Characterization of the acidity of Mu-14 by solid-state NMR and NH3-STD

文献情報

出版日 2001-01-23

DOI 10.1039/B008553G

インパクトファクター 3.676

著者

Angélique Simon, Jean-Louis Paillaud, Valentin Valtchev, Henri Kessler

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要旨

The distribution and strength of the Brönsted acid sites in three Mu-14 (ITE structure type) samples with different Si/Al ratios (17, 28 and 35) were studied by 1H MAS (magic angle spinning), 1H-{27Al} TRAPDOR (transfer of population in double resonance), 1H-29Si CP-MAS (cross-polarisation magic angle spinning)/ HETCOR (two-dimensional heteronuclear correlation) NMR, and NH3-STD (stepwise thermal desorption). The 1H MAS NMR spectra exhibit two different types of bridging OH groups associated with proton chemical shifts of ca. 4.2 and 5.3 ppm. From the 1H-29Si HETCOR experiments a single Brönsted [Si-(OSi)3(OAl)1] Q3 site resonating at δ(29Si) = − 108 ppm, can be distinguished from two different [Si-(OSi)3(OH)1] Q3 sites, at δ(29Si) = − 101 and − 104 ppm, and one of the Q4 sites resonating at δ(29Si) = − 108.5 ppm. Aluminum is not randomly distributed in the structure of Mu-14, but rather sits at preferred places isolated from silanols. The acid strength of the Brönsted acid sites, determined by NH3-STD, is slightly higher in Mu-14 than in a HZSM-5 with a similar Si/Al ratio.

掲載誌

Physical Chemistry Chemical Physics

CiteScore: 5.5

自己引用率: 10.3%

年間論文数: 3036

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