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Previous issue date: 2010-05-27 / Mesoporous molecular sieves of MCM-41 type are considered as
promising support for metal in the refining processes of petroleum-based
materials as catalysts and adsorbents for environmental protection. In this work,
mesoporous molecular sieves MCM-41 were modified with different rare earth
ions (La, Eu e Yb) for the obtaining nanostrutured materials with catalytic
properties. The catalysts were synthesized by the hydrothermal method at
100oC for 120 h, presenting, all the samples, in the gel of synthesis molar ratio
Si/Ln = 50. The obtained materials after calcination at 500oC for 2 h were
characterized by XRD, surface area BET, TG/DTG, FTIR, and hydrothermal
stability at 700?C. The XRD analysis of the catalysts indicated that the materials
containing rare earth presented characteristic hexagonal structure of the
mesoporous materials of the type MCM-41. The TG curves showed that the
decomposition of the structural template occurs in the materials at temperatures
lower than 500oC. The samples presented variations as the specific superficial
area, average diameter of pores and thickness of the silica wall, as a function of
the nature of the rare earth impregnated in the mesoporous material.
Hydrotermal stability was evaluated through the exposition of the materials to
water vapour at 700?C. The thiophene adsorptions reach a maximum at 80% of
conversion and incorporation of the rare earths showed influence in the
process. Adsorption capacity followed the sequence: Yb-MCM-41 < La-MCM-41
< Eu-MCM-41 < MCM-41 / As peneiras moleculares mesoporosas do tipo MCM-41 s?o
consideradas promissoras como suporte para metais em processos de refino
de materiais a base de petr?leo, como catalisadores e como adsorventes para
prote??o ambiental. Neste trabalho a peneira molecular mesoporosa tipo
MCM-41 foi modificada com diferentes terras raras (La, Eu e Yb) para a
obten??o de materiais nanoestruturados com propriedades catal?ticas. Os
catalisadores foram sintetizados pelo m?todo hidrot?rmico a 100 oC por 120
horas, apresentando, todas as amostras, no gel de s?ntese raz?o molar Si/Ln =
50. Os materiais resultantes, ap?s calcina??o a 500 oC por 2 horas, foram
caracterizados por: DRX, ?rea superficial pelo m?todo de BET, TG/DTG, FTIR
e testes hidrot?rmicos a 700oC. As an?lises de DRX dos catalisadores
indicaram que os materiais contendo as terras raras apresentaram estrutura
hexagonal caracter?stica do material mesoporoso tipo MCM-41. As curvas TG
mostraram que a decomposi??o do direcionador estrutural ocorre nos materiais
em temperaturas inferiores a 500oC. As amostras apresentaram varia??es
quanto ? ?rea superficial espec?fica, di?metro m?dio de poros e espessura da
parede de s?lica, em fun??o da natureza da terra rara impregnada no material
mesoporoso. A estabilidade hidrot?rmica foi avaliada atrav?s da exposi??o dos
materiais a vapor d ?gua a 700oC. A adsor??o de tiofeno atingiu valores
m?ximos de 80% e a incorpora??o das terras raras influenciaram no processo.
A ordem crescente de capacidade de adsor??o seguiu a seguinte seq??ncia:
Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17638 |
| Date | 27 May 2010 |
| Creators | Alves, Jos? Ant?nio Barros Leal Reis |
| Contributors | CPF:06117988320, http://lattes.cnpq.br/3318871716111536, Vitor Sobrinho, Eledir, CPF:64656969915, http://lattes.cnpq.br/8488499388852606, Barros, Joana Maria de Farias, CPF:85239658404, http://lattes.cnpq.br/1016070459137884, Melo, Dulce Maria de Ara?jo |
| 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/masterThesis |
| 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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