Olefin metathesis is an outstandingly versatile methodology for the catalytic assembly of carbon-carbon bonds. Metathesis methodologies have been widely embraced since the advent of easily-handled ruthenium catalysts. However, industrial implementation has lagged. Problems of reliability and productivity arising from catalyst decomposition have impeded broad uptake of metathesis in process chemistry. Such challenges also hamper deployment of metathesis in forefront applications such as chemical biology. Better understanding of the mechanisms by which catalysts decompose can thus improve performance in demanding applications, as well as providing guidelines for informed process and catalyst design. Oxygen is often viewed as a relatively innocuous contaminant in reactions promoted by these late transition metal catalysts. Indeed, multiple reports comment on the desirability and operational simplicity of metathesis in air. We suspected, however, that deleterious impacts of O2 may be masked by the high catalyst loadings typically deployed in such reports. The first part of this thesis focuses on examining the robustness of leading metathesis catalysts toward oxygen. Systems examined include the classic, dominant N-heterocyclic carbene (NHC) derivatives, as well as recent breakthrough analogues containing cyclic alkyl amino carbene (CAAC) ligands. Both are shown to be decomposed by oxygen, but the CAAC catalysts are found to be not only more productive, but significantly more O2-tolerant. This is important as it overturns the widespread belief that high catalyst activity is invariably a trade-off against higher sensitivity. Studies of the initial oxidation event for the second-generation Grubbs catalyst RuCl2(H2IMes)(PCy3)(=CHPh) suggest that [2+2] cycloaddition of O2, as well as bimolecular decomposition of the four- coordinate species generated by PCy3 oxidation, account for ca. 90% of the observed decomposition. A previously-proposed pathway involving attack of O2 at the benzylidene ligand appears to be a minor contributor. In Chapter 3 of this thesis, a new strategy for inhibiting catalyst decomposition is examined. Specifically, cationic metathesis catalysts were encapsulated within a supramolecular resorcinarene capsule, which self-assembles around the catalysts in water-saturated toluene. Encapsulation nearly doubles RCM yields relative to the parent, neutral catalyst in water-saturated toluene. The increased catalyst productivity is enabled by site-isolation of the catalyst within the capsule, which prevents bimolecular decomposition, and by the hydrophobic nature of the capsule interior, which limits decomposition by water. A final study focuses on attempts to identify a more robust catalyst via ligand redesign. Examined for this purpose are recently reported, electron-rich pyridinylide aminophosphines (PyAPs; these take the general form R2P–N=Ar), which exhibit enhanced s-donor properties relative to NHCs. Strategies for incorporation of PyAP ligands into Ru metathesis catalysts are developed, and the catalytic activity of these species is described. PyAP catalysts are found be significantly less active than the corresponding NHC catalysts, despite their higher donicity. Poor performance results from facile catalyst decomposition. Where the N=Ar group lacks substituents at the ortho sites, o- metalation enables decomposition of the precatalyst. More problematically, the nitrogen atom appears to participate in nucleophilic attack on the key, metathesis-enabling [Ru]=CHR functionality, limiting the potential use of this class of phosphine in metathesis. Criteria for the development of more robust second-generation phosphine catalysts are proposed.

With the increase in production of biodiesel, a glut of glycerol has resulted in the world market. Glycerol, once a valuable chemical, has become a recalcitrant byproduct. It is also a potential renewable feedstock for hydrogen production. This study is focused on hydrogen production from glycerol steam reforming. During the initial stage, effect of process variables, such as system pressure (1-5 atm), temperature (327 – 727 oC), and water/glycerol molar ratio of (1:1-9:1) on hydrogen yield was investigated using a thermodynamic analysis. The equilibrium concentrations of different compounds were calculated by the method of Gibbs free energy minimization. The study revealed that the best conditions for producing hydrogen is at temperature > 627 oC, atmospheric pressure, and water/glycerol molar ratio (WGMR) 9:1. As a part of catalysts screening, 14 catalysts were prepared on monoliths and tested for their activity. Effects of those catalysts on hydrogen selectivity and glycerol conversion in temperatures ranging from 600-900 oC were discussed. Ni/Al2O3 and Rh/CeO2/Al2O3 were found to be the best performing catalysts based on hydrogen selectivity and glycerol conversion under the conditions investigated in this study. Also, the effect of WGMR, metal loading, and feed flow rate (FFR) were analyzed for the two best performing catalysts. Subsequently, effect of CeO2, MgO, and TiO2 supported Ni catalysts on hydrogen production from glycerol was studied. Effects of reaction temperature, FFR, and WGMR on hydrogen selectivity and glycerol conversion were also analyzed. Ni/CeO2 was found to be the best performing catalyst when compared to Ni/MgO and Ni/TiO2 under the experimental conditions investigated. The activation energy of glycerol reforming reaction was found to be 103 kJ/mol, and the reaction order with respect to glycerol was 0.23 over Ni/CeO2 catalysts based on the power law.

The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play a critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition, polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers. / Master of Science

This proposes a model for a microwave heated fluidized bed by ceramic pellets to highlight the possibility to obtain a temperature gradient between the gas and the pellets. After a review of the recent work on microwave effects on chemical reactions, a short description of fluidization is given for a better understanding of the phenomena, followed by a development of a model of the heat transfer processes taking place in the fluidized bed. A parameter study describes the trends that should be expected despite the numerous restrictions and assumptions. Also, a set of parameters is proposed for optimal conditions that are close to the real conditions often encountered in practice. Numerous figures and tables are added, completing the main argument advanced in the thesis: it is possible to obtain a temperature difference between the gas and the pellets of a chemical bed reactor heated by microwaves by carefully choosing the following parameters: pellet diameter, bed height, gas velocity, pellet density and electric field. / Master of Science

No / Discovery of new catalysts for demanding aqueous reactions is challenging. Here, we describe methodology for selection of catalytic phages by taking advantage of localized assembly of the product of the catalytic reaction that is screened for. A phage display library covering 109 unique dodecapeptide sequences is incubated with nonassembling precursors. Phages which are able to catalyze formation of the self-assembling reaction product (via amide condensation) acquire an aggregate of reaction product, enabling separation by centrifugation. The thus selected phages can be amplified by infection of Escherichia coli. These phages are shown to catalyze amide condensation and hydrolysis. Kinetic analysis shows a minor role for substrate binding. The approach enables discovery and mass-production of biocatalytic phages.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18290号 / 工博第3882号 / 新制||工||1596(附属図書館) / 31148 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 秋吉 一成, 教授 澤本 光男, 教授 松原 誠二郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

"Catalytic growth of Carbon Nanotubes (CNT) provides important advantages of controlling their diameters and possibly chirality. Our work involved growing CNT on model and supported catalyst by catalytic decomposition of carbon source such as benzene, methane and propylene. On supported catalyst, iron nitrate was deposited on alumina and reduced to form metallic iron clusters. These were reacted at 700 - 950 C under varying benzene concentrations. Multi Walled CNT (MWNT) grew below 800 C and Single Wall CNT (SWNT) are observed at 850 C and above as confirmed by TEM and Raman. Model catalysts were studied by producing CNT from ferrocene which acted as the carbon and catalyst source on Silica/Si (100). Large yield of MWNT was observed at 900 C. MWNT grew perpendicular to the model support as seen by SEM. In another model catalyst study, iron salt clusters were deposited on silica/Si (100) by spin coating, controlling their diameters by solution concentration and speed of spinning. Agglomeration of clusters at high temperatures produces only MWNT on silica/Si (100). Cluster agglomeration can be reduced with strong support metal interaction such as with alumina. We deposited alumina on silica/Si (100) by atomic layer deposition, with conformal coatings on surface and low relative roughness. Alumina film was stable under reaction temperatures of 900 C. Cluster deposition on alumina by spin coating was difficult because of different surface acidity compared to silica. Clusters on alumina did not agglomerate at high reaction temperatures. We report effect of parameters such as the temperature of reaction, conditions of pretreatment such as reduction and oxidation of catalyst precursor, type of precursor, type of carbon source, and type of support material on growth of CNT. The role of spin coating in controlling the diameter of salt clusters deposited is discussed. We also report deposition of alumina on top of silica/Si (100) by atomic layer deposition and the effect of deposition and calcination temperatures on the alumina film integrity."

No description available.

abstract: The utilization of solar energy requires an efficient means of its storage as fuel. In bio-inspired artificial photosynthesis, light energy can be used to drive water oxidation, but catalysts that produce molecular oxygen from water are required. This dissertation demonstrates a novel complex utilizing earth-abundant Ni in combination with glycine as an efficient catalyst with a modest overpotential of 0.475 ± 0.005 V for a current density of 1 mA/cm<super>2</super> at pH 11. The production of molecular oxygen at a high potential was verified by measurement of the change in oxygen concentration, yielding a Faradaic efficiency of 60 ± 5%. This Ni species can achieve a current density of 4 mA/cm<super>2</super> that persists for at least 10 hours. Based upon the observed pH dependence of the current amplitude and oxidation/reduction peaks, the catalysis is an electron-proton coupled process. In addition, to investigate the binding of divalent metals to proteins, four peptides were designed and synthesized with carboxylate and histidine ligands. The binding of the metals was characterized by monitoring the metal-induced changes in circular dichroism spectra. Cyclic voltammetry demonstrated that bound copper underwent a Cu(I)/Cu(II) oxidation/reduction change at a potential of approximately 0.32 V in a quasi-reversible process. The relative binding affinity of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) to the peptides is correlated with the stability constants of the Irving-Williams series for divalent metal ions. A potential application of these complexes of transition metals with amino acids or peptides is in the development of artificial photosynthetic cells. / Dissertation/Thesis / Doctoral Dissertation Biological Design 2014