Brazilian Mineral Clays: Classification, Acid Activation and Application as Catalysts for Methyl Esterification Reactions

• Autor(a) principal: Dill,Laís P.
• Data de Publicação: 2021
• Outros Autores: Kochepka,Débora M., Lima,Larissa L., Leitão,Alexandre A., Wypych,Fernando, Cordeiro,Claudiney S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532021000100145
• topic: montmorillonite; surface acidity; catalysis; methanolysis

In this study, three raw Brazilian clays from João Pessoa, Paraíba State (Aço AP, AVL and Verde Lodo) were characterized before and after purification and acid activation. Several instrumental techniques were used, and the raw clays were classified as dioctahedral smectites with different compositions, where the AVL sample had the highest content of montmorillonite. In addition, analyses showed modification in clay mineral compositions, mainly due to removal of impurities and octahedral sheet cation leaching during acid activation, which resulted in specific areas ranging from 42 to 93 m2 g-1 and increase of the Brønsted/Lewis acid site ratio, until 1.52 (AVL). Then, methyl esterification reactions were performed using the acid-activated clays as catalysts. The maximum acid conversions obtained were of 92 and 64%, for acetic acid using activated AVL and for lauric acid using activated Verde Lodo, respectively, and these data were correlated mainly to the Brønsted-Lowry acidity.