A study of modification of natural zeolite-clinoptilolites for its application in capture and storage of gases

V.C. DE SOUZA; K. SAPAG; J. VILLARROEL ROCHA; S.B.C. PERGHER; M.J.G. DE ARAÚJO

Santa Catarina-Brasil

Otro; XVIII B-MRS Meeting - Sociedade Brasileira de Pesquisa em Materiais (SBPMat); 2019

Brazilian Materials Research Society

Natural zeolites are research focus materials in the quest to minimize environmental problems, this due to their interesting properties and its considerable abundance in nature. Thus, the work seeks to improve physical-chemical properties of natural zeolites for environmental applications. Three natural clinoptilolites (ZNcelta, ZNchile and ZMcelta) were used, where these zeolites were modified with nitric acid (of 4mol/L, at 363K for 4h) to achieve a demetallization (nomenclatures after the modification: ZNceltaac, ZNchileac and ZMceltaac). X-ray diffraction and X-ray fluorescence analysis were carried out to evaluate the structure crystalline and Si/Al ratio of the materials obtained. The acid treatment of the natural zeolites yields a reduction of the crystallinity (ZNceltaac 21%, ZMceltaac 41% and ZNchileac 22%) due to the removal of aluminum of the clinoptilolite structure (by mean of hydrolysis) [1, 2, 3]. In addition, textural properties were evaluated by N2 adsorption/desorption analysis at 77K and CO2 adsorption at 273K, where the results show a significant improve of the textural properties (specific surface area and pore volume) for all materials treated. This fact it is related to a widening of the pore window and/or pore formation by the removal of aluminum and/or exchangeable ions and impurities, which allowed access to the internal porous structure of these zeolites. ZNchileac (240m²/g) has the highest specific surface area among the 3 treated samples. The modified clinoptilolites were applied in CO2 capture at 35°C where the best adsorbent (ZNchileac) reach an adsorption capacity of 1.9mmol/g (at 1000 kPa), where this capacity increase in 0.6mmol/g when compared to the same sample before treatment (1.3mmol/g with ZNchile). For H2 storage at 77K the ZMceltaac sample had an adsorption capacity of 2.52mmol/g (at 800 kPa), where this capacity increase in 2.35mmol/g when compared to the same sample before treatment (0.17mmol/g with ZMcelta). So the treated zeolites have shown promise for CO2 capture and H2 storage.