Dissertations / Theses on the topic 'Molybdenum oxide catalysts'
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Wawata, Ibrahim. "Methanol oxidation on molybdenum oxide catalysts." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/74613/.
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.
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/.
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.
Kuma, Ryoji. "Studies on Transition Metal Oxide Catalysts for Waste Gas Treatment." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263353.
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.
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.
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/.
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/.
Amakawa, Kazuhiko [Verfasser], and 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.
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.
Scholz, Juliane [Verfasser], Thorsten [Akademischer Betreuer] Ressler, and 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.
Kühn, Sven [Verfasser], Thorsten [Akademischer Betreuer] Ressler, Thorsten [Gutachter] Ressler, and 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.
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.
This 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
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.
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.
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.
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.
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.
Title from first page of PDF file. Document formatted into pages; contains xiv, 157 p.; also includes graphics. Includes bibliographical references (p. 145-153).
Schuh, Kirsten [Verfasser], and 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.
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.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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.
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.
Woods, Matthew P. "Activity and Selectivity in Oxidation Catalysis." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228175906.
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.
The 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
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.
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.
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.
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.
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.
Pillay, Bavani. "A study of nickel molybdenum oxide catalysts for the oxidative dehydrogenation of n-hexane." Thesis, 2009. http://hdl.handle.net/10413/8827.
Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2009.
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.
Wang, Ching-Huei, and 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.
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
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.
Chen, Chun-Wei, and 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.
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.
Dieterle, Martin, martin dieterle@dieterle-wolfach de, 1968-10-06, and Alpirsbach. "In Situ Resonance Raman Studies of Molybdenum Oxide Based Selective." Phd thesis, 2001. http://edocs.tu-berlin.de/diss/2001/dieterle_martin.pdf.
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.
Julião, Diana Cristina dos Santos Neto. "Oxometal hybrid materials for oxidative desulfurization technology." Doctoral thesis, 2019. http://hdl.handle.net/10773/26664.
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
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.