Navegando por Autor "Schmall, M."
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Artigo Preparartion and characterization of terbium over paligorsquite clay as acid catalyst(Elsevier, 2000-08-01) Melo, Marcus Antônio de Freitas; Ruiz, Juan Alberto Chavez; Melo, Dulce Maria de Araújo; Vitor Sobrinho, Eledir; Schmall, M.Palygorskite clays containing 5% and 10% terbium (W/W) were prepared by ion exchange from acid-leached naturalclay. Samples were calcined at 523, 573, 623 and 673 K to verify the e ect of the temperature over the physical±chemicalproperties. Characterization was using X-ray di raction, infrared spectroscopy (n-butylamine adsorption), UV±visibledi use reØectance spectroscopy and N2adsorption. Isopropyl alcohol (IPA) transformation was also performed inorder to improve the acid behavior. TB3áintroduction does not change the palygorskite structure, albeit leading to anincrease in the surface area and generation of Lewis acid sites. Results from the DRS spectra along with a decrease inthe catalytic activity suggested the formation of terbium oxide for relatively high TB3ácontents