Atomic Description of the Interface between Silica and Alumina in Aluminosilicates through Dynamic Nuclear Polarization Surface-Enhanced NMR Spectroscopy and First-Principles Calculations

• Published in: Journal of the American Chemical Society Vol. 137; no. 33; pp. 10710 - 10719
• Main Authors: Valla, Maxence, Rossini, Aaron J, Caillot, Maxime, Chizallet, Céline, Raybaud, Pascal, Digne, Mathieu, Chaumonnot, Alexandra, Lesage, Anne, Emsley, Lyndon, van Bokhoven, Jeroen A, Copéret, Christophe
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.08.2015
• Subjects: acidity; active sites; aluminum; aluminum oxide; Analytical chemistry; catalysts; Chemical Sciences; nuclear magnetic resonance spectroscopy; silica; silicon; AL-27 NMR; SOLID-STATE NMR; RESOLUTION SI-29 NMR; AMORPHOUS SILICA; INTEGER QUADRUPOLAR NUCLEI; M-XYLENE ISOMERIZATION; MAGNETIC-RESONANCE; BRONSTED ACID SITES; GAMMA-ALUMINA; SN-BETA ZEOLITE
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.5b06134

Despite the widespread use of amorphous aluminosilicates (ASA) in various industrial catalysts, the nature of the interface between silica and alumina and the atomic structure of the catalytically active sites are still subject to debate. Here, by the use of dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP SENS) and density functional theory (DFT) calculations, we show that on silica and alumina surfaces, molecular aluminum and silicon precursors are, respectively, preferentially grafted on sites that enable the formation of Al­(IV) and Si­(IV) interfacial sites. We also link the genesis of Brønsted acidity to the surface coverage of aluminum and silicon on silica and alumina, respectively.