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. Issue 3 (21st January 2014)

• Record Type: Journal Article
• Authors: Caillot, Maxime; Chaumonnot, Alexandra; Digne, Mathieu; Van Bokhoven, Jeroen A.
• Is Part Of: ChemCatChem. Volume 6:Issue 3(2014:Mar.)
• Page Start: 832
• Page End: 841
• Publication Date: 2014-01-21
• Subjects: Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201300824
• Languages: English
• ISSNs: 1867-3880

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>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 <italic>m</italic>‐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 <italic>m</italic>‐xylene isomerization (4.3×10⁻⁴ s⁻¹ site⁻¹ at 350 °C, atmospheric pressure, and 0.6 cm³ h⁻¹ of <italic>m</italic>‐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.</p> </abstract>