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.
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Journal articles
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Submitted on : Thursday, September 25, 2014 - 4:54:33 PM
Last modification on : Tuesday, March 5, 2019 - 9:30:12 AM

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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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