Thèses sur le sujet « Sulfure de zirconium »

Biodiesel is currently produced by homogeneous catalysis. More recently however, heterogeneous catalysis is being considered as a cheaper alternative to the homogeneous process. In this research project, heterogeneous catalysts of zirconium oxide were produced by impregnation. Zirconium oxide impregnation with sulfuric acid produced acidic solid catalysts. It was determined that impregnation and calcination at 550^oC (SO₄/ZrO₂-550^oC) produced the best catalyst for palmitic acid esterification with 10 wt % as the optimum concentration in esterification of palmitic acid. SO₄/ZrO₂-550^oC was successfully recycled for eight consecutive runs before permanent deactivation. Its sulfur content was 1.04 wt % using SEM-EDS and 2.05 wt % using XPS for characterization. BET surface area was 90.89 m2/g. The reaction mechanism over Brønsted acid (SO₄/ZrO₂-550^oC) and Lewis acid (Al₂O₃) catalysts obeyed Eley-Rideal kinetics with palmitic acid and methanol adsorbed on the active site respectively. Zirconium oxide was also impregnated with sodium hydroxide to produce basic catalysts. The best catalyst was produced when zirconium oxide was impregnated with 1.5 M NaOH and calcined at 600^oC. Soybean oil was completely converted to biodiesel with 10 wt % catalyst and 1:6 oil to methanol. A mixture of the base catalyst with 30 wt % SO₄/ZrO₂-550^oC effectively converted soybean oil containing 5% oleic acid indicating that this mixture could be used for waste oils. The reaction was first order with respect to triglyceride and second order with respect to methanol. The activation energy was 49.35 kJ/mol and the reaction mechanism obeyed Langmuir-Hinshelwood kinetics.
Master of Science

The threat of chemical warfare agent (CWA) attacks has persisted into the 21st century due to the actions of terror groups and rogue states. Traditional filtration strategies for soldier protection rely on high surface area activated carbon, but these materials merely trap CWAs through weak physisorption. Metal-organic frameworks (MOFs) have emerged as promising materials to catalyze the degradation of CWAs into significantly less toxic byproducts. The precise synthetic control over the porosity, defect density, and chemical functionality of MOFs offer exciting potential of for use in CWA degradation as well as a wide variety of other applications. Developing a molecular-level understanding of gas-MOF interactions can allow for the rational design of MOFs optimized for CWA degradation. Our research investigated the fundamental interfacial interactions between CWA simulant vapors, specifically sulfur mustard (HD) simulants, and zirconium-based MOFs (Zr-MOFs). Utilizing a custom-built ultrahigh vacuum chamber with infrared spectroscopic and mass spectrometric capabilities, the adsorption mechanism, diffusion energetics, and diffusion kinetics of HD simulants were determined. For 2-chloroethyl ethyl sulfide (2-CEES), a widely used HD simulant, infrared spectroscopy revealed that adsorption within Zr-MOFs primarily proceeded through hydrogen bond formation between 2-CEES and the bridging hydroxyls on the secondary building unit of the MOFs. Through the study of 1-chloropentane and diethyl sulfide adsorption, we determined that 2-CEES forms hydrogen bonds through its chlorine atom likely due to geometric constraints within the MOF pore environment. Temperature-programmed desorption experiments aimed at determining desorption energetics reveal that 2-CEES remain adsorbed within the pores of the MOFs until high temperatures, but traditional methods of TPD analysis fail to accurately measure both the enthalpic and entropic interactions of 2-CEES desorption from a single adsorption site. Infrared spectroscopy was able to measure the diffusion of adsorbates within MOFs by tracking the rate of decrease in overall adsorbate concentrations at several temperatures. The results indicate that 2-CEES diffusion through the pores of the MOFs is a slow, activated process that is affected by the size of the pore windows and presence of hydrogen bonding sites. We speculate that diffusion is the rate limiting step in the desorption of HD simulants through Zr-MOFs at lower temperatures. Stochastic simulations were performed in an attempt to deconvolute TPD data in order to extract desorption parameters. Finally, a combination of vacuum-based and ambient-pressure spectroscopic techniques were employed to study the reaction between 2-CEES and an amine-functionalized MOF, UiO-66-NH2. Although the presence of water adsorbed within UiO 66 NH2 under ambient conditions may assist in the reactive adsorption of 2-CEES, the reaction proceeded under anhydrous conditions.
Doctor of Philosophy

Nos travaux de recherche portent sur l’étude théorique de la structure électronique de molécules diatomiques environnementales telles que le monoxyde de cérium et de lutétium (CeO et LuO), le monofluorure de cérium (CeF) et le monosulfure de zirconium (ZrS). Pour réaliser ces études, nous avons eu recours aux méthodes ab initio de chimie quantique qui englobent les méthodes de Hartree-Fock, la méthode du champ auto-cohérent complet de l'espace actif (CASSCF) et les méthodes d'interaction de configuration multi-référence (MRCI) à simple et double excitation. Le progiciel MOLPRO a été utilisé pour les calculs sans et en incluant le couplage spin-orbite, avec la correction de Davidson et en symétrie C2v. Pour chaque molécule des fonctions de bases atomiques spécifiques ont été déterminées et différents modèles théoriques testés. Les courbes d’énergie potentielle des états électroniques 2S+1L+/- et des composantes O+/- ont été tracées sur un intervalle de distance internucléaire conséquent puis ajustées au potentiel de Morse pour en déduire les constantes spectroscopiques (l’énergie électronique à l’équilibre Te, la distance internucléaire d’équilibre Re, les constantes vibrationnelles harmonique ωe et anharmonique ωeXe et, la constante rotationnelle Be). Les moments dipolaires de transition et permanents ont ensuite été calculés pour les états 2S+1L+/-. Pour identifier les composantes O+/-, la composition en pourcentages des états parents S-L+/- ont été obtenus via le calcul tenant compte du couplage spin-orbite.Nos résultats sans et avec spin-orbite sont comparés à ceux trouvés expérimentalement et montrent un bon accord. Globalement, une erreur relative inférieure à 6% est retrouvée pour toutes les constantes spectroscopiques des molécules étudiées
Our research work focuses on the theoretical investigation of the electronic structure of environmental diatomic molecules such as the cerium and the lutetium monoxides (CeO and LuO), the cerium monofluoride (CeF) and the zirconium monosulfide (ZrS). For these studies, we used ab initio quantum chemistry methods which encompass the Hartree-Fock methods, the complete active space self-consistent field (CASSCF) method and the multi-reference configuration interaction methods (ICMR) with single and double excitation. The MOLPRO software package is used to perform the calculations with and without the inclusion of the spin-orbit coupling. The Davidson's correction is considered and the calculations are elaborated in the C2v symmetry. For each molecule, corresponding atomic basis functions are adopted and theoretical models are tested. As result, the potential energy curves are plotted and then fitted to the Morse potential in order to determine the spectroscopic constants (the equilibrium electronic energy Te, the equilibrium internuclear distance Re, the harmonic ωe and anharmonic ωe vibrational constants and the rotational constant Be) of the electronic states 2S+1Lambda+/- and the respective Omega+/- components. The transition and permanent dipole moments are estimated for the Lambda+/- states. The Omega+/- components and the mixing percentages that provide the parental states Lambda+/- are obtained from the ICMRSD(+Q) calculations including the spin-orbit coupling.Our results with and without taking into consideration the spin-orbit effect are very satisfactory. They are compared with the experimental data and show good agreement and in general the relative error is found of less than 6% for all the spectroscopic constants of the studied molecules

La methode sol-gel a ete utilisee pour effectuer la synthese de zro#2 et de composes mixtes sio#2-zro#2 sulfates. L'incorporation du zr dans le reseau de la silice a conduit a des oxydes mixtes sio#2-zro#2 avec un accroissement de l'acidite de brnsted. Ces solides montrent une activite elevee, exprimee par site de zr, dans l'hydroisomerisation du n-hexane. Ceci confirmerait l'hypothese selon laquelle les atomes de zr de faible coordination sont a l'origine des centres acides les plus actifs. En utilisant la methode sol-gel, noua avons developpe une methode de synthese en une seule etape de zircones sulfatees, par incorporation du sulfate dans le reseau du gel de zircone au moment de sa preparation. Ces solides sont catalytiquement actifs pour l'hydroisomerisation du n-hexane a 150c. Dans ces memes conditions une zircone sulfatee preparee en deux etapes selon une methode plus conventionnelle, par sulfatation ulterieure d'un gel de zircone, se revele peu active. Les caracterisations par tpd-nh#3 et spectroscopies drifts et rmn mas #1h montrent que l'activite catalytique est plutot liee a la nature et la force qu'au nombre des sites acides des solides. Ainsi, la presence de groupements -oh, caracterises par une bande ir large a 3280 cm#-#1 et un pic de resonance rmn a 5. 85 ppm, etablissant une liaison de type hydrogene avec les oxygenes superficiels de la zircone est mis en evidence. Ces types de groupements oh absents sur l'echantillon prepare en deux etapes, semblent jouer un role determinant dans les proprietes catalytiques des zircones sulfatees. L'interaction du benzene avec ces solides montre que ces types de -oh possedent une force acide capable d'effectuer l'echange isotopique h-d avec la molecule de c#6d#6 a temperature ambiante.

Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed. In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration. In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning.

QC 20150213

Several types of novel proton exchange membranes which could be used for both direct methanol fuel cells (DMFCs) and hydrogen/air fuel cells were investigated in this work. One of the main challenges for DMFC membranes is high methanol crossover. Nafion, the current perfluorosulfonic acid copolymer benchmark membrane for both DMFCs and hydrogen/air fuel cells, shows very high methanol crossover. Directly copolymerized disulfonated poly(arylene ether sulfone)s copolymers doped with zirconium phosphates and phenyl phosphonates were synthesized and showed a significant reduction in methanol permeability. These copolymer/inorganic nanocomposite hybrid membranes show lower water uptake and conductivity than Nafion and neat poly(arylene ether sulfone)s copolymers, but in some cases have similar or even slightly improved DMFC performance due to the lower methanol permeability. These membranes also show advantages for high temperature applications because of the reinforcing effect of the filler, which helps to maintain the modulus of the membrane, allowing the membrane to maintain proton conductivity even above the hydrated glass transition temperature (Tg) of the copolymer. Sulfonated zirconium phenyl phosphonate additives were also synthesized, and membranes incorporating these materials and disulfonated poly(arylene ether sulfone)s showed promising proton conductivity over a wide range of relative humidities. Single-Tg polymer blend membranes were studied, which incorporated disulfonated poly(arylene ether sulfone) with varied amounts of polybenzimidazole. The polybenzimidazole served to decrease the water uptake and methanol permeability of the membranes, resulting in promising DMFC and hydrogen/air fuel cell performance.
Ph. D.

Les mécanismes contrôlant l'extraction d'ions par flottation ionique à l'aide de tensioactifs ioniques à longue chaîne sont décrits à travers l'étude de la récupération du baryum par le laurylsulfate de NA. Mise au point d'un modèle, appliqué à la récupération du zirconium dans les solutions acides de nitrate d'uranyle

Reformage vapeur selectif du methyl-1-naphtalene en vue d'obtenir le "btx" (benzene-toluene-xylene). Utilisation d'un catalyseur mixte supporte niw/al::(2)o::(3) ou zro::(2). Etude de l'influence de promotteurs alcalins

碩士
國立臺灣大學
環境工程學研究所
94
Two novel magnetic zirconia adsorbents were synthesized employing precipitation (called MZHP) and sol-gel (called MZSG) methods, respectively, in this study. However, only MZSG possessed homogeneous property so that MZSG was the main adsorbent discussed in this study. MZSG was prepared with three sequentical steps: formation of Fe3O4 (magnetitie) as magnetic core via precipitation method; coating of SiO2 (silica) film on magnetite as magnetic carrier with sol-gel method; coating of ZrO2 as magnetic adsorbent via sol-gel method. The physicochemical characteristics of adsorbents, adsorption behavior of various anions, such as F-, SO42-, Cl-, Br- and NO3-, and regeneration processes of aged adsorbents from fluoride adsorption were investigated. In addition, effects of operating parameters, such as ionic strength, pH value and initial concentration were also were also examined. Langmuir and Freundlich isotherms can well describe the adsorption of F- and SO42- on MZSG from solutions, and MZSG possessed high potentical to remove F- and SO42-. However, the adsoption capacities of Cl-, Br- and NO3- were considerably low. There sults indicated MZSG was a good adsorbent for selective adsorption of F- and SO42-.

M. Tech. Metallurgical Engineering.
StudIes the tribocorrosion behaviour of copper-nickel-titanium shape memory composite reinforced by zirconia,synthesized through powder metallurgy process. The research aims to achieve the following objectives: 1. Study the tribocorrosion mechanisms of the composites in NaCl solution (typical human body fluid). 2. Investigate the tribocorrosion mechanisms of the composites in other environments typical of some engineering applications.The proposed study on incorporating zirconia into the matrix NiTiCu through powder metallurgical process and investigations of the phenomenon of joint wear-corrosion synergism occurring in sodium chloride considered typical of human body system and sulphuric acid environment typical of wide range engineering applications is therefore very novel. It is therefore aimed that information on the tribocorrosion behaviour of NiTiCu as well as with zirconia incorporation will form basis for typical compositional formulation approaches for improved bio-tribocorrosion improvement in biomedical applications and actuators used in other engineering applications.

A radio frequency (rf) quadrupole instrument, currently known as an Isobar Separator for Anions (ISA), has been integrated into an Accelerator Mass Spectrometry (AMS) system to facilitate anion–gas reactions before the tandem accelerator. An AMS Cs+ sputter source provided > 15 keV ions that were decelerated in the prototype ISA to < 20 eV for reaction in a single collision cell and re-accelerated for AMS analysis. Reaction based isobar suppression capabilities were assessed for smaller AMS systems and a new technique for gas–phase reaction studies was developed. Isobar suppression of 36S– and 12C3– for 36Cl analysis, and YF3– and ZrF3– for 90Sr analysis were studied in NO2 with deceleration to < 12 eV. Observed attenuation cross sections, σ [x 10^–15 cm^2], were σ(S– + NO2) = 6.6, σ(C3– + NO2) = 4.2, σ(YF3– + NO2) = 7.6, σ(ZrF3– + NO2) = 19. With 8 mTorr NO2, relative attenuations of S–/Cl– ~ 10^–6, C3–/Cl– ~ 10^–7, YF3–/SrF3– ~ 5 x 10^–5 and ZrF3–/SrF3– ~ 4 x 10^–6 were observed with Cl– ~ 30% and SrF3– > 90% transmission. Current isobar attenuation limits with < 1.75 MV accelerator terminal voltage and ppm impurity levels were calculated to be 36S–/Cl– ~ 4 x 10^–16, 12C3–/Cl– ~ 1.2 x 10^–16, 90YF3–/SrF3– ~ 10^–15 and 90ZrF3–/SrF3– ~ 10^–16. Using 1.75 MV, four 36Cl reference standards in the range 4 x 10^–13 < 36Cl/Cl < 4 x 10^–11 were analyzed with 8 mTorr NO2. The measured 36Cl/Cl ratios plotted very well against the accepted values. A sample impurity content S/Cl < 6 x 10^–5 was measured and a background level of 36S–/Cl < 9 x 10^–15 was determined. Useful currents of a wide variety of anions are produced in AMS sputter sources and molecules can be identified relatively unambiguously by stripping fragments from tandem accelerators. Reactions involving YF3–, ZrF3–, S– and SO– + NO2 in the ISA analyzed by AMS are described, and some interesting reactants are identified.