Porous texture of silica aerogels made with ionic liquids as gelation catalysts |
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Authors: | Ali Karout Alain C Pierre |
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Institution: | (1) CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon, Université Lyon 1, 2 avenue Albert Einstein, F-69626 Villeurbanne, France |
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Abstract: | The effect of four ionic liquids on the porous texture of silica aerogels synthesized from mixed tetramethoxysilane and methyltrimethoxysilane
and dried by the CO2 supercritical method, was studied. Two of these ionic liquids were composed of BF4
− anions while the other two included Cl− anions. The synthesis of gels from ionic liquids did not require another acidic catalyst for silica hydrolysis, nor a basic
catalyst for silica condensation. These aerogels were compared with traditional aerogels made according to a double step catalysis,
which first involved hydrolysis with HCl followed by condensation with pH 9 Tris HCl buffer. Gel mass analysis and thermogravimetric
data showed that, when the initial molar of ionic liquid to Si was 1.58, only ~2% (by mass) of the initial ionic liquids consisting
of BF4
− anions and ~10% (by mass) of ionic liquids containing Cl− anions, remained in the aerogels after supercritical drying. Moreover, X-ray diffraction confirmed that in ionic liquids
based on BF4
− anions, evaporation of the volatile components before supercritical CO2 drying led to the formation of regularly ordered mesopores. |
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Keywords: | Silica Aerogels Ionic liquids Texture Templating |
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