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This thesis is missing page 89, no other copy of the thesis has this page. -Digitization Centre / The vanadium mediated electrolysis of hydrogen sulphide has been demonstrated in a bench top pilot plant. The first step in the process is the absorption of hydrogen sulphide from a sour gas stream into an carbonate buffered liquor, pH 9. In the presence of citrate ion, the vanadium (V) in the liquor is reduced to vanadium (IV) by (hydro) sulphide ion, which is oxidized to yellow elemental sulphur. The vanadium (IV) rich solution is then pumped to an electrolysis cell where the vanadium (IV) is reoxidized to vanadium (V) and protons are reduced to elemental hydrogen. The reoxidized liquor is then returned to the absorber. The oxidation of vanadium (IV) to vanadium (V) in the liquor was found to be electrochemically irreversible. The current efficiency for vanadium (IV) oxidation exceeded 90 percent. The voltametric half-wave potential at platinum, was 0.34 v (vs Ag/AgCl, sat. KC1). With the slippage of sulphide or polysulphide ion into the electrolysis cells, the electrodes became passivated with electrodeposited sulphur. This resulted in an increased anode potential demand which may promote the electrosynthesis of oxygen and sulphate ion. The oxidation of vanadium (IV) at the anode releases 4 protons and acidifies the solution adjacent the electrode surface. This may induce carbon dioxide evolution and inhibit the discharge of vanadium (IV). The inhibition appears as a suppressed current and an anodic shift in the voltametric half-wave potential. This inhibition can be minimized at high pH levels in the liquor, buffer capacity., and citrate concentration. The irreversibility of the vanadium (IV/V) couple allows electrolysis cells to be constructed without a cell membrane. This is a significant advantage which will offset the cost of large electrolysis cells. Large cells will enable high energy efficiencies to hydrogen production to be realized. Energy efficiencies greater than 0.28 m3 /kwhr may be indicated. This study features a critical review of sulphide electro-oxidation, a factorial designed voltametric experiment, and a newly identified catalytic response in the polarographic analysis of sulphide ion. / Thesis / Master of Science (MS)

Several new families of organic acceptors that are candidates as building blocks of molecule-based ferrimagnets were synthesized and characterized. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The magnetic networks were synthesized by reacting each acceptor with V(CO)6. The magnets synthesized in this study were characterized using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Although some combinations failed to yield magnetically ordered materials, others exhibited ordering temperatures in the range of 95 K – 260 K. The ordering temperatures and saturation magnetizations were compared among families of acceptors and correlated with individual properties of the acceptors such as reduction potential and structure. / Doctor of Philosophy / Several new families of organic molecules have been created and examined for use as building blocks of molecule-based magnets. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The 3-D magnetic scaffoldings were created by combining an individual organic molecule in one of the families listed above with vanadium. The magnets created in this study were examined using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Some of the combinations of the organic molecules with vanadium failed to result in a 3-D magnetic scaffolding and showed no magnetic properties. Others showed magnetic properties in the below certain temperatures in the range of 95 K – 260 K. The magnetic properties were compared among families of molecules and correlated with individual properties of each molecule such as electronic effects and structure.

[EN] The project of this Ph.D. thesis is based on a co-supervised collaboration between Università di Bologna, ALMA MATER STUDIORUM (Italy) and Instituto de Tecnología Química, Universitat Politècnica de València ITQ-UPV (Spain). This Ph.D. thesis is about the synthesis, characterization and catalytic testing of complex mixed-oxide catalysts mainly related to the family of Hexagonal Tungsten Bronzes (HTBs). These materials have been little explored as catalysts, although they have a great potential as multifunctional materials. Their peculiar acid properties can be coupled to other functionalities (e.g. redox sites) by isomorphous substitution of tungsten atoms with other transition metals such as vanadium, niobium and molybdenum. In this PhD thesis, it was demonstrated how it is possible to prepare substituted-HTBs by hydrothermal synthesis; these mixed-oxide were fully characterize by a number of physicochemical techniques such as XPS, HR-TEM, XAS etc. They were also used as catalysts for the one-pot glycerol oxidehydration to acrylic acid; this reaction might represent a viable chemical route to solve the important issue related to the co-production of glycerin along the biodiesel production chain. Acrylic acid yields as high as 51% were obtained and important structure-reactivity correlations were proved to govern the catalytic performance; only fine tuning of acid and redox properties as well as the in-framework presence of vanadium are fundamental to achieve noteworthy yields into the acid monomer. The overall results reported herein might represent an important contribution for future applications of HTBs in catalysis as well as a general guideline for a multifaceted approach for their physicochemical characterization. / [ES] El proyecto de esta tesis doctoral está basado en un convenio de cotutela firmado por la Università di Bologna, ALMA MATER STUDIORUM (Italia) y el Instituto de Tecnología Química, Universitat Politècnica de València ITQ-UPV (España). La presente tesis doctoral muestra el estudio sobre la síntesis, caracterización y ensayos catalíticos de materiales complejos a base de óxidos mixtos relacionados con la familia de los bronces de tungsteno hexagonales. Estos materiales han sido utilizados minoritariamente como catalizadores, aunque tienen un potencial importante come materiales multifuncionales. Sus peculiares propiedades acidas pueden ser acopladas con otras características (por ejemplo, sitios oxido-reductivos) a través de la substitución isomórfica de átomos de tungsteno con otros metales de transición como vanadio, niobio y molibdeno. En esta tesis doctoral se ha demostrado como sea posible preparar bronces de tungsteno hexagonales substituidos a través de síntesis hidrotermal; estos óxidos mixtos fueron caracterizados por completo empleando numerosas técnicas de caracterización quimico-fisicas como XPS, HR-TEM, XAS etc. Fueron también utilizados como catalizadores para la síntesis directa de acido acrílico de glicerol; esta es una reacción que puede representar una solución viable para el problema relacionado con la coproducción de glicerina a lo largo de la cadena productiva del biodiesel. Rendimientos en acido acrílico hasta el 51% fueron obtenidos y importantes relaciones entre las estructuras y la actividad catalítica fueron demostradas ser determinantes para el proceso catalítico; solo la afinación de las propiedades acidas y redox tanto como la presencia en-red de vanadio son esenciales para conseguir rendimientos relevantes en el monómero acido. En general, los resultados presentados en esta tesis doctoral pueden ser una contribución relevante para futuras aplicaciones de los bronces de tungsteno hexagonales en catálisis y también como una guía general para un completa caracterización quimico-fisica de estos oxidos. / [CA] Esta tesi doctoral està basada en un conveni de cotutela signat per la Università di Bologna, ALMA MATER STUDIORUM (Italia) i el Institut de Tecnologia Química , Universitat Politècnica de València ITQ-UPV(Espanya). La present tesi doctoral estudia la síntesis, caracterització i assajos catalítics de òxids mixtes relacionats amb la família dels bronzes de tungstèn hexagonals. Aquestos materials presenten un gran potencial com materials multi funcionals, encara que no han sigut molt emprats com catalitzadors. Les propietats àcides particulars de aquestos materials poden ser potenciades amb altres característiques (per exemple, llocs redox) mitjançant la substitució isomòrfica d'àtoms de tungstèn amb altres metalls de transició com vanadi, niobi i molibdè. En aquesta tesi doctoral es demostra com es possible sintetitzar bronzes de tungstèn hexagonals substituïts a partir de síntesis hidrotermal. Aquestos òxids mixtes han segut caracteritzats emprant diverses tècniques de caracterització físico-químiques com XPS, HR-TEM, XAS, etc... Per altra part, s'han utilitzat com catalitzadors per a la síntesis directa de àcid acrílic a partir de glicerol, aquesta reacció pot representar una solució viable per al problema relacionat amb la coproducció de glicerina al llarg de la cadena productiva de biodiesel. S'han obtingut rendiments a àcid acrílic del 51%. A més, s'han observat importants relacions entre les estructures i la activitat catalítica, les quals han sigut determinants per al procés catalític. El ajust de les propietats àcides i redox i la presència en red de vanadi són essencials per a obtindre rendiments rellevants en el monòmer àcid. En general, el resultats presentats en aquesta tesi doctoral poden ser una contribució rellevant per a futures aplicacions del bronzes de tungstèn hexagonal en catàlisis i també com una guia general per a una completa caracterització físico-química d'aquestos òxids. / Chieregato, A. (2015). Glycerol oxidehydration to acrylic acid on complex mixed-metal oxides [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/49558

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Gelöster Wasserstoff in Metallen führt in vielen Fällen zu einer Reduzierung der Güte von mechanischen Eigenschaften. Dies äußert sich auf vielfältige Weise und wird unter dem Begriff Wasserstoffversprödung zusammengefasst. Für ein grundlegendes Verständnis dieses Phänomens müssen die Vorgänge im Metall auf mikroskopischer Skala ergründet werden. Im Rahmen dieser Arbeit wurde daher ein Aspekt der Wasserstoffversprödung, die Interaktion von Wasserstoff mit Versetzungen, näher untersucht. Zur Untersuchung des Einflusses von Wasserstoff auf die Versetzungsbildung wurden verschiedene Verformungsexperimente an Palladium und Vanadium durchgeführt. Prinzipielle Vorgänge der Defektbildung wurden durch Versuche an einzelnen Versetzungen unter Verwendung von Nanoindentation und Zugexperimenten im ETEM durchgeführt, um einen breiten Überblick zu erlangen. Zusätzlich wurden zum besseren Verständnis der Vorgänge Molekulardynamiksimulationen von derartigen Versuchen ausgeführt. Zur Untersuchung der Interaktion von Versetzungen miteinander wurden Säulen im Mikrometerbereich verformt und Blech durch Kaltwalzen verformt. Des Weiteren wurde durch Hochdruck-Torsion maximale Verformungen realisiert. Die verwendeten Modellmaterialien erlauben es verschiedene prinzipielle Vorgänge der Defektbildung zu untersuchen und so einen breiten Überblick über prinzipielle Vorgänge im kfz Gitter (Palladium) bzw. krz Gitter (Vanadium) zu erhalten.

Made available in DSpace on 2014-10-09T12:36:25Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:28Z (GMT). No. of bitstreams: 1 03874.pdf: 1911480 bytes, checksum: 99b2300cf5d2fd80de82f5c202570b88 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:36:25Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:28Z (GMT). No. of bitstreams: 1 03874.pdf: 1911480 bytes, checksum: 99b2300cf5d2fd80de82f5c202570b88 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Elektroden aus Legierungen der Übergangsmetalle Vanadium, Titan und Niob und der reinen Metalle reagieren in Abhängigkeit von der Zusammensetzung und des mit ihnen im Kontakt stehenden wässrigen Elektrolyten in höchst unterschiedlicher Weise. Für eine systematische Untersuchung der elektrochemischen Eigenschaften der Elektroden wurden neben den reinen Metallen binäre und ternäre Legierungen aus Vanadium, Titan und Niob, die jeweils Vanadium enthalten, hergestellt. Es wurden zum ersten Mal zusammenhängend ihre physikalischen und chemischen Eigenschaften durch Strukturuntersuchungen und Untersuchungen der Zusammensetzung der Oberfläche sowie der Morphologie bestimmt. Von den, sich mit einer halbleitenden Oxidschicht überziehenden Metallen, wurden die Halbleitereigenschaften im Elektrolytkontakt studiert, die grundlegenden Korrosionseigenschaften sowie ihr elektrochemisches Verhalten als Elektrodenmaterial in potentiometrischen Zellen und durch Strom-Spannungsmessungen bestimmt. Zur Aufklärung der Kinetik der Oxidschichtbildung wurden potentiostatische Stromtransienten ermittelt und mit bekannten Modellen verglichen.