Isopropanol Dehydration on Amorphous Silica–Alumina: Synergy of Brønsted and Lewis Acidities at Pseudo-Bridging Silanols
Résumé
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 Brønsted 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@1 sitenm@2 on
the silica-doped alumina surface under investigation, by
combining information from experiments and theoretical
calculations.