Acetonitrile-d3 as a probe of Lewis and Broensted acidity of zeolites

Abstract

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Efficient Approach for the Computational Study of Alcohol and Nitrile Adsorption in H-ZSM-5

“…Pelmenschikov pointed out that the CN stretching frequency is an efficient probe to distinguish different adsorption sites in zeolites, in particular Lewis acid sites, terminal silanol groups, and the bridging Brønsted acid site, which will be discussed in this work. 55,56 Related work of Simperler et al obtained a ranking of seven different high silica zeolites based on the hydrogen-bond strength as a predictor of acidity. 60 In this study, the shift in the ν(OH) region will be investigated for all adsorption complexes.…”

Computation of the Infrared Spectrum of an Acidic Zeolite Proton Interacting with Acetonitrile

“…[3][4][5] Splitting of the XH stretch bands has been explained by Fermi resonances of overtones of XH bending modes. 3,5 On the basis of a comparison of the in-plane bending modes of an acidic OH group in a zeolite and peak minima in the infrared spectrum, Pelmenschikov et al 6 proposed a Fermi resonance of the downward shifted OH stretch mode and the upward shifted in-plane bending overtone.…”

FTIR spectroscopic and1 H MAS NMR studies of the influence of lattice chemistry and structure on Brønsted acidity in zeolites

“…Therefore, the acidic strength has been varied by isomorphous substitution of AI by Fe. molecule) in a characteristic way due to a Br0nsted complex (to about 2300 cm -1) or a Lewis bonded molecule (to 2320-2330 cm -1) [20]. The "Br0nsted bands" shift downwards by 1000 cm -1, typical for strong bridging OH in zeolites.…”

“…Interestingly, the adsorption of the base on the acidic OH leads to a shifted broad band split into two or three pseudo-bands, the so-called A, B and C branches. This is due to resonant interactions between the OH stretching and overtone bending modes (dip at 2600 cm -1 of the perturbed bridging OH) [20,21]. Thus the frequency of the shifted v(OH) has to be estimated by evaluating the centre of gravity of these pseudo-bands.…”