Inserção controlada de pilares de óxido de alumínio em argilas bentonitas

Abstract

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.