Carbonyl allylation and propargylation reactions have been an important tool for the stereocontrolled formation of carbon-carbon bonds for synthetic chemists. The chiral homoallylic and homopropargylic alcohols obtained from these reactions serve as versatile intermediates for the synthesis of natural and pharmaceutical products. Over the past three decades and continuing on, various synthetic groups around the globe have directed their research towards the efficient synthesis of these chiral moieties. In spite extensive research, asymmetric allylation and propargylation reactions remain an enduring challenge in organic chemistry. Chapter 1 of this thesis describes the first phosphoric acid catalyzed asymmetric allylboration of aldehydes. We found that the BINOL-derived phosphoric acids can efficiently catalyze the allylation reaction under specific conditions. Homoallylic alcohols were obtained in high yields and enantioselectivities from a wide variety of substrates. The optimized conditions were also found to be effective towards crotylboration of aldehydes. Chapter 2 describes the extension of the Br[o/]nsted acid catalyzed allylboration methodology to the propargylation of aldehydes. Homopropargylic alcohols were obtained with high selectivities with TRIP-PA as the catalyst. Synthesis of various important synthetic scaffolds from these chiral alcohols is also presented. The mechanistic insights studied by research groups of Kendall Houk and Jonathan Goodman have been outlined in chapter 3. These studies show that the major isomer is formed via a transition state involving the hydrogen bonding interaction between the hydroxyl group of the catalyst and the pseudoaxial oxygen of the boronate, with a stabilizing interaction of the phosphoryl oxygen to the formyl hydrogen. These insights helped us in developing new and highly efficient boronates that are described in the next chapter.

Nanoparticles are involved in a broad range of applications, including heterogeneous catalysis. Nanoparticles tend to quickly lose their well-defined shapes and facets due to aggregation under duress such as heat. A series of highly studied materials are explored as support materials for nanoparticle supports. These supports include metal-organic frameworks (MOF), graphene oxide (GO), and a MOF-PRGO (partially reduced graphene oxide) hybrid. The inclusion of a support with the palladium increased lifespan of the catalyst by separation of nanoparticles. The choice of support material not only allowed for supporting of palladium nanoparticles, but allowed for rational catalyst synthesis in order to design catalysts with improved catalytic activity. CO oxidation, vanillin hydrogenation, and Suzuki cross coupling were studied. For the CO oxidation reaction, a cerium-based MOF, Ce-MOF, is shown to increase activity of palladium nanoparticles by capturing reactant gases and acting as an oxygen reservoir that cycles between (III) and (IV) states while transferring oxygen to palladium nanoparticles at the Pd/Ce-MOF interface. A hybrid Ce-MOF-PRGO was synthesized to increase the surface area and acidity of Ce-MOF materials and was shown to be active for vanillin hydrogenation. Smaller rod-like Ce-MOF crystals were observed, indicating intercalation of crystals on GO. Zirconium-based MOF UiO-66-NH2 was acidified via incorporation of tungstophosphoric acid (HPW), which increased the selectivity of products by adjusting the mechanistic pathway. GO was partially functionalized with aromatic amines to improve the coupling of bromobenzene and phenylboronic acid. Small amounts of aromatic amines increased the Pd(0) content and decreased nanoparticle size.

This dissertation thesis consists of six chapters. The main focus of this study is the need for understanding the reaction mechanism and intermediates formed on Pt-modified Au surface as anode catalysts in the formic acid fuel cells. Chapter 1 gives an introduction to formic acid and methanol fuel cells, an overview of the current catalysts employed at the anode of the fuel cells, specifically the Pt-modified Au electrodes as potential catalysts and the different deposition methods for preparing this catalytic surface. Information about different electrochemical methods used like cyclic voltammetry and potential step method along with other characterization methods and spectroscopic techniques has also been given. As one of the main methods to characterize the catalysts, Raman and surface enhanced Raman spectroscopy have been discussed in detail. The electrooxidation of formic acid and the nature of the intermediates at a platinum-modified gold surface prepared through spontaneous deposition were characterized using a combination of electrochemistry and in situ surface enhanced Raman spectroscopy (SERS). Spontaneously deposited platinum on gold showed unique high catalytic activity for formic acid electrooxidation. The oxidation current of formic acid is more than five times higher on the Pt-modified gold electrode surface than on a bare Pt surface and about 72 times higher than on a bare Au surface. SERS results reveal the involvement of a novel HCOO− adsorbate at 300 cm−1. Both electrochemical and spectroscopic results suggest that the formic acid electrooxidation takes place by the dehydrogenation pathway involving a low frequency formate intermediate on the Pt-modified gold electrode catalyst. Next, the effect of the deposition solution employed in the spontaneous deposition process was explored and demonstrated to play an important role in catalytic activity of these surfaces. Electrochemical studies show that Pt-modified Au surfaces prepared from bromoplatinate solution are most active in oxidizing formic acid. The second most active surface for formic acid electrooxidation was that from chloroplatinate followed by that from the iodoplatinate solutions. Also, the optimal condition to prepare the most active surface is different for various haloplatinate solutions. In situ surface enhanced Raman spectroscopy (SERS) with potential control revealed the presence of formate at 300 cm-1 as the reaction intermediate in the catalytic processes on all three Pt-modified Au surfaces, but with different potential-dependent behaviors. A clear and transparent bis ethylenedioxy tetrathiafulvalene iodine doped polymer films (BEDO-TTF) was successfully prepared by electrochemical method of cyclic voltammetry. The formation of the transparent films has been linked to the reduction of the iodine species in the film to iodide species giving rise to colorless films. Furthermore, Raman studies have revealed the presence of different iodide species like triodide, pentaiodide and iodine when anodic and cathodic potentials were applied to the films. Also, it was seen that the iodine was complexed with the BEDO-TTF polymer in a stoichiometry of 2.4: 3 [(BEDO-TTF) 2.4I3] at certain concentration in the doping technique. Raman studies were also conducted on single walled carbon nanotubes (SWCNTs) to study the defects introduced during the ball milling procedure and Ru doping. The Raman results reveal that both ball milling procedure and Ru doping leads to the formation of more defects and carbonaceous species in the SWCNTs. Thus, both electrochemical and Raman method were demonstrated to characterize the composition and properties of various materials including conducting polymer and carbon nanotubes

Thesis (Ph.D. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2009.

Hydrogen production from reforming bio-fuels is considered as one of the major ways of utilizing renewable energy sources. Conventionally, most reforming catalysts are noble metal catalysts with high operation temperature above 1000 °C, which result in low thermal efficiency, long start-up time and use of high grade materials. These reasons hinder the development of hydrogen production technology. Novel self-sustained electrochemical promotion (SSEP) catalysts were developed and evaluated for heavy hydrocarbon reforming at relatively low temperatures, 450 to 650 °C. Typically, the SSEP catalysts contain NiO/Ni/CuO/Cu/CeO2 as a selective anodic phase, La0.9Sr0.1MnO3 (LSM) as a selective cathodic phase, yttria stabilized zirconia (YSZ) as an oxygen ion conduction phase, and Ni/Cu also as an electronic conduction phase. The reforming performance of the SSEP catalysts was evaluated using a fixed bed reforming reactor for n-pentadecane. A commercially available noble metal containing catalyst, 2.4 %Pt on CeO2 support, was evaluated using exactly the same method. The following conclusions can be drawn as a consequence of this study: 1) The fuel conversion for the SSEP catalyst was 10 folds of that for the noble metal catalyst and the yield of hydrogen and carbon monoxide for the SSEP catalysts was 100 folds of that for the noble metal catalyst at 450°C. 2) The mechanism of the SSEP catalysts was proved by the experimental results. 3) The study of the effect of each component and the effect of the concentration clearly reveals that the performance of the SSEP catalysts can be further improved to a higher level by many ways. In addition, all the catalysts were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM) and Accelerated Surface Area and Porosimetry Analyzer 2020 (ASAP 2020).

This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.

Denna studie har sammanställt kunskap och erfarenhet från drift av SCR-anläggningar påfartyg med syftet att fastställa de huvudsakliga orsakerna bakom problem som uppstår ikatalysatoranläggningar inom Nord- och Östersjöfarten. Undersökningen utfördes meden kvalitativ intervjumetod. För att få en bra täckning riktade sig undersökningen motbåde rederier och fartyg med erfarenhet av SCR, samt tillverkare av systemen.Intervjuerna utfördes per telefon och analyserades sedan mot frågeställningarna. Iresultatet framkom att ett stort antal anläggningar genomgått modifieringar eftersomproblem uppstått. Ett antal vanligt förekommande problem identifierades. Någrakomponenter är särskilt kritiska att designa och dimensionera, såsom utrusning förureainjicering och magnetventiler för sotblåsning. Vidare framkom att avgastemperatursåväl som bränslet och ureans kvalité var viktiga faktorer för att uppnå god prestandaoch livslängd. Studien visar även att ökad kompetens krävs både hos befintlig ochblivande maskinpersonal för att underhållsåtgärder ska ske på rätt sätt och i rätt tid. Föratt möta eventuella framtida behov av SCR kombinerat med scrubberteknik krävs fortsattteknikutveckling. / The objective of the project was to compile knowledge and experience from the operationof SCR-installations on vessels in order to determine the main causes behind theproblems that arise in the catalyst systems within North- and Baltic Sea shipping. Thestudy was performed as a qualitative interview method. In order to get a good coverage,the study was directed against both companies and ships with experience of SCR andmanufacturers of systems. The interviews were conducted by telephone, and thenanalyzed against the objective. The result showed that a large number of plants haveundergone modifications since problems has occurred. A number of common problemswere identified. The study identified some components that are particularly critical todesign and dimension, such as equipment for urea injection and solenoid valves for sootblowing. It was also found that the exhaust temperature as well as fuel and urea qualitywere important factors in achieving good performance and lifetime. Increasedcompetence is required from both existing and future engine personnel so thatmaintenance can be done the right way and at the right time. To meet future demands ofSCR combined with scrubber technique further technical development is required.

Sol-gel (solution-gelation) method was used to prepare Ni-Ti and Ni-Ti-Al catalysts for reforming of methane with carbon dioxide. This method, after optimizing the parameters such as hydrolysis and acid/alkoxide ratio, is able to make a Ni-Ti catalyst with a surface area as high as 426m2/g when calcined at 473K; but calcination at higher temperature lead to dramatic decrease in surface area. XRD, XPS, TEM and SEM were used to understand this change. Using a packed bed reactor, the catalysts were evaluated with the reforming reaction. It was found that the activity of the Ni-Ti catalyst increases with the Ni loading in the range of 1-10wt%. The reduction temperature has strong effect on activity of the reduced catalyst. Up to 973K, the activity increases with the reduction temperature; but after 973K, the activity decreases and become 0 when the temperature is over 1023K. The Ni-Ti catalyst also deactivated as 15% after 4h of time on stream. The XRD analysis shows that Ti3O5 formed in the catalyst after higher-temperature reduction as well as after the reaction for a period of time. The formation of Ti3O5 may render the catalyst to loss its activity. However, further study is expected to understand the mechanism. TG/DTA analysis shows that both Ni-Ti and Ni-Ti-Al catalysts had carbon deposition; but the latter maintained higher activity in a longer period of time.

In nature, transition metal containing enzymes display many biologically important, attractive and efficient catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in nature, namely, the cytochrome P450 enzymes. Ruthenium porphyrin complexes have been the center of this research and have successfully been utilized, as catalysts, in major oxidation reactions, such as the hydroxylation of alkanes. The present work focuses on photocatalytic studies of aerobic oxidation reactions with well characterized ruthenium porphyrin complexes. The photocatalytic studies of aerobic oxidation reactions of hydrocarbons The photocatalytic studies of aerobic oxidation reactions of hydrocarbons catalyzed by a bis-porphyrin-ruthenium(IV) μ-oxo dimer using atmospheric oxygen as the oxygen source in the absence of co-reductants were investigated. The ruthenium(IV) μ-oxo bisporphyrin (3a-d) was found to catalyze aerobic oxidation of a variety of organic substrates efficiently. By comparison, 3d was found to be a more efficient photocatalyst than the well-known 3a under identical conditions. A KIE at 298K was found to be larger than those observed in autoxidation processes, suggesting a nonradical mechanism that involved the intermediacy of ruthenium(V)-oxo species as postulated. The reactivity order in the series of ruthenium(IV) μ-oxo bisporphyrin complexes follows TPFPP>4- CF3TPP>TPP, and is consistent with expectations based on the electrophilic nature of the ruthenium(IV) μ-oxo bisporphyrin species. The trans-dioxoruthenium(VI) porphyrins have been among the best characterized metal-oxo intermediates and their involvement as the active oxidant in the hydrocarbon oxidation have been extensively studied. In addition to the well-known chemical methods, we developed a novel approach for generation of trans-dioxoruthenium( VI) porphyrins with visible light by extension of the known photoinduced ligand cleavage reactions. A series of trans-dioxoruthenium(VI) porphyrin complexes (6a-d) were photochemically synthesized and spectroscopically characterized by UV-vis, and 1H-NMR.

Due to the petroleum crisis and its consequent emission problems, fuel cells gain an important place in the application of alternative energy. They are a kind of electrochemical device that converts chemical energy directly into electrical energy. The Direct Methanol Fuel Cells (DMFC) use polymer membranes as the electrolyte; the polymer membranes are capable of conducting hydrogen protons. The fuel cell system is still expensive and the proton exchange membrane has contributed significantly the high cost. At present, perfluorosulfonic acid membranes (PFSA) (e.g. Nafion®, by DuPont) have been widely investigated. However they showed high methanol crossover and high swelling that lead low cell efficiency. The main goal of the thesis is to prepare novel proton exchange membranes to apply in the DMFC. PEG and PA membranes compuestas fueron preparadas. Derivados del ácido fosfórico y lignosulfonados (LS) fueron incluidos en la estructura de la PA para actuar como agentes transportadores de protones. El mecanismo de la conductividad de protón es "hopping". Ellos mostraron el más baja del transporte de metanol.Se obtuvieron también membranas híbridas de LS, preparadas mediante la mezcla de los dos polímeros, LS y PSU, siguiendo el método de precipitación en inmersión. Las propiedades electroquímicas de las membranas de LS fueron caracterizadas. Las membranas de LS alcanzaron conductividades de protón aceptables (10-20 mS/cm) con capacidad de intercambio iónico muy baja (IEC) (60 veces más baja que Nafion). "Membrane electrode assemblies" (MEAs) fueron preparadas y sus rendimientos de celda fueron medidos en una celda individual directa de metanol (DMFC). LS membrana is the highlight point of this thesis. It demonstrated the first that LS is a good proton exchange material although it is a waste from the paper industry. It also proved that porous membrane can be used in the DMFC with acceptable proton conductivity and low methanol permeability, which is a totally new way from the existing literatures.The results have been published on international journals and have been presented on international conferences:1. X. Zhang, A. Glüsen, R. Garcia-Valls, Porous Lignosulfonate membrane for direct methanol fuel cells, accepted by Journal of Membrane Science, 20052. X. Zhang, J. Benavente, R. Garcia Valls, Lignin-based Membranes for Electrolyte Transference, Journal of Power Sources, 145 (2005) 2923. X. Zhang, L. Pitol Filho, C. Torras, R. Garcia Valls, Experimental and Computational Study of Proton and Methanol Permeability through Composite Membranes, Journal of Power Sources, 145 (2005) 2234. J. Benavente, X. Zhang, R. Garcia Valls, Modification of Polysulfone Membranes with Polyethylene Glycol and Lignosulfate: Electrical Characterization by Impedance Spectroscopy Measurements, Journal of Colloid and Interface Science, 285 (2005) 273-2805. X. Zhang, R. Garcia-Valls, Proton transport membrane containing lignin compound for direct methanol fuel cells (Poster), 5th Ibero American Congress on Membrane Science and Technology, 2005, Valencia- Spain 6. X. Zhang, J. Benavente and R. Garcia-Valls, Lignin-based membranes for electrolyte transference (Oral presentation), Fuel Cell Science & Technology, Oct. 2004, Munich- Germany. 7. X. Zhang, R. Garcia-Valls, New membranes for Proton Transport in DMFC (Poster), Euromembrane Sep. 2004, ISBN: 3-930400-65-0, p. 64, Hamburg- Germany, 8. X. Zhang, R. Garcia-Valls, Lignosulfonate Application in Proton Transport Membrane (Oral presentation), 2nd World Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, May. 2004, Rome- Italy9. X. Zhang, R. Garcia-Valls, Proton Selective Composite Membrane for Direct Methanol Fuel Cell (Oral presentation), 5th NYM (Network Young Membrains) Oct. 2003, ISBN: 84-688-3132-8, p. 199, Barcelona, Spain10. X. Zhang, R. Garcia-Valls, A. Jiménez-López, E. Rodríguez-Castellón and J. Benavente, Electrical and Chemical Surface Characterization of Lignosulfate/Polysulfone Membranes for Fuel Cells Application, International Conference on "New Proton Conducting Membranes and Electrodes for PEM FCs", Oct. 2005, Assisi, Italy. / Debido a la crisis de petróleo y a los problemas de emisión, las pilas de combustible adquieren un lugar importante en la aplicación de la energía alternativa. Son una clase de dispositivo electroquímico que convierte la energía química directamente en energía eléctrica. Las celdas de combustible de metanol (DMFC) usan membranas de polímero como el electrolito; las membranas de polímero son capaces de transportar protones de hidrógeno. El sistema de la celda de combustible todavía es costoso y las membranas de intercambio de protón han contribuido significativamente para el costo elevado.Actualmente, las membranas de ácido perfluorosulfonico (PFSA) (por ejemplo, Nafion ®, de DuPont) ten sido investigadas extensamente. Sin embargo mostraron alto paso de metanol e alto "swelling" lo que lleva a una eficiencia de celda baja.El objetivo principal de la tesis es preparar membranas de intercambio de protón nuevas para la aplicación en DMFC. Membranas compuestas de PEG y de PA fueron preparadas. Derivados del ácido fosfórico y lignosulfonados (LS) fueron incluidos en la estructura de la PA para actuar como agentes transportadores de protones. El mecanismo de conductividad de protón es "hopping". Ellos mostraron el transporte de metanol más bajo.Se obtuvieron también membranas híbridas de LS, preparadas mediante la mezcla de los dos polímeros, LS y PSU, siguiendo el método de precipitación en inmersión. Las propiedades electroquímicas de las membranas de LS fueron determinadas. Las membranas de LS alcanzaron conductividades de protón aceptables (10-20 mS/cm) con capacidad de intercambio iónico muy baja (IEC) (60 veces más baja que Nafion). "Membrane electrode assemblies" (MEAs) fueron preparadas y sus rendimientos de celda fueron medidos en una celda individual directa de metanol (DMFC).Las membranas de LS son el punto principal de esta tesis. Primero se demostró que LS es un material de intercambio de protón muy bueno aunque sea un residuo de la industria de papel. También se probó que membranas porosas pueden ser usadas en DMFC con una conductancia de protón aceptable y baja permeabilidad de metanol, lo que es una manera totalmente nueva comparada a la literatura existente.Los resultados han sido divulgados en revistas internacionales y han sido presentados en conferencias internacionales:1. X. Zhang, A. Glüsen, R. Garcia-Valls, Porous Lignosulfonate membrane for direct methanol fuel cells, accepted by Journal of Membrane Science, 20052. X. Zhang, J. Benavente, R. Garcia Valls, Lignin-based Membranes for Electrolyte Transference, Journal of Power Sources, 145 (2005) 2923. X. Zhang, L. Pitol Filho, C. Torras, R. Garcia Valls, Experimental and Computational Study of Proton and Methanol Permeability through Composite Membranes, Journal of Power Sources, 145 (2005) 2234. J. Benavente, X. Zhang, R. Garcia Valls, Modification of Polysulfone Membranes with Polyethylene Glycol and Lignosulfate: Electrical Characterization by Impedance Spectroscopy Measurements, Journal of Colloid and Interface Science, 285 (2005) 273-2805. X. Zhang, R. Garcia-Valls, Proton transport membrane containing lignin compound for direct methanol fuel cells (Poster), 5th Ibero American Congress on Membrane Science and Technology, 2005, Valencia- Spain6. X. Zhang, J. Benavente and R. Garcia-Valls, Lignin-based membranes for electrolyte transference (Oral presentation), Fuel Cell Science & Technology, Oct. 2004, Munich- Germany.7. X. Zhang, R. Garcia-Valls, New membranes for Proton Transport in DMFC (Poster), Euromembrane Sep. 2004, ISBN: 3-930400-65-0, p. 64, Hamburg- Germany,8. X. Zhang, R. Garcia-Valls, Lignosulfonate Application in Proton Transport Membrane (Oral presentation), 2nd World Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, May. 2004, Rome- Italy9. X. Zhang, R. Garcia-Valls, Proton Selective Composite Membrane for Direct Methanol Fuel Cell (Oral presentation), 5th NYM (Network Young Membrains) Oct. 2003, ISBN: 84-688-3132-8, p. 199, Barcelona, Spain10. X. Zhang, R. Garcia-Valls, A. Jiménez-López, E. Rodríguez-Castellón and J. Benavente, Electrical and Chemical Surface Characterization of Lignosulfate/Polysulfone Membranes for Fuel Cells Application, International Conference on "New Proton Conducting Membranes and Electrodes for PEM FCs", Oct. 2005, Assisi, Italy La tesis tuvo la cooperación del Forschungszentrum Jülich, Alemania y la doctoranda esta solicitando el titulo de Doctorado Europeo.