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Previous issue date: 2009-08-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The nanostructured molecular sieve SBA-15 was synthesized by the hydrothermal
method, and modified with lanthanum with Si/La molar ratios of 25, 50, 75 and 100. The
materials were evaluated as catalysts for the cracking of n-hexane model reaction. Type SBA-
15 and LaSBA-15 mesoporous materials were synthesized using tetraetilortosilicato as a
source of silica, hydrochloric acid, heptahydrate lanthanum chloride and distilled water.
Pluronic P123 triblock. polymer was used as structure template. The syntheses were carried
out by 72 hours. The obtained SBA-15 samples were previously analyzed by
thermogravimetry, in order to check the conditions of calcination for removal of organic
template. Then, the calcined materials were characterized by X-ray diffraction, infrared
spectroscopy, adsorption and desorption of nitrogen, scanning electron microscopy and X-ray
microanalysis by dispersive energy. The acidity of the samples was determined using
adsorption of n-bulinamina and desorption followed by thermogravimetry. It was found that
the hydrothermal synthesis method was suitable for the synthesis of the SBA-15 mesoporous
materials, with an excellent degree of hexagonal ordering. The reactions of catalytic cracking
of n-hexane were carried out using a fixed bed continuous flow microreactor, coupled on-line
to a gas chromatograph. From the catalytic evaluation, it was observed that the mesoporous
materials containing lanthanum showed different results for the reaction of cracking of nhexane
compared to the unmodified mesoporous material SBA-15. As a result of cracking
was obtained as main products hydrocarbons in the range of C1 to C5. The catalyst that
showed better properties in relation to the acidity and catalytic activity was LaSBA-15 with
the ratio Si/La = 50 / A peneira molecular nanoestruturada SBA-15 foi sintetizada pelo m?todo
hidrot?rmico, e modificada com lant?nio com raz?es molares Si/La de 25, 50, 75 e 100. Os
materiais obtidos foram avaliados como catalisador para a rea??o modelo de craqueamento de
n-hexano. Os materiais mesoporosos tipo SBA-15 e LaSBA-15 foram sintetizados utilizando
tetraetilortosilicato, como fonte de s?lica, ?cido clor?drico, cloreto de lant?nio heptahidratado e
?gua destilada. Como direcionador estrutural foi utilizado copol?mero tribloco Pluronic P123.
As s?nteses foram realizadas durante 72 horas. As amostras de SBA-15 modificadas foram
avaliadas por termogravimetria para verificar as condi??es de calcina??o para remo??o do
direcionador org?nico. Ap?s a retirada do direcionador as amostras de SBA-15 modificadas
com diversas raz?es Si/La (25, 50, 75 e 100) foram caracterizadas por an?lises por difra??o de
raios-X, espectroscopia na regi?o do infravermelho, adsor??o e dessor??o de nitrog?nio,
microscopia eletr?nica de varredura e microan?lise de raios X por energia dispersiva. A
acidez das amostras foi determinada utilizando adsor??o de n-bulinamina seguido de
dessor?ao por termogravimetria. Verificou-se que o m?todo de s?ntese hidrot?rmica foi
adequado ? s?ntese dos materiais mesoporosos modificados com excelente grau de ordena??o
hexagonal. As rea??es de craqueamento catal?tico do n-hexano foram realizadas em um
microreator catal?tico de leito fixo com fluxo cont?nuo acoplado em linha com um
cromat?grafo a g?s. A partir da avalia??o catal?tica, foi observado que os materiais
mesoporosos contendo lant?nio foram mais ativos que o SBA-15, para a rea??o de
craqueamento do n-hexano, obtendo-se como produto hidrocarbonetos na faixa de C1 a C5. O
catalisador que apresentou melhores propriedades, em rela??o ? acidez e a atividade catal?tica
foi o sintetizado com a raz?o Si/La=50
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17726 |
| Date | 06 August 2009 |
| Creators | Quintella, Solange Assun??o |
| Contributors | CPF:35530502415, http://lattes.cnpq.br/9770622597949866, Silva, Zelma Rocha da, CPF:09155546315, http://lattes.cnpq.br/9530744851546230, Delgado, Regina Celia de Oliveira Brasil, CPF:87774151400, http://lattes.cnpq.br/1862313412291911, Barros, Joana Maria de Farias, CPF:85239658404, http://lattes.cnpq.br/1016070459137884, Ara?jo, Ant?nio Souza de |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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