Isopropanol Dehydration on Amorphous Silica-Alumina: Synergy of Broensted and Lewis Acidities at Pseudo-Bridging Silanols

• Published in: Angewandte Chemie Vol. 129; no. 1; pp. 236 - 240
• Main Authors: Larmier, Kim, Chizallet, Celine, Maury, Sylvie, Cadran, Nicolas, Abboud, Johnny, Lamic-Humblot, Anne-Felicie, Marceau, Eric, Lauron-Pernot, Helene
• Format: Journal Article
• Language: English
• Published: 01.01.2017
• Subjects: Activation; Aluminum oxide; Dehydration; Density; Density functional theory; Isopropanol; Mathematical analysis; Surface chemistry
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201609494

The mechanism of isopropanol dehydration on amorphous silica-alumina (ASA) was unraveled by a combination of experimental kinetic measurements and periodic density functional theory (DFT) calculations. We show that pseudo-bridging silanols (PBS-Al) are the most likely active sites owing to the synergy between the Broensted and Lewis acidic properties of these sites, which facilitates the activation of alcohol hydroxy groups as leaving groups. Isopropanol dehydration was used to specifically investigate these PBS-Al sites, whose density was estimated to be about 10 super(-1)sitenm super(-2) on the silica-doped alumina surface under investigation, by combining information from experiments and theoretical calculations.Original Abstract: Zusammenspiel zweier Arten von Saeure: Periodische Ab-initio-Rechnungen und kinetische Messungen wurden kombiniert, um die katalytisch aktiven Zentren bei der Dehydratisierung von Isopropylalkohol ueber amorphem SiO sub(2)/Al sub(2)O sub(3 ) zu bestimmen. Pseudo-verbrueckende Silanole, die Lewis- und Broensted-Saeuren sind, spielen in dieser Reaktion eine entscheidende Rolle.