Preparation of Magnesia-Silica Oxides: Effect of Mg/Si Ratio and Sulfate on Acidity |
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Authors: | T Lopez ME Llanos J Navarrete I Schifter P Salas R Gomez |
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Institution: | (1) Dept. de Química, Universidad Autónoma Metropolitana Iztapalapa, P.O. Box 55-534, México, D.F., México;(2) Universidad de Guanajuato, Lascurain de Retana s/n, Guanajuato, Gto, México;(3) Instituto Mexicano del Petróleo, SGIDTTI, P.O. Box 14-805, México, D.F. |
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Abstract: | Mg−Si binary oxides were prepared by the sol-gel method, using magnesium diethoxide and tetraethoxysilane as starting materials.
Mg−Si mixed oxides were prepared at pH3 and 9 at nominal concentrations of 1.3, 4.0, and 6.7 mole% MgO. Density and strength
of the acid sites were determined by pyridine thermal programmed desorption. Comparable Lewis acidity was found in pH3 and
9 preparations. However, when the samples were sulfated with sulfuric acid, strong Bronsted acidity was developed, reaching
a maximum at 6.7 mole% MgO. The strong acidity of sulfated samples was corroborated using the isopropanol decomposition reaction
as catalytic test. Similar conversions are obtained at 100°C on sulfated samples, whereas 260°C are required for non-sulfated
ones. |
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Keywords: | magnesia-silica mixed oxides sol-gel magnesia-silica magnesia-silica acidity sulfated magnesiasilica isopropanol decomposition |
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