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Ruthenium-based homogenous catalysis is a broad and extremely useful branch of transition metal catalysis. Surely, the most famous example is olefin metathesis, for which Yves Chauvin, Robert Grubbs and Richard Schrock were awarded the 2005 Chemistry Nobel Prize. Although some of the most well-known catalysts are widely used and considered benchmark catalysts, the research around this topic has not stopped. The modification of known systems to achieve better performance and better understanding of the catalytic mechanism is very important and an example of such modification is reported in this thesis. The newly synthesised catalysts were compared to the parent commercially available catalyst showing better reactivity. Ruthenium catalysis, though, is not limited to olefin metathesis and C-H activation, for example, it has become a useful approach to the functionalisation of organic molecules. In this field, the deuteration of C-H bonds is an interesting transformation, which has many applications. The synthesis of new hydridosilylruthenium complexes and their application in the deuteration of a variety of substrates is reported in this manuscript. The unprecedented synthesis of tetradeuterated Ketoprofene is also reported. Recently, ruthenium-based catalysts have found application in the dehydrogenation of suitable compounds, such as formic acid, ammonia-borane and other hydrogen-rich substances. The driving force behind these discoveries is the use of H2 as an energy vector in place of fossil fuels. A hydrido-ruthenium catalyst was shown to catalyse the decomposition of formic acid in CO2 and H2 and to catalyse the reduction of olefinic substrates. The released CO2 from the reaction did not interfere with the fuel cell due to its inertness. This property makes its employment as C1 source very challenging, although its use would also be extremely attractive because of the abundance of this gas. In these regards, both frustrated Lewis pairs (FLPs) and gold catalysts have shown interesting reactivity in the activation of CO2. A new FLP and a silica supported gold catalyst were synthesised to test them in CO2 activation and the results are reported in this manuscript.

A dissertação está dividida em duas partes. A primeira trata da eletroquímica fundamental utilizando líquidos iônicos como eletrólito suporte e molécula de estudo. São abordados os fenômenos de estabilidade anódica e catódica, com ênfase no mecanismo de degradação do líquido. Além disso, é apresentado um estudo sobre a oxidação eletrocatalítica de hidrogênio nesse ambiente. Quanto a esse aspecto são abordados aspectos mecanísticos e físico-químicos da reação. Técnicas eletroquímicas, modelagem e simulações numéricas foram utilizadas para investigação e hipotetização dos processos. A segunda parte da dissertação consiste do estudo da interação entre óxidos de platina e alguns compostos orgânicos (ácido fórmico, metanol e etanol). O estudo foi realizado em termos da evolução do potencial de circuito aberto com acompanhamento das espécies reativas através da espectroscopia de infravermelho in situ. Os dados obtidos são analisados sob a luz dos conhecimentos levantados pela área de eletrocatálise e sistemas dinâmicos. Modelagem e simulação do sistema permitiram o entendimento do papel individual das diversas etapas envolvidas sobre o comportamento geral do sistema. / This dissertation is divided on two parts. The first one deals with fundamental electrochemistry employing an ionic liquid as supporting electrolyte and as a subject of study by itself. Phenomena like the anodic and cathodic stability of the liquid, emphasizing its degradation mechanism is presented. It is also shown a study of the electrocatalytic oxidation of hydrogen in this environment. For this case, efforts were made to unravel mechanistic aspects of the reaction, as well as physical chemical features. Electrochemical techniques and numerical simulations were used for investigation and understanding of that system. The second part presents a study of the interaction between platinum oxides and some organic compounds, namely: formic acid, methanol and ethanol. The study was performed under open circuit conditions by following the temporal evolution of the potential and also the concentration of some chemical species by using in situ infrared spectroscopy. Data were analyzed under the guide of knowledge constructed by the fields of electrocatalysis and dynamical systems. Modelling and simulation allowed understanding the individual role of the various participants species on the global behavior of the system.

Abstract The thesis consists of seven studies dealing with high resolution vibration-rotation spectra of planar asymmetric tops. Six studies deal with D212CO and D213CO species of the formaldehyde molecule and one study is from DCOOH specie of the formic acid molecule. The measurements were carried out at high accuracy and the rotational analyses of the recorded spectra were performed. The observed anharmonic and Coriolis resonances were taking into account in the analyses. The rotational constants of the present and literature studies were used in evaluation of the planarity defects of formaldehyde and formic acid molecules in the summary part of the thesis. Finally, a semi-experimental structure for formaldehyde was obtained by employing experimental and theoretical data.

Selective corrosion of type 316L austenitic stainless steel welds during the production of organic acids resulted in losses in production due to unscheduled downtimes to perform repairs. Estimated corrosion rates of type 316L filler material welds were an order of magnitude higher than that of the base material. Alternative higher alloyed commercial filler materials were evaluated under actual production conditions. The evaluated filler materials were types 316L, 317L, 309L, 309MoL, 2205, 2507, 625, 825 and 904L. The effect of nitrogen on the corrosion properties of type 309L filler material was evaluated by manipulating the nitrogen concentration of the shielding gas during MIG welding. These changes in nitrogen concentration did not influence the corrosion resistance of the type 309L filler material. No correlation could be established between the corrosion rates, analysed chemical composition of the product and operating temperature during production. In almost all the cases where the chemical composition of the filler material was comparable with that of the base material the corrosion rates of the filler materials were higher than that base material. It might be expected that the ferrite phase with higher molybdenum and chromium should be more corrosion resistant while the austenite should be less resistant. This was, however, not the case with the corrosion of type 309L filler material. It would thus appear that in this case nickel enrichment of the austenite phase had a larger influence on the corrosion resistance of the austenite phase than the chromium and molybdenum had on the corrosion resistance of the ferrite phase. It appears that nickel and molybdenum had the largest contribution to the corrosion resistance of stainless steels welds under these operating conditions. It is, however, believed that a certain minimum concentration of chromium is also required to provide corrosion resistance to these alloys in hot organic acid environments. In contrast with the fact that a substantial alloying content is required to improve corrosion resistance of the filler material, the small difference in composition between ferrite and austenite phases, due to micro segregation, appeared to affect the corrosion resistance on micro scale. This is illustrated by the micrographs, which show corrosion to etch out the dendrite structure. Since the morphology of the austenite and ferrite phases is so similar, it could not always be conclusively established which one of the two phases corroded selectively. Analyses performed on the austenite and ferrite phases did not indicate a concentration difference within the phases itself. However, there were significant differences in the concentration of elements between the phases, with the austenite stabilising elements reporting to the austenite phase and the ferrite stabilizing elements reporting to the ferrite phase, in line with thermodynamic predictions. In the case of the filler materials following the austenite mode of solidification, no significant concentration differences were detected within the matrix. Although all highly alloyed high nickel alloyed filler materials (types 904L, 825 and 625) corroded at a lower rate than the type 316L base material, type 625 filler material was the filler material of choice due to the lack of any pitting of the weld. Pitting was detected in both the 825 and 904L filler materials. Galvanic corrosion was not noted at any of the weld/HAZ interfaces and in no case did the type 316L parent metal adjacent to the weld corrode preferentially to the material further away from the weld. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Materials Science and Metallurgical Engineering / unrestricted

Title: Controllable synthesis, treatment and characterization of anodes for Direct Formic Acid Fuell Cell Author: Mgr. Igor Bieloshapka Department/Institute: Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University Supervisor of the doctoral thesis: Ing. Petr Jiříček, CSc., Institute of Physics of the Czech Academy of Sciences, Division of Solid State Physics, Department of Optical Materials Abstract: At this doctoral thesis, anodes were prepared by novel DC magnetron sputtering technique for direct formic acid fuel cells (DFAFCs). Anode part consisted of support material and catalyst. Carbon cloth and polyaniline were used as a support. Palladium and palladium-copper bimetallic catalysts were deposited on the top of the support. Scanning electron microscope (SEM) and atomic force microscope (AFM) were used for investigation of the morphology of the anodes. Composition and chemical states on the anode part were studied by x-ray photoelectron spectroscopy (XPS). Transmission electron microscope (TEM) together with the XPS technique were used for characterizing graphene oxide (GO) and reduced graphene oxide (RGO) as a promising support for the polymer membrane fuel cells. For decreasing the role of substoichiometric PdCx phase and other contaminations on the surface of...

Title: Controllable synthesis, treatment, and characterization of anodes for Direct Formic Acid Fuel Cell Author: Igor Bieloshapka Department: Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University Supervisor of the doctoral thesis: Ing. Petr Jiříček, CSc., Institute of Physics of the Czech Academy of Sciences, Division of Solid State Physics, Department of Optical Materials Abstract: This doctoral thesis concerns the preparation of anodes with Pd-based catalysts. Anodes were deposited on a support surface with magnetron sputtering. The prepared samples were tested in a direct formic acid fuel cell (DFAFC) station. Polyaniline, graphene oxide (GO) and reduced graphene oxide (RGO) have been additionally investigated as promising support material for polymer membrane fuel cells (FCs). A scanning electron microscope (SEM) and a transmission electron microscope (TEM) were used to observe the morphological differences between the prepared samples. Elemental composition and chemical states on the anode part were studied through X-ray photoelectron spectroscopy (XPS). The results show that the power density of the prepared anodes with 3 nm of palladium thickness is lower only by 30% in comparison with chemically prepared catalysts. The highest power density results were achieved for the...

A systematic silylation approach using mono-, di-, and trichlorosilanes with different alkyl chain lengths was employed to enhance the hydrothermal stability of zeolite Y. DRIFT spectra of the silylated zeolites indicate that the attachment of the silanes takes place at surface silanol groups. Regarding hydrothermal stability under aqueous-phase processing (APP) conditions, i.e., pH ≈ 2, 473 K and autogenous pressure, the selective silylation of the zeolite surface usingmonochlorosilanes has no considerable influence. By using trichlorosilanes, the hydrothermal stability of zeolite Y can be improved significantly as proven by a stability test in an aqueous solution of 0.2M levulinic acid (LA) and 0.6M formic acid (FA) at 473 K. However, the silylationwith trichlorosilanes results in a significant loss of total specific pore volume and total specific surface area, e.g., 0.35 cm3 g−1 and 507m2 g−1 for the silylated zeolite Y functionalized with n-octadecyltrichlorosilane compared to 0.51 cm3 g−1 and 788 m2 g−1 for the parent zeolite Y. The hydrogenation of LA to g-valerolactone (GVL) was conducted over 3 wt.-% Pt on zeolite Y (3PtY) silylated with either n-octadecyltrichlorosilane or methyltrichlorosilane using different reducing agents, e.g., FA or H2. While in the stability test an enhanced hydrothermal stability was found for zeolite Y silylated with n-octadecyltrichlorosilane, its stability in the hydrogenation of LA was far less pronounced. Only by applying an excess amount of methyltrichlorosilane, i.e., 10 mmol per 1 g of zeolite Y, presumably resulting in a high degree of polymerization among the silanes, a recognizable improvement of the stability of the 3 PtY catalyst could be achieved. Nonetheless, the pore blockage found for zeolite Y silylated with an excess amount of methyltrichlorosilane was reflected in a drastically lower GVL yield at 493 K using FA as reducing agent, i.e., 12 vs. 34% for 3PtY after 24 h.

No description available.

Surface catalysed reactions play an important role in chemical productions. Developments of catalyst requiring high activity whilst improving on product selectivity can potentially have a profound effect in the chemical industry. Traditional catalyst modifications were focused on tuning the size, shape and foreign metal doping to form well defined metal nanoparticles of unique functionalities. Here, we show new approach to engineering of metal nanocatalysts via a subsurface approach can modify the chemisorption strength of adsorbates on the surface. Carbon modified nanoparticles were synthesised using glucose to stabilise Pd nanoparticles at a molecular level. Upon heat treatment, the carbonised glucose encapsulated the Pd nanoparticles with carbon atoms take residence in the octahedral holes (15 at.%). These materials were tested in liquid phase stereoselective hydrogenations of 3-hexyn-1-ol and 4-octyne. The former has importance in the fragrance industry towards the production of leaf fragrance alcohol. It was shown for the first time that the geometrically and electronically modified Pd with interstitial carbon atoms reduced the adsorption energy of alkenes, ultimately leading to higher reaction selectivity. Boron modified Pd nanoparticles was synthesised using BH₃.THF in the liquid phase. The material possess high B interstitial saturation (20 at.%), which can be synthesised for the first time below 100°C. These materials were tested in the liquid phase selective hydrogenation of various alkynes and 2-chloronitrobenzene, of which the latter has importance in the pesticides industry. Kinetic modelling on the hydrogenation of 4-octyne suggests these subsurface occupied B does play a pivotal role on increasing the reaction selectivity, as removal of these species lead to decreased selectivity. Au nanoparticles were synthesised and characterised using H¹³COOH NMR. The new liquid NMR characterisation method is successfully applied to examine the chemisorption strength of metal nanoparticles. An attempt to synthesise PVP capped B modified Pd nanoparticles with the above NMR characterisation was investigated. It is believed the examples of subsurface atom modifications as shown here may offer future catalyst developments in this area.