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1
Wawata, Ibrahim. "Methanol oxidation on molybdenum oxide catalysts". Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/74613/.
2
Kornic, Steven Alexander. "Spectroscopic and chemical characterisation of heterogeneous molybdenum oxide catalysts". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ33241.pdf.
3
Bamroongwongdee, Chanut. "Surface science studies of model oxide catalysts : molybdenum oxide on single crystal iron oxide". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54989/.
Resumen
This thesis is concerned with the study of molybdenum oxide layer deposited on a single crystal iron oxide substrate. The surface structure of an iron oxide single crystal was investigated by X-ray photoelectron (XPS), low-energy He+-ion scattering (LEIS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). XPS measurement reveals the presence of both Fe2+ and Fe3* oxidation states. LEED and STM results obtained from this surface were consistent with a formation of an Fe304(III) surface termination. LEED pattern and STM images reveal an hexagonal array with a periodicity of 6 A and steps in multiples of 5 A. LEIS result shows the presence of both Fe and O in the topmost layer. Well ordered epitaxial molybdenum oxide films were grown on iron oxide single crystal substrates. Their surface structure, morphology and composition were characterized by XPS, LEIS, LEED, and STM. They were prepared by depositing molybdenum oxide onto the substrate and then oxidizing it in 10"7 mbar of oxygen. In the sub-monolayer regime, molybdenum oxide formed islands of ordered structure. XPS measurement yields a Mo 3dsn binding energy consistent with the presence of Mo6*. High resolution STM images reveal a large hexagonal lattice of protrusions with a 12 A periodicity. This pattern is consistent with a p(4x4) structure. At the monolayer coverage, a (23 x 23 )R30 surface structure is produced by annealing in oxygen (107 mbar) at 973 K. STM topographies show clear hexagonal distribution with the period of 1.1 nm corresponding to the pattern observed in LEED. These results suggest that molybdenum oxide may interact with Fe304(III) to form iron molybdate which is stable on the surface.
4
Zoumot, Rowaida George. "Partial oxidation of methanol to formaldehyde over molybdenum-tin oxide catalysts". Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/11094.
Resumen
The vapor phase air oxidation of methanol to formaldehyde was investigated over molybdenum oxide, tin oxide and their mixtures in an integral flow reactor at atmospheric pressure between temperature of 513 and 573 K, a space time of 10-40 hr g-cat/g-mol methanol and a molar ratio of 0.04-0.1 mol CH3OH/mol air. Experiments were done under such conditions that the effects of internal and external heat and mass transfer effects were negligible. The effects of several process variables, temperature, space time and methanol/air ratio on the conversion of methanol and the selectivity of the catalyst for formaldehyde production were determined. The results indicated that the impact of the process variables on the conversion, selectivity and yield of formaldehyde were in the following decreasing order T > W/F > R. A screening study indicated the optimum catalyst composition to be 50% SnO2 and 50% MoO3, while conversion increased with temperature and W/F selectivity decreased. This catalyst proved to be highly active and selective to formaldehyde production. Selectivity and yield of up to about 100% were obtained at 100% conversion at a temperature of 553 K, a space time (W/F) of 40 g-cat/g-mol methanol per hour and a molar ratio (R) of 0.04 mol CH3 OH/mol air. The rate expression r=k1P2M 1+k1P2M2k 2PO2 was deduced assuming a steady-state involving two-stage irreversible oxidation-reduction process. It represented the experimental data satisfactorily. Arrhenius plots of the two rate constants gave activation energies of 31.7 and 18.1 kcal/g-mol.
5
Kuma, Ryoji. "Studies on Transition Metal Oxide Catalysts for Waste Gas Treatment". Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263353.
6
Oloye, Femi Francis. "Synthesis and characterisation of zirconia supported molybdenum oxide and molybdenum carbide catalysts for hydroconversion of n-heptane". Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230933.
Resumen
The current upgrading catalysts are mainly based on the use of expensive noble metals, which are subject to deactivation due to sintering and coking. An alternative would be to introduce a non-noble metal-based catalyst. In this work, supported molybdenum carbide based systems have been assessed for this purpose. These catalysts were formed by impregnation of zirconia (and zirconium hydroxide) and sulfated zirconia (and zirconium hydroxide) with different loadings of MoO3, with an aim of finding a balance between acid sites and metal-like sites (a site capable of performing dehydrogenation and hydrogenation function without necessarily being a metal). The synthesised catalysts were carburised between 823 and 1123 K using a mixture of methane and hydrogen (4:1) in an attempt to obtain β-Mo2C/ZrO2 or β-Mo2C/S ZrO2. Carburisation at 923 K and above resulted in molybdenum carbide with minimal or no oxygen contents. The conversion and specific rate increased with temperature. Conversion was inversely proportional to space velocity. Analysis of the products distribution as a function of conversion implies that the reaction did not simply follow a consecutive reaction pathway, but that other parallel routes were involved. Conversion increased the research octane number (RON) to ca. 66 due to the increased fraction of pentane isomers. Catalyst carburised at 823 K was approximately four times more active compared to those carburised at 923 K and above, but were of similar activity with Pt/sulfated zirconia. The non-noble metal based catalysts were stable at the reaction temperature while the Pt/sulfated zirconia catalyst deactivates.
7
Smith, Marianne R. "The partial oxidation of methane to formaldehyde over molybdenum oxide-based catalysts /". The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487780865409586.
8
Pollard, Ashleigh J. J. "Silica and boron nitride supported molybdenum and vanadium oxide catalysts for alkane oxidation". Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55535/.
Resumen
A range of silica supported molybdenum catalysts and vanadium catalysts have been prepared and tested for alkane oxidation. Further vanadium catalysts supported on boron nitride have also been prepared and tested for alkane oxidation. The silica supported molybdenum oxide catalysts demonstrated appreciable activity for propane total oxidation to carbon oxides with some trace acrolein. The silica supported vanadium catalysts were also active for propane oxidation, and although the major product was carbon dioxide, higher selectivity to acrolein was observed when compared to the silica supported molybdenum catalysts. The use of boron nitride as a support significantly increased the selectivity towards acrolein and other selective oxidation products like acrylic acid. These results lead to the catalysts being tested for propene oxidation, which produced similar results that showed the boron nitride supported vanadium catalysts were more selective than the silica supported catalysts for acrolein. Further tests were carried out on methane and ethane, which produced mostly carbon oxides as a result. The effect of co-feeding water was also tested when performing propane oxidation with the presence of water effecting the selectivity and activity of the catalysts. Some catalyst's activity was suppressed with increased selectivity to acrolein and other catalysts activity was promoted which led to total oxidation to carbon oxides. This study aim is to compare and contrast the different catalysts produced and give evidence about how the use and development of a hydrophobic support may lead to better catalyst design in the future.
9
Dyer, Philip William. "Studies on molecular Oxo and Imido complexes of the group 6 metals and supported chromium oxide polymerisation catalysts". Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5778/.
Resumen
This thesis describes studies directed towards the preparation of bis (imido) complexes of the Group 6 metals containing olefin, phosphine, acetylene, and alkyl ligands with particular emphasis on their relationship with Group 4 bent metallocenes. The polymerisation mechanism of the Phillips catalyst (CrO(_3)/SiO(_2)) is examined using XPS (X-Ray Photoelectron Spectroscopy) and in situ mass spectroscopy. Chapter 1 highlights properties of some of the important ligand classes that are used throughout the remainder of this thesis. Chapter 2 describes a high yield one-pot synthesis of molybdenum bis (imido) complexes of the type Mo(NR')(NR")Cl(_2).DME. In addition a number of attempts to extend this strategy to other metals are described, including a novel synthesis of the chromium complex [Cr(_2)Cl(_9)] [NHEt(_3)](_3). Chapter 3 describes the synthesis, characterisation, and reactivity of the bis (imido) bis (phosphine) complexes Mo(NAr)(_2)(PMe(_3))(_2) and [Mo(N(^t)Bu)(µ-N(^t)Bu)(PMe(_3))](_2). Further studies on bis (imido) olefin complexes of the type Mo(NAr)(_2)(PMe(_3))2(η(^2)-C(_2)H (_2)) and Mo(N(^t)Bu)(_2)(PMe(_3))(η(^2)-C(_2)H(_4)) was undertaken and concentrated on their structural relationship to Group 4 metallocene species. Chapter 4 describes the preparation, structure, and reactivity of some bis (imido) acetylene complexes Mo(NR)(_2)(PMe(_3)) (PhC=CR’) (R= Ar, (^t)Bu; R'= Ph, H). Preparation of bis (imido) alkyls was undertaken in attempts to generate benzyne and alkylidene derivatives. Chapter 5 studies the Phillips polymerisation catalyst using XPS and mass spectroscopy. Model systems were used to probe reactive surface species their use reveals a number of features that are difficult to observe with the actual catalyst. Aspects of molecular chemistry have been examined which are believed to relate directly to the heterogeneous system allowing a possible polymerisation mechanism to be postulated. Chapter 6 gives experimental details for Chapters 2-5. Philip William Dyer (November 1993)
10
Amakawa, Kazuhiko [Verfasser] y Reinhard [Akademischer Betreuer] Schomäcker. "Active Site for Propene Metathesis in Silica-Supported Molybdenum Oxide Catalysts / Kazuhiko Amakawa. Betreuer: Reinhard Schomäcker". Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1067384308/34.
11
Okatsu, Hiroko. "New synthetic methods to alter catalytic properties of supported K/MoS₂ catalysts for syngas conversion to higher alcohols". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/48996.
Resumen
The purpose of this study is to develop catalysts for conversion of synthesis gas (H₂ and CO) to higher alcohols, primarily ethanol and propanol. Crude oil is consumed at a rate of more than 20 million barrels a day in the United States, mainly for producing fuels and chemical feedstocks. However, the total amount of crude oil is limited, and alternative ways of producing alcohols as precursors for chemical feedstocks are desirable. In this study, using a known K/MoS₂/metal oxide catalyst as the starting point, two different approaches were explored to improve catalytic properties: 1) Co promotion on K/MoS₂/mixed metal oxide (MMO) catalysts, and 2) Preparation of K/MoS₂/metal oxide catalysts with molybdenum carbide as a precursor, instead of molybdenum oxide. With respect to Co promotion on K/MoS₂/MMO catalysts, the effect of varying the Co content in the K/Mo-Co/MMO catalysts prepared by a co-impregnation method did not produce significant changes in catalytic acitivities or selectivities. It was due to the premature precipitation of cobalt molybdate during synthesis. Cobalt molybdate precipitation can generally be prevented by using water as a solvent, but this approach is not appropriate for this study because of the use of hydrotalcite-derived mixed metal oxide as the support. Co loadings on K/Mo/MMO-Co catalysts did not change selectivities significantly, either. However, they changed catalytic activities, represented by gas hourly space velocity (GHSV) required to obtain 8% conversion while maintaining high selectivities for higher alcohols. As a result, C ₂₊ alcohol productivities reached 0.01g(alcohol)/g(catalyst)/hr with Co loadings higher than 8%. With respect to using Mo2C as the precursor of Mo species instead of MoO3, comparisons between catalysts with different precursors for Mo species and different pretreatments were investigated. In this study, both K/Mo catalysts supported on MgO and α-Al₂O₃ showed similar tendencies of catalytic activities and selectivities. The highest C₂₊ alcohol selectivities and productivities were obtained on presulfided MoO₃ catalysts on both supports. In comparison of K/Mo ₂C catalysts with different pretreatments, higher C₂₊ alcohol selectivities and lower MeOH selectivities were obtained on presulfided catalysts compared to non-pretreated catalysts.
12
Scholz, Juliane [Verfasser], Thorsten [Akademischer Betreuer] Ressler y Christian [Akademischer Betreuer] Hess. "Structure activity correlations of Vanadium and Molybdenum Oxide catalysts supported on nanostructured materials / Juliane Scholz. Gutachter: Thorsten Ressler ; Christian Hess. Betreuer: Thorsten Ressler". Berlin : Technische Universität Berlin, 2014. http://d-nb.info/106566947X/34.
13
Kühn, Sven [Verfasser], Thorsten [Akademischer Betreuer] Ressler, Thorsten [Gutachter] Ressler y Peter [Gutachter] Strauch. "Structure-function relationships of molybdenum-based oxide nitrides as model catalysts in selective oxidation of propene / Sven Kühn ; Gutachter: Thorsten Ressler, Peter Strauch ; Betreuer: Thorsten Ressler". Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156346630/34.
14
Farah, Bertha. "Développement de catalyseurs d'HDO à base de molybdène et à valence mixte pour la valorisation de la lignine". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2023/2023ULILR047.pdf.
Resumen
Ce projet de thèse s'intéresse à la réaction catalytique d'hydrodésoxygénation (HDO) appliquée pour convertir la biomasse en biocarburants et en produits à haute valeur ajoutée, réduisant ainsi la dépendance aux combustibles fossiles et favorisant une économie durable. Industriellement, les catalyseurs sulfures CoMoS et NiMoS supportés sur alumine sont les plus utilisés en HDO, mais ils se désactivent en absence d'une source continue de souffre pendant la réaction et entrainent éventuellement à la contamination des produits finaux. Afin de remédier à ces problèmes, des recherches sont en cours pour développer de nouvelles formulations de catalyseurs exemptes de souffre, parmi lesquelles les catalyseurs à base d'oxydes de molybdène distingués par leur sélectivité élevée aux composés aromatiques. Ces catalyseurs étant généralement moins actifs que les sulfures, des stratégies d'optimisation sont mises en place dans ces travaux de thèse pour améliorer leur performance catalytique. Il convient en premier lieu d'identifier le support le plus approprié pour maximiser l'efficacité du catalyseur. Pour cela, des matériaux ayant différentes propriétés texturales, oxophiles et réductrices seront analysés. Ensuite, des promoteurs seront ajoutés au catalyseur le plus performant afin de créer une potentielle synergie avec le molybdène en améliorant sa réductibilité, paramètre clé en HDO puisque les espèces réduites Mo5+ sont proposées comme phases actives du processus. Enfin, les catalyseurs préparés seront caractérisés par diverses techniques expérimentales et leurs performances seront évaluées dans des tests réalisés sur un micro-pilote sous pressionThis thesis project focuses on the catalytic hydrodeoxygenation (HDO) reaction applied to convert biomass into biofuels and high-value-added products, thereby reducing dependence on fossil fuels and promoting a sustainable economy. Industrially, sulfide catalysts CoMoS and NiMoS supported on alumina are the most commonly used in HDO, but they deactivate in the absence of a continual sulfur source throughout the reaction, and eventually lead to end-product contamination. To address these issues, research is underway to develop new sulfur free catalyst formulations, among which molybdenum oxide catalysts known for their high selectivity toward aromatic compounds. Since theses catalysts are generally less active than sulfides, optimization strategies are implemented in this thesis work to improve their catalytic performance. The first step consists in identifying the most suitable support to maximize the catalyst's efficiency. This is achieved by analyzing several materials having different textural, oxophilic and redox properties. Then, promoters will be added to the most efficient catalyst in order to create a potential synergy with molybdenum by increasing its reducibility to Mo5+ species that are proposed to be the active sites of this reaction. Finally, the prepared catalysts will be characterized using various experimental techniques and their catalytic performances will be evaluated with tests conducted in a high-pressure micro-pilot
15
Shukri, Rashid Jaber Asa'd. "Supported oxide catalysts : cobalt oxide and molybdena on titania". Thesis, Brunel University, 1989. http://bura.brunel.ac.uk/handle/2438/7385.
Resumen
TiO2 supported MoO3 catalysts were prepared by aqueous impregnation of low area anatase (10 m2g-1) with solutions of (NH4)6Mo7024,4H20 (MT/C series), and H2[Mo03(C204)].H20 (MOT /C series), Three series of CoOx/Ti02 catalysts were fabricated by aqueous impregnation of the same support with solutions of Co(N03)2,6H20 (CT/C series), and Co(CH3COO)2.4H20 (CAT/C series), and by homogeneous precipitation using Co(N03)2,6H20 (CT/HP series), CoO and Mo03 were deposited on Degussa P-25 (55 m2g-1) by aqueous impregnation using (NH4)6Mo7024,4H20 and Co(N03)2,6H20 in three ways: ( i) CoO impregnated first, Mo03 second (CMT series); (ii) Mo03 impregnated first, CoO second (MCT series); and (iii) CoO and Mo03 together (CMTg series). The catalysts were characterized by laser Raman spectroscopy (LRS) , temperature-programmed reduction (TPR) , X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), Monolayer coverage by XPS was independent of the precursor for the MoOx/Ti02 catalysts, but a function of the method of preparat ion and the precursor for the CoOx /Ti02 catalysts. XPS results for the CMTg series differed from those for the CMT and MCT series, suggesting different surface species had been formed by varying the mode of impregnation, Phase diagrams relating semiquantitatively to the oxide contents are presented. 2-propanol decomposition was studied to probe the acid-base properties of the catalysts, Ti02 and Mo03 exhibi ted dehydration activity, whereas CoO showed dehydrogenation activity, All the supported catalysts gave activation energies for dehydration higher than dehydrogenation. In the sub-monolayer region, the catalytic activity for dehydration was in the order: MCT > CMTg > CMT > MT/C > CT/C, while the selectivity remained almost unchanged, In the monolayer region, the activity was: MT/C > CMT > CMTg > MCT > CT/C and the selectivity increased compared with the sub-monolayer region. In the four-monolayer reg ion, the activity decreased compared with the sub-monolayer and monolayer regions, but the selectivity increased relative to the previous two regimes. "Compensation effect 0, plots revealed different types of active centres responsible for dehydration and dehydrogenation processes in the MoOx /Ti02 and CoO-Mo03/Ti02 catalysts, while active centres were almost identical with the CoOx /Ti02 system.
16
Beato, Pablo. "Synthesis and characterization of realistic molybdenum oxide based model systems in heterogeneous catalysis". [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976464330.
17
Rellán, Piñeiro Marcos. "Molybdenum Oxides as Catalyst for Biomass-derived Compounds: a Theoretical Approach". Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/552410.
Resumen
Per al desenvolupament d'una indústria química més sostenible la revaloració de compostos derivats de la biomassa és un objectiu important. En aquesta tesi, la conversió d'hidrocarburs oxigenats derivats de la biomassa catalitzada per òxids de molibdè és estudiada a través de la teoria del funcional de la densitat (DFT).
El primer objectiu es l'estudi de l'oxidació selectiva de metanol a formaldehid. Aquesta és una important reacció en la indústria química sobre la qual es discuteixen diverses qüestions. El camí de reacció és calculat en la superfície d'òxids de molibdè i l'activitat i selectivitat de cada superfície són estudiades. A més, el paper que té el ferro en el catalitzador industrial és desxifrat estudiant la reactivitat de la superfície de MoO3 dopada. En el següent objectiu, el mètode DFT + U és optimitzat per a descriure correctament les propietats redox del MoO3. Amb el mètode optimitzat els defectes per vacant en la superfície MoO3 (010) són caracteritzats doncs tenen un paper essencial en l'activitat catalítica de l'òxid. Un altre objectiu és l'estudi de la reducció selectiva de glicerol a propilè catalitzada pel MoO3 reduït. A través d'un procés de hidrodeoxigenació (HDO) el trencament selectiu dels enllaços C-O sobre els C-C porta a la formació del producte desitjat. Un estudi de la xarxa de reaccions va ser realitzat per il•lustrar el trencament d'enllaç selectiva i obrir la porta a un millor enteniment dels processos HDO. Finalment, la epimerització selectiva de glucosa a manosa és estudiada. El mecanisme per a la inversió de configuració del C2 a través d'una transposició de carboni 1,2 es calculat en polioxometalats de molibdè i la superfície contínua α-MoO3. Va ser trobat que els centres de molibdè actuen com un amortidor electrònic en aquestes reaccions i, per tant, la redutcibilitat dels centres de molibdè pot ser usada com a descriptor de l'activitat del catalitzador.Per al desenvolupament d'una indústria química més sostenible la revaloració de compostos derivats de la biomassa és un objectiu important. En aquesta tesi, la conversió d'hidrocarburs oxigenats derivats de la biomassa catalitzada per òxids de molibdè és estudiada a través de la teoria del funcional de la densitat (DFT). El primer objectiu es l'estudi de l'oxidació selectiva de metanol a formaldehid. Aquesta és una important reacció en la indústria química sobre la qual es discuteixen diverses qüestions. El camí de reacció és calculat en la superfície d'òxids de molibdè i l'activitat i selectivitat de cada superfície són estudiades. A més, el paper que té el ferro en el catalitzador industrial és desxifrat estudiant la reactivitat de la superfície de MoO3 dopada. En el següent objectiu, el mètode DFT + U és optimitzat per a descriure correctament les propietats redox del MoO3. Amb el mètode optimitzat els defectes per vacant en la superfície MoO3 (010) són caracteritzats doncs tenen un paper essencial en l'activitat catalítica de l'òxid. Un altre objectiu és l'estudi de la reducció selectiva de glicerol a propilè catalitzada pel MoO3 reduït. A través d'un procés de hidrodeoxigenació (HDO) el trencament selectiu dels enllaços C-O sobre els C-C porta a la formació del producte desitjat. Un estudi de la xarxa de reaccions va ser realitzat per il•lustrar el trencament d'enllaç selectiva i obrir la porta a un millor enteniment dels processos HDO. Finalment, la epimerització selectiva de glucosa a manosa és estudiada. El mecanisme per a la inversió de configuració del C2 a través d'una transposició de carboni 1,2 es calculat en polioxometalats de molibdè i la superfície contínua α-MoO3. Va ser trobat que els centres de molibdè actuen com un amortidor electrònic en aquestes reaccions i, per tant, la redutcibilitat dels centres de molibdè pot ser usada com a descriptor de l'activitat del catalitzador.
For the development of a more sustainable chemical industry the upgrading of biomass derived compounds to valuable chemicals in selective and non-contaminant processes is an important target. In this thesis, the conversion of oxygenated hydrocarbons derived from biomass catalyzed by Mo-oxides is studied by means of Density Functional Theory (DFT). The first objective is the study of the selective methanol oxidation to formaldehyde. This is an important reaction in chemical industry that has several issues under discussion. The reaction path is calculated on Mo-oxides surfaces and the activity and selectivity of each surface are studied. Moreover, the role of the iron in the industrial catalyst is unraveled by the study of the reactivity of the doped MoO3 surface. In the following objective, the DFT+U method is optimized to correctly describe the redox properties of MoO3. With the optimized method, the MoO3 (010) surface vacancy defects are characterized since they play an essential role in the catalytic activity of the oxide. Other objective is the study of the selective reduction of glycerol to propylene catalyzed by reduced MoO3. Through a hydrodeoxygenation (HDO) process the selective C-O bond cleavage over C-C bonds leads to the formation of the desired product. A study of the reaction network has been performed to illustrate this selective bond cleavage and pave the way to a better understanding of HDO processes. Finally, the selective epimerization of glucose to mannose is studied. The mechanism for the inversion of C2 configuration through a 1,2 C-shift is calculated on Mo-based polyoxometalates and continuous α-MoO3 surface. It was found that the Mo-centers act as electron buffer in these reactions and, therefore, the reducibility of the Mo-centers can be traced back as the descriptor for catalyst activity.
18
Liu, Chang. "The spectroscopic and structural characterization of chlorine modification of MoOx catalysts supported over silica/titania mixed oxides for the oxidative dehydrogenation of ethane and propane". Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1095645498.
Resumen
Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xiv, 157 p.; also includes graphics. Includes bibliographical references (p. 145-153).
19
Schuh, Kirsten [Verfasser] y J. D. [Akademischer Betreuer] Grunwaldt. "Hydrothermal synthesis of molybdenum based oxides for the application in catalysis / Kirsten Schuh. Betreuer: J.-D. Grunwaldt". Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1068263164/34.
20
KONDO, FERNANDO M. "Estudo do efeito da radiação ionizante na utilização dos catalisadores desativados de craqueamento". reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23494.
Resumen
Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2015-02-23T19:40:28Z
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
21
Karslioglu, Osman. "Structural and chemical characterizations of Mo–Ti mixed oxide layers". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16767.
Resumen
In dieser Arbeit wurde ein Modell-Katalysator-Ansatz angewandt um Mischoxide mit Molybdän und Titan zu untersuchen. Die Schichten wurden auf TiO2(110) Einkristallen durch Verdampfen der Metalle in einer O2 Atmosphäre und in UHV und Nachbehandlung der Filme vorbereitet. Verschiedene Präparationen wurden in der Studie untersucht und diese werden in sechs Kategorien dargestellt. Wenn Mo und Ti in O2 gemeinsam aufgedampft wurden, wurde das meiste Mo an der Oberfläche abgeschieden mit einer nur geringen Mo-Konzentration in tieferen Schichten. Eine Mischung von Mo in TiO2 war sehr begrenzt, und die stimmt mit dem Phasendiagramm MoO2 und TiO2 überein. Mo6+ und Mo4+ sind die dominierenden Oxidationsstufen in den meisten der Schichten, wobei Mo6+ stets näher an der Oberfläche war als Mo4+. Schichten, in denen Mo vollständig in TiO2 gelöst ist, konnten durch Abscheidung von Metallen in UHV und Post-Oxidation der Filme erstellt werden. Im Inneren des TiO2 Gitters hat Mo die Oxidationsstufe 4+. Aufdampfen von Mo in O2 bei Raumtemperatur und anschließendes Tempern in UHV führte zur Bildung zweier Arten von Merkmalen in den STM-Bildern. Diese waren im UHV stabil bis mindestens 1000 K. Die Schichten mit hoher Mo-Konzentrationen erschienen uneinheitlich in den STM-Bildern aber sie zeigte das TiO2(110)-(1x1) LEED-Muster. Der Anstieg in der Mo-Konzentration führte zur Blockierung der Überbrückung Sauerstoffleerstellen (BOVs), was durch STM und Wasser-TPD nachgewiesen wurde. Die Reaktivitäten der Schichten wurden mit Methanol- und Ethanol-TPD getestet. Eine unerwartete Formaldehyd/Methanbildung bei hohen Temperaturen (~650 K) wurde bei der Methanol-TPD von reinem TiO2(110) beobachtet und mit BOVs in Verbindung gebracht. Der Anstieg der Mo-Konzentration unterdrückte diesen Effekt sowie die Ethylenbildung (~600 K) beim Durchführen von Ethanol-TPD. Sowohl in Ethanol als auch Methanol-TPD wurden neue Reaktionswege zu Ethylen und Methan-Bildung bei ~500 K beobachtet.In this work, a model-catalyst approach has been taken to study oxide mixtures containing molybdenum and titanium. The layers were prepared on TiO2(110) single crystals by evaporating the metals in an O2 atmosphere or in UHV and post treating the deposited material. Different preparation procedures were employed in the study and these are presented in six categories. When Mo and Ti were co-deposited in O2, most of the molybdenum stayed at the surface with only a small Mo concentration in deeper layers. Mixing of Mo into TiO2 was very limited, consistent with the phase diagram of MoO2 and TiO2. Mo6+ and Mo4+ were the dominant oxidation states in most of the layers and Mo6+ was always nearer to the surface than Mo4+. Layers where Mo was completely mixed into TiO2 could be prepared by depositing metals in UHV and post-oxidizing the deposited material. Inside the TiO2 lattice, Mo had an oxidation state of 4+. Depositing Mo in O2 at room temperature and post annealing in UHV led to the formation of two types of features in the STM images. These features were stable in UHV up to at least 1000 K. The layers with high Mo concentrations appeared patchy in the STM images but they still exhibited the TiO2(110)-(1x1) LEED pattern. The increase in Mo concentration led to the blocking of the bridging oxygen vacancies (BOVs) as evidenced by STM and water TPD. The reactivities of the layers were tested by methanol and ethanol TPD. An unprecedented high temperature (~650 K) formaldehyde/methane formation channel was observed in the methanol TPD of clean TiO2(110) and was associated with BOVs. The increase in the Mo concentration led to the vanishing of this channel as well as the ethylene formation channel (~600 K) in the case of ethanol TPD. In both ethanol and methanol TPD, new reaction channels towards ethylene and methane formation at ~500 K appeared.
22
Woods, Matthew P. "Activity and Selectivity in Oxidation Catalysis". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228175906.
23
Bouchmella, Karim. "Synthèse par procédé sol-gel non-hydrolytique de catalyseurs oxydes mixtes pour la métathèse d'oléfines". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20088.
Resumen
Les synthèses par sol-gel non-hydrolytique (SGNH) d'oxydes mixtes Re-Si-Al et Mo-Si-Al sont présentées comme une voie innovante pour la préparation en une étape de catalyseurs hétérogènes de métathèse. Les catalyseurs supportés à base d'oxyde de molybdène sont intéressants du fait de leur faible coût d'achat, de leur résistance mécanique et de leur bonne activité à température modérée. Les catalyseurs supportés à base d'oxyde de rhénium sont connus pour être très actifs et sélectifs même à température ambiante. Cependant ils sont chers et la sublimation de l'oxyde de rhénium pose problème lors de leur synthèse. La synthèse utilisée est basée sur la réaction en une étape des précurseurs chlorés (ReCl5 ou MoCl3, SiCl4, AlCl3) avec du diisopropyléther (iPr2O) à 110 °C dans le dichloromethane. Le faible coût des précurseurs, l'absence de modificateurs de réactivité et de templates ainsi que la simplicité de synthèse rendent le procédé SGNH particulièrement attractif. Les catalyseurs oxydes mixtes obtenus présentent des compositions bien contrôlées, des textures mésoporeuses et avec des densités en sites acides élevées. La caractérisation par DRX, XPS et ToF-SIMS montre que les catalyseurs peuvent être décrits comme une matrice silice-alumine amorphe avec des espèces de surface Mo et Re bien dispersées. Pour les catalyseurs à base de Re, dans les compositions riches en silice, des pertes de rhénium ont été observées durant la calcination. Cette perte de rhenium peut être évitée en augmentant le taux d'alumine dans la composition. De plus, nous avons montré que la sublimation de Re, au cours de la calcination dans les compositions riches en silice, n'a pas lieu quand toutes les étapes du procédé (synthèse, lavage, séchage et calcination) sont réalisées en l'absence d'humidité. Nous avons étudié l'influence de la composition sur la texture, la structure, l'acidité et les propriétés de surface, qui sont corrélées aux performances catalytiques. Les performances des catalyseurs Re-Si-Al et Mo-Si-Al ont été évaluées en métathèse du propène et en métathèse croisée de l'éthène et du trans-2-butène. Les catalyseurs SGNH sont comparés à des catalyseurs avec des compositions similaires préparés par d'autres méthodes (imprégnation, thermal spreading, flame spray pyrolysis). Les catalyseurs préparés par SGNH présentent une très bonne activité spécifique en métathèseThe non-hydrolytic sol-gel synthesis (NHSG) of Re-Si-Al and Mo-Si-Al mixed oxides was proposed as an innovative one step route to heterogeneous olefin metathesis catalysts. Supported molybdenum oxide catalysts are receiving much attention as a result of their relatively low price, robustness and good activity at low temperature. Supported rhenium oxide catalysts are known to be highly active and selective even at room temperature. However, they are expensive and moderately stable because of the sublimation of the rhenium oxide. The NHSG synthesis used in this work is based on the one pot reaction of chloride precursors (ReCl5 or MoCl3, SiCl4, AlCl3) with diisopropylether (iPr2O) at 110 °C in dichloromethane. The simplicity of NHSG makes it attractive: multi-step procedures, expensive precursors, or reactivity modifiers are not needed. The mixed oxide catalysts exhibited well-controlled compositions and mesoporous textures, with high acid site densities. XRD, XPS and ToF-SIMS showed that the catalysts could be described as an amorphous silica-alumina matrix with well-dispersed Re or Mo surface species. In the case of Re-based catalysts, rhenium losses by sublimation during calcination were observed for the silica-rich formulations. The loss of rhenium could however be avoided by increasing the Al content. More importantly we demonstrate that Re sublimation during calcination of silica-rich formulations is suppressed when the whole preparation procedure (synthesis, washing, drying and calcination) is carried out in the absence of water. Particular attention was devoted to the study of the influence of the composition on texture, structure, acidity and surface properties, which were correlated with the catalytic performances. The performance of selected Re-Si-Al and Mo-Si-Al catalysts was evaluated in the metathesis of propene and in the cross-metathesis of ethene and trans-2-butene. The NHSG catalysts were compared to catalysts of similar compositions prepared by other more methods (impregnation, thermal spreading, flame spray pyrolysis). The catalysts prepared by NHSG have a high specific activity in the metathesis reaction
24
Santos, Thatiane Veríssimo dos. "Avaliação dos catalisadores SnO2, MoO3 e SnO2/MoO3 na conversão da frutose". Universidade Federal de Alagoas, 2017. http://www.repositorio.ufal.br/handle/riufal/2381.
Resumen
The development of heterogeneous catalysts, which are efficient and easy recovery, is major technological challenges faced, linked to environmental and economic concerns. In the present work we studied the catalytic SnO2 systems, MoO3 and SnO2/MoO3 in the conversion of fructose, with particular attention to SnO2/MoO3 systems, which were synthesized in various proportions by weight of molybdenum oxide, using the impregnation technique By wet method, aiming to obtain materials with high industrial applicability. The catalysts were characterized using various techniques, including, thermogravimetric analysis (TG/DTA), absorption spectroscopy in the infrared (FTIR) spectroscopy, Raman spectroscopy, diffraction X-ray (XRD), FTIR using pyridine as probe molecule spectroscopy Diffuse ultraviolet-visible reflectance (DRS) and fisistion analysis (BET). In addition to these techniques, the acid sites of the catalysts were measured by the aqueous method using sodium hydroxide and hydrochloric acid as the titrant. The results show that the main factor that influences the conversion of fructose are present the acid sites in the catalysts. This study shows that the molybdenum oxide obtained high fructose conversions at temperatures of 150 ° C and 190 ° C, but this does not reflect the products quantified by HPLC, with a large production of insoluble materials in the reaction medium, which are the main cause fouling of catalysts. On the other hand, tin oxide presented low activity in the conversion of fructose, but high selectivity to Hydroxymethylfurfural (HMF). In this context, the catalyst that provided good conversions and less formation of insoluble materials was SnMo25, being HMF selective. On the other hand, SnMo50 and SnMo75 provided high selectivity to lactic acid, but with the inconvenience of formation of insoluble products in appreciable quantity. The impregnation was an effective strategy for the formation of new sites and reuse leaching test and showed promising results.Conselho Nacional de Desenvolvimento Científico e Tecnológico
O desenvolvimento de catalisadores heterogêneos, que sejam eficientes e de fácil recuperação, é um dos principais desafios tecnológicos enfrentados atualmente, atrelado às preocupações ambientais e econômicas. Assim, no presente trabalho foram estudados os sistemas catalíticos SnO2, MoO3 e SnO2/MoO3 na conversão da frutose, com especial atenção ao sistema SnO2/MoO3, os quais foram sintetizados em diversas proporções em massa de óxido de molibdênio, utilizando a técnica de impregnação por via úmida, visando obter materiais com alta aplicabilidade industrial. Os catalisadores foram caracterizados utilizando várias técnicas, nomeadamente, análise termogravimétrica (TG/DTA), espectroscopia de absorção na região do infravermelho (FTIR), espectroscopia Raman, difração de raio-x (DRX), FTIR utilizando a piridina como molécula sonda, espectroscopia de refletância difusa no ultravioleta-visível (DRS) e análises de fisissorção (BET). Além dessas técnicas, os sítios dos catalisadores foram medidos pelo método aquoso utilizando hidróxido de sódio e ácido clorídrico como agente de titulação. Os resultados mostram que o principal fator que influência a conversão da frutose são os sítios ácidos presentes nos catalisadores. Com esse estudo pode-se constatar que o óxido de molibdênio obteve altas conversões de frutose nas temperaturas de 150 °C e 190 °C, porém isso não reflete os produtos quantificados por HPLC, havendo grande produção de materiais insolúveis, que são a principal causa de incrustação dos catalisadores. Por outro lado, o óxido de estanho apresentou baixa atividade na conversão da frutose, porém alta seletividade a Hidroximetilfurfural (HMF). Nesse contexto, o catalisador que proporcionou boas conversões e menor formação de materiais insolúveis foi o SnMo25, sendo seletivo a HMF. Por outro lado, o SnMo50 e SnMo75 proporcionaram altas seletividade a ácidos orgânicos, porém com o inconveniente da formação de produtos insolúveis em quantidade apreciável. A impregnação foi uma estratégia eficiente, para a formação de novos sítios e os testes de reuso e lixiviação exibiram resultados promissores.
25
Stampfl, Sharon Rae. "Laser Raman spectroscopic characterization of mixed tin-antimony oxide catalysts and supported molybdenum oxide catalysts". 1986. http://catalog.hathitrust.org/api/volumes/oclc/14397270.html.
26
Thielemann, Jörg. "Synthesis, Characterization and in situ Catalysis of Silica SBA-15 Supported Molybdenum Oxide Model Catalysts". Phd thesis, 2011. https://tuprints.ulb.tu-darmstadt.de/2546/1/Doktorarbeit_-_Thielemann.pdf.
Resumen
This work describes the synthesis, the structural characterization and the catalytic testing of silica SBA-15 supported molybdenum oxide model catalysts. Additionally, a solvent induced washing effect during the SBA-15 synthesis and its scale up on the SBA-15 structure was studied. The MoxOy/SBA-15 catalysts were prepared with a Mo loading between 1.0 and 21.1 wt.% Mo (0.2 to 9.8 Mo/nm2) by a grafting/ion exchange procedure and incipient wetness impregnation. The catalyst structure was analyzed with Raman-, UV/Vis-, Photoelectron-, X-ray absorption- and IR spectroscopy. Furthermore, the catalyst structure was studied under reaction conditions in presence of propylene/oxygen and steam in an in situ Raman-MS setup, which was constructed in the course of this work. The study of washing SBA-15 with two solvents (water and ethanol) with nitrogen adsorption and XRD revealed that the surface area can be increased by 25% to 800 m2/g compared to washing with a single solvent. Moreover, it was found that huge solvent quantities for washing should be avoided, as they induce hydrolysis reactions, which alter the SBA-15 structure and lead to a widening and narrowing of certain mesopore sections. This decreases the surface area and pore volume of the support. The effect decreases with up-scaling of the synthesis. For the MoxOy/SBA-15 catalysts the molybdenum oxide was observed on the support in a dispersed state up to a loading of 12.1 wt.% Mo (3.5 Mo/nm2). Above this loading crystalline -MoO3 and as minority phase-MoO3 are formed. In this loading region the fraction of dispersed molybdenum oxide was almost constant at 12 to 13 wt.% Mo. Regarding the dispersed molybdenum oxide two structurally different states were observed. The hydrated state exists in the presence of moisture at room temperature, whereas the dehydrated state is obtained after treatment over 350°C in synthetic air. The molybdenum oxide structure in the hydrated state can be described as preferentially octahedral centres, which also exhibit connections and form di- or oligomers beside monomers. Comparing the XPS data of the dehydrated and the hydrated state showed that the molybdenum oxide was higher dispersed in the dehydrated state. UV/Vis spectroscopy supported this finding and showed that beside monomeric also di- or oligomeric species were present at Mo densities in the range of dispersed molybdenum oxide (≤3.5 Mo/nm2). Connections between neighbouring molybdenum oxide centres were detected by EXAFS and IR Spectroscopy using nitric oxide as probe molecule. Furthermore, a octahedral to tetrahedral ratio of 1 : 3 was found by a XANES fit. Therefore, the molybdenum oxide structure of the dehydrated state can be described as dispersed tetrahedral and octahedral molybdenum oxide centres, which coexist as monomers and connected di- or oligomers on the silica support surface. Moreover, the size distribution of the dispersed molybdenum oxide species in the hydrated and dehydrated state seems to be independent of the loading. MoxOy/SBA-15 was catalytically tested in the selective oxidation of propylene and propane. Whereas propylene was oxidized selectively to propionaldehyde, acetone and acrolein as major products, the oxidation of propane led unselectively to COx. In situ Raman investigations reveal that during the propylene oxidation or in the presence of steam, the structure of the catalyst largely resembles the structure of dehydrated dispersed molybdenum oxide.
27
Thielemann, Jörg [Verfasser]. "Synthesis, characterization and in situ catalysis of silica SBA-15 supported molybdenum oxide model catalysts / von Jörg Thielemann". 2011. http://d-nb.info/1011311178/34.
28
Pillay, Bavani. "A study of nickel molybdenum oxide catalysts for the oxidative dehydrogenation of n-hexane". Thesis, 2009. http://hdl.handle.net/10413/8827.
Resumen
Nickel molybdenum oxide catalysts with different chemical compositions have been synthesized
and tested for the oxidative dehydrogenation of n-hexane. The co-precipitation method was used
for the synthesis and several methods were used to characterize these catalysts. These include
inductively-coupled plasma optical emission spectroscopy, Raman spectroscopy, infrared
spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, temperature
programmed reduction, temperature programmed desorption, X-ray photo-electron spectroscopy
and X-ray diffraction spectroscopy techniques as well as the Brauner-Emmet-Teller technique for
surface area determination. The phase composition of the catalysts was largely dependent on the
chemical composition.
Catalyst testing on n-hexane feed was done with a fixed bed continuous flow reactor and
experiments were performed with feed/air ratios above and below the flammability limit. Varied
reaction conditions were used for the catalytic testing. Prior to the catalytic testing, blank
experiments were performed. Analysis of the products were done both online and offline in
conjunction with gas chromatography employing FID and TCD detectors.
The influence of the catalyst on the conversion of n-hexane and selectivity to dehydrogenation
products is reported. Products observed were the carbon oxides (CO and CO2), isomers of hexene
(1-hexene, 2-hexene and 3-hexene), cyclic C6 products (cyclohexene and benzene), cracked
products: alkanes/alkenes (propane/ene, butane/ene) and oxygenates (ethanal, acetic acid and
propanoic acid). B-NiMoO4 was most selective to the hexenes, especially, 1-hexene and a reaction
scheme is proposed.Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2009.
29
Wilson, James Harvey. "Raman spectroscopic studies of iron/molybdenum oxide catalysts for the oxidation of methanol to formaldehyde". 1986. http://catalog.hathitrust.org/api/volumes/oclc/15650531.html.
30
Wang, Ching-Huei y 王清輝. "A Study on the Oxidative Decomposition of Dimethyl Disulfide over Supported Copper-Molybdenum Oxide Catalysts". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/38946124733791505522.
Resumen
博士國立成功大學
化學工程學系
86
ABSTRACT The incipient wetness impregnation and the coprecipitation method were employed0 to prepare catalysts. Catalytic activities of the prepared catalysts for oxidative decomposition of dimethly disulfide were measured by a packed-bed reactor. The results indicate that active species (CuO), support and promoter (metal oxide) are important factors affecting catalyst activity. CuO/Al2O3 was the most active catalyst among eight prepared supported single metal oxide catalysts (CuO, MoO3, Cr2O3, Fe2O3, MnO2, NiO, ZnO, Co3O4). Among nine metal oxides (MoO3, Cr2O3, NiO, MnO2, La2O3, Fe2O3, Co3O4, SrO, and ZnO) MoO3 has the best promoting effect to CuO/Al2O3. The CuO-MoO3/Al2O3 catalyst exhibits a higher activity and a better resistance to deactivation by sulfur compounds than a commercial platinum catalyst. A formation of Cu3Mo2O9 and CuMoO4, as confirmed by XRD , TPR and XPS analyses, plays a prominent role in the catalyst activity. Such a formation markedly enhanced the catalytic activity when the added amount of Mo is not too large. However, the activity declines when the content of Mo exceeds 10 wt %. Furthermore, NH3-TPD demonstrates that adding of Mo to CuO/Al2O3 elevates the catalyst''s acidity and acidic strength. A kinetic study on the oxidation decomposition of dimethyl disulfide over CuO(5)-Mo03(10)/Al2O3 catalyst was carried out in a differential reactor. Power-rate law, Langmuir-Hinshelwood, and Mars-Van Krevelen models were used to analyze the results of oxidative decomposition of dimethyl disulfide. The results show that the Mars-Van Krevelen model is suitable for oxidative decomposition of dimethyl disulfide. The reaction rate can be expressed by: Where a=5.5, CR and CO are the concentrations of (CH3)2S2 and O2 , respectively. Knowing that a higher acidity might benefit the catalyst to catalyze the reactions involving cracking and decomposition, we further investigated the effect of acid treatment on the performance of CuO-MoO3/Al2O3 catalyst. Four different kinds of inorganic acids (HCl, H2SO4, HNO3, H3PO4) were used to treat the (-Al2O3 support before impregnating it with copper and molybdenum metal salts. The prepared catalysts were then used for the destructive oxidation of (CH3)2S2. Experimental results indicate that HCl-treat ed and H2SO4-treated catalysts exhibit a higher activity than those without acid treatment. In addition, the H2SO4-treated catalyst (CuO-MoO3/sulfated-Al2O3) displays the best stability. As BET surface area analysis demonstrates, the surface area and average pore diameter of the H2SO4-treated catalysts are larger than those without treatment; however, the increase in surface area is not the main factor in promoting the activity. XRD analysis reveals that the CuO-MoO3/sulfated-Al2O3 catalyst also has the cryst alline structure of Cu3Mo2O9 and CuMoO4 which have been found in the CuO-MoO3/Al2O3. XPS and TGA analysis suggest that it might have the functional group of SO4-2 which exists on the surface of the CuO-MoO3/sulfated-Al2O3 catalyst. The NH3-TPD pattern shows that the acidity is remarkably enhanced when the catalyst is treated with an H2SO4 solution. We believe that the substantial increase in act ivity is attributed primarily to the presence of SO4-2 group on the
31
Dieterle, Martin [Verfasser]. "In situ resonance raman studies of molybdenum oxide based selective oxidation catalysts / von Martin Dieterle". 2001. http://d-nb.info/961815868/34.
32
Chen, Chun-Wei y 陳俊瑋. "Preparation of Amorphous Metal Oxide Catalysts Containing Iron, Cobalt and Molybdenum for Oxygen Evolution Reaction". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8zsb3d.
Resumen
碩士國立臺灣科技大學
化學工程系
105
Water splitting reaction costs a lot of energy to produce oxygen and hydrogen. The best catalysts for water oxidation (oxygen evolution reaction, OER) are expensive metal oxides, such as RuO2 and IrO2; however, they cannot be used widely due to their rarity. In this research, we used photochemical metal-organic depositions (PMOD), a convenient, low-cost technique capable of producing highly active amorphous mixed-metal oxide OER catalysts. In this study, trying to find the abundant material on the crust of the earth, and promoting the activity of OER is our main purpose. Molybdenum is a widely used material in industry, and it also can prove the stability when it is mixed with other metal oxides. Therefore, this research will focus on the series of molybdenum oxides for OER. PMOD method was used to synthesize the amorphous mixed metal oxide films containing specific ratio of iron, cobalt, and molybdenum to figure out how metal affects OER. The compositions were the same and uniform distributed as they were in the precursor solution based on EDS analysis. In order to check the performance of metal oxides, Linear sweep voltammetry, and Tafel slope were plotted. The onset potential of Fe10Co25Mo65Ox was only 1.52 V, but FeOx and MoOx required 1.64 Vand 1.86 V, respectively. When the current density reached 1 mA cm-2, the potential for Fe10Co25Mo65Ox required 1.55 V, and 1.70 V for iron oxides. From Tafel slope, the value of Fe10Co25Mo65Ox was only 31 ± 1 mV dec-1, comparing to 44 ± 2 mV dec-1 for cobalt oxides, that meant Fe10Co25Mo65Ox had better catalytic ability. Stability was also a crucial property for electrodes. In this research, checking the stability by using chronopotentiometry set the current at 1 mA, reacted for 24 hours. The potential of Fe10Co25Mo65Ox almost unchanged. From these results, we can confirm that Fe10Co25Mo65Ox is an outstanding catalyst for OER.
33
Dieterle, Martin, martin dieterle@dieterle-wolfach de, 1968-10-06 y Alpirsbach. "In Situ Resonance Raman Studies of Molybdenum Oxide Based Selective". Phd thesis, 2001. http://edocs.tu-berlin.de/diss/2001/dieterle_martin.pdf.
34
Beato, Pablo [Verfasser]. "Synthesis and characterization of realistic molybdenum oxide based model systems in heterogeneous catalysis / vorgelegt von Pablo Beato". 2005. http://d-nb.info/976464330/34.
35
Julião, Diana Cristina dos Santos Neto. "Oxometal hybrid materials for oxidative desulfurization technology". Doctoral thesis, 2019. http://hdl.handle.net/10773/26664.
Resumen
Crude oil contains four classes of compounds: aromatics, cycloalkanes,
alkanes and compounds with atoms of sulfur, nitrogen and/or oxygen. The
presence of sulfur brings a lot of damage, for the petroleum industry itself as
well as for the environment, where is a major contributor of air pollution. The
EU has imposed strict legislations on the S content in transportation fuels.
However, the production of such ultra-low sulfur fuels by conventional
hydrodesulfurization technologies is very costly, due to the harsh conditions
(high temperatures and high H2 pressures) needed that are incompatible with
other important fuel requirements. The development of alternative technologies
that could successfully remove sulfur under sustainable and inexpensive
conditions is very important. Oxidative desulfurization (ODS) has proven to be
an effective approach for this purpose. In this process the sulfur compounds
are oxidized by the combination of a suitable catalyst with an oxidant. The
oxidized species are removed by extraction with appropriate polar solvents.
Following this strategy, in the present work novel catalytic systems were
developed based on the unexplored combination Mo(VI)-oxo/H2O2 for efficiently
desulfurizing model and real liquid fuels. Special attention was given to the
experimental conditions, particularly the substitution of organic volatile solvents
by more sustainable options, such as ionic liquids (ILs), deep-eutectic solvents
(DES) or solvent-free systems. Also, low H2O2/S ratios and low temperatures
(50 or 70 °C) were considered to achieve the optimal conditions. Directly or
indirectly (when dissolved) all the catalysts were reused and/or recycled for
several ODS cycles. In general, the desulfurization efficiency was maintained at
least until the third consecutive cycle. Of all the catalysts studied, the species
{PO4[MoO(O2)2]4}3- stood out due to its remarkably recyclability and stability
performance for desulfurization of a model diesel for ten consecutive cycles
under eco-sustainable conditions (H2O2/S = 3.7 and solvent-free system), with
its immiscibility in the reaction environment being of added value. The complex
IndMo(CO)3Me also displayed a remarkable behaviour under similar conditions.
Both catalysts were treated as heterogeneous catalysts and recovered and
reused without further treatment. Despite these outstanding results, the
absence of solvent during the ODS was detrimental to the treatment of real
diesel samples (2300 ppm S). The highest and the best ODS results were
achieved using biphasic systems (diesel/[BMIM]PF6): IndMo(CO)3Me (95 ppm),
[MoO2Cl2(DEO)] (129 ppm), CpMo(CO)3Me (372 ppm), [MoO2Cl2(DMB)2] (381
ppm), {PO4[MoO(O2)2]4}3- (500 ppm), [MoO2Cl2(di-tBu-bipy)] (621 ppm) and two
hybrid molybdenum compounds (740 and 741 ppm). The species
{PO4[WO(O2)2]4}3- also displayed high catalytic efficiency but using MeCN as
reaction medium.O petróleo contém quatro classes de compostos: aromáticos, cicloalcanos, alcanos e compostos com átomos de enxofre, azoto e/ou oxigénio. A presença de enxofre é prejudicial, para a indústria do petróleo como também para o ambiente, onde é o maior contribuinte para a poluição ambiental. A UE impôs legislações restritas para o conteúdo de enxofre nos combustíveis. No entanto o tratamento destes combustíveis, resulta num processo dispendioso devido às condições severas aplicadas (elevadas temperaturas e pressões de H2) incompatíveis com outros requisitos necessários para o combustível. O desenvolvimento de tecnologias alternativas que consigam remover o enxofre sob condições sustentáveis e economicamente mais viáveis é por isso bastante importante. A dessulfurização oxidativa (ODS) tem revelado ser um processo eficaz, no qual os compostos de enxofre são oxidados através da combinação de um catalisador e um oxidante, sendo as espécies oxidadas removidas facilmente por extração com solventes polares apropriados. Seguindo esta palavra de ordem, durante o presente trabalho foram desenvolvidos novos sistemas catalíticos, baseados na combinação pouco explorada Mo(VI)-oxo/H2O2, para eficientemente dessulfurizar diesel modelo e combustíveis reais. Deu-se especial atenção às condições experimentais, a partir das quais tentou-se substituir solventes orgânicos voláteis por opções mais sustentáveis, como líquidos iónicos (LIs), solventes eutécticos (DES) ou sistemas livres de solvente. Os rácios H2O2/S e temperatura reacional foram otimizados de forma a alcançar-se elevada eficiência de dessulfurização e economia do processo. De forma direta ou indireta (quando em solução) todos os catalisadores foram reutilizados e/ou reciclados por vários ciclos de ODS. De uma forma geral a eficiência de dessulfurização foi mantida por pelo menos três ciclos consecutivos. De todos os catalisadores aplicados, o {PO4[MoO(O2)2]4}3- sobressaiu pela sua extraordinária performance de reutilização e estabilidade na dessulfurização de um diesel modelo por dez ciclos consecutivos sob condições sustentáveis (H2O2/S = 3,7 na ausência de solvente). O IndMo(CO)3Me revelou ser um catalisador eficaz sob condições similares. Ambos foram tratados como catalisadores heterogéneos e recuperados e reutilizados sem tratamento adicional. Apesar dos valores sensacionais obtidos em meio monofásico, quando aplicados num gasóleo real (2300 ppm S), não exibiram a mesma eficácia. Os melhores resultados obtidos neste trabalho e quando comparados com o descrito na literatura foram alcançados em meio bifásico (gasóleo/[BMIM]PF6): IndMo(CO)3Me (95 ppm), [MoO2Cl2(DEO)] (129 ppm), CpMo(CO)3Me (372 ppm), [MoO2Cl2(DMB)2] (381 ppm), {PO4[MoO(O2)2]4}3- (500 ppm), [MoO2Cl2(di-tBu-bipy)] (621 ppm) e dois materiais híbridos à base de molibdénio (740 e 741 ppm). O {PO4[WO(O2)2]4}3- (259 ppm) também revelou elevada eficiência catalítica, mas na presença de MeCN como solvente de extração.
Programa Doutoral em Química Sustentável
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Ronge, Emanuel. "In-Situ Environmental TEM Studies of Electro- and Photo-Electrochemical Systems for Water Splitting". Doctoral thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-157D-8.