Creation of brønsted acidity by grafting aluminum isopropoxide on silica under controlled conditions : determination of the number of brønsted sites and their turnover frequency for m-xylene isomerization.

Abstract : There is not a unique Brønsted acid site for aluminosilicates (ASAs). IR spectroscopy following CO adsorption proves the creation of Brønsted acid sites on Al/SiO2 ASAs, which are synthesized by the deposition of aluminum species on hydroxylated silica. These sites are active for ethanol dehydration and m-xylene isomerization. Controlled deposition under anhydrous conditions optimizes the number of sites, whereas the presence of water leads to alumina agglomerates with no Brønsted acidity. The turnover frequency for m-xylene isomerization (4.3 10 4 s 1 site 1 at 350 8C, atmospheric pressure, and 0.6 cm3h 1 of m-xylene) is approximately 3 times lower than that of the Brønsted acid sites of Si/Al2O3 and 75 times lower than that of an ultrastable Y-type zeolite without extra-framework aluminum.
Type de document :
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ChemCatChem, Wiley, 2014, 6 (3), pp. 832-841. 〈10.1002/cctc.201300824〉
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Contributeur : Françoise Bertrand <>
Soumis le : jeudi 25 septembre 2014 - 16:54:33
Dernière modification le : jeudi 25 septembre 2014 - 16:54:33

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Maxime Caillot, Alexandra Chaumonnot, Mathieu Digne, J. A. Van Bokhoven. Creation of brønsted acidity by grafting aluminum isopropoxide on silica under controlled conditions : determination of the number of brønsted sites and their turnover frequency for m-xylene isomerization.. ChemCatChem, Wiley, 2014, 6 (3), pp. 832-841. 〈10.1002/cctc.201300824〉. 〈hal-01068511〉

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