Inserção controlada de pilares de óxido de alumínio em argilas bentonitas
Clays are minerals widely available in nature. They are applied as catalysts in various chemical processes, such as oil cracking, and chemical transformations in soils. Some specific clays (such as bentonites) have characteristics that allow us to modify their properties, such as increased specif...
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| Formato: | doctoralThesis |
| Idioma: | pt_BR |
| Publicado em: |
Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/47203 |
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| Resumo: | Clays are minerals widely available in nature. They are applied as catalysts in various
chemical processes, such as oil cracking, and chemical transformations in soils. Some
specific clays (such as bentonites) have characteristics that allow us to modify their
properties, such as increased specific area, increased active sites and greater thermal
stability. Among the chemical modification processes of clays, there is pillarization,
which consists of inserting pillars between the lamellae, increasing the basal spacing
and consequently the accessibility of the clay galleries, thus intensifying its adsorptive
and catalytic characteristics. A system for the synthesis of pillarization with Al30 was
studied, which made it possible to obtain a material with properties superior to those
synthesized using traditional methods with Al13. In order to obtain Al30 and its use for
pillaring bentonite clays, the following synthesis parameters were studied: study of preexpansion of clay [with cetyltrimethylammonium hydroxide (CTMA-OH),
tetrapropylamonium hydroxide (TPA-OH) ) and ethyleneglycol (EG)]; temperature,
time and molar ratio [OH]/[Al] in the preparation of the pillaring solution; The synthesis
temperature of the pillaring solution as well as the heating time together proved to be
the primary factor in relation to the size of the basal spacings. The concentration of
reagents also contributed to obtain Al30. The best results were obtained for the pillaring
solution with ratio [OH]/[Al] = 2.4; temperature of 95°C for 12 h. The results showed
that it is possible to obtain some control over the insertion and size of columns in pillars
with bentonite-type clays by adjusting the parameters of the synthesis system commonly
used for pillars with Al13. |
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