FTIR adsorption studies of H2O and CH3OH in the isostructural H-SSZ-13 and H-SAPO-34: formation of H-bonded adducts and protonated clusters.

Détails

ID Serval
serval:BIB_7847BE3C3047
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
FTIR adsorption studies of H2O and CH3OH in the isostructural H-SSZ-13 and H-SAPO-34: formation of H-bonded adducts and protonated clusters.
Périodique
Journal of Physical Chemistry. B
Auteur⸱e⸱s
Bordiga S., Regli L., Lamberti C., Zecchina A., Bjørgen M., Lillerud K.P.
ISSN
1520-6106
Statut éditorial
Publié
Date de publication
04/2005
Volume
109
Numéro
16
Pages
7724-7732
Langue
anglais
Résumé
The acidity of the isostructural H-SSZ-13 and H-SAPO-34 has been investigated by transmission FTIR spectroscopy using H2O and CH3OH as molecular probes. Interactions between the zeolitic samples and the probe molecules led to perturbations and proton transfers directly related to the acidity of the materials. The entire set of acidic sites in H-SSZ-13 interacts with H2O and CH3OH to give H-bonded adducts or protonated species. H3O+ is not formed in appreciable amounts upon H2O adsorption on H-SSZ-13, but at high coverages H2O generates clusters that have a proton affinity sufficiently high to abstract protons from the zeolite framework. Parallel experiments carried out for H-SAPO-34 showed that the H2O clusters abstract protons from Brønsted sites only to a minor extent. Moving to CH3OH, even if it has a higher proton affinity than H2O and should expectingly experience an easier protonation, proton transfer is totally absent in H-SAPO-34 under our set of conditions. The clear evidence of methanol protonation in H-SSZ-13 definitely states the strong acidic character of this material. When irreversibly adsorbed CH3OH is present in H-SSZ-13, an appreciable amount of (CH3)2O is formed upon heating to 573 K. Compared to its SAPO analogue, the present set of data indisputably points to H-SSZ-13 as the strongest Brønsted acidic material.
Pubmed
Web of science
Création de la notice
25/01/2008 13:10
Dernière modification de la notice
20/08/2019 14:35
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