Dissertations / Theses on the topic 'Zsm-5'
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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 textFörbränning 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.
Nada, Majid Hameed. "Greener synthesis of nanocrystalline ZSM-5." Thesis, University of Iowa, 2016. https://ir.uiowa.edu/etd/3149.
Full textBalakrishanan, I. "Catalytic reactions over zsm-5 zeolites." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1985. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3229.
Full textAlbahar, Mohammed. "Selective toluene disproportionation over ZSM-5 zeolite." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/selective-toluene-disproportionation-over-zsm5-zeolite(bcc7a677-3234-470f-be44-fdefa2bd7350).html.
Full textAguilar-Mamani, Wilson. "Crystallization of NBA-ZSM-5 from kaolin." Doctoral thesis, Luleå tekniska universitet, Kemiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-63169.
Full textCallahan, 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 textWinstanley, Alastair W. "Characterisation and catalytic studies of ZSM-5 zeolite." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334462.
Full textFergie-Woods, J. W. "NMR studies on the din zeolite ZSM-5." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304211.
Full textCowley, Michele. "Conversion of n-pentenes over H-ZSM-5." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5370.
Full textThe skeletal isomerisation of I-pentene provides the feed stock 2-methyl-2-butene and 2-methyl-I-butene for the production of tertiary amyl methyl ether (TAME), an octane booster for petrol. Benzene, toluene, xylenes and ethylbenzene (BTX+EB) are good or even better octane boosters, although the use of benzene is limited due to its carcinogenic nature. From an industrial point of view, these compounds are therefore of importance. The conversion of I-pentene over H-ZSM-5 zeolite catalyst was studied in a fixed-bed micro reactor.
Lai, Re Gavalas George R. "Synthesis and characterization of ZSM-5 zeolite membranes /." Diss., Pasadena, Calif. : California Institute of Technology, 2001. http://resolver.caltech.edu/CaltechETD:etd-11102005-103556.
Full textBarros, 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.
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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
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.
SCHEIBLER, Janaina Rafaella. "Síntese de membranas zeolíticas (ZSM-5/y-ALUMINA e ZSM-5/a-ALUMINA) por Pore-Plugging para permeação de gás N2." Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/315.
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Entre as membranas inorgânicas microporosas, as membranas zeolíticas constituem uma tecnologia promissora, devido às suas potenciais aplicações normalmente na desidratação do álcool, separação de moléculas de gás, separação de isômeros ou em processos químicos, incluindo reações de esterificação. Sob este aspecto, torna-se imprescindível o estudo das rotas de preparação desses materiais, visando desenvolver produtos com qualidade e a baixo custo. Portanto, a inovação deste estudo se dá na síntese de membranas zeolíticas via método de síntese poreplugging visando a utilização das membranas inorgânicas para permeação gasosa de N2. Neste trabalho foram desenvolvidos os seguintes materiais: zeólita ZSM-5, membranas cerâmicas (γ-alumina e α-alumina) e as membranas zeolíticas (ZSM5/γ-alumina e ZSM-5/α-alumina). A zeólita ZSM-5 foi sintetizada por meio do método hidrotérmico. As membranas cerâmicas (γ-alumina e α-alumina) foram preparadas a partir da técnica de conformação de pós cerâmicos e posteriormente submetidas à sinterização a uma temperatura de 1000 ºC/1h e 1200 ºC/1h respectivamente. A preparação das membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina) foi realizada com base no método pore in plugging. As amostras foram caracterizadas a partir das técnicas de difração de raios X e Microscopia Eletrônica de Varredura. Os resultados experimentais permitem diversas conclusões acerca do desenvolvimento dos materiais: zeólita ZSM-5, membranas cerâmicas (γ-alumina e α-alumina) e membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina). A partir da difração de raios X, foi possível verificar que o método de síntese empregado, foi efetivo na obtenção da zeólita ZSM-5. O difratograma apresentou picos característicos de uma zeólita ZSM-5 quando comparada ao padrão. Os resultados obtidos por DRX para as membranas cerâmicas (γ-alumina e α-alumina) demonstraram a formação de picos característicos do óxido de alumínio, os materiais são cristalinos e puros. Para o método pore-plugging pode se dizer que é um método promissor, pois mostrou uma formação satisfatória da camada zeolítica no resultado do DRX de ambas as membranas zeolíticas (ZSM-5/γ-alumina e ZSM-5/α-alumina).
Among the microporous inorganic membranes, zeolite membranes are a promising technology due to their potential applications normally in alcohol dehydration, separation of gas molecules, separation of isomers or chemical processes, including esterification reactions. In this regard, it is essential to study the preparation of these materials routes in order to develop products with quality and low cost. Therefore, innovation of this study gives the synthesis of zeolite membranes via pore-plugging synthesis method aimed at the use of inorganic membranes for gas permeation N2. In this work the following materials were developed: ZSM-5 zeolite, ceramic membranes (γ-alumina and α-alumina) and zeolitic membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina). Zeolite ZSM-5 was synthesized by the hydrothermal method. Ceramic membranes (γ-alumina and α-alumina) were prepared from the ceramic powder forming technique, and subsequently subjected to a sintering temperature of 1000 °C/1h and 1200 °C/1h respectively. The preparation of zeolite membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina) was carried out based on the method in pore plugging. The samples were characterized from the techniques of X diffraction and scanning electron microscopy rays. The experimental results allow several conclusions about the development of materials: zeolite ZSM-5, ceramic membranes (γ-alumina and α-alumina) and zeolite membranes (ZSM-5/γ-alumina and ZSM-5/αalumina). From the X-ray diffraction, it found that the method of synthesis used was effective in obtaining the zeolite ZSM-5. The XRD pattern showed peaks characteristic of ZSM-5 compared to the standard. The results obtained by XRD ceramic membranes (γ-alumina and α-alumina) showed the formation of peaks characteristic of aluminum oxide, the materials are crystalline and pure. For the poreplugging method can be said to be a promising method because it showed a satisfactory formation of the zeolite layer on the result of XRD both zeolite membranes (ZSM-5/γ-alumina and ZSM-5/α-alumina).
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 textUniversidade Federal de Sao Carlos
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.
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.
Ohayon, David. "Thermally stable ZSM-5 zeolite materials with new microporosities." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39073.pdf.
Full textSeyedeyn-Azad, Fakhry. "Nitrogen monoxide reduction over ZSM-5 zeolite-supported catalysts /." Title page, summary and contents only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phs519.pdf.
Full textAlnaimi, 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 textManstein, Heiko. "The chemical vapour deposition of Tetraethoxysilane on Zeolite ZSM-5." Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5290.
Full textThis thesis reports on the investigation of a cyclic chemical vapour deposition (CVD) method eliminating unwanted surface reactions and enhancing shape selective properties by depositing inert silica onto the external surface of zeolite ZSM-5. A CVD treatment consists out of a deposition, flushing and heating step followed by calcination in flowing air. Modifications are carried out in up to 33 cycles on one and the same sample employing tetraethoxysilane (TEOS) as silica precursor at deposition temperatures ranging from 50 to 400°C. After each CVD treatment the catalyst is tested with appropriate test reactions in order to quantify the extent of modification. The gradual inertisation of the external surface is followed with the catalytic cracking of 1,3,5-triisopropylbenzene (1,3,5-TiPB) which is too bulky to enter the micro-pore structure of ZSM-5. The disproportination of toluene (TDP) is employed to monitor changes of the internal activity and alterations in the shape selective properties of the catalyst. The analysis of reactor effluent during the deposition, flushing and heating step of the modification cycle allows investingating the reaction pathway. The deposition reaction proceeds with the reaction of the alkoxy groups of TEOS with the terminal hydroxyls of the zeolite under the formation of ethanol.
Nash, Robin John. "Aromatization of alkenes by gallium/H-ZSM-5 zeolite catalysts." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/21518.
Full textJunkes, Janaína Accordi. "Síntese in situ de zeólita ZSM-5 sobre substratos biomórficos." Florianópolis, SC, 2007. http://repositorio.ufsc.br/xmlui/handle/123456789/89667.
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Uma tecnologia desenvolvida recentemente para produzir materiais microcelulares é a fabricação de cerâmicas biomórficas, que é a reprodução das morfologias de madeira por biomodelagem, onde as características estruturais da madeira nativa são mantidas no produto cerâmico. O objetivo deste trabalho é o recobrimento in situ de diferentes substratos biomórficos (Al2O3, TiO2 e SiAlON) com a zeólita ZSM-5. Para conseguir o revestimento in situ, uma síntese hidrotérmica foi usada. A síntese hidrotérmica foi realizada a 150ºC em uma autoclave, variando os tempos de síntese em 72, 96, 120, 144 e 168h. Subseqüentemente a cerâmica foi calcinada a 550ºC durante 5h. Adicionalmente, diversas razões molares de SiO2/Al2O3 (17, 27, 37, 47 e 57) foram testadas para verificar sua influência na cristalização da zeólita. A composição das fases dos produtos cerâmicos foi determinada por difração de raios X. A microestrutura foi caracterizada pelo microscópio eletrônico de varredura, e a área de superfície específica foi determinada por isotermas de adsorção de N2 usando o método de B.E.T. A área de superfície específica aumentou significativamente, até 30 vezes, para todas as amostras, que faz os compósitos de cerâmica-zeólita candidatos potenciais para aplicações catalíticas e tecnologias de adsorção/separação devido a sua porosidade específica e hierárquica, capacidade de peneira molecular e força termomecânica relativamente elevada.
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 textThis 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
Aguilar, Wilson. "Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials." Licentiate thesis, Luleå tekniska universitet, Kemiteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16976.
Full textGodkänd; 2014; 20140430 (andbra); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Wilson Aguilar-Mamani Ämne: Kemisk teknologi/Chemical Technology Uppsats: Study of the Synthesis of ZSM-5 from Inexpensive Raw Materials Examinator: Biträdande professor Johanne Mouzon, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Ph.D. Linda Sandström, Energy Technology Centre in Piteå Tid: Torsdag den 19 juni 2014 kl 14.00 Plats: C305, Luleå tekniska universitet
LETICHEVSKY, SONIA. "SYNTHESIS AND CHARACTERIZATION OF NANOCRYSTALLINE MORDENITE, FERRIERITE AND ZSM-5 ZEOLITES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12172@1.
Full textCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho, as zeólitas mordenita, ferrierita e ZSM-5 foram preparadas através de síntese hidrotérmica com a variação dos parâmetros fontes de alumínio e silício, quantidade de água, utilização de sementes, temperatura e tempo de cristalização com a finalidade de obter zeólitas nanocristalinas. As amostras preparadas foram caracterizadas por espectrofotometria de absorção atômica, difração de raios-X com refinamento através do método de Rietveld, adsorção física de N2, microscopia de força atômica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão e ressonância magnética nuclear no estado sólido de 27Al e 29Si. Para se obter um controle do tamanho de cristal foi importante encontrar um equilíbrio entre temperatura e tempo de síntese. A fonte de alumínio mais adequada seria o aluminato de sódio enquanto que a de silício variou de acordo com tipo de zeólita. Foram obtidas amostras de mordenita de tamanho médio de cristalito entre 56 e 292 nm com diferentes percentuais de cristalinidades. As amostras de ferrierita preparadas possuíam tamanho médio de cristalito entre 61 e 82 nm. Já em relação à ZSM-5, foram obtidas uma amostra de tamanho médio de cristalito de 46 nm e uma de 58 nm. Este estudo mostrou a necessidade do conhecimento aprofundado da influência dos diversos parâmetros, individualmente, no processo de cristalização de cada uma zeólitas para se obter um controle eficaz do tamanho da zeólita. Finalmente, foi possível propor um mecanismo de cristalização para cada zeólita estudada.
In this work, the mordenite, ferrierite and ZSM-5 zeolites were prepared by hydrothermal synthesis, modifying the parameters aluminium and silicium sources, water content, seeding, crystallization time and temperature. The objective was to obtain nanocrystalline zeolites. The prepared samples were characterized by atomic absorption spectrophotometry, X-ray diffraction with Rietveld refinement, N2 physical adsorption, atomic force microscopy, scanning electronic microscopy, transmission electronic microscopy and 27Al and 29Si solid state nuclear magnetic resonance. To achieve crystal size control it was important to find the equilibrium between synthesis time and temperature. Sodium aluminate was found to be the most suitable aluminium source. As for the silicium source, each zeolite type had a more suitable source. Mordenite samples with crystallite size between 56 and 292 nm and different crystallinity percentages were obtained. Ferrierite samples with crystallite size between 61 and 82 nm were obtained. Two ZSM-5 samples with crystallite size of 46 nm and 58 nm were prepared. This study showed that to obtain an efficient crystal size control, it is necessary to have a deep knowledge of the influence of all individual parameters in each zeolite`s crystallization process. Finally, it was possible to propose a crystallization mechanism to each zeolite studied.
Zhang, Yanping. "Nitric oxide decomposition over metal ion-modified Cu-ZSM-5 catalysts." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11260.
Full textCapdeillayre, Chloé. "Reduction catalytique sélective de NO par NH3 sur Fe-ZSM-5." Montpellier 2, 2007. http://www.theses.fr/2007MON20156.
Full textWeber, Reinier Willem. "The characterization and elimination of the external acidity of ZSM-5." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18301.
Full textKhangkham, 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 textPrechtl, Petra. "Study of N₂O decomposition over Fe-ZSM-5 with transient methods /." Lausanne : EPFL, 2007. http://library.epfl.ch/theses/?nr=3884.
Full textRäuchle, Konstantin. "Untersuchungen an nickelhaltigen ZSM-5-Zeolith-Katalysatoren zur simultanen Stickoxidreduktion mit Propen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1141740585628-02228.
Full textNitric and nitrous oxides (NOx, N2O) are part of toxic and climate damaging airborne pollutants and will be produced by combustion of fossil fuels in present of air. In this work the simultaneous reduction of NOx and N2O with propene has been investigated using nickel impregnated zeolites of type H-ZSM-5 as catalytic active material. The experiments have been done using one catalyst bed and a synthetic gas mixture according to real existing environment conditions. The influence of nickel content as well as acidity of the support material on conversion and selectivity have been discussed. Using the experimental results a possible reaction mechanism has been submitted
Welscher, Julia [Verfasser]. "Untersuchungen zur Aufkristallisation von ZSM-5 Zeolithen auf sphärische Trägermaterialien / Julia Welscher." München : Verlag Dr. Hut, 2017. http://d-nb.info/1149579579/34.
Full textConnerton, Jan. "Cu-ZSM-5 zeolite catalysts for the selective catalytic reduction of NOx." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302406.
Full textFergie-Woods, J. W. "NMR studies on the dynamics of small molecules in zeolite ZSM-5." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355099.
Full textArmstrong, Robert. "Partial oxidative upgrading of ethane with Fe- and Cu-ZSM-5 catalysts." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/59701/.
Full textBiriaei, Rouholamin. "Synthesis of mesoporous ZSM-5 zeolites and their application in furan deoxygenation." Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/70276.
Full textDepleting fossil fuel reserves and increase of energy demands along with economical,political, and environmental issues related to the fossil fuels have made it imperative to develop processes to produce renewable fuels and chemicals. The most plentiful and cheap sustainable source of carbon that can be used as a feedstock for the production of renewable fuels and commodity chemical feedstocks is lignocellulosic biomass. The liquid produced from the pyrolysis of biomass is designated as pyrolysis oil or bio-oil. This liquid contains acomplex mixture of compounds resulting from the degradation of biomass building units,cellulose, hemicellulose, and lignin. It has a low heating value and high oxygen content, isacidic, contains solid char particles, is incompatible with current petroleum-based fuels, isthermally unstable, and degrades with time. Therefore, upgrading of bio-oil is inevitable inorder to resolve the issues associated with pyrolysis oils and to use them as renewable fuelsand chemicals. Catalytic deoxygenation is one the promising methods which have been extensively studied in order to remove atomic oxygen and valorizing these oils. However, there are still several issues such as low selectivity into aromatics and olefins and coke formation. Thus, developing new catalysts and processes is a must to overcome the mentioned concerns.In the first part of this thesis, the synthesis and characterization of a series of mesoporousZSM-5 samples are discussed. Pluronic P123 triblock copolymer (EO20PO70EO20) was used as the meso-phase template and synthesis was followed by a pH adjusting methodallowing obtaining a well-crystallized ZSM-5 material with meso-channels of size of 8-10nm. The resulting materials were characterized using X-ray diffraction, transmission electronmicroscopy (TEM), nitrogen adsorption/desorption, scanning electron microscopy (SEM),solid-state nuclear magnetic resonance (MAS-NMR) and ammonia temperature programmed desorption (TPD) analyses. The significance of the developed method is to perform the growth of zeolite crystals with a mesostructured pore lattice in a cooperative manner,avoiding both a phase separation between the surfactant and zeolite units during crystallization and the formation of a separate amorphous mesoporous material. In the second part, the effect of mesoporosity on deoxygenation of furan in terms of aromatic production and catalyst deactivation through a comparative study between mesoporous andmicroporous ZSM-5 samples, is studied. The mesoporous catalysts were prepared accordingto the method described in part one with Si/Al ratios of 30 and 60. Moreover, two differentWHSV rates of 5.5 and 11 h-1 were employed in the reaction tests. It was found that the initialfuran conversion was higher over the microporous catalysts, which however deactivated rapidly, over 2 hours of time on-stream. On the other hand, the mesoporous catalysts showeda steadier activity with a slight deactivation rate. The overall selectivity to aromatics over the mesoporous catalysts was higher than over the microporous ones. In chapter 4, the effect of the incorporation of zinc metallic active sites on the conversion,aromatic production and coke formation rates is discussed. Two series of microporous and mesoporous catalyst with Si/Al=30 were prepared at different metal loadings of 2 and 5 wt.%.The results of X-ray diffraction (XRD) patterns revealed no extra peaks compared to thoseof the Zn free materials, indicating the good dispersion of zinc. The initial furan conversionrate was higher over the microporous catalysts, and increased by increasing the metal loading,however the microporous samples, deactivated rapidly after 2 hours of time on-stream. Inaddition, the aromatic selectivity with benzene as the major product was increased and coke formation was reduced over the mesostructured zeolites.
Räuchle, Konstantin. "Untersuchungen an nickelhaltigen ZSM-5-Zeolith-Katalysatoren zur simultanen Stickoxidreduktion mit Propen." Doctoral thesis, Technische Universität Dresden, 2005. https://tud.qucosa.de/id/qucosa%3A24674.
Full textNitric and nitrous oxides (NOx, N2O) are part of toxic and climate damaging airborne pollutants and will be produced by combustion of fossil fuels in present of air. In this work the simultaneous reduction of NOx and N2O with propene has been investigated using nickel impregnated zeolites of type H-ZSM-5 as catalytic active material. The experiments have been done using one catalyst bed and a synthetic gas mixture according to real existing environment conditions. The influence of nickel content as well as acidity of the support material on conversion and selectivity have been discussed. Using the experimental results a possible reaction mechanism has been submitted.
Modutwane, Angel Tumelo. "The optimization of the ZSM-5 catalyst activity with respect to crystallinity." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/6697.
Full textAndersen, Bo. "Propene oligomerization over steam dealuminated and boron and phospherous modified ZSM-5." Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/22049.
Full textZSM-5 was modified with boron and phosphorus compounds in an attempt to improve the selectivity of the catalyst with respect to the linearity of the liquid product of propene oligomerization. Boron was incorporated into the zeolite framework by inclusion in the synthesis gel. Boralite catalysts made in this way and containing very low Al contents had only weak acidity as was evident from only one, low temperature NH3 desorption peak at ca. 190 °C. These catalysts showed poor propene oligomerization activity as a result of the weak acidity arising from the weak B(OH)Si site and reduced catalyst free volume. The latter was ascribed to occluded B₂O₃ species. Activity of these catalysts was proportional to Al, rather than B content. No appreciable selectivity changes were observed for any of these catalysts. In an attempt to enhance the acidity and hence the activity of the boralite catalysts, mild fluorination treatments were carried out. A boralite catalyst containing 550 ppm Al and 1.2 wt% boron was treated with mild HF at room temperature. The activity of the catalyst was significantly reduced. The activity of the catalyst was essentially restored to its former level upon subsequent NH₄F treatment. The catalyst then contained 120 ppm Al and 0.8 wt% boron. Although some activity enhancement was achieved through mild fluorination, the catalyst utilization values (CUV) remained an order of magnitude lower than the CUV of unmodified ZSM-5. Catalytic activity remained proportional to trace Al content.
Freiding, Jens. "Extrusion von technischen ZSM-5-Kontakten und ihre Anwendung im MTO-Prozess." Karlsruhe Univ.-Verl. Karlsruhe, 2009. http://d-nb.info/996982949/04.
Full textEgues, Silvia Maria da Silva. "Utilização de zeolitas ZSM-5 na decomposição direta do monoxido de nitrogenio." reponame:Repositório Institucional da UFSC, 1996. http://repositorio.ufsc.br/xmlui/handle/123456789/76544.
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Este trabalho apresenta a atividade catalítica das zeólitas ZSM-5, para a reação de decomposição do NO, com diferentes razões molares de sílica/alumina (SAR), trocadas ionicamente com cobre e com cério. Foram estudados os efeitos de temperatura de reação, tempo de contato e concentração de NO na alimentação sobre a conversão do NO a N2. Também analisou-se a influência da SAR e do tipo de cátion trocado (Cu+2 e Ce+4). A temperatura variou entre 250-650°C, o tempo de contato (massa / fluxo) foi de 1,0-2,0 g.s.cm-3 e a concentração foi de 1,0-5,0% vol de NO em hélio. As atividades das Cu-ZSM-5 iniciaram-se por volta de 300°C alcançando seu máximo a 400-500°C, a temperaturas mais altas a atividade decaiu. O tempo de contato onde houve maior conversão foi de 2,0 g.s.cm-3 com concentração de NO/He no gás de alimentação de 3,0%. A atividade das zeólitas demonstrou forte dependência com o SAR, aumentando com a diminuição deste. A zeólita trocada com íon cério não apresentou atividade catalítica nas condições de reação empregadas.
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 textThe 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 (916), 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.
Chupin, Cédric. "Réduction sélective du monoxyde d'azote par le méthane en présence d'oxygène sur Co-ZSM-5 et Fe-ZSM-5 : optimisation des catalyseurs, étude mécanistique et cinétique de la réaction." Lyon 1, 2001. http://www.theses.fr/2001LYO10236.
Full textGöhlich, 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 textGuerra, 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 textSmith, Gordon Christopher. "Catalytic cracking of n-alkanes and n-alkylbenzenes over H-ZSM-5 zeolite." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12550.
Full textMlimi, Kenneth Mpemane. "Metal modified mesoporous ZSM-5 as catalysts for the oligomerization of 1- hexene." University of Western Cape, 2021. http://hdl.handle.net/11394/8423.
Full textThe use of diesel engines in vehicles and heavy machinery throughout the world has been slowly increasing in the past few decades. This has led to high demand for diesel and gasoline with high octane number. Diesel and gasoline are in high demand due to its qualities as fuels containing low or no sulfur and nitrogen compounds, making them environmentally friendly and the anti- knocking properties respectively. With these reasons and more, researchers have been studying processes like the catalytic oligomerization of olefins to produce synthetic fuels with augmented qualities and properties. The effectiveness of the process will depend on the quality of the catalyst.
Langford, Steven Thomas. "The effect of oxygenates on the oligomerisation of propene over zeolite ZSM-5." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18297.
Full textDIMON, BIAOU. "Cinétique de formation de coke et régénération de zéolithes Y et ZSM 5." Poitiers, 1993. http://www.theses.fr/1993POIT2318.
Full textFoletto, Edson Luiz. "Estudos da decomposição direta do monóxido de nitrogênio sobre zeólitas ZSM-5 modificadas /." Florianópolis, SC, 1998. http://repositorio.ufsc.br/xmlui/handle/123456789/77446.
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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 textThe 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
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 textUniversidade Federal de Sao Carlos
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.
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.
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 textThe 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.
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.