70% at 0.36% H2, and, since the sensors’ signal is very stable in pure nitrogen or air environments, it allows to reliably detect in about 30 s a small hydrogen leak. In addition, sensors’ response is not affected by other gases possibly present in ambient air and by ambient air humidity, making them suitable for applications in a real – life environment.
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Khumalo, Zakhelumuzi Mesuli. "Growth and characterisation of platinum and palladium catalysed silicon based nanostructures for nano-device fabrication." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29422.
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This thesis first describes the application of ion beam techniques for the analysis of synthesised metal silicide nano-droplets which are used to synthesis silicon nanowires. This analysis was performed for both Molecular Beam Epitaxy (MBE) and Electron Beam Evaporator (EBE) deposited metal coated silicon substrates. The formation of platinum silicide phases as a function of annealing temperature and time was investigated using in situ real-time Rutherford Backscattering Spectrometry (RBS). In situ real-time RBS revealed the reaction of platinum and silicon to start at about 200 °C and 230 °C, for MBE and EBE coatings respectively, forming platinum silicide phases (Pt2Si and PtSi) in sequence. Further analysis on the EBE deposited coatings using a scanning electron microscope confirmed the formation of droplets at 800 °C. Particle induced X-ray emission analysis showed the variation of platinum concentration, in droplets regions, between 1600 and 2000 counts. The surrounding regions were left almost uncovered due to platinum coating dewetting. Work was then carried out to investigate the growth of silicon nanowires from the produced droplets. Silicon nanowires were observed to form at 800 °C and 1000 °C using pulsed laser ablation and thermal annealing techniques, respectively, for the EBE deposited coatings. Furthermore, MBE was shown to produce self-aligned platinum silicide (PtSi) nanoclusters and nanowires on Si (111) substrates near the eutectic point (T = 978 °C and 67 at% Si) of the platinum silicon system. With an added silicon source in the MBE annealing chamber, the formation of two different silicon steps (straight and wave-like) is reported. The steps determine the position and the shape of the thermomigrating PtSi droplets. Nanoclusters preferentially form in the triple point of the wave-like steps while nanoclusters that form on the straight steps combine and grow into silicide nanowires. We report, for the platinum (MBE deposited) catalysed core-shell silicon nanowires, a reproducible method for eliminating hazardous acids during lithography device preparation with the use of silicide forming metal. With regard to palladium coatings, self-aligned polycrystalline palladium-silicide nanowires and palladium catalysed crystalline core-amorphous shell silicon nanowires were synthesised. The catalyst (palladium) was deposited on a silicon substrate using MBE. As a result of thermal annealing in the silicon flux, self-aligned and fully crystalline palladium-silicide nanowires were synthesised while crystalline core-amorphous shell silicon nanowires were grown when an argon gas was introduced. These results highlight the mechanisms to synthesise specific types of nanowires to be used in a variety of electronic devices depending on their applications. Furthermore, for the application of the produced core-shell nanowires in nanodevice fabrication, we present two approaches to reduce the oxidation of the nanowires during the thermal annealing growth method. The ratios of the amorphous shell to crystalline core on the nanowires produced, from the two methods, are compared and show a remarkable drop in oxide thickness when compared to nanowires fabricated using the current techniques available. In addition, focused ion beam was utilised to contact the oxide reduced nanowires, without first removing the thin oxide shell, for transport measurements. The oxygen reduced core-shell silicon nanowires showed very low electrical resistivity (4×10-1 Ω.cm). The techniques employed presents a new alternative to the production of low cost, high yield, high conducting silicon nanowires that will find use in a range of semiconductor based technology.
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Klaas, Lutho Attwell. "Synthesis and characterization of binary Palladium based electrocatalysts towards alcohol oxidation for fuel cell application." University of the Western Cape, 2018. http://hdl.handle.net/11394/6448.
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Magister Scientiae - MSc (Chemistry)The anode catalyst is one of the important parts of the direct alcohol fuel cell (DAFC); it is responsible for the alcohol oxidation reaction (AOR) takes place at the anode side. Pd has been reported to have good alcohol oxidation reactions and good stability in alkaline solution. Better stability and activity has been reported for Pd alloyed catalysts when compared to Pd. Choosing a suitable alcohol also has an effect on the activity and stability of the catalyst. This study investigates the best catalyst with better AOR and the best stability and also looks at the better alcohol to use between glycerol and ethanol for the five in-house catalysts (20% Pd, PdNi, PdNiO, PdMn3O4 and PdMn3O4NiO on multi walled carbon nanotubes) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectrometry (EIS) and chronoamperometry. HR-TEM and XRD techniques were used to determine the particle size and average particle size, respectively while EDS used to determine elemental composition and ICP was used to determine catalyst loading. It was observed from LSV that PdNiO was the most active catalyst for both ethanol and glycerol oxidation, and it was the most stable in ethanol while PdMn3O4 proved to be the most stable catalyst in glycerol observed using chronoamperometry. The best alcohol in this study was reported to be glycerol having given the highest current densities for all the inhouse catalysts compared to ethanol observed using LSV. From XRD and HR-TEM studies, particle sizes were in the range of 0.97 and 2.69 nm for XRD 3.44 and 7.20 nm for HR-TEM with a little agglomeration for PdMn3O4 and PdMn3O4NiO.
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Sanchez, Trujillo Felipe Juan. "Investigation of the catalytic performance of palladium-based catalysts for hydrogen production from formic acid decomposition." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/117629/.
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The objective of this work is to present formic acid as a suitable compound to be used in a hydrogen economy. Catalytic decomposition of formic acid at mild conditions is evaluated as a model reaction for hydrogen generation, making emphasis on the productivity, reusability of the catalysts, and quantification of concomitant CO evolved from the reaction. Characterisation of the fresh and used catalysts is performed to study the activity/structure relationship and investigate the possible reasons for its deactivation. Computational calculations are used to support experimental data and correlate productivity and CO evolution with the elementary steps of the reaction and the most common surfaces of the catalyst. Synthesis of materials with different surface properties and preparation methods is a fundamental part of this work. In Chapter 3, a commercial Pd/C catalyst is used as a reference to establish the reaction conditions that lead to a kinetically limited reaction. Reusability tests and subsequent characterisation of the used catalyst in conjunction with computational studies are performed to investigate its stability. Continuous flow experiments are carried out as a preliminary test to improve the reusability. Following the identification of the main parameters and characteristics of the catalysts involved in formic acid decomposition, in Chapter 4, materials with different properties (graphitisation degree and acid/base surface functionalisation) are synthesised by two preparation methods (sol-immobilisation and impregnation) using carbon nanofibers as supports. Once the optimal preparation method is identified, a set of parameters are modified in Chapter 5 to investigate the effects it has on the structure and morphology of the catalysts. Besides this optimisation, two supports (activated charcoal and titania) are investigated and an initial study of bimetallic catalysts and its properties is explored. Chapter 6 presents the main consequences of these results and a set of possibilities to continue this research.
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Pritchard, James. "Preparation and characterisation of gold and palladium based catalysts for the direct synthesis of hydrogen peroxide." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/47059/.
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I The research presented in this thesis describes the direct synthesis of hydrogen peroxide from H2 and O2 using supported gold-palladium based catalysts. The direct synthesis process offers a green and sustainable approach compared to the anthraquinone autoxidation (AO) process, which is currently used on an industrial scale to produce >95% H2O2 worldwide. The work presented in this thesis is an attempt to examine the direct synthesis process in terms of determining optimum catalyst compositions for potential scale-up in the near-future. The primary aim of this investigation is centred on catalyst design and characterisation. The first part of this work is a catalyst optimisation study for 2.5 wt% Au-2.5 wt% Pd/TiO2, and involved changing the amount of water used in the catalyst preparation, in this case wet impregnation. It was found that the addition of small amounts of water resulted in approximately 100% enhancement in activity for TiO2-supported catalysts but not for carbonsupported Au-Pd catalysts. The rate of Au/Pd uptake was contrasted and it was determined that the isoelectric point of the support was highly influential. While the activity can be enhanced for TiO2-supported catalysts, both catalyst nanostructure and stability were detrimentally affected by the addition of water during the impregnation step. The second part of this work is focussed on understanding the precise nature of the acid pre-treatment effect, where treatment of a carbon support in dilute nitric acid prior to the impregnation of Au and Pd precursors can result in the complete switching-off of sequential H2O2 hydrogenation activity over the catalyst. Characterisation and heat treatment studies gave an improved understanding of the relationship between Au/Pd and the carbon support. The next part of the study addresses the use of a colloidal immobilisation method to pre-fabricate Au-Pd ‘designer’ nanoparticles onto supports and is accompanied by extensive advanced aberration corrected electron microscopy studies. The effect of acid pre-treating silica based supports is then considered for catalysts prepared by wet-impregnation, specifically the fact that acid pre-treatment of silica is required to induce synergy between Au and Pd metals for the direct synthesis of hydrogen peroxide. The final part of this work considers the effect of introducing a third metal into the catalyst design, specifically the addition of Pt to Au/Pd compositions. An extensive catalyst screening study is undertaken for Au-Pd-Pt/CeO2 catalysts.
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Liu, Meimei. "Development of Sol-Gel Prepared Palladium-Based Sulfated Zirconia Catalysts for Nitrogen Oxides Reduction with Methane." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253296767.
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Shahreen, Laila. "Palladium Doped Titanium Dioxide Nanofiber Based Catalytic Support To Reduce Nitric Oxide Over Carbon Monoxide Gas." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1375362737.
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Fayemi, Omolola E., Adeniyi S. Ogunlaja, Edith Antunes, Tebello Nyokong, and Zenixole R. Tshentu. "The Development of Palladium(II)-Specific Amine-Functionalized Silica-Based Microparticles: Adsorption and Column Separation Studies." Taylor & Francis Group, 2015. http://hdl.handle.net/10962/d1020278.
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The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl6]2− and [PdCl4]2−) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl62− and PdCl4]2−. The adsorption model for both [PtCl6]2− and [PdCl4]2− on the different sorbent materials fitted the Freundlich isotherm with R2 values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl6]2− with 0.5 M of NaClO4 in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.Original publication is available at http://dx.doi.org/10.1080/01496395.2014.978017
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Holmgreen, Erik Michael. "Nitrogen dioxide reduction with methane over palladium-based sulfated zirconia catalysts a componant [i.e. component] of a lean exhaust aftertreatement system /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155739813.
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Kautto, Per. "Influences of palladium ceramics on valuable metal losses to a PbO-SiO2-Sb2O3 based silver smelting slag." Thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81308.
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Silver and palladium can be found in the so called palladium-ceramics which comes from catalyst production. These valuable metals needs to be recovered from these wastes in order to further increase both the environmental and economic sustainability of our society. This material has also been suspected of causing some problems at Boliden’s smelter Rönnskär during the silver smelting. Unfortunately due to the nature of massive economics at work in precious metal production there has not been much published work around this subject. Therefore this works seeks to increase the understanding of how this waste affects the A-slag in the precious metal production at Rönnskär. This work takes a look at how certain fluxes and temperatures affects the slag and metal phases, as well as how increasing the addition of the palladium-ceramic affects the melt. It does so by making screening tests with a basic setup of slag from the process, silver granules and additions of coke and sodium carbonate at different temperatures. The results show that using a reducing environment by adding coke does increase the recovery of the precious metals. Increasing the temperature of the melt also shows an improvement in the recovery of the precious metals. Furthermore the basis to an alternative way of using this material, consisting of smelting it together with silver and fluxing materials has been suggested in this work in order to eliminate the possible problems it causes in the current process.Silver och palladium kan finnas i materialet som kallas katalysatormassa som kommer från framställningen av katalysatorer. Dessa värdefulla metaller måste återvinnas från detta avfall för att öka hållbarheten i vårt samhälle både miljömässigt och ekonomiskt. Materialet har också varit en möjlig orsak till problem vid silversmältningen på Bolidens smältverk, Rönnskär. Tyvärr på grund av den enorma ekonomin kring ädelmetaller och deras produktion har det inte publicerats många artiklar om detta ämne. Därför försöker detta arbete att öka förståelsen av hur detta avfall påverkar A-slaggen hos ädelmetallframställningen på Rönnskär. Detta arbete undersöker på hur olika flussmedel och temperaturer påverkar slaggen och metallfasen, samt hur en ökad mängd katalysatormassa påverkar smältan. Det görs genom att göra flera testsmältor med en bas med slagg från processen, silvergranuler samt tillsatser av koks eller natriumkarbonat vid olika temperaturer. Resultaten visar att användandet av en reducerande miljö genom tillsättningen av koks ökar återvinningen av ädelmetallerna. En ökad temperatur på smältan har också visat på en ökad återvinning. Utöver detta så har grunden till ett alternativt sätt att använda sig av materialet tagits fram. Detta alternativ består av att smälta materialet tillsammans med silver och flussmedel och har tagits fram för att undvika möjliga problem i befintlig process.
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Srinivasan, Guruprasad. "Evaluation of secondary wire bond integrity on silver plated and nickel/palladium based lead frame plating finishes." Diss., Online access via UMI:, 2008.
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Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2008.Includes bibliographical references.
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Ma, Liang-Chih. "Palladium/Alloy-based Catalytic Membrane Reactor Technology Options for Hydrogen Production: A Techno-Economic Performance Assessment Study." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/535.
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Hydrogen (H2) represents an energy carrier endowed with the potential to contribute to the design of a robust and reliable global energy system by complementing electricity as well as liquid fuels use in an environmentally responsible manner provided that the pertinent H2 production technologies (conventional and new ones) can reach techno-economically attractive performance levels in the presence of irreducible (macroeconomic, fuel market, regulatory) uncertainty. Indeed, the role of H2 in the global energy economy is widely recognized as significant in light also of fast-growing demand in the petrochemical and chemical processing sector as well as future regulatory action on greenhouse gas emissions. Pd and Pd/Alloy-based catalytic membrane reactor (CMR) modules potentially integrated into H2 production (HP-CMR) process systems offer a promising technical pathway towards H2 production with enhanced environmental performance in a carbon-constrained world. However, the lack of accumulated operating experience for HP-CMR plants on the commercial scale poses significant challenges. Therefore, any preliminary attempt to assess their economic viability is certainly justified. A comprehensive techno-economic performance assessment framework has been developed for HP-CMRs with CO2 capture capabilities. A functional Net Present Value (NPV) model has been developed first to evaluate the economic viability of HP-CMRs. The plant/project value of HP-CMR is compared to other competing technology options such as traditional coal-gasification and methane steam reforming-based hydrogen production plants with and without CO2 capture. Sources of irreducible uncertainty (market and regulatory) as well as technology risks are explicitly recognized and the effect of these uncertainty drivers on the plant’s/project’s value is taken into account using Monte-Carlo techniques. Therefore, more realistic distribution profiles of the plant’s economic performance outcomes are generated rather than single-point value estimates. It is shown that future regulatory action on CO2 emissions could induce appealing NPV-distribution profiles for HP-CMRs in the presence of uncertainty and technology risks. Finally, the valuation assessment is complemented with a sensitivity analysis for different representative values of the discount rate that span a reasonable range associated with business and financing risks. It apparently indicates that creatively structured financing mechanisms leading to a reduction of the cost of capital/discount rate could induce more appealing economic performance outcomes and valuation profiles. Furthermore, the proposed research work aims at the development of a methodological framework to assess the economic value of flexible alternatives in the design and operation of HP-CMR plants with carbon capture capabilities under the aforementioned sources of uncertainty. The main objective is to demonstrate the potential value enhancement associated with the long-term economic performance of flexible HP-CMR project investments by managing the uncertainty associated with future environmental regulations. Within the proposed context, promising design flexibility concepts for HP-CMR plants are introduced and operational as well as constructional flexibility options are identified and assessed. In particular, operational flexibility will be realized through periodic and temporary shutdowns of the carbon capture unit in response to regulatory uncertainties. Constructional flexibility will be realized by considering the installation of a carbon capture unit at three strategic periods: 1) installation in the initial design phase, 2) retrofitting at a later stage and 3) retrofitting with preinvestment. Monte Carlo simulations and financial analysis will be conducted in order to demonstrate that, in the presence of irreducible uncertainty, design flexibility options could lead to economic performance enhancement of HP-CMR plants by actively responding to the above sources of uncertainty as they get resolved over the plant’s lifetime.
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Martínez, Agramunt Víctor. "Nickel and palladium supramolecular organometallic complexes based on NHC-ligands with polyaromatic moieties for host-guest chemistry studies." Doctoral thesis, Universitat Jaume I, 2020. http://dx.doi.org/10.6035/14104.2020.366143.
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Se ha obtenido una nueva familia de cuatro Complejos Organometálicos Supramoleculares (SOCs) basados en pireno. Dentro de los cuales se ha desarrollado un nuevo receptor de PAH, capaz de discernir entre los diferentes PAH en función de su forma, tamaño, y número de electrones-pi. Hemos desarrollado una estrategia eficiente para la extracción de PAH, que son compuestos tóxicos y carcinogénicos, en disolventes orgánicos. Paralelamente, se han obtenido dos receptores de fulereno, capaces de adaptar su tamaño a la forma del fulereno. Debido a la mayor afinidad respecto a un fulereno específico, mostramos un potencial nuevo método de purificación de fulerenos. Describimos el primer sistema host-guest utilizado como fotosensibilidazor en la generación de oxígeno singlete. Este SOC con fulereno atrapado, fue capaz de oxidar una gran variedad de alquenos utilizando el oxígeno singlete generado a partir de aire a presión atmosférica y luz visible. Finalmente se encapsularon multiples guests.Three nickel-based and one palladium-based supramolecular organometallic cages have been prepared. These four cages are based on a N-heterocyclic carbene ligand with a pyrene tag, that has been key in the subsequent applications of the cage together with the inner cavity. By pi-stacking interactions, it has been possible to encapsulate both polycylic aromatic hydrocarbons and fullerenes. The interest on first group of compounds is based on their accurate toxicity while the fullerenes are interesting due to their added value. It was possible to extract the first group of molecules from an organic media through the encapsulation inside the supramolecular cages. The host-guest adduct formed with fullerenes encapsulated inside the palladium cage was used as photocatalyst of aromatic, cyclic and acyclic substrates via singlet oxygen generation. The same palladium cage was used as receptor for multiple stacks of polyaromatic compounds.
Programa de Doctorat en Ciències
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Kula, Lungelwa Ethel. "Development of a palladium based membrane reactor system for production of ultra-pure hydrogen from liquefied petroleum gas." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2598.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.Hydrogen is widely regarded as the clean energy carrier for future use in both transportation and electricity sectors. It has become an important new focus as an alternative fuel for cleaner energy technologies especially in the Polymer Exchange Membranes (PEM) fuel cells. However, specific technical and marketing demands must be met by a fuel processor for ultra-pure hydrogen production and at a very competitive cost. Liquid Petroleum gas (LPG) is seen as a potential source for low cost hydrogen production due to its relatively high energy density, easy storage and well-established infrastructure for fuel. There is a growing interest in the use of membrane in reaction engineering with the selective separation of the products from the reaction mixture provided opportunities to achieve higher conversion. Membrane separation technologies have potential to reduce operating costs, minimise unit operations and lower energy consumption. The overall goal of this project is to investigate the engineering feasibility associated performance of employing a palladium or palladium alloy membrane reactor for the production of ultra-pure hydrogen from the products of a liquefied petroleum gas (LPG) pre-reformer in determining the optimal process conditions for the production of high purity hydrogen from the LPG feedstock and evaluating of the performance of a Pd-based membrane in relation to maximizing the yield of hydrogen from the feedstock as well as minimizing the CO content of the reformate.
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Dhawan, Rajiv. "The palladium catalyzed multicomponent synthesis of Münchnones : novel one-pot metal catalyzed routes to heterocycles and peptide-based molecules." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85065.
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The purpose of this study was to develop new routes to couple commercially and/or readily available starting materials into biologically relevant structures via one-pot transition metal catalyzed multicomponent coupling reactions. More specifically, we showed that a palladium catalyst could couple imines, acid chlorides and carbon monoxide to directly generate 1,3-oxazolium-5-oxides (Munchnones).Chapter 2 of this thesis describes a new palladium catalyzed multicomponent synthesis of beta-lactams. This reaction was developed based upon previous work in this laboratory, which showed that imidazoline-carboxylates could be generated from coupling two imines, an acid chloride and CO. Mechanistic studies suggested that this product arose from a 1,3-dipolar cycloaddition of an imine-HCl molecule with Munchnone. Removal of this acid combined with adjusting reactant ratios, and the utilization of ligands generated 3-amido substituted beta-lactams in moderate to good yields.
Chapter 3 discusses studies that further explain the origin of the beta-lactam and imidazoline-carboxylate products obtained from catalysis. These studies demonstrate that imidazoline-carboxylates are generated either directly through a 1,3-dipolar cycloaddition reaction of imine-HCl with Munchnone, or indirectly from acid catalyzed rearrangement of an initially formed beta-lactam. In addition, the potential intermediates in the catalytic cycle, including the palladium bound carbonyl complex are completely characterized.
Chapter 4 describes the first example of a metal-catalyzed synthesis of Munchnones. Reaction optimization focused on modifying the catalyst structure to {Pd(Cl)[eta2-CH(R1)NR 2COR3]}2 (formed by pre-treating Pd 2(dba)3 CHCl3 with imine (R1C(H) = NR2) and acid chloride (R3COCl)), increasing CO pressures and employing bromide salts to stabilize the palladium catalyst. These modifications to the reaction enabled the development of a catalytic Munchnone synthesis from imines, acid chlorides, and CO.
Chapter 5 describes the development of a highly modular one-step palladium catalyzed synthesis of pyrroles. This reaction shows that pyrroles can be thought of as being a coupling product of an imine, acid chloride and an alkyne, formed via the in situ trapping of Munchnones with alkynes. In addition, further improvements to the Munchnone synthesis through the utilization of sterically bulky phosphine ligands (i.e. [P(o-Tol) 3]) will be discussed. As well as broadening the scope of accessible Munchnones, this ligand also increased the rate of product formation.
Chapter 6 describes some preliminary studies on the mechanism of Munchnone synthesis. Based upon kinetic data and catalyst resting state analyses, the rate determining step was suggested to possibly be N-acyliminium salt oxidative addition to Pd(0). In addition, crystal structures of {[P( o-Tol)3]Pd(eta2-CH(Tol)N(PMB)COPh)} and its dimeric precursor {Pd(eta2-CH(Tol)N(PMB)COPh)}2 were obtained.
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Chen, Xi. "Application of in-situ IR spectroscopy for the evaluation of new palladium based catalysts for the hydrogenation of anthraquinone." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/43156.
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The anthraquinone process is the most important method in the manufacture of hydrogen peroxide. The hydrogenation of anthraquinone is the key reaction in this method. Because of the instability of the product in this reaction, and the lack of anthraquinone measuring method during the reaction, the mechanism study on this reaction was exclusively based on the hydrogen consumption and the stoichiometry relationship between hydrogen and anthraquinone. Hence we introduce IR in situ detection, which is a powerful technique that has the ability to directly study the mechanism by monitoring not only the anthraquinone consumption but also the product formation in the hydrogenation of anthraquinone. It is worth to notice that this is the first time that the unstable product anthrahydroquinone be detected by the researchers. By using in situ IR and hydrogen consumption measurement orthogonality, a great advantage had been shown not only in the study of the kinetic of the primary hydrogenation of anthraquinone, but also in studying the degradation of the primary product anthrahydroquinone when comparing to the conventional methods. In situ IR shows its potential to be a powerful technique in the mechanism study of reactions that involve intermediate detection. Different supports for palladium loading had be studied for the hydrogenation of anthraquinone. Among these supports, the dealuminated Y zeolite supported Pd catalyst shows a 38% improve in the activity to γ-alumina supported Pd catalyst, the latter is widely used as a commercial catalyst in the hydrogen peroxide manufacture. Besides this, water promotes both the primary hydrogenation rate and degradation rate in the hydrogenation of anthraquinone. Phenyl grafted MCM41 support suppresses the water effect in the degradation, showing a 42% less degradation rate and 15% more selectivity to active quinone when compared to commercial catalyst. The possible explanation is that its hydrophobic property hinder the contact between catalyst and primary product.
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Holmgreen, Erik M. "Nitrogen dioxide reduction with methane over palladium-based sulfated zirconia catalysts: a componant of a lean exhaust aftertreatement system." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1155739813.
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Alrawashdeh, Albara I. S. "From Mono- to Tetraphosphines – A Contribution to the Development of Improved Palladium Based Catalysts for Suzuki- Miyaura Cross Coupling Reaction." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-80110.
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Im ersten Teil der Arbeit wird die Synthese neopentyl- und neosilylsubstituierter Phosphane zur Verwendung als Liganden in katalytisch aktiven Palladiumkomplexen beschrieben. Die Aktivität wurde in der Suzuki-Miyaura Kreuzkupplungsreaktion getestet. Während die neosilylsubstituierten Phosphane 2:1 Addukte (5b und 5d) mit geeigneten Palladiumsalzen bilden, welche moderate Katalyseaktivität zeigen, untergehen die neopentylsubstituierten Komplexe schnelle Cyclometalierungsreaktionen in Gegenwart von Basen und bilden die katalytisch wenig aktiven Palladacyclen (6a, 6e, and 6g). Die deaktivierende Cylometallierung konnte durch Darstellung der Palladiumcomplexe ausgehend von Pd(cod)Cl2 in Abwesenheit von Basen vermieden werden. Die erhaltenen 2:1 Phosphaneaddukte zeigten deutlich verbesserte Aktivität. Daraus wurde geschlossen, dass die Cyclomettalierung als Nebenreaktion eine wichtige Deaktiverungsmöglichkeit darstellt, diese Überlegung veranlasste uns Trialkylphosphane mittlerer Größe, mit Substituenten die nur schwer eine Cyclometallierungen eingehen können zu testen. Die Verwendung der Phosphoniumsalze 4h (R = Cy, R‘ = neopentyl) und 4m (R = iPr, R‘ = CH2Cy) führt zu höheren Aktivitäten in der Suzuki-Miyaura Kreuzkupplung, als bestes Katalysatorsystem hat sich die Kombination aus Pd2(dba)3 oder Pd(OAc)2 und entsprechendem Phosphoniumsalz ergeben. Im zweiten Teil dieser Arbeit werden Synthesen zu neuen biphenylbasierten Diphosphanen (70, 71, 76, and 77) vorgestellt. Die Palladiumkomplexe wurden ebenfalls auf ihre Eignung als Katalysatoren in palladiumkatalysierten Suzuki-Miyaura Kreuzkupplungen getestet und zeigen für diese Klasse von Komplexen gute Aktivität. Das Tetraphosphan 82 wurde für die Synthese des zweikernigen Palladium(II)-komplex 83 eingesetzt. Durch die Koordination des D2h-symmetrischen Tetraphosphanes an die Palladiumatome wird die Symmetrie des Moleküls erniedrigt und folglich erhält man den formal D2-symmetrischen Komplex 83In the first part of this thesis, the synthesis and catalytic activity of neopentyl and neosilyl substituted phosphine palladium complexes is described. The complexes have been tested in the Suzuki-Miyaura cross-coupling reaction. Whereas the neosilyl substituted phosphines form 2:1 adducts (5b and 5d) with Palladium salts which showed moderate activity, the neopentyl complexes quickly undergo cyclometallation in presence of bases to form Palladacycles (6a, 6e, and 6g) which showed only moderate catalytic activity. Cyclometallation could be avoided by the preparation starting from Pd(cod)Cl2 in the absence of bases. The obtained 2:1 phosphine adducts showed superior activity. We concluded that cyclometallation process is an important deactivation pathway, this prompted us to test trialkyl phosphine ligands with medium size but substituents not reliable to cyclometallation. We have been pleased to find that 4h (R = Cy, R‘ = neopentyl) and 4m (R = iPr, R‘ = CH2Cy) showed good activity in the Suzuki-Miyaura cross-coupling reaction. The best results have been obtained by in situ preparation of active catalyst from Pd2(dba)3 or Pd(OAc)2 and the appropriate phosphonium salt. In the second part of this thesis, the first synthesis of a new family of biphenyl based bisphosphine ligands (70, 71, 76, and 77) has been reported. Their palladium complexes were successfully tested as catalyst in the Suzuki cross-coupling reaction. Within the class of bisphosphine based palladium complexes they show good activity in Suzuki-Miyaura cross-coupling reaction. Systematically, was expanded our synthesis strategy and we were able to introduce the first synthesis of a highly symmetric 2,2',6,6'-tetraphosphinobiphenyl. Tetraphosphine 82 was used as ligand in a dinuclear palladium(II) complex 83. Upon complexation the D2h symmetric 2,2’,6,6’-tetraphosphine lead to a chiral D2 symmetric complex 83
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Watson, Junko Mitome. "Spectroscopic characterization of Palladium based catalysts supported on Titania prepared by sol-gel for reduction of Nitrogen Oxides using Methane /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486474078050559.
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Anselment, Timo [Verfasser]. "Development of Novel Phosphine Sulphonate-Based Palladium Catalysts for Ethene Homo- and Co-Polymerisation Reactions with Polar Functionalised Olefins / Timo Anselment." München : Verlag Dr. Hut, 2011. http://d-nb.info/1018981675/34.
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Fashedemi, Omobosede Oluwatoyin. "Microwave-assisted synthesis of palladium-based core-shell nanocatalysts and iron phthalocyanines and their applications in direct alkaline alcohol fuel cells." Thesis, University of Pretoria, 2013. http://hdl.handle.net/2263/79234.
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Palladium-based nano-alloys are well-known for their unique electrocatalytic properties for direct alcohol alkaline fuel cells (DAAFCs). This dissertation describes, for the first time, the synthesis of a novel ternary palladium-based core-shell nanocatalyst containing iron, cobalt and palladium (i.e., FeCo@Fe@Pd) using a microwave-assisted solvothermal technique. This microwave-induced fast and efficient synthesis of sub-10 nm sized palladium-decorated FeCo@Fe core-shell nanoparticles (ca. 3 – 7 nm) from a large-sized FeCo@Fe (0.21 – 1.5 μm) precursor, clearly suggests a ‘top-down’ nanosizing. I have termed this technique the “microwave-induced top-down nanostructuring and decoration (MITNAD)”. The nanocatalysts were successfully supported on commercial carbon (C, Vulcan®) and carboxy- and sulphonate-functionalised multi-walled carbon nanotubes (CNT-OH and CNT-SO3). They were thoroughly characterised using HRTEM, HAADF-STEM, EELS, SAED, FESEM, and EDX. The characterisation clearly proved the elemental composition, nanoparticulate nature, particle size ranges, core-shell nature, and morphology of the nanocatalysts. The nanocatalysts were subjected to electrochemical characterisation to establish their possible application as viable catalysts for DAAFCs. Half-cell anodic oxidation studies were carried out in alkaline medium using both monohydric alcohols (i.e., methanol and ethanol) and polyhydric alcohols (i.e., ethylene glycol and glycerol). Oxygen reduction reaction (ORR) was done in alkaline medium. Electrocatalytic parameters like oxidative onset potential, current response, electron transfer capabilities, Tafel values, ion exchange current densities, catalytic rate constants, and cycling stability as well as alcohol cross-over tests were all determined using various electrochemical techniques. Interestingly, the nanocatalysts exhibited excellent resistance to possible alcohol cross-over during ORR, which gives excellent promise for application in direct alkaline alcohol fuel cells (DAAFC).
In general, the electrochemical performance of the nanocatalysts follows this trend: FeCo@Fe@Pd/CNT-OH >> FeCo@Fe@Pd/CNT-SO3 ≈ FeCo@Fe@Pd/C. Based on the findings in the half-cell studies, a preliminary screening of the FeCo@Fe@Pd/CNT-OH and FeCo@Fe@Pd/C were carried out in the complete single fuel cell membrane electrode assembly (MEA) test. The catalysts were tested in DAAFCs using the above stated four alcohols. Faradaic and Energy efficiency performances were obtained in the monohydric fuel cells, while the fuel cell exhaust components were analysed in the polyhydric fuel cells to determine their capability for complete oxidation of these fuels. Using NMR, the exhaust products were carefully determined and, surprisingly, the FeCo@Fe@Pd/CNT-OH showed excellent selectivity towards complete oxidation of the polyhydric alcohols.
The second aspect of this research deals with the study of the electrocatalytic properties of a novel N4-macrocyclic complex (i.e., metallophthalocyanine, MPc) catalysts for ORR in alkaline fuel cells. A new hydrophobic form of Fe (II) tetrasulfophthalocyanine was synthesized. As a cathode catalyst for fuel cells, its exceptional resistance to high concentrations of methanol during the cathodic reaction has been quite surprising. It was able to selectively continue the ORR even in the presence of high quantities of alcohol in the electrolyte. This clearly proves that a cheap MPc can serve as an alternative to the costly noble metal catalyst for ORR. Further studies using MEA in real fuel cells will be necessary to ascertain this assumption.Thesis (PhD)--University of Pretoria, 2013.
Chemistry
PhD
Unrestricted
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Mketo, Nomvano. "Palladium and copper complexes based on dendrimeric and monofunctional N, N’ chelating ligands as potential catalysts in the oxidative carbonylation of alcohols." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4288.
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Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: In this thesis we describe the synthesis of several new N-(n-propyl)-1-(2-pyridyl and quinolyl)-imine ligands (ML1-ML4) as well as peripheral functionalised iminopyridyl and iminoquinolyl poly(propylene-imine) dendrimeric ligands (DL1-DL8) with a 1,4- diaminobutane core. The dendrimeric ligands were obtained by modification of the peripheral groups of Generation 1 and Generation 2 poly(propylene-imine) dendrimers, (DAB-(NH2)n which are commercially available, with a series of aldehydes. All the ligands were fully characterised by ESI-mass spectrometry, elemental analysis, 1H&13C{1H}-NMR, FT-IR and UV/Vis spectroscopies. These ligands were utilised to synthesise Pd(II) and Cu(I) complexes using appropriate metal precursors. Some of mononuclear complexes, [N-(n-propyl)-(2-pyridyl and quinolyl) methanimine] dichloro Pd(II) complexes (C1-C4) and bis[N-(n-propyl)-(2-pyridyl and quinolyl) methanimine] copper(I) tetrafluoroborate complexes (C14) were structurally characterised. Pd(II) complexes adopted a distorted square-planar geometry around the metal centre while Cu(I) complex exhibit a distorted tetrahedral arrangement around the metal centre. Both Pd(II) and Cu(I) multinuclear complexes (metallodendrimers) were characterised using a range of analytical techniques.
AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van verskeie nuwe N-(n-propiel)-1-(2-piridiel) en kinolielimien ligande (ML1-ML4) sowel as gefunksioneerde imienopiridiel en imienokinoliel poli(propilien-imien) dendrimeriese ligande (DL1-DL8) beskryf. Die dendrimeriese ligande was behaal deur die modifikasie van perifere groepe van Generasie 1 en Generasie 2 poli(propilien-imien) dendrimere met ‘n reeks aldehiede. Alle ligande was volledig deur ESI-massaspektrometrie, elementele analiese, 1H en 13C{1H} – KMR, FT-IR en UV/Sigbare spektroskopie gekarakteriseerd. Hierdie ligande was gebruik om Pd(II) en Cu(I) komplekse te berei om van die gepaste metaal voorlopers te gebruik te maak. Sommige van die mono-kern komplekse, [N-(npropiel)-( 2-piridiel) en kinoliel metanimien] dikloor Pd(II), komplekse (C1-C4) en bis[N-(npropiel)-( 2-piridiel) metanimien] koper(I) tetrafloorboraat, kompleks (C14) was struktureël gekarakteriseerd. Pd(II) komplekse neem ‘n versteurde vierkant valk geometrie om die metaal senter aan, terwyl die Cu(I) kompleks, ‘n versteurde tetrahedriese opset rondom die metaal toon. Beide Pd(II) en Cu(I) multikern komplekse (metaaldendrimere) was deur ‘n verskeidenheid van analitiese tegnieke gekarakteriseerd.
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Brüllingen, Eric [Verfasser], Bernd [Gutachter] Goldfuß, and Axel [Gutachter] Griesbeck. "P-biphenyl-2,2’-bisfenchol phosphite (P-BIFOP-X) based palladium-, copper- and iron-catalysts in enantioselective C–C couplings / Eric Brüllingen ; Gutachter: Bernd Goldfuß, Axel Griesbeck." Köln : Universitäts- und Stadtbibliothek Köln, 2020. http://d-nb.info/1225478499/34.
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Anselment, Timo Martin Jürgen [Verfasser], Bernhard [Akademischer Betreuer] Rieger, and Wolfgang [Akademischer Betreuer] Eisenreich. "Development of Novel Phosphine Sulphonate-Based Palladium Catalysts for Ethene Homo- and Co-Polymerisation Reactions with Polar-Functionalised Olefins / Timo Martin Jürgen Anselment. Gutachter: Wolfgang Eisenreich. Betreuer: Bernhard Rieger." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1019588837/34.
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Anselment, Timo [Verfasser], Bernhard [Akademischer Betreuer] Rieger, and Wolfgang [Akademischer Betreuer] Eisenreich. "Development of Novel Phosphine Sulphonate-Based Palladium Catalysts for Ethene Homo- and Co-Polymerisation Reactions with Polar-Functionalised Olefins / Timo Martin Jürgen Anselment. Gutachter: Wolfgang Eisenreich. Betreuer: Bernhard Rieger." München : Universitätsbibliothek der TU München, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20110811-1079636-1-4.
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Bridget, Tshamano Matamela. "Synthesis & characterization of yttria stabilised zirconia (YSZ) hollow fibre support for Pd based membrane." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/3832.
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Inorganic based membranes which have a symmetric/asymmetric structure have been
produced using an immersion induced phase inversion and sintering method. An organic binder solution (dope) containing yttria-stabilised zirconium (YSZ) particles is spun through a triple orifice spinneret to form a hollow fibre precursor, which is then sintered at elevated temperatures to form a ceramic support. The phase inversion process for the formation of hollow fibre membranes was studied in order to produce the best morphological structure/support for palladium based membranes. The spinning parameters, particle size, non-solvent concentration, internal coagulant as well as the calcination temperature were investigated in order to determine the optimum values. Sintering temperature was also investigated, which would yield a sponge-like structure with an optimized permeability, while retaining a smooth outer surface. The supports produced by phase inversion were characterized in terms of dimension by mercury porosimetry, compressed air permeability, Surface Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The morphology of the produced ceramic support showed either dense or porous characteristics governed by the dynamics of the phase inversion process. The particle size of YSZ was examined in order to decrease the amount of agglomerates in the spinning suspension. Zetasizer tests indicated that at 15 minutes, the ultrasonic bath effectively homogenised the YSZ particles and prohibited soft agglomerates from reforming in the spinning suspension. In this study, an increase in air gap had no noticeable effect on the finger like voids but it had a considerable effect on both the inner diameter (ID) and outer diameter (OD) of the green fibres, while an increase in bore liquid flow rate and extrusion pressure promoted viscous fingering and significant effect on the ID and OD of the fibres, respectively. There was a decrease in porosity and permeability with increasing sintering temperature, addition of water concentration in the spinning suspension and varying Nmethylpyrrolidone
(NMP) aqueous solution of the internal coagulant. The amount of YSZ added to the starting suspension influenced the properties of the support structure. Viscous
deformation was observed for dope with lower particle loading thus resulted in the formation of cracks and defects during sintering.>Magister Scientiae - MSc
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Alrawashdeh, Albara I. S. [Verfasser], Heinrich [Akademischer Betreuer] Lang, Heinrich [Gutachter] Lang, and Wolfgang [Gutachter] Weigand. "From Mono- to Tetraphosphines – A Contribution to the Development of Improved Palladium Based Catalysts for Suzuki- Miyaura Cross Coupling Reaction / Albara I. S. Alrawashdeh ; Gutachter: Heinrich Lang, Wolfgang Weigand ; Betreuer: Heinrich Lang." Chemnitz : Universitätsbibliothek Chemnitz, 2011. http://d-nb.info/1214008410/34.
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Liu, Dan, Xuan Xie, and Rudolf Holze. "Corrosion Stability of Metallic Materials in Dentistry as Studied with Electrochemical Impedance Measurements." Electrochemical Science Group, 2019. https://monarch.qucosa.de/id/qucosa%3A34300.
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The corrosion susceptibility of selected metallic materials frequently employed in prosthetic dentistry has been examined with electrochemical methods. Results have been compared with data derived from breakthrough potential measurements performed with these materials before. Mostly agreement and/or close correlation were found, discrepancies are discussed and tentatively assigned to the different experimental conditions.
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Bush, Alexander Graham. "Part A: Design of new camphor-based hydrazide organocatalysts and their applications to enantioselective Friedel-Crafts alkylations Part B: The development of the palladium catalyzed addition of organoborates to alkynyl esters: Synthesis of trisubstituted olefins as single isomers." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28272.
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Part A. Asymmetric synthesis is a growing field in synthetic and medicinal chemistry. Investigations into the use of organocatalysts to engender chirality into organic molecules is of particular interest. Herein we present the study of the efficiency of camphor-based hydrazide organocatalysts in the asymmetric Friedel-Crafts alkylations of N-methylindole with alpha,beta-unsaturated aldehydes. In addition, the applicability of newly designed second-generation camphor-based hydrazide catalysts will be examined.*
Part B. The synthesis of trisubstituted olefins represents an intriguing target in organic chemistry. However, the stereocontrolled synthesis of trisubstituted olefins can prove to be difficult, as mixtures of isomers are often obtained. A new methodology is presented herein that allows for the synthesis of single isomer trisubstituted olefins by a palladium catalyzed reaction of alkynyl esters with aryl and vinyl boronic acids under mild reaction conditions by using the simple phosphine ligand Et3P. The process provides alpha,beta-unsaturated esters with complete control of the stereochemistry and regiochemistry at the newly formed the double bond.*
*Please refer to dissertation for diagrams.