Influence of the lanthanum exchange degree on the concentration and acid strength of bridging hydroxyl groups in zeolites La,Na-X

J. Huang*, Y. Jiang, M. Hunger

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Citation (Scopus)

Abstract

1H MAS NMR spectroscopy was applied for the quantitative investigation of the concentration of hydroxyl groups in zeolites La,Na-X with different lanthanum-exchange degrees as a function of the dehydration temperature. A maximum concentration of Brønsted acidic bridging OH groups (SiOHAl) corresponding to ca. 1 OH per lanthanum cation was reached upon dehydration of zeolites La,Na-X at 423 to 473 K. Further raise of the dehydration temperature led to a dehydroxylation of the above-mentioned zeolites, while the dealumination of the framework was negligible. By adsorption of deuterated acetonitrile as probe molecule, a significant increase of the acid strength of bridging OH groups was found with increasing lanthanum exchange degree. This finding is explained by the polarizing effect of the multivalent lanthanum cations, which leads to a withdrawal of electrons from the O-H bonds of Brønsted acid sites in zeolites La,Na-X possessing a high concentration of these multivalent extra-framework cations.

Original languageEnglish
Title of host publicationFrom zeolites to porous MOF materials
Subtitle of host publicationthe 40th anniversary of international zeolite conference
EditorsRuren Xu, Zi Gao , Jiesheng Chen, Wenfu Yan
Place of PublicationAmsterdam; Oxford
PublisherElsevier
Pages622-628
Number of pages7
Volume170
ISBN (Print)0444530681, 9780444530684, 9780444531858, 9780444531865
DOIs
Publication statusPublished - 2007
Externally publishedYes

Publication series

NameStudies in Surface Science and Catalysis
NumberA
Volume170
ISSN (Print)01672991

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