Estudo das propriedades de zeólitas naturais modificadas por tratamentos ácidos e/ou básicos
The zeolites are crystalline materials constituted by the union of tetrahedra (SiO4 and AlO4) that generate channels and cavities of molecular dimensions, with pore openings of up to 2 nm. The natural zeolite Clinoptilolite (Si / Al ≥ 4) belongs to that of the Heulandite group and presents select...
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| Formato: | doctoralThesis |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/26502 |
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| Resumo: | The zeolites are crystalline materials constituted by the union of tetrahedra (SiO4 and
AlO4) that generate channels and cavities of molecular dimensions, with pore
openings of up to 2 nm. The natural zeolite Clinoptilolite (Si / Al ≥ 4) belongs to that of
the Heulandite group and presents selectivity for small-radius ions due to the size of
its cavities. These natural materials are low cost and associated with modifications
can give rise to a material with improved properties and consequently promising for
catalytic cracking and gas storage. In this work structural modifications were carried
out in natural zeolites Clinoptilolite, with acid and basic treatments, for the
improvement of textural properties employing an experimental statistical planning to
control process variables. X-ray diffraction, X-ray fluorescence, adsorption /
desorption N2, CO2 adsorption, pyridide adsorption, transmission electron
microscopy, CO2 capture and H2 storage were used. The acid treatment was the
most effective for improving the textural properties obtained by adsorption and
desorption analysis of N2 (SBET increased from 27 to 165 m2
/g, V0 increased from
0.00 to 0.04 cm³ / g and Vmeso of 0.10 to 0.16 cm³ / g), although the basic although
not having greatly increased the textural properties of the material, greatly increases
the Brönsted acidity of the sample by preserving the aluminum. The zeolites
clinoptilolites obtained from different deposits (ZNcelta and ZMcelta from cuba and
ZNchile from Chile) were treated with acid (ZNceltaac, ZNchileac and ZMceltaac) that
showed improvements in their textural properties, with ZNchile being the one that
presented a larger area increase (from 47 to 240 m²/g). These samples were used in
CO2 adsorption (308K) and presented efficient with an increase in capture of 1.33
mmol / g (ZNchile) to 1.9 mmol / g (ZNchileac) and for storage of H2 (77 K) if showed
with a considerable increase in storage capacity that went from 0.17 mmol / g
(ZMcelta) to 2.52 mmol / g (ZMceltaac). |
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