Probing the Surface Acidity of Modified γ-Alumina with H and 15N High-Resolution Solid State NMR Spectroscopy
Reaction Kinetics and Catalysis Letters
, E-ISSN: 1588-2837
||Brönsted and Lewis acidic sites, Nuclear magnetic resonance, γ-alumina
Federal Scientific Center, Boreskov Institute of Catalysis, Novosibirsk 630090, Russia
1H MAS NMR and15N NMR studies of adsorbed N2 and N2O molecules were used to characterize Brönsted and Lewis acidic sites of unmodified γ-Al2O3 and γ-Al2O3 modified with NaOH. Changes in the concentrations of surface hydroxyls with the increase in the number of more “basic” OH groups for NaOH/γ-Al2O3 have been found by1H MAS NMR experiments. Two different types of Lewis acidic sites in γ-Al2O3 have been revealed using15N NMR studies. The strongest sites are poisoned even at small NaOH concentrations (ca. 0.05 wt.%). Not only the number of electron-accepting sites but also their strength are supposed to decrease for modified γ-alumina.