Deuterium NMR characterization of Bronsted acid sites and silanol species in zeolites

Journal Article · Thu Apr 13 04:00:00 EDT 1995 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100015a035· OSTI ID:41841

Kobe, J M; Gluszak, T J; Dumesic, J A; Root, T W ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)

Solid-state deuterium NMR has been used to characterize Bronsted acid sites and nonacidic silanol species in D-Y, D-mordenite, and D-ZSM-5 zeolites. Bronsted acid deuterons may be static, with quadrupole coupling constants (QCC) near 240 kHz and asymmetries ({eta}) of 0. These acidic deuterons may also be motionally averaged to give QCC = 120 kHz and {eta} = 1, consistent with jumping between two oxygen sp{sup 3} orbitals. These results indicate that the acid deuteron does not remain fixed in the Al-O-Si plane. Isolated silanol species display a narrow, axially symmetric powder pattern, consistent with an Si-O-D bond angle of 116{degree}. Most of the silanol species are more densely packed, and the variety of hydrogen-bonded positions possible results in a Gaussian peak about 56 kHz wide. Deuterium NMR shows promise as a technique for characterizing both acidic and nonacidic hydroxyl groups in zeolites. 55 refs., 7 figs., 2 tabs.

• OSTI ID: 41841
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 15 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
BOND ANGLE
CHEMICAL BONDS
DEUTERONS
INORGANIC ACIDS
MORDENITE
NMR SPECTRA
RELAXATION TIME
SILICON COMPOUNDS
ZEOLITES