Highly Dispersed SiO(x)/Al2O3 Catalysts Illuminate the Reactivity of Isolated Silanol Sites.

Abstract

The reaction of γ-alumina with tetraethylorthosilicate (TEOS) vapor at low temperatures selectively yields monomeric SiO(x) species on the alumina surface. These isolated (-AlO)3Si(OH) sites are characterized by PXRD, XPS, DRIFTS of adsorbed NH3, CO, and pyridine, and (29)Si and (27)Al DNP-enhanced solid-state NMR spectroscopy. The formation of isolated sites suggests that TEOS reacts preferentially at strong Lewis acid sites on the γ-Al2O3 surface, functionalizing the surface with "mild" Brønsted acid sites. For liquid-phase catalytic cyclohexanol dehydration, these SiO(x) sites exhibit up to 3.5-fold higher specific activity than the parent alumina with identical selectivity.

• Authors: Aidan R Mouat, Cassandra George, Takeshi Kobayashi, Marek Pruski, Richard P van Duyne, Tobin J Marks, Peter C Stair
• Journal: Angewandte Chemie (International ed. in English) (Angew Chem Int Ed Engl) Vol. 54 Issue 45 Pg. 13346-51 (Nov 02 2015) ISSN: 1521-3773 [Electronic] Germany
• PMID: 26398359 (Publication Type: Journal Article)
• Copyright: © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.