Estudo das propriedades de zeólitas naturais modificadas por tratamentos ácidos e/ou básicos

Abstract

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).