To see the other types of publications on this topic, follow the link: ZWM.
Dissertations / Theses on the topic 'ZWM'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'ZWM.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Callahan, Jordan J. "Silver-embedded ZSM-5 Zeolites: a Reliable SERS Substrate." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342104242.
Full text
2
Fernandes, Juliana Esteves. "Catalisadores Cu-, Co- ou Fe-ZSM-5 caracterização e avaliação na redução de NO a N2 com hidrocarbonetos na presença ou ausência de vapor de água." Universidade Federal de São Carlos, 2005. https://repositorio.ufscar.br/handle/ufscar/4146.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:56:55Z (GMT). No. of bitstreams: 1
DissJEF.pdf: 1826030 bytes, checksum: a3043074648b14bbec76bd05d3190200 (MD5)
Previous issue date: 2005-03-04<br>Universidade Federal de Sao Carlos<br>The minimization of the emissions of nitrogen oxides (NOx) in the atmosphere has been one of the great goals in the area of environmental
protection. Among the possible processes to treat the NOx, the selective catalytic reduction of NO with hydrocarbons (SCR-HC) has presented
important expectations. For this process, the metal/ZSM-5 type catalysts have appropriate levels of conversion in oxidative conditions.
In this context, the aim of this work was to prepare Cu, Co and FeZSM-5 catalysts. The samples were characterized by XRD, DRS-UVVIS, FTIR, H2-TPR, SEM and tested in the reduction of NO to N2 with propane or methane in oxidative atmosphere in the presence or absence of water steam. The H2-TPR data showed that the cationic species present in the
prepared Cu, Co and FeZSM-5 catalysts, after thermal activation, were mainly Cu2+ (Cuα
2+ e Cuβ 2+), Co2+ and Fe3+ cations located in charge compensation sites in the zeolite, respectively. From FTIR and DRS-UVVIS
it was also possible identify oxide species, which were present in a lower content.
In the reduction of NO to N2 in the absence of water steam, the CuZSM-5 catalysts showed higher levels of conversion of NO than those
based in Co and Fe. However, the FeZSM-5 catalysts showed, in this condition, activity at lower temperatures. This behavior makes them
potentially interesting to be applied for practical purposes. On the other hand, in the presence of water steam, it was verified a higher loss of
activity of the CuZSM-5 catalyst, which was totally restored removing the water in the feed. For the Co and FeZSM-5 catalysts, the activity loss in
the presence of water steam was partially recovered during time on stream.<br>A minimização das emissões de óxidos de nitrogênio (NOx) na atmosfera tem sido um dos grandes desafios da área de proteção
ambiental. Dentre os processos para o tratamento dos NOx possíveis, a redução catalítica seletiva do NO com hidrocarbonetos (RCS-HC) vem apresentando excelentes perspectivas. Para este processo os
catalisadores metal/zeólita ZSM-5 possuem adequados níveis de conversão em condições oxidantes. Dentro deste contexto, este trabalho teve como objetivo preparar catalisadores Cu, Co e FeZSM-5. As amostras foram caracterizadas por DRX, DRS-UVVIS, FTIR, RTP-H2, MEV e sua atividade verificada através da redução de NO a N2 com propano ou metano em atmosfera oxidante, na presença ou ausência de vapor de água. Os resultados de RTP-H2 mostraram que as espécies presentes nos catalisadores Cu, Co e FeZSM-5, após ativação térmica, foram
principalmente os cátions Cu2+ (Cuα
2+ e Cuβ 2+), Co2+ e Fe3+ compensando
carga na zeólita, respectivamente. A partir de FTIR e DRS-UVVIS foi possível, também, identificar espécies oxidas, as quais estavam presentes em teores menores. Na redução de NO a N2 na ausência de vapor de água os
catalisadores CuZSM-5 apresentaram maiores conversões de NO que os contendo Fe ou Co. Entretanto, os catalisadores FeZSM-5 apresentaram, nessa condição, atividade em temperaturas menores, o que mostra uma
vantagem para o seu uso prático. Na presença de vapor de água, verificou-se uma maior queda da atividade no catalisador CuZSM-5,
somente recuperada com a retirada desse composto na alimentação, sendo que para os catalisadores CoZSM-5 e FeZSM-5 a perda de
atividade foi parcialmente recuperada ao longo do tempo.
3
Barros, Ivoneide de Carvalho Lopes. "Estudo e aplicação dos Sistemas ZSM-5 contendo nióbio." reponame:Repositório Institucional da UnB, 2007. http://repositorio.unb.br/handle/10482/1363.
Full textAbstract:
Tese (doutorado)—Universidade de Brasília, Instituto de Química, 2007.<br>Submitted by Luis Felipe Souza (luis_felas@globo.com) on 2009-01-08T12:20:12Z
No. of bitstreams: 1
Tese_2007_IvoneideBarros.pdf: 3390296 bytes, checksum: 2bd94256449111f511c6d9dad708ee99 (MD5)<br>Approved for entry into archive by Georgia Fernandes(georgia@bce.unb.br) on 2009-02-27T14:59:03Z (GMT) No. of bitstreams: 1
Tese_2007_IvoneideBarros.pdf: 3390296 bytes, checksum: 2bd94256449111f511c6d9dad708ee99 (MD5)<br>Made available in DSpace on 2009-02-27T14:59:03Z (GMT). No. of bitstreams: 1
Tese_2007_IvoneideBarros.pdf: 3390296 bytes, checksum: 2bd94256449111f511c6d9dad708ee99 (MD5)<br>A incorporação do metal nióbio em peneiras moleculares microporosas promove novas propriedades a esses materiais. Nesse sentido, foram preparados catalisadores suportados com 2 - 25 % em massa de óxido de nióbio(V) sobre zeólita ZSM-5 de duas fontes: Zeolyst e FCC/Petrobrás. A natureza do metal tem um papel importante na alteração da distribuição e força dos sítios ácidos na superfície do suporte. As amostras foram submetidas a um estudo térmico a fim de otimizar parâmetros e evitar uma possível redução das propriedades ácidas do catalisador por desidroxilação. Os catalisadores modificados, Nb(x)HZSM-5, foram caracterizados através da combinação de métodos térmicos (TG, DTA, DSC) e espectroscópicos (FT-IR e FT-Raman e IR-DRIFT), bem como de RMN-MAS de 29
vi Si e 27Al e CP/MAS de 29Si, DRX, ICP-AES e medidas de área superficial específica (método BET), visando a obtenção de informações estruturais e de estabilidade dos sólidos. As propriedades catalíticas foram verificadas com auxílio das reações modelo de dessulfurização do tiofeno e esterificação do ácido oléico. Para monitorar o rendimento desses processos, foram utilizadas as técnicas de FRX e RMN 1H. Resultados de RMN e DRX indicaram que a estrutura da zeólita contendo Nb não sofreu desaluminização após tratamento térmico, explicada pela presença da unidade Si-O-Nb na estrutura das zeólitas por espectroscopia de FT-IR e Raman. Análises térmicas comfirmaram que a impregnação de NbO25 reduziu a desidroxilação da zeólita ZSM-5, promovendo uma estabilização térmica. A área BET e o volume de poro diminuem gradualmente nesses sólidos com o aumento da quantidade de Nb após calcinação. Outrossim, investigou-se a natureza dos sítios ativos pelo método de pré-adsorção de uma base, utilizando piridina como molécula prova. Bandas de absorção de piridina no infravermelho referentes a sítios ácidos de Brönsted e de ligação de hidrogênio foram observadas para os sistemas derivados de ZSM-5 da Zeolyst. Nos sistemas Nb(x)HZSM-5 derivados da FCC/Petrobrás foram observados, além dos dois sítios citados, uma pequena fração de sítios ácidos de Lewis. Isto justifica a maior acidez apresentada nas zeólitas impregnadas com 2 e 5 % de NbO25, quando comparadas às suas correspondentes amostras da Zeolyst, independente da calcinação. As análises de FRX indicaram que a adsorção de tiofeno sobre os catalisadores modificados foi bem superior (quase o dobro nas amostras derivadas da Petrobrás) ao do catalisador de partida, destacando maior interação do organossulfurado quando o catalisador contém 5 % de NbO25, e observando uma queda a partir de 15 %, sendo explicado pelo excesso da monocamada do óxido, conforme DRX e FT-Raman. A presença do cobre também exerce influência sobre a eficiência do processo de dessulfurização, otimizando-o. Finalmente, foi mostrado que entre as amostras modificadas, a melhor conversão na esterificação do ácido oléico ocorre com Nb(5)HZSM-5, corroborando com os resultados da dessulfurização, embora o catalisador sem Nb tenha apresentado maior atividade catlítica nas mesmas condições. __________________________________________________________________________________________ ABSTRACT<br>Incorporation of niobium into microporous molecular sieves brings up new properties for these materials. Supported catalysts containing 2 - 25 wt.% of niobium oxide were prepared over ZSM-5 from two manufacturers: Zeolyst e FCC/Petrobrás. The metal nature has a fundamental role in the changes of distribution and strength of acid sites on the original support surface. The samples were subjected to thermal studies optimizing parameters to avoid a possible reduction of acid properties by dehydroxylation. The modified catalysts, Nb(x)HZSM-5, were characterized by the combination of thermal (TG, DTA, DSC) and spectroscopic (FT-IR, FT-Raman and IR-DRIFT) methods, besides 29 viiSi and 2729Al MAS and Si CP-MAS NMR, XRD, ICP-AES and measurements of specific surface area (BET method) in order to obtain structural and stability information about the solids. Catalytic properties were verified through model reactions of thiophene desulfurization and oleic acid esterification. XRF and 1H NMR were used to monitor yields. NMR and XRD results showed that the zeolite structure containing Nb did not undergo dealumination after thermal treatment, according to the presence of Si-O-Nb units on the zeolites structure by FT-IR and Raman studies. Thermal analyses confirm that the impregnation of NbO25 reduces ZSM-5 dehydroxylation, thus promoting a thermal stabilization. BET method for Zeolyst ZSM-5 indicated that area and pore volume decreased with the increase of Nb on the calcined samples. In addition, it was investigated the nature of active sites by pre adsorption of pyridine. Infrared pyridine absorption bands related to Brönsted and hydrogen bond acid site types were observed for Zeolyst ZSM-5 systems. For the systems Nb(x)HZSM-5 using HZSM-5 from FCC/Petrobrás it was observed, besides the two abovementioned acid sites, a small faction of Lewis acid sites. This justifies the higher acidity showed by 2 and 5 wt.% NbO25 impregnated on zeolite, when compared to the Zeolyst samples, independent of calcination procedure. XRF analyses indicated that the thiophene adsorption over modified catalysts was improved in relation to the parent catalyst, emphasizing higher interaction of organosulfur compound when the catalyst has 5 wt.% of NbO25. It was observed a decrease for 15 wt.% explained by excess of oxide monolayer, according to XRD and FT-Raman results. Copper presence also affects the efficiency of desufurization process, optimizing it. Finally, it was showed that among the modified samples, the better conversion of oleic acid esterification occurs to Nb(5)HZSM-5 in agreement to desulfurization results, although the parent catalyst has showed higher catalytic activity at same conditions.
4
Alnaimi, Essa. "Maximizing propylene selectivity while minimizing dry gas yield in FCC unit through post synthetic modifications of nano ZSM-5." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/maximizing-propylene-selectivity-while-minimizing-dry-gas-yield-in-fcc-unit-through-post-synthetic-modifications-of-nano-zsm5(fca15721-f78d-47b8-aec6-586c880fecba).html.
Full textAbstract:
This research explored different catalytic cracking zeolite additives to improve propylene selectivity and minimize dry gas yield. A comprehensive study of the effect of zeolite structure, pore system and crystal size on maximizing propylene production in FCC unit and the effect of post synthetic modifications on the physicochemical properties and cracking activity of ZSM-5 was investigated using X-ray diffraction (XRD), pyridine adsorption fourier transform infra-red (FTIR), 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and the catalytic cracking using n-heptane, as a model compound for heavy naphtha. The catalytic performances of these additives were evaluated in a fixed-bed reactor unit using n-heptane as a model compound for naphtha at temperatures 450 - 500 oC and W/F 38 - 92 gcat.h/mol. A range of zeolites were tested with ZSM-5 showing the optimum results at high feed conversion. Further studies on ZSM-5 crystal size illustrated that nano ZSM-5 (300 nm) was superior compared to the regular ZSM-5 (2000 - 4000 nm) in achieved conversion level and propylene selectivity. These improvements were attributed to the shorter path lengths for the reactant reducing diffusion constraints significantly. Modifying nano ZSM-5 acidity using steaming, acid leaching and silanation showed significant improvement over nano ZSM-5 parent. Mild steaming of nano ZSM-5 improved both n-heptane conversion and propylene selectivity whilst severe steaming only improved propylene selectivity. This work attempted to address the often discussed catalytic activity enhancement from mild steaming and identified newly created moderate acid sites as the source of increased activity. Dealumination by acid leaching decreased the total aluminium content of nano ZSM-5 and changed the Brønsted/Lewis ratio. Increasing the B/L ratio, increased the conversion and propylene selectivity. In addition, this research focussed for the first time on the silanation of nano ZSM-5 and its effect on n-heptane cracking, in particular, propylene and dry gas selectivity. Silica was deposited on the external surface of nano ZSM-5 neutralising the acidic sites and as a result, dry gas yield was significantly decreased due to the elimination of non-selective cracking. However, the trade off with conversion was high.
5
Losch, Pit. "Synthesis and characterisation of zeolites, their application in catalysis and subsequent rationalisation : methanol-to-olefins (MTO) process with designed ZSM-5 zeolites." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF035/document.
Full textAbstract:
Cette thèse s'articule autour des zéolithes, plus particulièrement leur synthèse, leur caractérisation et leur application comme catalyseurs hétérogènes. Dans certains cas, la compréhension des phénomènes encontrés au cours de ce processus nécessitait un travail de rationalisation. Ce dernier ingrédient permet une réelle amélioration continue, ou une conception sur mesure d'un catalyseur pour une réaction. Les zéolithes sont des aluminosilicates, microporeux et cristallins, qui se définissent et se différencient de part leur arrangement 3D de tétraèdres (SiO4 et AlO4) . Il a été essayé d'utiliser des zéolithes conçues sur mesures en tant que catalyseurs pour des réactions faisant partie d'une chimie renouvelable. Ainsi, ces travaux s'inscrivent dans le cadre des concepts de la chimie verte et de l'addition graduelle de complexité moléculaire. Au cours de cette thèse, la boucle itéative de l'amélioration continue a mené à deux reprises à un catalyseur très adapté au processus catalytique en question: d'une part l'halogènation d'aromatiques a été effectuée en phase liquide, il s'agit d'un procédé liquide-solide pour lequel le meilleur catalyseur résulte en une zéolithe béta (H-*BEA) avec une porosité hiérarchisée. Au contraire, la réaction de la conversion du méthanol en oléfines (MTO) une réaction gas-solide semble avoir comme catalyse uroptimal des zéolithes de type ZSM-5 sans porosité hierarchisée, mais ayant des tailles cristallines élevées, une qualité cristalline proche de la perfection (sans défauts) et une densité de sites acides très disperses<br>This work revolved around the synthesis, characterisation and application of zeolites in heterogeneous catalysis. In some cases, counterintuitive observations and results needed a thorough rationalisation, which allowed a truly continuous improvement, or rational design of a catalyst for a given reaction. Zeolites are crystalline and microporous aluminosilicates, which are defined and differ one from another through their 3D arrangement of tetrahedra (SiO4 and AlO4).It has been aimed to design heterogeneous catalysts for reactions that fit in the concepts of a sustainable chemistry. Thus, this works describes and tried to respect the concepts of green chemistry and carbon upgrading. Remarkably, during this thesis the feedback looped continuous improvement approach has led twice to adapted catalysts for a catalytic chemical transformation: the liquid-solid continuous flow halogenation of aromatics was best performed with nanosized H-*BEA zeolites exhibiting a hierarchical porosity. In contrast, the gas-solid Methanol-to-Olefins (MTO) process needed an unusual catalyst. Indeed based on our study, large and perfectly crystalline H-ZSM-5 crystals with a disperse Brønsted acidity were the optimum catalyst
6
Sousa, Jennifer Caroline de. "Efeitos de glicocorticoide sobre a expressão de genes de relógio nas células ZEM-2S de Danio rerio." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/41/41135/tde-20052015-104948/.
Full textAbstract:
O estudo da expressão circadiana de genes de relógio tem sugerido hormônios como potenciais agentes sincronizadores. A regulação da ritmicidade de relógios periféricos é, aparentemente, mais um dentre os diferentes efeitos fisiológicos atribuídos aos glicocorticoides (GCs), que se constituem como candidatos a zeitgeber dado ao fato de que seus níveis circulantes apresentam padrões diários robustos e são uma das principais eferências do relógio central em mamíferos. Entretanto, em outros vertebrados, o papel dessa classe hormonal em relação a este aspecto ainda é pouco explorado e se a regulação é direta ou indireta, quais suas consequências e de que maneira ela ocorre são indagações a serem respondidas. Empregando a técnica do PCR quantitativo, avaliamos o perfil de expressão dos genes da alça negativa do núcleo da maquinaria molecular do relógio, per1b e cry1b, em células ZEM-2S do teleósteo Danio rerio expostas ao regime fotoperiódico 12:12 CE ou mantidas em escuro constante (EE) e mantidas em EE, mas condicionadas a trocas diárias de meio de cultura ou a pulsos diários de dexametasona a 10-7 M (DEXA), agonista sintético de glicocorticoide. Em 12:12 CE, ambos os genes apresentaram variação temporal, com picos de expressão observados na fase clara do ciclo. Em EE, per1b mostrou um perfil oscilatório de amplitude atenuada, enquanto para cry1b, não foi detectada oscilação ao longo das 24 h. Trocas de meio em EE alteraram significativamente o padrão de expressão de per1b e cry1b, no entanto, os pulsos diários de DEXA promoveram uma oscilação temporal muito mais pronunciada para per1b, modulando positiva ou negativamente sua expressão nos diferentes pontos temporais. O emprego do antagonista RU 486 na concentração de 10-5 M aboliu o pico de expressão detectado no ZT 16, porém, na concentração de 10-6 M, a expressão gênica foi aumentada em cerca de 3 vezes comparado ao tratamento apenas com DEXA. O gene cry1b, por sua vez, não se apresentou suscetível aos pulsos diários de DEXA. Estes resultados permitem confirmar as células ZEM-2S como modelo de relógios periféricos em cultura dada a fotossensibilidade intrínseca das mesmas, reafirmando o papel do ciclo CE como principal agente sincronizador. Os glicocorticoides certamente exercem modulação de per1b por meio da via genômica direta, sem, no entanto excluir uma possível ação via receptor de membrana, tendo em vista a atividade agonista de RU 486, podendo se constituir em um dos fatores que regulam o complexo funcionamento da maquinaria molecular do relógio biológico de zebrafish<br>Studies on the circadian expression of clock genes have suggested hormones as potential synchronizing agents. Regulation of rhythmicity of peripheral clocks is among the various physiological effects of glucocorticoids (GCs), which are candidate to zeitgeber, since their circulating levels present robust daily patterns and are one of the major outputs of the mammalian central pacemaker. However, in other vertebrates, such a feature has yet to be clarified as well as if the hormonal regulation is direct or indirect, what are its mechanisms and consequences. Applying qPCR technique, we evaluated the gene expression profile of per1b and cry1b, negative feedback loop members of the molecular machinery of biological clock, in ZEM-2S cells of the teleost Danio rerio. The cells were exposed to photoperiod regimen of 12:12 LD; kept in constant darkness (DD); kept in DD but subject to medium changes or treated with daily pulses of 10-7 M dexamethasone (10-7 M DEXA), a glucocorticoid synthetic analogue. In 12:12 LD, both genes presented temporal variation, with peaks of expression in the light phase. In DD, per1b showed an oscillatory profile with attenuated amplitude, whereas cry1b did not oscillate throughout 24 h. DEXA-free medium changes in constant DD conditions altered significantly per1b and cry1b expression profiles. Nevertheless, DEXA daily pulses promoted a temporal oscillation much more pronounced for per1b, modulating positively or negatively its expression at different time points, whereas cry1b was not susceptible to the hormone. RU 486 at 10-5 M abolished the peak of expression of per1b previously observed at ZT 16. On the other hand, RU 486 at 10-6 M increased the gene expression around 3-fold in comparison to just DEXA treatment. These results confirm ZEM-2S cells as a model of peripheral clocks in culture due to their intrinsec photosensitivity, emphasizing the light/dark cycle as a major synchronizing agent. The glucocorticoid modulates per1b expression, probably through a direct genomic pathway, without excluding however its possible action through membrane receptors, since RU 486 exerted agonistic activity. Glucocorticoids could, therefore, be one of the factors that regulate the complex molecular machinery of zebrafish biological clock
7
Khangkham, Supaporn. "Catalytic degradation of poly(methyl methacrylate) by zeolites and regeneration of used zeolites via ozonation." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/9227/1/khangkham.pdf.
Full textAbstract:
Catalytic degradation of PMMA was successfully performed at temperatures below 300°C. The use of zeolite catalyst could reduce reaction temperature in comparison with an ordinary thermal degradation process. It was found that the product distribution obtained from batch experiment depends on zeolite acid properties whereas the composition of the liquid fraction is directly related to the shape selectivity of the catalyst. A continuous fixed bed process was designed that allowed to obtain MMA monomer as main product. The increase of reaction temperature from 200 to 270°C showed a positive effect on the liquid product yield. However, at higher temperatures, the light product was further cracked into gaseous products. Significant deactivation of ZSM-5 catalyst was observed after 120 hours of operation, resulting in a decrease in liquid product yield. Regeneration of the coked ZSM-5 extrudates was achieved by oxidation with ozone at low temperatures, below 150°C. The effects of temperature, GHSV and inlet concentration of ozone on carbon removal efficiency were studied. Carbon removal with ozone started at 50°C and reached a maximum of 80% at 100°C. Higher temperatures were not beneficial due to the strong limitation of ozone diffusion which confines radical production then the regeneration process to the outer surface. In optimal conditions, ozonation almost fully restored the zeolite activity without damaging the texture and active sites of zeolite, as shown from the results of regenerated catalyst in PMMA cracking
8
Backhaus, Sita. ""Buffy" und "Sabrina" - Mystery für Mädchen Untersuchungen zu neueren TV-Serien und deren Begleitbüchern sowie ihrer Rezeption /." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11612104.
Full text
9
Silva, Silvia Caroline Gomes dos Santos. "Síntese de materiais compósitos micro-mesoporosos visando a captura de CO2." Universidade Federal de Sergipe, 2015. http://ri.ufs.br:8080/xmlui/handle/123456789/3479.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>factor responsible for climate change worldwide. In recent years, several research are intended to developing new methods and technologies to capture and separation CO2.
The use of the adsorption method for separating CO2 is a promising alternative in view of the potential to reduce energy costs by eliminating aqueous solutions and providing capture and regeneration rates adequate. In this context, this paper presents the synthesis of composite type materials ZSM-12 / MCM-41 and ZSM-12 / MCM-48, seeking to combining the properties of the zeolitic material to the structural advantages of mesoporous materials, resulting in obtaining materials with high CO2 adsorption capacity. For this, the materials were synthesized by hydrothermal method and mechanosynthesis. The materials were characterized by XRD, absorption spectroscopy in the infrared, thermal analysis, adsorption-desorption analysis of N2 A 77 K, SEM and TEM. The CO2 adsorption capacity of these materials were investigated by gravimetric analysis. The results obtained from the characterization techniques showed that the synthesis methodology, used for desilication phase of ZSM-12, was efficient in obtaining a composite material with integrated micro and mesoporous phases. On the other hand, the results showed that by mechanosynthesis was possible to obtain materials formed by mixing between the micro and mesoporous phases. Also, comparing the results of adsorption CO2 the obtained composite materials by hydrothermal method with those obtained by mechanosynthesis it was concluded that the adsorption capacity is influenced by crystallinity and amount of the phase ZSM-12. The results showed from adsorption, in general, ZM48-75 samples, ZM41 A/MH R3 and ZM41-50 showed higher adsorption capacity than pure zeolitic and mesoporous materials, respectively. Thus, the composite materials of the type ZSM-12/ZSM-41 and MCM-12/MCM-48 are promising adsorbents for CO2 separation.<br>O aumento da concentração de dióxido de carbono na atmosfera é apontado como o principal fator responsável pelas mudanças climáticas em escala mundial. Nos últimos anos, várias pesquisas têm por finalidade o desenvolvimento de novos métodos e tecnologias para captura e separação de CO2. A utilização do método de adsorção para separação de CO2 é uma alternativa promissora, tendo em vista o potencial para reduzir os custos energéticos, eliminando soluções aquosas e proporcionando captura e taxa de regeneração adequadas. Nesse contexto, neste trabalho apresenta-se a síntese de materiais compósitos do tipo ZSM-12/MCM-41 e ZSM-12/MCM-48, visando combinar as propriedades do material zeolítico com as vantagens estruturais dos materiais mesoporosos, resultando na obtenção de materiais com elevadas capacidades de adsorção de CO2. Para isto, os materiais foram sintetizados pelo método hidrotérmico e por mecanosíntese. Os materiais obtidos foram caracterizados por DRX, espectroscopia de absorção na região do infravermelho, análise térmica, analise de adsorção-desorção de N2 A 77 K, MEV e TEM. A capacidade de adsorção de CO2 destes materiais foi investigadas através da análise gravimétrica. As técnicas de caracterização mostraram que a metodologia de síntese adotada via dessilicalização da fase ZSM-12 foi satisfatória na obtenção de um material compósito com as fases micro e mesoporosas integradas. Por outro lado, os resultados evidenciaram que através da mecanosíntese foi possível obter materiais formados pela mistura entre as fases micro e mesoporosas. Além disso, comparando-se os resultados de adsorção de CO2 dos materiais compósitos obtidos via método hidrotérmico com os obtidos via mecanosíntese foi possível concluir que a capacidade de adsorção é influenciada pela cristalinidade ou teor da fase ZSM-12. Considerando-se os resultados de adsorção apresentados, de maneira geral, as amostras ZM48-75, ZM41-A/R3-MH e ZM41-50, apresentaram maior capacidade de adsorção que os materiais zeolíticos e mesoporosos puros, respectivamente. Sendo assim, os materiais compósitos do tipo ZSM-12/MCM-41e ZSM-12/MCM-48 são promissores adsorventes para separação de CO2.
10
Göhlich, Maik. "Zum Einfluss textureller, struktureller und acider Eigenschaften phosphorsäuremodifizierter ZSM-5-Zeolithe auf die heterogen-katalysierte Umsetzung von Glycerol." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-66789.
Full textAbstract:
Die Nutzung von Kraftstoffen auf der Basis von Biodiesel erlaubt es, konventionelle, etablierte Antriebstechniken mit Nachhaltigkeit zu kombinieren. Daher kann in den nächsten Jahren mit einer weiteren weltweiten Steigerung der Biodieselproduktion gerechnet werden. Damit verbunden ist jedoch auch ein Anstieg der anfallenden Menge an Glycerol, das bei der Herstellung von Biodiesel als Koppelprodukt entsteht. Da traditionelle Märkte für Glycerol kaum mehr Wachstum zeigen, müssen neue Wege zur effizienten Verwertung von Glycerol gefunden werden. Die vorliegende Arbeit beschäftigt sich mit der heterogen-katalysierten Umsetzung von Glycerol zu Acrolein. Unter Verwendung von ZSM-5-Katalysatorproben mit unterschiedlichem Si/Al-Verhältnis und phosphorsäure-modifizierten Katalysatorproben konnte die Existenz von Synergieeffekten zwischen den texturellen, strukturellen und aciden Eigenschaften in der heterogen-katalysierten Glyceroldehydratisierung zu Gunsten der Acroleinselektivität eindeutig nachgewiesen werden. Eine selektive Umsetzung von Glycerol zu Acrolein wird daher an solchen Katalysatorproben ermöglicht, die ausgewogene texturelle, strukturelle und acide Eigenschaften aufweisen.
11
Sousa, Zilacleide da Silva Barros. "Transformação de metanol em olefinas leves catalisada por zeólitas HZSM-5." Universidade do Estado do Rio de Janeiro, 2007. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3225.
Full textAbstract:
A reação de transformação de MeOH em olefinas leves foi investigada sobre zeólitas HZSM-5 com razões SiO2/Al2O3 (SAR) iguais a 30, 80 e 280. As propriedades ácidas e texturais da amostra com SAR 30 foram modificadas por impregnação com ácido fosfórico. A caracterização físico-química das amostras foi realizada empregando-se as técnicas de FRX, fisissorção de N2, DRX, DTP de NH3 e IV com adsorção de piridina. O desempenho catalítico das mesmas foi comparado tanto em condições reacionais similares (mesma T, pressão parcial de MeOH e WHSV) como em condições de isoconversão. Verificou-se, que quanto maior a SAR da zeólita, menor a densidade total e a força dos sítios ácidos presentes, sendo este efeito mais significativo para os sítios de Brönsted. O efeito do aumento da SAR favoreceu a estabilidade catalítica e a formação de olefinas leves, principalmente propeno. No caso das amostras contendo fósforo, foi observada uma redução linear na área específica BET e no volume de microporos com o aumento do teor de fósforo. Estes resultados, aliados aos obtidos por DRX, sugerem que a redução mais significativa na área específica e no volume de microporos pode ser associada à redução na cristalinidade e à formação de espécies amorfas contendo fósforo, que bloqueariam a estrutura porosa da zeólita. Não se observou alteração significativa na força dos sítios fracos, enquanto a força dos sítios fortes diminuiu significativamente. As amostras apresentando menor SAR e menor teor de fósforo foram mais ativas. Por outro lado, em condições de isoconversão de 916%, a amostra mais seletiva à formação de olefinas foi aquela com maior SAR. Dentre as amostras impregnadas, aquela contendo 4% de fósforo foi a mais seletiva a propeno, enquanto a que continha 6% foi mais seletiva a eteno. A amostra com SAR igual a 280 foi investigada variando-se a temperatura de reação (400, 500 e 540C) e a pressão parcial de metanol (0,038; 0,083 e 0,123 atm), através de um planejamento experimental do tipo Box-Benhnken (32). O rendimento otimizado em olefinas leves foi alcançado a 480C e 0,08 atm. O modelo proposto descreveu bem os dados experimentais e evidenciou a existência de uma faixa ótima de temperatura para maximização do rendimento em propeno e eteno, o qual foi também afetado pela pressão parcial de MeOH na faixa estudada.
Palavras-chave: ZSM-5, olefinas, propeno, eteno, processo MTO, fósforo.<br>The MeOH transformation into light olefins was investigated over HZSM-5 zeolites with SiO2/Al2O3 (SAR) = 30, 80 and 280. The acidic and textural properties of the SAR 30 were modified by impregnation with orthophosphoric acid. Textural characterization and physiochemical like FRX, fisisorption of N2, DRX, DTP of NH3 and IR with pyridine adsorption were used. The catalytic performance of the samples evaluated and compared at both isoconversion and iso-operacional. It was verified, that the increase in SAR of the zeolite reduced acid site density and strenght of the acid sites, particularly for the Brönsted acid sites, favoring the catalytic stability and the formation of light olefins, mainly propene. The characterizations indicated a linearr reduction in the specific BET surface area and in the microporous volume with the increase of the phosphorous incorporation. These results, together with over obtained by DRX, suggest that the most significant reduction in the specific area and in the microporos volume can be associated to the reduction in the cristalinity as well as to the formation of amorphous species containing phosphorous, that would block the zeolite porous structure . No significant alteration was observed in the strenght of the weak sites, although the strong acid sites strenght significantly decreased. The low SAR and slow phosphorous incorporation ware more active. On the other hand, at isoconversion conditions (916), the most selective samples to olefins formation were those with high SAR. Among the impregnated samples, the one containing 4% of phosphorous was more selective to olefins. The sample with SAR equal to 280 was investigated under different reaction temperature (400, 500 and 540C) and methanol partial pressure (0,038; 0,083 and 0,123 atm), following Box-Benhnken (32) experimental planning type. The optimized light olefins yield was reached at 480C and 0,08 atm. The proposed model described well the experimental data and evidenced the existence of a range of temperature for maximization of the propene and ethene, which was also affected by the partial pressure of methanol in the studied range.
12
Kielisch, Jürgen. "Die Geschichte der griechisch-orthodoxen Kirchengemeinde zum Erlöser in München 1828-1944 /." Hamburg : Lit, 1999. http://catalogue.bnf.fr/ark:/12148/cb388003460.
Full text
13
Coskun, Zuhal. "Synthesis And Characterization Of Zsm-35." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1167535/index.pdf.
Full text
14
Yu, Fang. "Abiotic Degradation of Chlorinated Hydrocarbons (CHCs) with Zero-Valent Magnesium (ZVM) and Zero-Valent Palladium/Magnesium Bimetallic (Pd/Mg)-Reductant." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1373881146.
Full text
15
Gruber, Julia. "Film- und Fernsehbegleitbücher in Öffentlichen Bibliotheken Untersuchung zu Angebot und Nutzung im Regierungsbezirk Tübingen /." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11675515.
Full text
16
Raad, Mira. "Aromatisation du propane sur des catalyseurs bifonctionnels de type Ga-MFI : impact de la hiérarchisation de la zéolithe ZSM-5." Thesis, Poitiers, 2017. http://www.theses.fr/2017POIT2298/document.
Full textAbstract:
Mélanger un oxyde de gallium avec une zéolithe H-ZSM-5 donne les mêmes résultats catalytiques en craquage du n-hexane, déshydrogénation du cyclohexane et en aromatisation du propane qu'un catalyseur préparer par échange cationique avec un sel de gallium. En fait, le véritable catalyseur est synthétisé lors du prétraitement sous hydrogène pendant lequel le suboxyde de gallium (Ga2O) issu de la réduction de Ga2O3 réagit avec les sites de Brønsted de la zéolithe pour donner des hydrures de gallium. La réaction de déshydrogénation des alcanes fait intervenir un site catalytique bifonctionnel composé d'un site de Lewis du Ga et d'un site basique généré par l'oxygène de la charpente zéolithique. L'activation du propane se produit sur un hydrure de gallium via un mécanisme de type alkyle. Les aluminosilicates dopés avec Ga sont plus performants que les gallosilicates, ce qui signifie que les espèces de gallium sont plus actives en extra-réseau que dans le réseau de la zéolithe.Le coke généré lors de l'aromatisation du propane est très polyaromatique avec plus de quinze noyaux benzéniques, localisé dans les micropores il s'avère très toxique. La création de mésopores intracristallins sans modifier les propriétés acides de la zéolithe (nombre et force des sites acides) est possible par un traitement alcalin. Leur présence permet de limiter les réactions de transfert d'hydrogène mais est peu efficace pour contrôler la croissance du coke, les mésopores sont mêmes négatifs pour la réaction de déshydrogénation rendant les catalyseurs bifonctionnels hiérarchisés inefficaces en aromatisation du propane ; l'étape cinétiquement limitante pour cette réaction étant la déshydrogénation<br>The mixing Ga2O3 with the H-ZSM-5 zeolite yields to the same catalytic performance in n-hexane cracking, cyclohexane dehydrogenation and propane aromatization than a bifunctional catalyst prepared by cationic exchange. The real catalyst appears upon hydrogen pretreatment in which gallium (Ga2O) suboxide that results from Ga2O3 reduction, reacts with the zeolite Brønsted sites to yield to gallium hydrides.The dehydrogenation reaction of alkanes involves a bifunctional catalytic site constituted of a Lewis site (Ga species) and basic site (an oxygen of the zeolite framework). The aluminosilicate catalysts loaded with Ga are more efficient than the gallosilicate catalysts, therefore extraframework gallium species is more active than the framework gallium species.The coke formed during the propane aromatization is very polyaromatic with more than fifteen benzenic rings, is very toxic. The creation of intracrystalline mesopores by alkaline treatment.preserves the acidic properties of the zeolite (number and strength of acidic sites). The mesopores allow limiting the hydrogen transfer reactions but is not very effective for impeding the growth of the coke, the presence of mesopores are even negative for the dehydrogenation reaction making inefficient the hierarchical bifunctional catalysts in propane aromatization; the kinetically limiting step for this reaction being dehydrogenation
17
Gomes, Fagner Alves. "Isomerização do n-Hexano por platina suportada na zeólita H-ZSM-5 : efeito do teor de alumínio." Universidade Federal de São Carlos, 2011. https://repositorio.ufscar.br/handle/ufscar/4078.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:56:44Z (GMT). No. of bitstreams: 1
3706.pdf: 2821060 bytes, checksum: 5975ad59eeeedfbd6e16578292306171 (MD5)
Previous issue date: 2011-08-01<br>Universidade Federal de Sao Carlos<br>The objective of this study was to verify the influence of the Si/Al ratio (11.5, 15.0, 25.0, 40.0 and 140.0) in zeolite ZSM-5 in the conversion, activity, selectivity and stability as bifunctional catalysts (Pt/H-ZSM-5) applied to the isomerization reaction of n-hexane. To prepare the bifunctional catalysts, initially the zeolites were submitted, successively, to ion exchange with ammonium cations, ion exchange cations with platinum, calcination and activation process. From the results of the isomerization of n-hexane, it was observed that with the increase of the Si/Al ratio, that is, decreasing the amount of aluminum, there was a reduction in activity and conversion. This is due to decrease the number of acid sites present, responsible to isomerize the carbocation generated in these sites. In contrast, the increase of the Si/Al ratio leads to a better selectivity to the formation of isomers. Among the catalysts, the Pt/H-ZSM-5 (15.0) showed the best result of conversion and activity. In order to compare the Pt/H-ZSM-5 catalysts, the reaction was carried out using the isomerization catalyst Pt/H-Beta (9.0). This catalyst had the best result that all the others, this result may possibly be due to increased acidity of the material and its morphological characteristics, such as type and diameter of pores etc. and/or the crystallite size of zeolites used.<br>O objetivo deste estudo foi verificar a influência da razão Si/Al (11,5, 15,0, 25,0, 40,0 e 140,0) na zeólita ZSM-5 através da conversão, atividade, seletividade e estabilidade de catalisadores bifuncionais (Pt/H-ZSM-5) aplicados a reação de isomerização do n-hexano. Para preparar os catalisadores bifuncionais, inicialmente as zeólitas foram submetidas, sucessivamente, a troca iônica das zeólitas com cátions amônio, troca iônica com cátions platina, processos de calcinação e ativação. A partir dos resultados da isomerização do nhexano observou que com o aumento da razão Si/Al, isto é, diminuição da quantidade de alumínio, obteve-se uma redução na atividade e conversão. Tal fato se deve a diminuição do número de sítios ácidos presentes, sendo que os mesmos são responsáveis por isomerizar os carbocátions gerados nos sítios. Em contrapartida, o aumento da razão Si/Al acarreta em uma melhor seletividade a formação dos isômeros. Dentre os catalisadores Pt/H-ZSM-5, o catalisador Pt/H-ZSM-5 (15,0) foi o que apresentou melhor resultado de atividade e conversão. A fim de comparar os catalisadores Pt/H-ZSM-5, a reação de isomerização do nhexano foi realizada utilizando o catalisador Pt/H-Beta (9,0). O mesmo obteve melhor resultado que todos os outros, podendo tal resultado ser, possivelmente, devido a maior acidez do material e suas características morfológicas, como tipo e diâmetro de poros etc. e/ou pelo tamanho do cristalito das zeólitas utilizadas.
18
Sieblist, Kerstin, and Barbara Wiermann. "Zum Ersten, zum Zweiten, zum Dritten." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-61234.
Full textAbstract:
Bei der Auktion „Music and continental books and manuscripts“ in London bei Sotheby’s wurden von der Leipziger Hochschule für Musik und Theater und dem Stadtgeschichtlichen Museum Leipzig zwei seltene Mendelssohn-Autographe erworben. Die Bibliothek der Hochschule für Musik und Theater Leipzig verfügt über eine Sondersammlung zur Geschichte des Hauses, die verschiedene Dokumente zu Mendelssohns Wirken umfasst. Daher passten die angebotenen Objekte in der Auktion in London in den Sammlungskontext der Leipziger Institution.
19
Silva, Júnior José Roberto da. "Craqueamento de hidrocarbonetos naftênicos sobre zeólitas HZSM-12 modificadas – rendimento e seletividade a olefinas leves." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8273.
Full textAbstract:
Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2016-10-21T11:11:40Z
No. of bitstreams: 1
TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5)<br>Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-11-08T18:37:37Z (GMT) No. of bitstreams: 1
TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5)<br>Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-11-08T18:37:44Z (GMT) No. of bitstreams: 1
TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5)<br>Made available in DSpace on 2016-11-08T18:37:52Z (GMT). No. of bitstreams: 1
TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5)
Previous issue date: 2015-09-30<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>It was studied the catalytic performance of ZSM-12 zeolites modified by desilication in the
cracking of naphthenic hydrocarbons. ZSM-12 zeolites with nominal a SiO2/Al2O3 ratio were
synthesized during 96 or 144 h under hydrothermal conditions and the obtained zeolites were
treated with NaOH solutions under different conditions. The samples were characterized by
thermogravimetric analysis (TA), X-ray diffraction (XRD), scanning electron microscopy
(SEM), N2 physisorption, temperature programmed desorption of ammonia (NH3-TPD), 27Al
MAS NMR spectroscopy, energy-dispersive X-ray spectroscopy (EDX) and infrared
spectroscopy (Py-FTIR). The treatment with NaOH solutions under mild conditions was more
effective for the ZSM-12 zeolite synthesized during 96 h. For the HZ12-96-0,2 sample,
obtained by treatment at 35 °C with 0.2 mol.L-1 NaOH solution during 15 min, it was verified
an increase in the external surface area and the formation of mesopores in the range of 2 to 14
nm. On that zeolite occurred a higher yields to light olefins during the cracking of
cyclohexane at 400 °C and also in the cracking of methyl and ethylcyclohexane at 450 °C.
This result was mainly related to the higher density of acid sites exhibited by the HZ12-96-0,2
zeolite compared with the parent ZSM-12 one, as consequence of the applied alkaline
treatment. It was also verified that the ZSM-12 zeolites modified by more severe alkaline
treatment (0.5 or 1.0 mol.L-1 NaOH solution at 80 °C for 30 min) presented significant
increase of the external surface area and mesopores volume. The catalytic cracking of
cyclohexane, methylcyclohexane and ethylcyclohexane at 500 °C, as well as the physicochemical
characteristics of the MZ12-96-0,5 zeolite enhanced the formation of light olefins.
The highest yield to light olefins was obtained on that zeolite during the cracking of
ethylcyclohexane, which increased 9% when compared with the yield obtained on the not
modified HZSM-12 zeolite. The selectivity to light olefins on the studied HZSM-12 zeolites
was strongly influenced by presence of a side chain in the naphthenic ring (methyl or ethyl),
as well as by the employed cracking operating conditions.<br>Estudou-se o desempenho de zeólitas ZSM-12 modificadas por dessilicalização no
craqueamento de hidrocarbonetos naftênicos. Zeólitas ZSM-12 com razão SiO2/Al2O3 igual a
80 foram sintetizadas em 96 ou 144 h sob condições hidrotérmicas. As zeólitas ZSM-12
obtidas foram modificadas sob diferentes condições de tratamento alcalino com soluções de
NaOH e posteriormente caracterizadas por termogravimetria, difratometria de raios X,
microscopia eletrônica de varredura, fisissorção de nitrogênio, dessorção de amônia à
temperatura programada, ressonância magnética nuclear do 27Al, espectroscopia de energia
dispersiva de raios X e espectroscopia na região do infravermelho com adsorção de piridina.
O tratamento alcalino, sob condições mais brandas, foi mais efetivo para a zeólita ZSM-12
sintetizada em menor tempo de cristalização (96 h). Para a zeólita HZ12-96-0,2, obtida por
tratamento com solução de NaOH 0,2 mol.L-1 a 35 °C por 15 min, verificou-se um aumento
na área superficial externa e distribuição de tamanho de mesoporos entre 2 e 14 nm. Nessa
zeólita, ocorreu um maior rendimento a olefinas leves no craqueamento de cicloexano a 400
°C e, também, no craqueamento de metil- e etil-cicloexano realizado a 450 °C. Esse resultado
foi relacionado, principalmente, com a maior concentração de sítios ácidos na zeólita HZ12-
96-0,2, em relação à zeólita HZSM-12 precursora, como consequência do tratamento alcalino.
Verificou-se, também, que as zeólitas ZSM-12 modificadas por tratamento alcalino, sob
condições mais severas (solução de NaOH 0,5 ou 1,0 mol.L-1
a 80 °C por 30 min), apresentaram
aumento significativo de área superficial externa e volume de mesoporos. O craqueamento de
cicloexano, metil- e etil-cicloexano realizado a 500 °C, assim como as características físicas e
químicas da zeólita MZ12-96-0,5, favoreceram a formação de olefinas leves. O maior
rendimento a olefinas leves ocorreu durante o craqueamento do etil-cicloexano sobre essa
zeólita, com aumento desse rendimento em torno de 9% quando comparado ao rendimento
obtido sobre a zeólita HZSM-12 não modificada. A seletividade a olefinas leves sobre as
zeólitas HZSM-12 preparadas neste estudo sofreu forte influência da presença da cadeia
lateral no anel naftênico (metil ou etil), assim como também das condições operacionais de
craqueamento empregadas.
20
Doege, Guilherme Martim. "Hipertexto : um protótipo implementado em Zim, para suporte da análise de requisitos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1991. http://hdl.handle.net/10183/27269.
Full textAbstract:
Neste trabalho se descreve a implementação de um protótipo de sistema de hipertexto, construído sobre o sistema de banco de dados ZIM, para uso na análise de requisitos de sistemas de informações de escritórios. Inicialmente, são apresentadas as principais características dos sistemas de hipertexto, destacando-se o hibridismo entre banco de dados, esquemas de representação e interfaces. Comenta-se a funcionalidade, aplicações, vantagens e desvantagens de hipertextos. A seguir, são mencionados diversos trabalhos apresentados na literatura universal, relacionados com hipertexto. Também são feitos comentários sobre diversos sistemas, acadêmicos, experimentais ou comerciais, citados na literatura. O protótipo de hipertexto foi implementado sobre a versão 3.11G, para MS-DOS, do sistema de banco de dados ZIM, em ambiente PC-XT, stand-alone. ZIM é um sistema de banco de dados baseado no modelo Entidade-Relacionamento. Possui uma Linguagem de Desenvolvimento de Aplicações completa, incluindo a definição e o tratamento de formulários. Possui um dicionário de dados totalmente integrado e permite o desenvolvimento e a adaptação progressiva das mais complexas estruturas de informação. O protótipo de hipertexto foi construído visando a coleta e a organização de informações exclusivamente textuais, através da interação do usuário com o computador, direcionadas para a análise de requisitos de sistemas de informação de escritórios. No modelo proposto se destacam os principais conjuntos de entidades utilizados: nodos e textos, links, autores, tipos de nodos e tipos de links. Os nodos e textos contêm as informações textuais e de controle que caracterizam a rede do hipertexto. Seu conteúdo é exibido dentro de janelas que são apresentadas na tela de vídeo. Os links armazenam as informações que relacionam os nodos entre si. São inseridos no texto, diferenciados visualmente do restante do texto, através de ícones. Quando ativados, as links permitem a navegação de um texto para outro. 0 conjunto de entidades "autores" contém informações sobre os usuários do sistema: administradores, escritores ou leitores. O sistema controla a autoria de nodos e links, garantindo ao autor do objeto sua modificação ou remoção. O sistema permite que um autor edite o texto, preservando os links que estiverem associados. Na dissertação também são comentados os principais atributos e operações dos objetos do sistema: autores, nodos e textos, links, tipos de nodos e tipos de links, janelas e ancoras ou ícones. Comenta-se o relacionamento entre os nodos e as janelas, e entre os ícones e os links. Também são mencionados a utilidade e exemplos de tipos de nodos e de links.<br>This dissertation describes the implementation of a prototype of hypertext system. It was constructed on the basis of the ZIM database system, for use in information systems requirement analysis. The work presents the most important features of hypertext systems, emphasizing the hibridism of database, representation scheme and interface modality. It also comments on their functions, applications, advantages and disadvantages. It mentions many works, presented on the universal literature, related with hypertext. It also comments various academic, experimental and commercial systems, mentioned on the literature. The hypertext prototype was implemented using the version 3.11G of the -LIM database system for MS-DOS, on the basis of a PC-XT environment. ZIM is a database system based on the Entity- Relationship model. It has a full Application Development Language, with the provision for definition and treatment of customized forms. It has a fully integrated data dictionary and allows the progressive development or adaptation of the most complex information structures. The prototype of hypertext was constructed for interactivelly collecting and organizing textual information, in the information systems requirement analysis. In the proposed model, the main entity sets are "nodes" and "texts", "links", "authors", "node types" and "link types". The nodes and texts contain the textual and control information, that characterize the nodes of the hypertext net Their contents are presented inside of windows, in the screen. The links store the informations that connect the nodes. They are inserted in the text by icons, visiblely differentiated to the remaining text. When they are activated, the links allow the navigation for a text to another. The "authors" entity set contains informations of the users: administrators, writers and readers. The hypertext system controls authorship of the nodes and links, specially for the modification and deletion of the objects. The system allows that the author edits their texts, preserving the associated links. This dissertation comments the main attributes and operations for the hypertext objects, like authors, nodes and texts, links, node types and link types, windows and anchors or icons. It comments the relationship between the nodes and windows, and between icons and links. It also mentions the use and examples of the nodes types and links types.
21
Boyd, Steven William. "The Use of ZAMAM and MEZIMMAH in Proverbs." Theological Research Exchange Network (TREN), 1985. http://www.tren.com.
Full text
22
Hausmann, Katharina. ""Die Chance, Bürger zu werden" deutsche Politik unter amerikanischer Besatzung ; die "Heidelberger Aktionsgruppe" ; 1946 - 47." Heidelberg Ubstadt-Weiher Weil am Rhein Basel Verl. Regionalkultur, 2002. http://deposit.ddb.de/cgi-bin/dokserv?id=2789878&prov=M&dok_var=1&dok_ext=htm.
Full text
23
Xu, Zhi. "Investigations on Molecular Sieve Zeolite Membranes as Proton-Selective Ion Separators for Redox Flow Batteries." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428049733.
Full text
24
Hepp, Frieder. "Religion und Herrschaft in der Kurpfalz um 1600 : aus der Sicht des Heidelberger Kirchenrates Dr. Marcus zum Lamm (1544-1606) /." [S.l. : s.n.], 1992. http://www.bsz-bw.de/rekla/show.php?mode=source&id=13.
Full text
25
Guerra, Patricia. "Effect of supercritical water on coke formed during dodecane cracking with ZSM-5." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1301.
Full textAbstract:
The objective of this work was to study the effect of supercritical water on coke formed on ZSM-5 during its use as a dodecane cracking catalyst. ZSM-5 coking was quantified at different reaction times, finding that the presence of supercritical water reduced coke formation by an order of magnitude or more. Coked samples were analyzed using several methods, including temperature programmed oxidation (TPO), attenuated total reflectance infrared (ATR-IR) spectroscopy, carbon-13 nuclear magnetic resonance (13C NMR), diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-vis) and UV-Raman. Coked produced in the absence of SCW was formed by polycyclic aromatic hydrocarbons (PAHs) with more than 4 aromatic rings containing alkyl side chains. Coke produced in the presence of SCW was formed by aromatics with 1 to 3 aromatic rings. The characteristics of coke formed in the absence of water on ZSM-5 that had been pretreated in SCW were intermediate to those of coke formed on fresh ZSM-5 in the presence and absence of water, suggesting that the presence of water influences coke properties. It was also verified that SCW can decrease coke formation due to its effect on Bronsted acidity of the catalyst and ability to promote coke gasification. The effect of coke deposits produced in the presence and absence of SCW on the rate of ethanol dehydration, a model reaction studied under diffusion-controlled conditions, indicated that SCD/SWC coke deactivated less the catalyst than SCD coke.
26
Albiero, Jalusa Konzen. "PRODUÇÃO DE OLEFINAS LEVES A PARTIR DE ETANOL EM ZSM-5 SINTETIZADA SEM DIRECIONADOR NITROGENADO." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/7987.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The petrochemical industry is currently strongly based on the production of light olefins ethylene and propylene, which are mainly produced by hydrocarbons from oil. Due to the environmental appeal and unstable oil market scenario, alternative routes to the production of these olefins are being developed, meanly regarding the use of alcohol as raw material. In this context, ethanol is highlighted with Ethanol to Olefins Process (ETO), in which there is catalytic conversion via reactions of dehydration, oligomerization, cracking, isomerization, among others. This work aims to obtain ethylene and propylene from ethanol using ZSM-5 zeolite as catalyst in its acid form. The synthesis of this material was performed using non-conventional sources of silicon and aluminum, kaolin and silica extracted from rice husk ash, and in the absence of nitrogenous templates. The use of seeds was employed together with ethanol, which acts as cotemplate of the zeolitic structure, in different quantities, and in different silica/alumina ratios and crystallisation times. The influence of each of these variables was evaluated with the support of a full factorial experimental design on the final characteristics of the synthesized samples, such as relative crystallinity, chemical composition and textural properties. All samples presented the characteristic crystal structure of ZSM-5 as verified by both X-ray diffractograms and infrared spectra. However, samples with small amounts of seed and ethanol added to short periods of crystallization presented lower crystallinities and specific areas in comparison to other samples. On the other hand, the use of high quantities of seed can lead to the formation of quartz when the crystallization time is extended. With the catalytic tests of ethanol conversion into olefins it was possible to evaluate the influence of synthesis variables, the residence time and the concentration of ethanol in feed, proving the importance of all synthesis variables in the distribution of the reaction products The total conversion of ethanol was observed in all tests made, evidencing the high activity of hZSM-5 in the dehydration of ethanol to ethylene, being the propylene yield strongly influenced by the reaction temperature and characteristics of the catalitic material, with a maximum yield of 27% at 500 °C. The HZSM-5 presented high stability under reaction conditions while maintaining the production of ethylene for more than 40 hours of reaction, whereas the coke formation drastically reduces the production of propylene still in the early hours of reaction.<br>A indústria petroquímica atualmente está fortemente baseada na produção das olefinas leves eteno e propeno, que são principalmente produzidas através de hidrocarbonetos oriundos do petróleo. Em virtude do apelo ambiental e do instável cenário do mercado de petróleo, rotas alternativas para a produção destas olefinas estão sendo desenvolvidas, principalmente no que tange a utilização de álcoois como matéria-prima. Neste contexto, o etanol ganha destaque com o processo Ethanol to Olefins (ETO), no qual se tem conversão catalítica via reações de desidratação, oligomerização, craqueamento, isomerização, entre outras. O presente trabalho tem por objetivo a obtenção de eteno e propeno através de etanol empregando como catalisador a zeólita do tipo ZSM-5 na forma ácida. A síntese deste material foi realizada utilizando fontes não convencionais de silício e alumínio, o caulim e a sílica extraída da cinza da casca de arroz, e na ausência de direcionadores de estrutura nitrogenados. O emprego de sementes foi adotado juntamente com etanol, que atua como codirecionador da estrutura zeolítica, em diferentes quantidades, assim como em diferentes razões sílica/alumina e tempos de cristalização. A influência de cada uma destas variáveis foi avaliada com o auxílio do planejamento experimental fatorial completo nas características finais das amostras sintetizadas, como cristalinidade relativa, composição química e propriedades texturais. Todas as amostras obtidas apresentaram estrutura cristalina característica da ZSM-5, comprovada tanto nos difratogramas de Raios-X como nos espectros de absorção na região do Infravermelho. Entretanto, as amostras com pequenas quantidades de sementes e de etanol somadas a curtos períodos de cristalização apresentaram cristalinidades e áreas específicas reduzidas em relação às demais amostras. Em contrapartida, o emprego de elevadas quantidades de sementes pode levar a formação de quartzo quando o tempo de cristalização é prolongado. Com os testes catalíticos de conversão de etanol em olefinas foi possível avaliar a influência das variáveis de síntese, do tempo de residência e a concentração de etanol na alimentação, comprovando a importância de todas as variáveis de síntese na distribuição dos produtos da reação. A conversão total de etanol foi observada em todos os testes realizados, evidenciando a elevada atividade da HZSM-5 na desidratação de etanol a eteno, sendo o rendimento a propeno fortemente influenciado pela temperatura de reação e características do material catalítico, com máximo rendimento igual a 27% na temperatura de 500°C. A HZSM-5 apresentou elevada estabilidade nas condições de reação, mantendo a produção de eteno por mais de 40 horas de reação, enquanto que a formação de coque reduz drasticamente a produção de propeno ainda nas primeiras horas de reação.
27
Carvalho, Kele Tatiane Gomes. "Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/3944.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:55:38Z (GMT). No. of bitstreams: 1
5665.pdf: 8947970 bytes, checksum: 3a1ee8be44b336d4926a11f4c9cc20eb (MD5)
Previous issue date: 2013-09-12<br>Universidade Federal de Sao Carlos<br>The research addressed the generation of mesoporosity in the zeolite ZSM-12 (MTW). In the first part we studied the synthesis of ZSM-12 via conventional methodology and in the presence of a mesopore directing agent, organosilane [3-(Trimethoxy-silyl)propyl] octadecyldimethylammonium chloride (TPOAC). It was verified to influence the TPOAC/SiO2 and H2O/SiO2 ratios and, also the aging of the reaction mixture, temperature and time of the hydrothermal treatment. In the second part we studied the formation of mesoporosity by post-synthesis treatment with alkaline solution (NaOH). For optimization of such treatment the concentration of the NaOH solution and the temperature were varied. The zeolites were characterized by X-ray diffraction, chemical analysis by energy-dispersive X-ray spectroscopy, N2 adsorption/desorption, scanning electron microscopy, nuclear magnetic resonance of 27Al, and temperature-programmed desorption of ammonia. By the analyses of X-ray diffraction and Rietveld refinement, we verified a decrease in crystallization kinetics with increasing TPOAC/SiO2 ratio and a tendency for simultaneous crystallization of MFI and MTW phases with increasing H2O/SiO2 ratio, temperature and aging time. It was possible to obtain mesoporous ZSM-12 with high purity and crystallinity with only small quantities of TPOAC and relatively long crystallization times. For ZSM-12 zeolites treated in basic medium, there was the formation of mesopores in the range from 2.9 to 23 nm due to the silicon extraction from the crystalline framework, which caused a decrease in the volume of micropores and an increase in the total acidity, assigned to the decrease in Si/Al ratio. In the cracking of cyclohexane at 400 °C, although the presence of mesoporosity had caused a decrease in the total acidity, the zeolites synthesized with TPOAC showed similar conversions to conventional zeolite with minimal catalytic deactivation, which was attributed to the better mass transfer and less coke formation. The ZSM-12 zeolites treated with NaOH exhibited activity and stability similar to those obtained in the presence of TPOAC. By its higher proportion of strong acid sites, the conventional ZSM-12 zeolite showed higher hydrocarbon yields in the range from C2 to C4 in comparison with the mesoporous zeolites, with the latter showing a higher yield for C6 hydrocarbons.<br>A pesquisa abordou a geração de mesoporosidade na zeólita ZSM-12 (MTW). Numa primeira parte estudou-se a síntese da ZSM-12 via metodologia convencional (hidrotérmica) e na presença de um agente direcionador de mesoporos, o organossilano cloreto de 3-(trimetoxi-silil)propil-octadecildimetil amônio (TPOAC). Verificou-se a influência das razões TPOAC/SiO2 e H2O/SiO2 e, também, da temperatura, tempo de envelhecimento da mistura reacional e tempo de tratamento hidrotérmico. Na segunda parte estudou-se a formação de mesoporosidade por tratamento pós-síntese com solução alcalina (NaOH). Para a otimização desse tratamento, variou-se a concentração da solução de NaOH e a temperatura. As zeólitas obtidas foram caracterizadas por difratometria de raios X, análise química por espectroscopia de energia dispersiva de raios X, fisissorção de N2, microscopia eletrônica de varredura, ressonância magnética nuclear do 27Al e dessorção de amônia à temperatura programada. Pelas análises de difratometria de raios X e refinamento de Rietveld, verificou-se um decréscimo da cinética de cristalização com o aumento da razão TPOAC/SiO2 e uma tendência à cristalização simultânea das fases MTW e MFI com o aumento da razão H2O/SiO2, da temperatura e do tempo de envelhecimento. Foi possível obter ZSM-12 mesoporosa com alta pureza e cristalinidade somente com pequenas quantidades de TPOAC e tempos de cristalização relativamente longos. Para as zeólitas ZSM-12 tratadas em meio básico, houve a formação de mesoporos na faixa de 2,9 a 23 nm devido à extração de silício da rede cristalina, o que provocou uma diminuição do volume de microporos e um aumento da acidez total pela diminuição da razão Si/Al. No craqueamento de cicloexano em fase gasosa a 400 °C, as zeólitas sintetizadas com TPAOC, embora a presença de mesoporosidade tenha provocado uma diminuição na acidez total, apresentaram conversões semelhantes às da zeólita convencional com mínima desativação catalítica, o que foi atribuído à boa transferência de massa e menor formação de coque. As zeólitas ZSM-12 tratadas com NaOH exibiram atividade e estabilidade similares às obtidas na presença de TPOAC. Pela sua maior proporção de sítios ácidos fortes, a zeólita ZSM-12 convencional apresentou rendimentos maiores a hidrocarbonetos C2 a C4 do que as zeólitas contendo mesoporos, com estas últimas apresentando maior rendimento a hidrocarbonetos C6.
28
Duman, Isa. "Coke characterization on HZSM-5, Fe/ZSM-5, Ni/ZSM-5, and Fe-Ni/ZSM-5 from Catalytic Fast Pyrolysis of Biomass." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226910.
Full textAbstract:
The combustion of fossil fuels has for a long time been a problem from an environmental and sustainability point of view, especially when it comes to the emissions of atmospheric carbon dioxide. The environmental concern has for instance shifted the attention towards finding new sustainable alternatives for producing chemicals and fuels, as a substitute to today’s dependence on fossil based crude oil. Catalytic Fast Pyrolysis of biomass is an excellent way to produce valuable chemicals and fuels using renewable resources. However, the process has some drawbacks, for example rapid deactivation of catalysts due to coke formation. Little is known about the characteristics of the formation of catalytic coke from pyrolysis processes, which should be a vital concern in future industrial processes. This thesis is dedicated to investigate the chemical coke characteristics found on zeolitic catalysts. Four zeolites of the type ZSM-5 were chosen for this thesis to deduce any chemical differences in the coke: HZSM-5, Fe/ZSM-5, Ni/ZSM-5, and Fe-Ni/ZSM-5. The coke were characterized by TGA, GC/MS, and FTIR. The results show that Fe/ZSM-5 produced the highest amount of coke compared to the other zeolites, where HZSM-5 had the lowest amount of coke formation. The coke consisted mainly of aromatic and cyclic hydrocarbons, dominated by polycyclic aromatic hydrocarbons. The content of ketones and alcohols in the coke found on HZSM-5 was higher compared to the metal-doped zeolites, while the formation of naphthalenes was lower. The FTIR results also show that coke was mainly comprised of aromatic hydrocarbons. However, traces of alkanes and alkenes reveal that the coke may have a greater variety than the GC/MS analysis suggests. The results show interesting features when metals are introduced to the zeolitic structure, at least when it comes to coke formation. The metal-doping of zeolites certainly seems to alter the chemistry of the catalytic reactions, compared to the parent zeolite. The differences in the chemical characteristics found in the coke are certainly interesting, and it could mean that the chemistry of the bio-oil also varies depending on the metals chosen for the ZSM-5. The new properties that metals introduce to the parent catalyst may open up new possibilities in industrial catalytic processes, and allow industries to take more advantage of the great benefits that biomass has to offer.<br>Förbränning av fossila bränslen har under lång tid utgjort ett problem ur miljö- och hållbarhetssynpunkt, i synnerhet gällande utsläppen av koldioxid. En större miljömedvetenhet har gett upphov till sökandet efter nya råvaror för att framställa bränslen och kemikalier, utan att förlita sig på fossil råolja. Katalytisk pyrolys av biomassa är ett utmärkt sätt att framställa värdefulla kemikalier från förnybara källor. Processen står dock inför en del tekniska utmaningar, bland annat en snabb deaktivering av använda katalysatorer genom koksning. Målet med detta examensarbete är att undersöka den kemiska sammansättningen av koks, som bildats på zeolitkatalysatorerna. Mer specifikt, att försöka undersöka huruvida den kemiska sammansättningen av koks skiljer sig mellan katalysatorn HZSM-5 och metalldopad HZSM-5. Fyra katalysatorer valdes för detta examensarbete, nämligen HZSM-5, Fe/ZSM-5, Ni/ZSM-5 och Fe-Ni/ZSM-5. Kokset har analyserats genom termogravimetrisk analys (TGA), gaskromatograf kopplad med en masspektrometer (GC/MS), samt Fourier-transform-infraröd-spektroskopi (FTIR). Resultaten visar att Fe/ZSM-5 bildade en större mängd koks jämfört med de andra zeoliterna, varpå HZSM-5 hade lägst halt koks. Utöver detta bestod kokset till största del av aromatiska- och cykliska kolväten, speciellt polycykliska aromatiska kolväten. Innehållet av ketoner och alkoholer i kokset var störst för HZSM-5, medan bildandet av naftalenföreningar ökade för de metalldopade zeoliterna. FTIR-analysen gav även upphov till signaler som är signifikanta för både alkaner och alkener. Därför kan det innebära att kokset innehar en större kemisk variation än vad GC/MS-analysen påvisade. Resultaten visar intressanta egenskaper hos metallmodifierade zeoliter, i synnerhet gällande koksbildning. Det verkar som att de metalldopade zeoliterna påverkar de katalytiska reaktionerna som sker i katalysatorn, jämfört med den obehandlade katalysatorn. Skillnaderna i den kemiska sammansättningen hos kokset för de olika katalysatorerna är definitivt intressant och kan indikera att det även kan föreligga skillnader i den kemiska sammansättningen hos bio-olja, beroende på vilken metall ZSM-5 har behandlas med. De nya egenskaperna som metaller bidrar med till ZSM-5 kan öppna upp nya möjligheter i industriella katalytiska processer, vilket även kan medföra att industrier bättre kan ta tillvara på de fantastiska egenskaper biomassa innehar.
29
Oliveira, Jivago Schumacher de. "AVALIAÇÃO CATALÍTICA DE ÓXIDO DE FERRO SUPORTADO EM ZEÓLITA MESOPOROSA EM SISTEMA FOTO-FENTON." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/8803.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Due to the problems presented with the use of photo-Fenton homogeneous system, for the decomposition of recalcitrant organic compounds, several studies have been conducted in order to replace it with heterogeneous processes. The heterogeneous reaction of photo-Fenton catalysts using iron oxide base (Fe2O3) is viable and reputable to overcome the problems presented by the homogeneous system. However, when used pure Fe2O3 has low efficiency due to the large size of the agglomerates formed, so deposition techniques on substrates used are seeking to reduce the size of the iron oxide agglomerates. Thus this study aimed to evaluate the efficiency of iron oxide nanoparticle supported on zeolite ZSM-5 mesoporous in removing organic pollutants contained in wastewater using photo-Fenton reaction system. The synthesis of zeolites ZSM-5, which served as a support, was performed using nucleating gel as driver structure and different amounts of carbon nanoparticles as mesoporosity agent. On the particles of hierarchical zeolites ZSM-5 were deposited iron oxide nanoparticles (Fe2O3). Supporters and materials after impregnation were characterized by diffraction of X-ray (DRX), scanning electron microscopy (SEM) and analysis of the adsorption / desorption of nitrogen (BET). The evaluation of different catalysts was carried out in photo-Fenton system employing different conditions reaction. From the characterization using x-ray diffraction, it was found that the only crystalline phase was formed from ZSM-5 with high crystallinity, which was adversely affected with increasing carbon content in the gel nanoparticles of crystallization. In the analysis of the BET was found that the formation of type IV isotherms, indicating the presence of mesoporosity in the ZSM-5 zeolites. It was found that with increasing content of carbon nanoparticles in the reaction medium resulted in an increase in the average size of the mesoporous formed. In the catalytic evaluation in the photo-Fenton reaction it was found that under the same reaction conditions, the iron oxide supported on hierarchical zeolite ZSM-5 showed higher activity for decomposition of dyes than pure iron oxide. It was also found that, the higher the degree of mesoporosity of support of iron oxide supported higher activity. The higher activity of supported iron oxide was attributed to the synergistic effect with the ZSM-5 zeolite, which has polar character, making the dye concentration in the catalyst system surface is high, providing conditions for the smooth progress of the reaction.<br>Devido aos problemas apresentados com a utilização do sistema foto-Fenton homogêneo, para a decomposição de compostos orgânicos recalcitrantes, diversos estudos tem sido realizados com a finalidade de substituí-lo por processos heterogêneos. A reação heterogênea de foto-Fenton empregando catalisadores a base de óxido de ferro (Fe2O3) é alternativa viável e bem conceituada para superar os problemas apresentados pelo sistema homogêneo. No entanto, o Fe2O3 quando utilizado puro em suspensão apresenta baixa efetividade devido ao grande tamanho dos aglomerados formados, fazendo com que técnicas de deposição sobre suportes sejam utilizadas buscando reduzir o tamanho dos aglomerados de óxido de ferro. Desta forma, este estudo objetivou avaliar a eficiência do óxido de ferro nanoparticulado suportado sobre zeólitas ZSM-5 mesoporosas na remoção de poluentes orgânicos contidos em efluentes aquosos empregando sistema foto-Fenton de reação. A síntese das zeólitas ZSM-5, que serviram de suporte, foi realizada utilizando gel nucleante como direcionador de estrutura e diferentes teores de nanopartículas de carbono como agente de mesoporosidade. Sobre as partículas das zeólitas ZSM-5 hierárquicas, foram depositadas nanopartículas de óxido de ferro (Fe2O3). Os suportes e os materiais após impregnação foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de varredura (MEV) e análise de adsorção/dessorção de nitrogênio (BET). A avaliação dos diferentes catalisadores foi realizada em sistema foto-Fenton empregando diferentes condições de reação. Da caracterização por difração de raios-X constatou-se que a única fase cristalina formada foi da zeólita ZSM-5 com elevado grau de cristalinidade, que foi afetada de forma negativa com a elevação do teor de nanopartículas de carbono no gel de cristalização. Na análise de BET constatou-se a formação de isotermas do tipo IV, indicando que a presença de mesoporosidade nas zeólitas ZSM-5. Constatou-se que com a elevação do teor de nanopartículas de carbono no meio reacional acarretou em aumento no tamanho médio dos mesoporosos formados. Na avaliação catalítica na reação de foto-Fenton constatou-se que, nas mesmas condições de reação, o óxido de ferro suportado sobre as zeólitas ZSM-5 hierárquicas apresentou maior atividade para decomposição de corantes que o óxido de ferro puro em suspensão. Também se constatou que, quanto mais elevado o grau de mesoporosidade do suporte maior a atividade do óxido de ferro suportado. A maior atividade do óxido de ferro suportado foi atribuído ao efeito sinérgico com a zeólita ZSM-5, que possui caráter polar, fazendo com que a concentração do corante na superfície do sistema catalítico seja elevado, propiciando condições para o bom andamento da reação.
30
Schmidt, Rafaela de Souza. "Síntese de zeólitas ZSM-5 a partir da casca de arroz e metacaulim comercial como fontes alternativas de sílica e alumina." Universidade do Estado de Santa Catarina, 2014. http://tede.udesc.br/handle/handle/1656.
Full textAbstract:
Made available in DSpace on 2016-12-08T17:19:22Z (GMT). No. of bitstreams: 1
Rafaela de Souza Schmidt.pdf: 1614603 bytes, checksum: 4583716d044cc6f09dfcf335690ab75e (MD5)
Previous issue date: 2014-01-31<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The synthesis of zeolites from alternative materials and low cost had great development in recent decades due to the fact of processes using conventional silicon and aluminum solutions are expensive .solutions of silicon and aluminum are extremely expensive. The synthesis can be carried out by any raw material containing predominantly silica and alumina, such as clays and rice husk. Thus, this study aims to develop an alternative methodology for the synthesis of zeolite ZSM-5, using silica extracted from rice husk and commercial metakaolin as raw materials in the composition of the mixture. The process of synthesis solution was hydrothermally sodium in the presence of TPABr and as a structural director. To assess the effect of temperature on the formation of ZSM-5, the synthesis procedure was carried out in temperature ranges between 100 and 170°C. Through the characterization of zeolitic material formed in the crystallization process, it was concluded that the methodology proposed in this work led typical crystalline phases of zeolite ZSM-5, as well as the formation of other zeolite phases.<br>A síntese de zeólitas a partir de materiais alternativos e de baixo custo teve grande desenvolvimento nas últimas décadas devido ao fato dos processos que utilizam soluções convencionais de silício e alumínio serem caros. A síntese pode ser realizada por qualquer matéria prima que contenha predominância de sílica e alumina, como por exemplo, argilas e casca de arroz. Sendo assim, este trabalho tem como objetivo desenvolver uma metodologia alternativa de síntese de zeólita ZSM-5, empregando sílica extraída da casca de arroz e metacaulim comercial, como matérias primas na composição da mistura reacional. O processo de síntese ocorreu hidrotérmicamente em solução sódica e na presença de TPABr como direcionador estrutural. Para avaliar o efeito da temperatura na formação da ZSM-5, o processo de síntese foi realizado em faixas de temperatura entre 100 e 170°C. Através da caracterização do material zeólítico formado no processo de cristalização, foi concluído que a metodologia proposta neste trabalho conduziu fazes cristalinas típicas de zeólita ZSM-5, bem como a formação de outras fases zeolíticas.
31
Zheng, Quanxing. "Conversion of 2,3-butanediol over bifunctional catalysts." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/34461.
Full textAbstract:
Doctor of Philosophy<br>Department of Chemical Engineering<br>Keith L. Hohn<br>In this study, Cu/ZSM-5 catalysts were used to catalyze the hydrodeoxygenation of 2,3-butanediol to butenes in a single reactor in the presence of hydrogen. The carbon selectivity of butenes increased with increasing SiO₂/Al₂O₃ ratio (lowering acidity of zeolite) and H₂/2,3-butanediol ratio. Cu/ZSM-5 with a SiO₂/Al₂O₃ ratio of 280 showed the best activity toward the production of butenes. On zeolite ZSM-5(280), the carbon selectivity of butenes increased with increasing copper loading and 19.2wt% of CuO showed the highest selectivity of butenes (maximum 71%). The optimal reaction temperature is around 250 °C. Experiments demonstrated that methyl ethyl ketone (MEK) and 2-methylpropanal are the intermediates in the conversion of 2,3-butanediol to butenes. The optimal performance toward the production of butene is the result of a balance between copper and acid catalytic functions.
Due to the functionalized nature of 2,3-butanediol, a variety of reactions can occur during the conversion of 2,3-butanediol, especially when multiple catalyst functionalities are present. To investigate the role of the metal (Cu) and acid sites in the process of reaction, the reaction kinetics for all major intermediate products (acetoin, MEK, 2-methylpropanal, 2-butanol and 2-methyl-1-propanol) were measured over Cu/ZSM-5(280), HZSM-5(280), and Cu/SiO₂ at 250 °C. The results showed that Cu is the active site for hydrogenation reactions, while the acidic sites on the zeolite are active for dehydration reactions. In addition, dehydration of alcohols over the zeolite is much faster than hydrogenation of ketone (MEK) and aldehyde (2-methylpropanal). A kinetic model employing Langmuir-Hinshelwood kinetics was constructed in order to predict 2,3-butanediol chemistry over Cu/ZSM-5(280). The goal of this model was to predict the trends for all species involved in the reactions. Reactions were assumed to occur on two sites (acid and metal sites) with competitive adsorption between all species on those sites.
Two different types of mesoporous materials (Al-MCM-48, Al-SBA-15) and hierarchical zeolite (meso-ZSM-5) were loaded with ~20wt% CuO and investigated in the conversion of 2,3-butanediol to butenes. The results showed that the existence of mesopores on the catalysts (Al-MCM-48 and Al-SBA-15 types) could decrease the selectivities of products from cracking reactions, especially C₃= and C₅=−C₇= by comparison with the catalyst with ~20wt% CuO loaded on the regular HZSM-5(280); meanwhile, the selectivity of C₈= from oligomerization of butenes was found to increase with increasing pore size of the catalysts. With respect to Cu/meso-ZSM-5(280) catalyst, it can be seen that the catalyst performs in a similar way to both Cu/ZSM-5(280) catalyst and mesoporous copper catalysts (Cu/Al-MCM-48 and Cu/Al-SBA-15) since both micropores (diameter of ~0.55 nm) and mesopores (pore size of ~23 nm) exist on meso-ZSM-5(280).
The results from Cu catalysts were compared with four other metal catalysts (Ni, Pd, Rh and Pt). It was found that Cu is not very active for hydrogenation of butenes, but is active for hydrogenation of carbonyl groups (C=O) to form hydroxyl groups (−OH). Pd, on the other hand, is active in further hydrogenating butenes and other unsaturated hydrocarbons. Both Ni and Rh catalysts are good for hydrogenation of olefins and cracking of heavy hydrocarbons; however, Rh is not as good as Ni for the hydrogenation of the carbonyl group (C=O) of MEK. In addition, Pt favors the formation of heavy aromatics such as 5-ethyl-1,2,3,4-tetrahydro-naphthalene, while Pd is active for the production of xylene.
32
Leblanc, Pascal. "Retrovirus d'invertebres : zam un nouveau candidat chez drosophila melanogaster." Clermont-Ferrand 1, 1998. http://www.theses.fr/1998CLF1MM12.
Full text
33
Banerjee, Sneharthi. "Identification of New Genes Involved in Meiosis by a Genetic Screen." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1376395687.
Full text
34
Grill, Marie. "Synthèse de catalyseurs zéolithiques supportés adaptés au craquage des carburants endothermiques en milieu supercritique." Paris 6, 2007. http://www.theses.fr/2007PA066440.
Full textAbstract:
Des catalyseurs pour le craquage d'hydrocarbures en milieu supercritique sont étudiés. L'application finale visée est la mise au point d'un système de refroidissement pour les véhicules hypersoniques. L'effet refroidissant est alors assuré par des réactions endothermiques de craquage d'un carburant dit "endothermique" à l'état supercritique. Des catalyseurs zéolithiques, de type Y et ZSM-5, déposés sur un support en acier inoxydable sont donc préparés. Deux modes opératoires sont élaborés pour la synthèse, permettant d'obtenir des dépôts d'épaisseur entre 2 et 3 µm. L'influence de l'état de surface initial du support sur les dépôts en terme de morphologie et d'adhérence est étudiée. Ensuite, les dépôts sont activés puis les sites acides présents sont dosés. Les mesures d'acidité montrent que les dépôts de zéolithe Y ont un nombre de sites de Brönsted plus élevé que les dépôts de ZSM-5. Cependant, des sites de Brønsted plus forts sont observés dans ces derniers. Des tests de craquage sont ensuite effectués avec les catalyseurs, sous forme de poudre et de dépôt. Ces tests sont réalisés avec un réacteur agité en statique. Les tests montrent que la ZSM-5 a une activité catalytique entre 375 et 425°C qui permet d'obtenir des taux de conversion supérieurs à ceux du craquage thermique. La zéolithe Y a une activité plus faible que celle de la ZSM-5. L'explication de cette différence est un effondrement total de la zéolithe Y pendant les tests.
35
Linder, Anne. "Bücher zu Disney-Filmen - Vergleich von ausgewählten Filmen und ihrer Umsetzung in Buchform." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11612102.
Full text
36
Salbego, Paulo Roberto dos Santos. "Síntese e caracterização de zeólitas ZSM-5 por diferentes rotas e seu emprego na produção de olefinas leves a partir de etanol." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/7986.
Full textAbstract:
Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>This work aims the synthesis and study of ZSM-5 catalysts for the conversion of
ethanol to light olefins, especially, using an alternative and inexpensive route. The
ethanol emerges as a renewable source for the production of olefins and the ZSM-5
catalyst has important characteristics for this type of reaction such as acidity, surface
area and particle size. The synthesis was carried out in hydrothermal treatment at 170
°C. Were performed two conventional synthesis with templates, using n-Butylamine
and tetrapropylammonium hydroxide (TPAOH), and an third and alternative route using
a nucleating gel. The catalyst characterization was performed using several techniques
(XRD, BET, XRF, SEM and TGA) and was observed the formation of the ZSM-5
structure in all the synthesis methods. The catalysts were evaluated in the ethanol to
olefins (ETO) reaction, and was evaluated the influence of the reaction temperature
(250 to 450 °C) and SAR (SiO2/Al2O2 ratio) in the selectivity for olefins. The products
analyses were made with a gas chromatograph with a FID-type detector. The ethylene
yield was above to 80 % for all catalysts, and some above 90 %. Lower SAR values
provided higher yields for propylene, around to 9 %. The temperature, SAR and
template used in the synthesis influenced in the selectivity. In addition, was evaluated
the influence of the catalyst mass, dilution and also its modification with different
metals. When the mass was increase, the yield for propylene increased. The catalyst
dilution with common sand provided, in some concentrations, greater propylene
formation. The nucleating gel method showed to be a viable alternative for ZSM-5
synthesis and its use in the ETO reaction.<br>Este trabalho relata o estudo da síntese e caracterização de catalisadores ZSM-5 para
seu posterior uso na reação de conversão de etanol para olefinas, especialmente
utilizando uma rota alternativa mais econômica. O etanol surge como uma fonte
renovável para a produção de olefinas e o catalisador ZSM-5 possui importantes
características para esse tipo de reação, tais como acidez, área superficial e tamanho de
partícula. A síntese foi conduzida de maneira hidrotérmica a 170 °C. Foram realizadas
duas sínteses convencionais com direcionadores de estrutura, utilizando n-butilamina e
hidróxido de tetrapropilamônio (TPAOH), e uma terceira rota alternativa utilizando um
gel nucleante. A caracterização dos compostos sintetizados foi realizada com diversas
técnicas (DRX, BET, FRX, MEV e TGA) sendo observada a formação da estrutura de
ZSM-5 em todas as técnicas de síntese utilizadas. Os catalisadores foram avaliados na
reação de conversão de etanol à olefinas (ETO) e foi avaliada a influência da
temperatura de reação (250 a 450 °C) e SAR (SiO2/Al2O3 ratio) na seletividade das
olefinas. A análise dos produtos formados foi realizada em um cromatógrafo a gás com
detector tipo FID. O rendimento para eteno foi superior a 80 % em todos os
catalisadores, sendo para alguns acima de 90 %. Baixos valores de SAR
proporcionaram maiores rendimentos para propeno, em torno de 9 %. A temperatura, o
valor de SAR e os direcionadores empregados na síntese influenciaram na seletividade.
Também, foi avaliada a influência da quantidade de massa do catalisador, a diluição e
também a modificação com diferentes metais (Ga, La, In) e um não metal (P). Quando a
massa foi aumentada, o rendimento para propeno aumentou consideravelmente. A
diluição com areia comum, em algumas concentrações, proporcionou maior formação
de propeno. O método de síntese via gel nucleante mostrou ser uma alternativa viável
para a síntese de ZSM-5 e seu uso como catalisador na reação ETO.
37
Menges, Markus [Verfasser], and B. [Akademischer Betreuer] Kraushaar-Czarnetzki. "Untersuchungen zum MTO-Prozess an AlPO4-gebundenen ZSM-5-Extrudaten und Beschreibung der Reaktionskinetik / Markus Menges ; Betreuer: B. Kraushaar-Czarnetzki." Karlsruhe : KIT Scientific Publishing, 2012. http://d-nb.info/1184492263/34.
Full text
38
Gonçalves, Marli Lansoni. "Sólidos micro-mesoestruturados tipo zeólita ZSM-5/peneira molecular MCM-41 - síntese e estudo de propriedades." Universidade Federal de São Carlos, 2006. https://repositorio.ufscar.br/handle/ufscar/3976.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:56:28Z (GMT). No. of bitstreams: 1
DissMLG.pdf: 4644860 bytes, checksum: 745bf2fba935eb4bb3fc032321ab36e7 (MD5)
Previous issue date: 2006-08-16<br>Universidade Federal de Sao Carlos<br>In the transformation of bulky molecules, the necessity of catalysts that allow the diffusion to and from the active sites located in the interior of the porous system has become of higher interest. The restriction for the diffusion of this type of molecule in zeolites has led the community to study routes that can make possible to obtain solids that allow the diffusion in mesoporous and
simultaneously possess the intrinsic properties of microporous zeolites. In this context, the objective of this work was the synthesis of micro-mesostructured Zeolite ZSM-5/MCM-41 Molecular Sieve type solids. These solids were
prepared under hydrothermal conditions in two stages. Initially was prepared a gel of ZSM-5 seeds, which was subsequently crystallized in the presence of cetyltrimetylammonium bromide (CTABr), used as structure directing agent in
the synthesis of the MCM-41. The influence of the Si/Al ratio in the seeding gel and the effect of both the time and temperature used in the preparation of such gel and during crystallization were evaluated. X-ray diffraction in the low and wide angle region, nitrogen adsorption/desorption, FTIR spectroscopy and scanning and transmission electron microscopy data evidenced the formation of micro-mesostructured ZSM-5/MCM-41 materials. It is suggested that the formation of the microporous
structure occurs by an intraparticle "solid-to-solid" process through the transformation of the walls of the mesoporous into crystalline structure. During
the growth of the crystals, the surfactant micelles are dislocated, causing loss of the symmetry of the mesoporous arrangement. However, the micelles remain unchanged in a random array, generating after calcination irregularly arranged
mesoporous, but possessing uniform diameters.
The cristallinity of the formed ZSM-5 crystals, the volume of the mesoporous and the specific surface area of the final solid were influenced by
the Si/Al ratio in the seeding gel and by the time and temperature used in the aging and during the stage of mesostructuration/crystallization. The optimization of this set of variables will allow the control of the ratio between the obtained
microporous and mesoporous phases, thus making possible the preparation of
tailor-made adsorbents and catalysts for the separation and transformation of bulky molecules.<br>No processamento de moléculas volumosas, é cada vez maior a necessidade de dispor-se de catalisadores que permitam a difusão para os
sítios ativos localizados no interior do sistema poroso. A restrição à difusão desse tipo de molécula em zeólitas tem levado a comunidade a estudar rotas que tornem possível a obtenção de um sólido que permita a difusão nos
mesoporos e que, ao mesmo tempo, possua as propriedades intrínsecas das zeólitas microporosas. Nesse contexto, este trabalho teve como objetivo a síntese de sólidos micro-mesoestruturados do tipo Zeólita ZSM-5/Peneira
Molecular MCM-41. Estes sólidos foram preparados sob condições hidrotérmicas em duas etapas. Inicialmente preparou-se um gel de sementes da zeólita ZSM-5, sendo estas posteriormente cristalizadas na presença de
brometo de cetiltrimetilamônio (CTABr), agente mesoestruturante utilizado na síntese da peneira molecular MCM-41. Nessas sínteses, foram avaliadas as influências da relação Si/Al no gel de síntese e o efeito do tempo e da
temperatura utilizados na etapa de preparação do gel e na de cristalização. Dados de difração de raios-X em pequenos e altos ângulos,
adsorção/dessorção de nitrogênio, espectroscopia no infravermelho e
microscopia eletrônica de varredura e de transmissão evidenciaram a formação
de materiais micro-mesoestruturados ZSM-5/MCM-41 a partir de géis de sementes , cristalizadas na presença do surfactante catiônico CTA+. Sugere-se que a formação da estrutura microporosa ocorre via um processo sólidosólido intrapartícula, com a transformação das paredes dos mesoporos em estrutura cristalina. Durante o crescimento dos cristais, as micelas do surfactante ocluídas nas partículas são deslocadas, ocasionando perda de
simetria do arranjo mesoporoso. Entretanto, as micelas permanecem inalteradas num arranjo aleatório, gerando após a calcinação mesoporos num arranjo irregular, mas possuindo diâmetros uniformes. A cristalinidade da fase ZSM-5 formada, o volume de mesoporos e a
área superficial específica do sólido final dependem da relação Si/Al no gel de sementes, do tempo e da temperatura usados durante o envelhecimento e na etapa de mesoestruturação/cristalização. A otimização desse conjunto de varáveis permitirá o controle da proporção entre as fases micro e mesoporosas possibilitando a preparação, sob medida, de novos adsorventes e catalisadores, para a separação e transformação de moléculas volumosas.
39
Kamieniak, Jean-Pierre. "Freud, un enfant de l'humour." Paris 7, 1998. http://www.theses.fr/1998PA070060.
Full textAbstract:
On ne peut que s'etonner de la relative mesestime en laquelle freud a tenu le mot d'esprit et sa relation a l'inconscient, bien que cet ouvrage ait contribue a l'evidence aux fondements de la science nouvelle. C'est que ce dernier appartient aussi aux materiaux de l'auto-analyse et que, a travers le witz, dans cet effort pour denouer les fils de l'etoffe dont il est fait, ce conquistador s'est trouve ici directement confronte a l'enigme de son identite. Une identite inscrite dans la judeite qui, si elle renvoie bien entendu a jacob le colporteur, ouvre plus surement encore sur ce personnage feminin/maternel des origines incarne par la belle amalia - au coeur meme du processus humoristique - et tenue dans le plus grand respect. Ce faisant - et bien qu'il s'en defende - c'est a l'elaboration metapsychologique du lien a la mere des origines que freud nous convie et nous conduit a travers l'humour dont elle constitue indeniablement la matrice<br>One cannot but wonder that jokes and their relation to the unconscious should be relativily inderrated by freud, also this work clearly contributed to founding the new science. It so happens that this latter work, also belongs to writings about his autoanalysis and that with witz, in the effort to unravel the threads of its very fabric, this conquistador finds himself in direct confrontation with the enigma of his identity. This identity is included within the framework of jewishness which, although refering back to jacob the peddlar, leads the way even more surely to the feminine/maternal character of the origins embodied by the lovely amalia - in the heart of the humoristic process - and held in the greatest respect. In this way, although he does'not admit to it, freud invites us to follow him in the metapsychological elaborationof the bond with the original mother using the humour which undeniably comprises the matrix
40
Al-Rubaye, Rana. "Generation and characterisation of catalytic films of zeolite Y and ZSM-5 on FeCrAlloy metal." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/generation-and-characterisation-of-catalytic-films-of-zeolite-y-and-zsm5-on-fecralloy-metal(de743286-52bd-4922-8de7-9a261283b6e5).html.
Full textAbstract:
The objective of this work was the development of structured zeolite catalysts by growing of ZSM-5 and Y zeolites layers on the pre-treated FeCrAlloy wires, which could now offer technical advantage in catalytic application. The advantages of implementation of zeolitic coatings in industrial applications are that they have; lower pressure drop, high heat and mass transfer rates compared to standard pelleted or extruded catalysts. The key focus of this research was the generation of thin films of zeolite ZSM–5 and Y zeolite catalysts on the surface of a FeCrAlloy metal substrate. Using in-situ hydrothermal synthesis, the influence of the synthesis parameters such as substrate oxidation and crystallisation time on the zeolite crystallisation process in both the bulk phase (powder) and on the structured zeolite was studied and optimised. Then powder and structured Na-ZSM-5 and Na-Y were treated by calcination and ion exchange in post-synthesis treatment. Further post-synthesis modification was required in the zeolite Y case to improve the catalytic properties. The post synthetic modification of zeolite Y was carried out using acidified ammonium nitrate which was optimised to produce dealuminated zeolite Y with good crystallinity and a Si/Al = 8. Characterisation was performed after each stage of this work to optimise catalyst development using XRD, SEM, EDAX, BET, MAS-NMR, and TGA. Once the optimised zeolite Y and ZSM-5 structured catalysts prepared, cracking of n-heptane was carried out to assess the in catalytic performance compared with Y and ZSM-5 pellets in a fixed-bed reactor under the same operation conditions. The cracking of n–heptane over the pellets and structured catalysts for both ZSM–5 and Y zeolite showed very similar product selectivities for similar amounts of catalyst with apparent activation energy of around 60 kJ mol-1. This research demonstrates that structured catalysts can be manufactured with excellent zeolite adherence and when suitably activated/modified give comparable cracking results to the pelleted powder forms. These structured catalysts will improve temperature distribution in highly exothermic and endothermic catalysed processes.
41
Darim, Hélio Rubens Abdo. "Propriedades ácidas e texturais de zeólitas ZSM-5 dessilicalizadas ou desaluminizadas – análise do rendimento e seletividade a olefinas leves durante a transformação de cicloexano e metilcicloexano." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8580.
Full textAbstract:
Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-02-09T10:54:21Z
No. of bitstreams: 1
DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5)<br>Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-20T17:16:45Z (GMT) No. of bitstreams: 1
DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5)<br>Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-20T17:16:55Z (GMT) No. of bitstreams: 1
DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5)<br>Made available in DSpace on 2017-03-20T17:24:11Z (GMT). No. of bitstreams: 1
DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5)
Previous issue date: 2015-03-13<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Nowadays, the Brazilian petroleum is extracted from very deep fields and possesses a high
naphthenic hydrocarbons composition, which imposes new challenges to refineries and
specially to the catalytic cracking process. In that process, the catalyst must act maximizing
the production of the highly demanded gasoline, diesel and light olefins from heavy fractions.
Taking into consideration the above discussed context, this work aimed to evaluate the effect
of basic or acid treatments applied on ZSM-5 zeolites (Si/Al=12 or 23) in the activity to
cyclohexane or methylcyclohexane transformation. XRD and 27Al-NMR showed that the dealuminated zeolites presented an increase in their crystallinity due to the extra-framework
aluminum lixiviation. On the other hand, in the desilicated zeolites occurred a decrease in
their crystallinity as a consequence of the extra-framework aluminum generation. MEV
images do not evidence any morphological change that could have been produced by the acid or basic treatments, however, the desilicated ZSM-5 zeolites treated under harder conditions
presented significant textural modifications. As expected, the chemical ICP analyses showed a
decrease in the Si/Al ratio in the desilicated zeolites and an increase of that ratio for those
dealuminated ones, being the last variation more significative in the external surface of the
zeolite crystals, as was evidenced by XPS analyses. Data from NH3-TPD showed that the
acid treatment resulted in a higher ratio of strong acid sites, which suffered more deactivation
during reaction. N2 fisisorption analyses of the ZSM-5 zeolites, showed that the desilication
done at higher temperature was more efficient to mesopore generation. In the cyclohexane
and methylcyclohexane transformation, the dealuminated zeolites were less active due to their lower aluminum content, nevertheless were more stable and presented a small increase to
light olefins selectivity. The desilicated ZSM-5 zeolites presented higher activity and higher
yield to light olefins that were supported by their lower Si/Al ratio and mainly by the presence
of mesoporosity that enhanced the reagents and products internal diffusivity.<br>A produção nacional de petróleo, extraído de jazidas cada vez mais profundas, possui um
elevado teor de hidrocarbonetos naftênicos, o que impõe novos desafios às refinarias
brasileiras e, em particular, ao processo de craqueamento catalítico. Nesse processo, o
catalisador deve maximizar a transformação das frações pesadas em produtos de alta demanda
como gasolina, diesel e olefinas leves. Nesse contexto, esta dissertação objetivou avaliar o
efeito de tratamentos de lixiviação ácida ou básica em zeólitas ZSM-5 (Si/Al=12 ou 23), na
atividade para a transformação de cicloexano ou metilcicloexano. Dados de DRX e 27Al-RMN
mostraram que as zeólitas desaluminizadas apresentaram um aumento da sua cristalinidade
devido à remoção de átomos de alumínio extra-rede, por outro lado, nas zeólitas
dessilicalizadas ocorreu uma redução da cristalinidade devido à geração de alumínio extra rede. As micrografias de MEV não evidenciaram modificação morfológica devido aos
tratamentos, entretanto nas amostras dessilicalizadas sob condições mais severas, houve significativa mudança das propriedades texturais. Como esperado, as análises químicas por ICP mostraram uma redução na razão Si/Al para as amostras dessilicalizadas e um aumento
dessa razão para as zeólitas desaluminizadas, sendo essa variação mais significativa na
superfície externa dos cristais, como mostraram resultados de XPS. As análises de DTP-NH3
mostraram que o tratamento ácido resultou numa maior proporção de sítios ácidos fortes, os
quais sofreram maior desativação durante a reação. Dados de fisissorção de N2 das zeólitas
mostraram que a dessilicalização em temperatura mais elevada foi mais eficiente na geração de mesoporos. Na transformação do cicloexano e do metilcicloexano, as zeólitas
desaluminizadas apresentaram menor conversão como resultado da diminuição do teor de
alumínio, entretanto tiveram maior estabilidade e apresentaram um ligeiro aumento na
seletividade a olefinas leves. As amostras dessilicalizadas apresentaram maiores conversões e rendimentos a olefinas leves, que se justificaram em função da diminuição da razão Si/Al, mas principalmente, como resultado da presença de mesoporosidade, que melhorou a difusão interna de reagentes e produtos.
42
Silva, Edilene Deise da. "Formação de mesoporosidade em zeólitas ZSM-5: avaliação do método de preparação e do potencial como catalisador ácido através do craqueamento de cicloexano." Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/3912.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:55:32Z (GMT). No. of bitstreams: 1
4445.pdf: 6135592 bytes, checksum: 9a1ebffa2ca083786400ffa973e8b424 (MD5)
Previous issue date: 2012-04-27<br>Universidade Federal de Sao Carlos<br>Due to their potential as acid catalyst and hydrothermal stability, USY, ZSM-5 and modernite zeolites are widely used in several processes of petroleum refining and petrochemical industries. With the discovery of new reserves in Brazil, the petroleum industry must adequate its technology to be able to process heavy oil fractions and satisfy the increased demand for more valuable derivatives (gasoline, diesel and olefins). To achieve this, a better performance of such zeolites needs to be reach by improvement of the active sites accessibility and/or diminishing the diffusion path inside of their microporous system. In this context, the objective of this research was to synthesize ZSM-5 zeolites with hierarchical pore structure and evaluate their potential as acid catalyst in the cracking of hydrocarbons, using cyclohexane as model molecule. In the synthesis of these materials, Black Pearls 2000 carbon and an organosilane surfactant molecule were employed as structure-directing agent for mesopores formation. Zeolites were characterized by X-ray fluorescence, X-ray diffraction, nitrogen physisorption, small-angle X-ray scattering, scanning electron microscopy, nuclear magnetic resonance of 27Al nucleus, Fourier transformed infrared spectroscopy and ammonium temperature programmed desorption. The properties and acid activity of the synthesized zeolites were compared with a ZSM-5 zeolite without mesopores. The results revealed that the used synthesis methodologies were effective in the formation of crystals of ZSM-5 zeolite containing the intrinsic micropores of the MFI structure combined with the presence of intracrystalline mesopores. The Black Pearls 2000 carbon generated mesopores that were an inverse replica of the carbon particles with an average diameter of 12 nm and the amphiphilic surfactant mesopores with diameters of about 4 nm. The cracking of cyclohexane showed that the solids with hierarchical structure of pores preserved the acid potential of ZSM-5 zeolites, with all the micro-mesoporous zeolites presenting similar catalytic behaviour related with the yield and selectivity in the considered reaction. Other hand, the presence of mesopores favoured the formation of products resulting from isomerization and hydrogen transfer reactions.<br>Devido ao seu potencial como catalisador ácido e estabilidade hidrotérmica, as zeólitas USY, ZSM-5 e mordenita são utilizadas em diversos processos no refino de petróleo e em petroquímica. Com a descoberta de novas jazidas no Brasil, a indústria do petróleo deve se adequar tecnologicamente para ter capacidade de processar frações pesadas e atender o aumento da demanda por derivados de maior valor agregado (gasolina, diesel e olefinas). Para isso, um desempenho mais eficiente no uso dessas zeólitas pode ser alcançado melhorando a acessibilidade aos sítios ativos e/ou reduzindo o caminho difusional no interior do seu sistema microporoso. Nesse contexto, o objetivo do estudo foi sintetizar zeólitas ZSM-5 com estrutura hierárquica de poros e avaliar seu potencial como catalisador ácido por meio do craqueamento de cicloexano, utilizado como molécula modelo. Na síntese desses materiais foram utilizados o carbono Black Pearls 2000 e uma molécula surfactante organossilano, como agentes direcionadores da formação de mesoporos. As zeólitas foram caracterizadas por difração de raios X, fisissorção de nitrogênio, espalhamento de raios X a baixos pequenos, microscopia eletrônica de varredura e transmissão, ressonância magnética nuclear do núcleo 27Al, fluorescência de raios X, espectroscopia na região do infravermelho com transformada de Fourier e dessorção de amônia a temperatura programada. As propriedades e atividade ácida das zeólitas sintetizadas foram comparadas às de uma zeólita ZSM-5 isenta de mesoporosidade. Os resultados revelaram que as metodologias de síntese foram efetivas na formação de cristais de zeólita ZSM-5 contendo a microporosidade intrínseca da estrutura MFI combinada à presença intracristalina de mesoporos. O carbono Black Pearls 2000 gerou mesoporos que foram uma replica inversa das partículas desse material com diâmetro médio de 12 nm e o surfactante anfifílico mesoporos com diâmetros em torno de 4 nm. O craqueamento de cicloexano mostrou que os sólidos com estrutura hierárquica de poros mantiveram o potencial ácido de zeólitas ZSM-5, sendo os rendimentos e seletividades dessa reação similares para todas as zeólitas micro-mesoporosas sintetizadas. A presença de mesoporos favoreceu, entretanto, a formação de produtos resultantes de isomerização e transferência de hidrogênio.
43
Hausmann, Katharina. ""Die Chance, Bürger zu werden" : deutsche Politik unter amerikanischer Besatzung ; die "Heidelberger Aktionsgruppe" ; 1946 - 47 /." Heidelberg ;Ubstadt-Weiher ;Weil am Rhein ;Basel : Verl. Regionalkultur, 2006. http://deposit.ddb.de/cgi-bin/dokserv?id=2789878&prov=M&dok_var=1&dok_ext=htm.
Full text
44
Zaker, Azadeh. "Supercritical Water Assisted Zeolite Catalyzed Upgrading of Hydrocarbons." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/579.
Full textAbstract:
Previous studies have successfully used near and supercritical water (SCW) for cracking and desulfurization of heavy crude oil and bio-oil, suppressing coke formation as a low-value by-product. Some of these studies benefited from using zeolite catalysts to increase the activity and selectivity toward targeted products; however, in depth studies are required to identify the role of water on zeolite catalysis under supercritical condition. Using three common zeolites, ZSM-5, HY, and β for supercritical water cracking of dodecane at 400°C, 24±2 MPa (in a 100 ml batch reactor), we showed that ZSM-5 is the only catalyst that partially retains its crystalline structure and activity under hydrothermal conditions. Further characterization of the ZSM-5 (used under 50/50 wt% SCW/dodecane feed) revealed 95% decrease in Brønsted acid site (BAS) density and 80% decrease in microporous area after 2 h reaction time. However, compared to the runs where SCW was absent, the apparent dodecane cracking rate constant in SCW decreased only by a factor of 2.6. Examining catalytic activity of ZSM-5 degradation products and re-using ZSM-5 showed that the unexpected activity cannot be ascribed to ZSM-5 degradation products. Using a group-type model, we showed that SCW accelerated gas and suppressed coke formations. Additionally a coke gasification pathway was suggested to account for formation of CO and CO2 in the presence of SCW. Additional experiments with two different ZSM-5 particle sizes suggested that dodecane cracking reaction is diffusion-limited in the absence of SCW and reaction-limited in its presence. Zero length chromatography of calcined and hydrothermally treated ZSM-5 showed 10 times greater apparent diffusivity for un-treated catalyst. This, according to Weisz-Prater analysis, suggested a 250 times greater dodecane surface concentration in the absence of SCW. We successfully optimized the water content of feed (5-15 wt%) to decrease the destructive effects of SCW on the structure, increase the selectivity toward BTEX products and eliminate coke formation.
45
Pettke, Sabine. "Das Rostocker Kloster zum Heiligen Kreuz vom 16. bis zum 20. Jahrhundert : kirchen- und staatsrechtliche Auseinandersetzungen im Rahmen der mecklenburgischen Kloster- und Verfassungsfrage /." Köln : Böhlau, 1991. http://catalogue.bnf.fr/ark:/12148/cb39035569s.
Full text
46
Sousa, Júnior Lenivaldo Valério de. "Síntese da Zeólita Zsm-22 a partir de sistema contendo sementes." Universidade Federal de Alagoas, 2015. http://www.repositorio.ufal.br/handle/riufal/1184.
Full textAbstract:
The ZSM-22 zeolite is a microporous crystalline structure which has dimensional solid belonging to the group called molecular sieves. It is common in their synthesis the use of structure direct agents (SDA's), also called direct organic only, which are costly and render the production of the material on an industrial scale. Furthermore, the crystallization times for the formation of the material are around 20 hours. In this work we propose the development of a synthesis route for the ZSM -22 more economically, from a reaction mixture free from organic director and containing seeds of crystallization. Seeds were synthesized by the hydrothermal method at 160 °C in the presence of 1,6- diaminohexane organic template. Samples of ZSM -22 was synthesized by hydrothermal and hydrosolvothermal at a temperature of 170 °C and fixed percentage of seeds (10%) methods, employing the following reagents: methanol, sodium silicate, aluminum sulfate, potassium hydroxide and sulfuric acid. Through systematic variations in synthesis parameters: content of methanol (0 and 4 mol), SiO2/Al2O3 ratio (50 and 100), alkalinity or basicity of the medium (0.2 and 0.4) and ratio of cations : Na + / Na + + K + ( 0 and 0.5) found that the best conditions for the formation of ZSM -22 . The products were characterized by diffraction X-ray method (XRD). According to the results of crystallinity, the best samples are also characterized by thermal analysis (TG/DTG), nitrogen adsorption at 77 K (BET) and scanning electron microscopy (SEM).<br>A ZSM-22 é uma zeólita que apresenta estrutura cristalina microporosa unidimensional pertencente ao grupo de sólidos denominados de peneiras moleculares. É comum em sua síntese à utilização de agentes direcionadores de estrutura (SDA's), também chamados apenas de direcionador orgânico, que são de custo elevado e inviabilizam a produção do material em escala industrial. Além disso, os tempos de cristalização para formação do material gira em torno de 20 horas. Neste trabalho é proposto o desenvolvimento de uma metodologia de síntese para a ZSM-22 mais econômica, partindo de uma mistura reacional isenta de agente direcionador de estrutura e contendo sementes de cristalização. As sementes foram sintetizadas pelo método hidrotérmico à 160ºC na presença do direcionador orgânico 1,6-diaminohexano. As amostras de ZSM-22 foram sintetizadas pelos métodos hidrotérmico e hidrosolvotérmico à temperatura de 170ºC e percentual fixo de sementes (10% em relação ao SiO2), empregando os seguintes reagentes: metanol, silicato de sódio, sulfato de alumínio, hidróxido de potássio e ácido sulfúrico. Através de variações sistemáticas nos parâmetros de síntese: teor de metanol (0 e 4 mol), razão SiO2/Al2O3 (50 e 100), alcalinidade ou basicidade do meio (0,2 e 0,4) e razão dos cátions: Na/Na + K (0 e 0,5), onde constatou-se as melhores condições de formação da ZSM-22. Os produtos obtidos foram caracterizados pelo método de difratometria de raios-x (DRX). Partindo dos resultados de cristalinidade, as melhores amostras também foram caracterizadas por análises térmicas (TG/DTG), adsorção de nitrogênio a 77 K (BET) e microscopia eletrônica de varredura (MEV).
47
Feger, Claudia. "Die dunkle Seite der Literatur." Universitätsbibliothek Chemnitz, 2005. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200501739.
Full text
48
Dahlhaus, Jörg. "Motivierung zum Alterssport : von Metatheorien zum fundierten Praxiskonzept /." Saarbrücken : VDM, Verl. Dr. Müller, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=3013940&prov=M&dok_var=1&dok_ext=htm.
Full text
49
Faisal, Abrar. "Zeolite adsorbents and catalysts for the recovery and production of biochemicals." Doctoral thesis, Luleå tekniska universitet, Kemiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60137.
Full textAbstract:
Fossil based energy resources are dominating the world’s primary energy consumption for the last century. However, with decreasing crude oil reservoirs and the role they play in global warming by emitting greenhouse gases, the focus has been turned towards improved utilization of renewable resources and the need for new, sustainable fuels and chemicals is more urgent than ever. Biomass is a carbon neutral resource that can be used to produce biofuels and other useful chemicals. One such chemical is 1-butanol (or simply butanol), which has great potential as a gasoline substitute because of its favorable fuel properties. Butanol can be produced from acetone, butanol and ethanol (ABE) fermentation using e.g. Clostridium acetobutylicum. However, the concentration of butanol in fermentation in the resulting broth is limited to ca. 20 g/L due to its toxicity for microorganisms. Butyric acid is a precursor to butanol, which is produced prior to butanol in ABE fermentation. Butyric acid is an important industrial chemical, which can be further converted into a number of commercial compounds e.g. acetate butyrate, butyl acetate and butanol. Arginine is a semi-essential amino acid that has vast applications in the field of pharmaceutical and food industry. In addition, arginine can replace inorganic nitrogen as nitrogen source in fertilizers. It can be produced via fermentation of sugars using engineered microorganism like E. Coli, but like butanol its concentration is restricted to approximately 12 g/L. Due to low concentration of these useful chemicals in the resulting fermentation broths recovery of these chemicals remain challenging with today’s options and therefore novel recovery process should be developed. In this study, zeolite adsorbents were used to recover butanol, butyric acid and arginine from model and real fermentation broths. Zeolite MFI adsorbent efficiently adsorbed butanol from model solutions with a saturation loading of 0.11 g/g- zeolite. On the other hand, adsorption of butyric acid was found to be strongly pH dependent, with high adsorption below and little adsorption above the pKa value of the acid. A structured adsorbent in the form of steel monolith coated with a silicalite-1 film was also used and performance was evaluated by performing breakthrough experiments at room temperature using model ABE fermentation broths and the results were compared with those obtained using traditional adsorbent sin the form of beads. Desorption studies showed that a high quality butanol product with purity up to 95.2% for butanol-water system and 88.5% for the ABE system can be recovered with the structured silicalite-1 adsorbent. Further, zeolite X adsorbents in the form of powder and extrudates was used to recover arginine from a real fermentation broth and also from aqueous model solutions. To the best of our knowledge, this is the first time recovery of arginine from real fermentation broths using any type of adsorbent is reported. Arginine loading of 0.15 g/g was observed at pH 11 using zeolite X powder. The selectivity for arginine over ammonia and alanine from the fermentation broth at pH 11 was 1.9 and 8.3, respectively, for powder and 1.0 and 4.1, respectively, for extrudates. Synthesis gas (CO + H2) can be produced e.g.by gasification of lignocellulose biomass. This synthesis gas can be used to produce methanol, which subsequently may be converted into gasoline using zeolite ZSM-5 catalyst. However, during Methanol to Gasoline (MTG) process, undesirable carbon residue (coke) is formed that gradually reduces the activity of catalyst. It was hypothesized that intracrystalline defects in the zeolite formed during conventional synthesis may accelerate the deactivation rate by coke formation. In this work, a novel ZSM-5 zeolite catalyst essentially free of intracrystalline defects was synthesized and evaluated in the MTG reaction,. The novel catalyst showed significantly higher resistance towards deactivation by coke formation as compared to a reference catalyst containing defects.
50
Silva, Camila Ramos da. "Formação de mesoporos na síntese de zeólitas ZSM-5 via nanomoldagem avaliação no craqueamento de n-decano." Universidade Federal de São Carlos, 2008. https://repositorio.ufscar.br/handle/ufscar/3993.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:56:30Z (GMT). No. of bitstreams: 1
1801.pdf: 7196962 bytes, checksum: d8036f105e4f745f6d5cca6487bfd320 (MD5)
Previous issue date: 2008-04-04<br>Universidade Federal de Minas Gerais<br>The use of zeolites in the cracking of hydrocarbons is limited because the molecules higher than 0.74 nm do not diffuse in their micropores. In the other hand, molecular sieves as MCM-41, MCM-48 ou SBA-15, whose diameters are up 10 nm for the two formers and up to 30 nm for the last, have low hydrothermal stability and catalytic activity. To overcome those limitations, many studies are devoted to
prepare materials, which can combine the high activity of zeolites with the better accessibility of the mesoporous materials. Among the possible methods, the synthesis of zeolites in confined
spaces (nanocasting) it is seem as a powerful alternative. In this method: 1) a mesoporous or non-porous silica is impregnated with an organic compound, which act as a carbon precursor, after being carbonized; 2) the porous carbon is
subsequently obtained by treatment with hydrofluoric acid or alkaline hydroxides; 3)
the porous of the carbon are filled with the zeolite synthesis gel, which is formed after crystallization; 4) finally, the mold of the carbon and the template of the zeolite microstructure are eliminated by calcination. In the present work, it was used the above described method for the synthesis of nanocasting ZSM-5 zeolites using porous carbon, which were prepared from non-porous or mesoporous silica moulds (MCM-41, MCM-48 e SBA-15). The XRD of the prepared zeolites did not show diffraction peaks in the low angle region (< 5°2θ), showing that the inverse replica of the mesoporous silicas was not obtained.
However, the nitrogen sorption measurements evidenced the presence of mesoporous, which resulted from the carbon nanotubes occluded during the ZSM-5 crystals formation. The mesopores observed in the Znp, nanocast from non-porous silica, were attributed to the inter-crystalline spaces generated by the agglomeration of ZSM-5 nanocrystals. The mesoporous formation in the ZSM-5 zeolites during the crystallization in a confined space (nanocating) was considerately favored by the
ageing of the synthesis gel at the laboratory temperature and without stirring. That
procedure allows the preparation at 180 °C of ZSM-5 zeolites with high crystallinity and in a lower time. Nevertheless, as verified by 27Al-NMR, the aluminum was incorporated partially in the zeolite microstructure, remaining as alumina in the crystal surface, which leads to a lower activity in the n-decane cracking when compared with a conventional ZSM-5 zeolite with a similar Si/Al ratio.<br>A utilização de zeólitas no craqueamento de hidrocarbonetos é limitada devido a não permitir a difusão de moléculas de tamanho maior que o diâmetro de seus microporos (< 0,74 nm). Por outro lado, as peneiras moleculares mesoporosas, como a MCM-41, MCM-48 ou SBA-15 com diâmetro de poros de até 10 nm, no caso das duas primeiras, e de até 30 nm no caso da última, possuem baixas estabilidade
hidrotérmica e atividade catalítica. Para superar essas restrições, estuda-se a preparação de materiais que combinem a elevada atividade catalítica das zeólitas com a melhor acessibilidade dos materiais mesoporosos. Dentre os métodos possíveis, a síntese de zeóltas em espaço confinado (nanomoldagem), surge como uma potencial alternativa. Nessa técnica: 1) uma silica mesoporosa ou não porosa é impregnada com um composto orgânico precursor de carbono, sendo o sólido
posteriormente carbonizado; 2) o carbono poroso é obtido após dissolução da sílica com ácido fluorídrico ou hidróxidos alcalinos; 3) os poros do carbono são preenchidos com o gel de síntese da zeólita, a qual se forma após cristalização; 4) finalmente o molde de carbono e o agente direcionador da microestrutura são eliminados via calcinação. No presente trabalho, utilizou-se a técnica descrita para a síntese de zeólitas ZSM-5 nanomoldadas em carbonos porosos, os que foram obtidos utilizando como molde sílicas não porosas ou mesoporosas (MCM-41, MCM-48 e
SBA-15). Os difratogramas de raios X das zeólitas preparadas não apresentaram
picos de difração em ângulos menores que 5°(2θ), mostrando que o ordenamento
das fases mesoporosas não foi replicado, porém, os resultados de fisissorção de nitrogênio indicaram a presença de mesoporos, sugerindo que nanotubos de carbono formados nos mesoporos dos moldes de sílica foram ocluídos nos cristais da ZSM-5. Os mesoporos observados nas zeólitas Znp, nanomoldadas em carbono obtido da sílica não porosa, foram atribuídos aos espaços intercristalinos resultantes do empacotamento de cristais nanométricos da zeólita ZSM-5. A formação de
mesoporos nas zeólitas ZSM-5 durante o processo de cristalização em espaço
confinado (nanomoldagem) foi consideravelmente favorecida pelo envelhecimento do gel de síntese à temperatura ambiente e sem aplicação de agitação. Esse
procedimento permitiu a obtenção a 180 °C de zeólitas com alta cristalinidade e em menor tempo de cristalização. Entretanto, como verificado por 27Al-RMN, o alumínio foi incorporado parcialmente na estrutura da zeólita, permanecendo como alumina na superfície dos cristais, o que provocou menor atividade para o craqueamento de n-decano quando comparado com uma zeólita ZSM-5 convencional com relação Si/Al próxima.