Zeólita Mordenita: um estudo sobre a formação e o tamanho dos cristais
The assimilation of the way a zeolite is formed from an amorphous system and the control over size and morphology of the synthesis products are fundamental aspects for "zeolitic engineering". A system for the synthesis of the mordenite zeolite was studied, which made it possible to obtain...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/24827 |
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| Resumo: | The assimilation of the way a zeolite is formed from an amorphous system and the control over size and morphology of the synthesis products are fundamental aspects for "zeolitic engineering". A system for the synthesis of the mordenite zeolite was studied, which made it possible to obtain MOR phase without indicating the presence of any other phase. Variations were made in the parameters: thermal treatment condition, temperature, time, gel dilution, water content and degree of purity, sodium content, aging and type of silica, aiming to establish the relationship between product size and morphology with the modifications made. The crystallization temperature showed to be a prime factor with respect to particle size and crystallites. Dilution of the synthesis gel (50% w / w) provided a reduction in the crystallite aggregation and the variation of the water content in the synthesis implied changes in zeolitization rates. The sodium content modified the growth of the crystals and the increase of intergrowths and aggregations of particles. Changes in the silica source increased the growth rate of the crystals and contributed to changes in their size. Larger crystals were obtained from systems with higher concentrations of sodium cations as nanocrystallite aggregates. Aggregates of small pure mordenite crystallites of up to about 50 nm were obtained with syntheses performed at 150 ° C and with the dilution of the already prepared gel. Lower sodium and water content and the use of silica sources with a greater specific area (relative to this type of material) also tend to result in smaller crystallites. Opposite conditions enabled the highest growth, generating crystals up to 1 μm on average. The results showed that it is possible to exert some control over the particle size and crystallites of the mordenite zeolite by adjusting parameters inherent to the conventional synthesis system. |
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