Study of the geometry and location of the bridging OH groups in aluminosilicate and silicoaluminophosphate type zeolites using 1H MAS NMR sideband analysis and CP/MAS NMR

Structural Analysis of High-Silica Ferrierite with Different Structure-Directing Agents by Solid-State NMR and Ab Initio Calculations

“…silanol, octahedral aluminum, and Brönsted acid species, respectively. 25,28 This confirms that the 27 Al MAS NMR spectra (not shown) indicate the greater presence of octahedral aluminum at 0 ppm in the H-piperidine-FER.…”

Solid-state nuclear magnetic resonance investigations of the nature, property, and activity of acid sites on solid catalysts

“…At d 1H ¼ À0.5 to 0.7 ppm, 1 H MAS NMR signals of non-interacting metal OH groups, such as AlOH groups at the outer surface of Al 2 O 3 [35] and metal hydroxyl groups in large cages of zeolites, occur [36]. Signals at d 1H ¼1.2-2.2 ppm indicate the presence of SiOH groups, e.g., at the outer surface of silicate and aluminosilicate particles or at framework defects of zeolites [37][38][39][40]. In the case of internal interactions of hydroxyl groups with neighboring framework atoms, slight low-field shifts (larger d 1H values) are observed.…”

A study of the acidity of SAPO-34 by solid-state NMR spectroscopy

“…7). In previous studies [34][35][36], the peaks at 3.7 and 1.6 ppm were unambiguously attributed to Brønsted acid sites and SiOH, respectively. However the assignment of the signal at 2.6 ppm is still not clear [37].…”