京都大学 / 新制・課程博士 / 博士(工学) / 甲第24105号 / 工博第5027号 / 新制||工||1784(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 江口 浩一, 教授 安部 武志, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Reaction rates of catalytic cycles over supported metal catalysts are normalized by the exposed metal atoms on the catalyst surface, reported as site time yields which provide a rigorous standard to compare distinct metal surfaces. Defined as the fraction of exposed metal surface atoms to the total number of metal atoms, it is important to measure the dispersion of supported metal catalysts to report standardized rates for kinetic investigations. Multiple characterization techniques such as electron microscopy, spectroscopy and chemisorption are exploited for catalyst dispersion measurements. While effective, electron microscopy and spectroscopy are not readily accessible due to cost and maintenance requirements. Commercial instruments therefore typically rely on chemisorption measurements, but can be cost prohibitive nonetheless, hindering the ability of catalysis research to report rigorous measures of activity. Thus, a dispersion measurement technique based on gas chromatograph (GC) ubiquitous in catalysis research is proposed, based on the principle of dynamic carbon monoxide (CO) chemisorption, where number of exposed metal surface atoms are estimated based on the amount of adsorbed CO. In this technique, the supported metal catalyst is packed into a liner, and inserted in the temperature-controlled inlet of the GC. The catalyst is pre-treated, purged with inert gas, and pulses of known amount of CO are passed through it via an automated sequence. The CO chemically adsorbs on the supported metal catalyst and the unadsorbed CO is detected by the flame ionization detector/methanizer on the GC. The amount of CO adsorbed is estimated by the difference between the amount of CO pulsed and detected, translated to estimate the number of exposed metal surface atoms using a stoichiometry factor. Dispersion measurements for several group VIII metal catalysts were conducted using this technique to demonstrate its applicability across a range of weight loadings and support identities. An agreement between catalyst dispersion measured using this technique and commercially available instruments indicated the reliability of this technique. The amount of dispersed metal as low as 0.02 mg could be estimated by this technique.

This thesis presents the development of bis-amino acid-based spiroligomer applications in the areas of molecular recognition and organocatalysis. By taking advantage of the high degree of functionality and chirality of the unique bis-amino acid building blocks, spiroligomer backbones can be synthesized with predefined shapes, functioning as molecular hosts or as enzyme active-site-like pockets. Firstly, we demonstrated that spiroligomers can be designed to act as anion receptors. We designed a collection of spiroligomers that each display two urea groups. The spiroligomer that displayed the two urea groups in a way that they pointed at each other acts as an anion receptor and binds hydrogen pyrophosphate H2PPi anion (H2P2O72−), as demonstrated by an NMR titration experiment. Other spiroligomers that displayed the two ureas demonstrated a variety of behaviors including self-association and gel formation. In later work we explored the use of spiroligomers to develop catalysts. We attempted to design bipyridine/TEMPO-based bifunctional catalysts but they failed to achieve a faster alcohol oxidation rate than the background reaction. We then demonstrated the successful incorporation of metal-salen functional groups into spiroligomers in Chapter 4. Several bis-amino acid-based metal-salen complexes were synthesized and examined as asymmetric catalysts. Although only moderate enantio-selectivity was detected from synthesized Mn-salen catalyzed epoxidation reactions, it provides the first direct evidence that chiral bis-amino acid backbone can act as a chiral pocket that influence substrate selection and the stereochemical outcome of reactions. / Chemistry

<p> The optimal temperature and catalyst renewal policies which maximize the average profit over a free time period in a tubular reactor with uniform temperature and decaying catalyst for a single irreversible reaction, are sought.</p> <p> In addition, the optimal initial catalyst activity and the optimal total time have been studied.</p> <p> A numerical procedure together with theoretical developments is used to solve the problem for a more general performance index (average profit function) which takes into account the value of the desired product, the cost for the regeneration of the catalyst and the cost of the fresh catalyst.</p> <p> The problem is treated in the format of Pontryagin's Maximum Principle.</p> / Thesis / Master of Engineering (MEngr)

Yes / Several new homemade nano-catalysts are prepared here to reduce sulfur compound found in light gas oil (LGO) utilizing the adsorption desulfurization technique. The effect of different support materials (Fe2O3, Cr2O3 and CdO) having the same particle size (20 nm) on the adsorptive desulfurization performance for loading 5% nickel sulfate (5 wt%NiO) as an active component for each catalyst, is studied. Oxidative desulfurization process (ODS) in a novel digital baffle batch reactor (DBBR) is used to evaluate the performance of the catalysts prepared. Moderate operating conditions are employed for the ODS process. The efficient new nano-catalysts with for the removal of sulfur are found to be 93.4%, 85.6% and 62.1% for NiO/Fe2O3, NiO/Cr2O3 and NiO/CdO, respectively at 175 deg C, 75 min and 2 ml of H2O2. The best kinetic model and the half-live period for the nano-catalysts related to the relevant reactions have also been investigated here.

Yes / Oxidative desulfurization process (ODS), enhanced with a novel metal oxide (Ag ions) as an active component over nano-zeolite that has not been reported in the literature, is used here to improve the fuel quality by removing mercaptan (as a model sulfur compound in the light naphtha). Nano-crystalline (nano-support (Nano-zeolite)) composite is prepared by Incipient Wetness Impregnation method loaded with a metal salt to obtain 0.5, 1 and 1.5% of Ag2O3 over Nano-zeolite. The new homemade nano-catalysts (Ag2O3/Nano-zeolite) prepared are characterized by Brunauer-Emmett-Teller (BET) (surface area, pore volume and pore size), X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscopy (SEM) analysis. The ODS process is then used to evaluate the performance of the catalysts for the removal of sulfur at different reaction temperatures (80-140 °C) and reaction times (30-50 min) in a batch reactor using the air as oxidant. 87.4% of sulfur removal has been achieved using 1% silver oxide loaded on Nano zeolite (1% of Ag2O3/Nano-zeolite) giving a clear indication that our newly designed catalyst is highly efficient catalyst in the removal of sulfur compound (mercaptan) from naphtha. A new mechanism of chemical reaction for sulfur removal by oxygen using the new homemade catalyst (Ag2O3/Nano-zeolite) prepared has been suggested in this study. The best kinetic model parameters of the relevant reactions are also estimated in this study using pseudo first order technique based on the experimental results.

Yes / In order to meet the environmental legislations related to sulfur content, it is important to find an alternative techniques for deep removal of sulfur components from fuels. So, in this study, a novel nano-catalyst based on iron oxide (Fe2O3) as active component prepared over composite support (γ-Alumina + HY-zeolite) is developed here for efficient removal of sulfur compounds from fuel via oxidation process. The precipitation method is employed first to prepare the composite support and then the impregnation method is utilized to generate a novel synthetic homemade (Fe2O3/ composite support) nanocatalysts that has not been developed in the literature (iron oxide over composite support). The characterizations of the prepared catalysts display that the surface area of the catalyst increases with increasing the amount of Y-zeolite in composite support. The effectiveness of the catalysts is tested by utilizing oxidative desulfurization (ODS) operation under several operating conditions. The results of the experimental work show that the activity of oxidative desulfurization enhances with increasing Y-zeolite, temperature, and batch time under moderate operating conditions. The oxidative desulfurization efficiency followed the order: CAT-1 < CAT-2 < CAT-3. The CAT-3 performed the high removal of sulfur compounds (90.73%) at 100 min and 423 K. The best values of the kinetic parameters of the ODS process are then determined based on experimental data and model based techniques within gPROMS package. Finally, the reactor model is used to determine the optimal operating conditions while maximizing the removal of sulfur compounds leading to cleaner fuel. Where, 99.3% of the sulfur removal has achieved at batch time of 190.6 min, temperature of 543.56 K and initial sulfur content at 0.8668 wt% in the presence of CAT-3 based on the optimal kinetic parameters (order of reaction (n) of 1.9865719, activation energy (EA) at 29.942 KJ/mol and pre-exponential factor (ko) with 622.926 wt-0.9865719. min-1).

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24627号 / 工博第5133号 / 新制||工||1981(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 中尾 佳亮, 教授 松原 誠二郎, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Cellulose nanocrystals (CNCs) are nanomaterials that have shown promise as reinforcement filler materials. Their small size, high modulus, and high aspect ratio makes CNCs good reinforcing materials. CNCs are typically introduced into softer polymer materials, which can have incompatible surface chemistry such as aliphatic chains, leading to aggregation and poor reinforcement of the material. The intrinsic hydrophobicity of the CNC surfaces suggests that dispersal into hydrophobic polymer matrices, which the CNCs could potentially reinforce, represent a significant challenge. Therefore, new non-traditional strategies are needed to introduce CNCs into polymer materials. The hydroxyl groups on the surfaces of CNCs can be functionalized using a variety of chemical techniques to yield materials that can interact better with solvents or polymers. Additionally, surface groups can allow the CNCs to react with environmental stimuli (smart materials). The primary focus of this work is the incorporation of CNCs in hydrophobic matrices. Herein we introduce a new method of dispersing CNCs in polyethylene (PE), a substance of legendary hydrophobicity that is also the most common synthetic polymer used in consumer packaging. The prospect of increasing the mechanical strength of PE by incorporating CNC materials as fillers may lead to the possibility of using less polymer to obtain the same strength. This thesis approaches the problem of dispersing CNCs within PE by first functionalizing the CNCs with a catalyst capable of polymerizing ethylene and other α-olefins. The catalyst 1,1'-bis(bromodimethylsilyl)zirconocene dibromide (catalyst 1) is equipped with anchoring groups that are capable of attachment to the surface hydroxyl groups of CNC particles. After immobilizing catalyst 1 onto various CNC samples, introduction of solvent, organoaluminum cocatalyst, and monomer (ethylene alone or ethylene plus 1-hexene) afforded high density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) samples, respectively, containing well-dispersed CNCs as filler materials. Chapter 2 provided important information on the attachment of catalyst 1 to cellulose nanocrystals and the successful polymerization of ethylene from the cellulose nanocrystals. The resulting composite materials showed a in Young's modulus that was three-fold that of PE samples we tested (1600 ± 100 vs 500 ± 30) and about 10% greater relative to a commercial high modulus PE sample (1450 MPa). The increase in Young's modulus along with the lack of macroscopic aggregates led to the conclusion that we have developed a viable method to disperse CNCs in polyolefin matrices. Chapter 3 focused on the dispersal of CNCs in a softer, more pliable polyethylene grade known as linear low-density polyethylene (LLDPE). LLDPE incorporates a small fraction of 1-hexene into polyethylene as a randomly inserted comonomer, giving rise to properties suitable for applications in plastic films and bags among other end uses. Catalyst 1 functionalized CNCs were added to a reaction vessel with both ethylene and 1-hexene to afford LLDPE CNC composites. Different loading of catalyst 1 on CNC aerogels afforded the same amount of catalyst in each reaction but allowed for different CNC loadings in each reaction. The composite materials showed increasing Young's modulus with increasing cellulose nanocrystal content. Chapter 4 describes how CNCs were functionalized with the intention of filling reverse osmosis membrane materials to have surface chemistry that could be impart antibacterial properties and increase flux. CNCs were functionalized with carboxylic acid by 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-mediated oxidation, then amine functionalization by carbodiimide coupling chemistry, and finally functionalized with a zwitterionic group by β-propiolactone ring opening. Amine coupling was confirmed with X-ray photoelectron spectroscopic analysis, and a second carboxylic acid peak was confirmed using infrared spectroscopy. These results were further verified with conductometric titration showing that after each respective reaction there were 1060 mmol kg-1 of carboxylic acid groups, 520 mmol kg-1 of amine groups, and 240 mmol kg-1 of zwitterionic groups. This CNC material was left to undergo future testing for desirable membrane properties. Chapter 5 assesses the possible value in creating a new composite material using a functionalized polynorbornene, poly(5-triethoxysilyl-2-norbornene) (PTESN). The composites were fabricated by using the solvent casting method, dispersing the CNCs in a toluene solution of polymer and drying. The composite materials showed an increase in Young's modulus with increased loading. The 20 wt% CNC in PTESN had a Young's modulus of 970 MPa, a significant increase over the Young's modulus of the polymer lacking the filler (540 MPa). In summary, this dissertation advances new techniques for the incorporation of CNCs as fillers in polymer-based nanocomposites. We are confident that further refinement and development of our results will find wide-ranging application. / Doctor of Philosophy / Cellulose nanocrystals (CNCs) are materials that can be added to polymers to form composite materials having increased stiffness. CNCs have the primary advantages over other filler materials of providing significant reinforcement without changing the color or increasing the density of the overall composite. CNCs are therefore good for designing polymer composites that need to be lightweight and aesthetically pleasing. Packaging materials (especially plastic bags and plastic films) are dominated by polyolefin materials such as polyethylene, which is already lightweight and colorless. The challenge of mixing polyethylene and CNCs is that their surface chemistry is incompatible, "like oil and water." To overcome the natural tendency for the CNC filler material to separate from the surrounding polyethylene matrix, a catalyst was attached to the surface of the CNCs and polymerization ensued from that catalyst leading to a composite material in which tiny CNC particles were trapped in the matrix Good dispersal of the component substances in the composite and of excellent overall reinforcement were proven by physical analysis.

A transient model of the cathode catalyst layer of a proton exchange membrane fuel cell is presented. The catalyst layer structure can be described as a superposition of the polymer membrane, the backing layer, and some additional platinum particles. The model, which incorporates some of the features of the pseudo-homogeneous models currently present in the literature, considers the kinetics of the electrochemical reaction taking place at the platinum surface, the proton transport through the polymer agglomerates, and the oxygen and water transport within the pores as well as the membrane material of the catalyst layer. Due to the lower porosity of this region and the higher liquid water content, the catalyst layer can be current limiting in the fuel cell. Furthermore, since the cost of the catalyst material is critical, it is important to have a model predicting the effective utilization of this catalyst layer as well as one, which gives insights into how it might be improved. Equations are presented for the mass conservation of reactants and products, the electrical and ionic currents, and the conservation of energy. A discussion of a number of the closure relations such as the Butler-Volmer equation employed is included as is a discussion of the initial and boundary conditions applied. The mathematical model is solved using a finite elements approach developed at the I.U.S.T.I. / Master of Science