Resumo

LARA PRADO, Ronald M.; LOPEZ N., Luis  e  CABRERA M., Saúl. El efecto de la temperatura del pre-tratamiento ácido de tierra de diatomeas natural en la relación SI/Al de zeolitas ZSM-5. Rev.Colomb.Quim. [online]. 2022, vol.51, n.2, pp.41-47.  Epub 12-Jan-2024. ISSN 0120-2804.  https://doi.org/10.15446/rev.colomb.quim.v51n2.100723.

Bolivian diatomaceous earth is a potentially lower cost silica source than conventional high purity reagents used in zeolite synthesis. Due to its complex composition, it is necessary to pre-treat it with sulfuric acid in order to reduce impurities and regulate the aluminum content. In the present work several experiments were carried out with natural Bolivian diatomaceous earth in the pre-treatment stage. In order to determine the effect on the final Si/Al ratio, the temperature of the acid pre-treatment was varied between 50 to 155 °C. The results show that the Si/Al ratio can be modulated from 6.2 up to 38.1. These treated diatomaceous earth samples were used to synthetise ZSM-5 zeolite. The obtained ZSM-5 zeolites have a Si/Al ratio in the following range: 9.6 to 40.2. XRD, NH3-TPD and Nitrogen Physisorption techniques were used to characterise the properties of the obtained zeolites. The degree of crystallisation and the specific surface area are directly related to the Si/Al ratio, resulting in high values at high Si/Al ratios. The acid sites are composed of strong Brönsted acid sites and, strong and weak Lewis acid sites. For the zeolite with a low Si/Al ratio a high total acidity was found (>0.51 molNH3/Kgzeolite), while at high Si/Al ratios the total acidity is reduced (<0.38 molNH3/Kgzeolite).

Palavras-chave : Diatomaceous earth; Si/Al ratio; acid pre-treatment temperature; ZSM-5 zeolite.

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