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Previous issue date: 2014-05-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Two pillaring methods were tested to synthesize pillared clays containing mixed Al/Co
pillars. Using the first method, based on the traditional procedure, were obtained materials
containing different Co concentrations: 10, 25, 50, 75 and 100 % of Co in the pillaring
solution. Just the experiments with low concentrations (10 and 25 % of Co) has formed
pillared clays, whereas the sample with 25 % of cobalt showed best results compared with the
one obtained just using Al as pillaring agent (basal spacing higher than 18 ? and surface area
bigger than 300 m?/g). The 27Al NMR results pointed out the formation of mixed Al/Co pillars
due to decreased between the intensities of AlVI/AlIV signals, indicating that the AlIV content
decreased while Co content increased, suggesting the isomorphic substitution of Al atoms for
Co in the Keggin ion structure (pillaring agent). For the samples containing 75 and 100 % of
cobalt, it was verified the formation of others materials, which could be identified as
hydrotalcite like compounds. The second pillarization method was named mixed layers,
because the objective was to intercalate clay layers with hydrotalcite layers. Thus, after
calcination, the hydrotalcite layers would dehydroxylate, resulting just in the metals oxides,
intercalated between the clay sheets, thus generating, a pillared clay. For this purpose, were
tested 4 synthesis procedures: physical mixture, mixture in water, ionic exchange under reflux
and in situ synthesis. Of these, the method which showed the best results was the in situ
synthesis, in which basal spacings of 14 ? (after calcination) were obtained, indicating that
the samples are intercalated with metal oxides (Mg and Al). This procedure was reproduced
with a Co-Al LDH (layered double hydroxide) and similar results were obtained, testifying
the method reproducibility / Dois m?todos de pilariza??o de argilas foram testados a fim de se obter argilas pilarizadas
com pilares mistos Al/Co. Utilizando o primeiro m?todo, baseado no procedimento
tradicional, foram obtidos materiais contendo diferentes teores de Co: 10, 25, 50, 75 e 100 %
de Co na solu??o pilarizante. Apenas os m?todos contendo baixos teores (10 e 25 % de Co)
resultaram na forma??o de argilas pilarizadas, sendo que, a amostra contendo 25 % de cobalto
apresentou resultados superiores aos obtidos apenas com Al (espa?amento basal acima de 18
? e ?rea espec?fica BET maior que 300 m?/g). Os resultados de RMN de 27Al indicaram a
forma??o de pilares mistos Al/Co devido ? diminui??o entre as intensidades dos sinais
AlVI/AlIV, indicando que o teor de AlVI diminuiu conforme ocorreu o aumento do teor de Co,
sugerindo a substitui??o isom?rfica de ?tomos de Al por Co na estrutura do ?on de Keggin
(agente pilarizante). Para as amostras contendo 75 e 100 % de cobalto, verificou-se a
forma??o de outros materiais, os quais foram identificados como sendo compostos do tipo
hidrotalcita. O segundo m?todo de pilariza??o foi chamado de lamelas mistas, pois o objetivo
era intercalar lamelas de argila com lamelas de hidrotalcita, assim ap?s a calcina??o, ocorreria
a desidroxila??o da camada de HDL (hidr?xido duplo lamelar), resultando apenas nos ?xidos
de metais, intercalados entre as lamelas da argila, gerando uma argila pilarizada. Para tal,
foram testados 4 procedimentos de s?ntese: mistura f?sica, mistura em ?gua, troca i?nica em
refluxo e s?ntese in situ. Desses, o m?todo que apresentou os resultados mais promissores foi
o de s?ntese in situ, no qual espa?amentos da ordem de 14 ? (ap?s calcinar) foram obtidos,
indicando que as amostras est?o intercaladas com ?xidos de metais (Mg e Al). Esse
procedimento foi reproduzido com uma HDL contendo Co-Al, e resultados semelhantes
foram obtidos, comprovando a reprodutibilidade do m?todo
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17753 |
| Date | 22 May 2014 |
| Creators | Bertella, Francine |
| Contributors | CPF:50942611004, http://lattes.cnpq.br/5249001430287414, Oliveira, Luiz Carlos Alves de, CPF:82248010630, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4795801A1, Alc?ntara, Ana Cl?cia Santos de, CPF:83221018568, http://lattes.cnpq.br/3149929057352643, Fernandes, Nedja Suely, CPF:44420773472, http://lattes.cnpq.br/9563490368583906, Pergher, Sibele Berenice Castella |
| 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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