Effects of structural characteristics of zeolites on the properties of their bridging and terminal hydroxyl groups

A. Chatterjee, T. Iwasaki, T. Ebina, H. Tsuruya, T. Kanougi, Y. Oumi, M. Kubo, A. Miyamoto

Research output: Contribution to journalConference article

6 Citations (Scopus)

Abstract

Hydrogen forms of zeolites are active catalysts in numerous acid-catalyzed reactions. Hydroxyl groups are responsible for the Bronsted acidity of amorphous silica-aluminas and of zeolites. Generally, the acid strength of OH groups in H forms of zeolite depends on the Si/Al ratio, the degree of cation exchange and the degree of dehydroxylation. The present aim of our investigation is to rationalize an understanding of the role of hydroxyl groups both bridging and terminal on the acidity of zeolites with the help of local density functional (LDF) vibrational frequency calculation. The effects of geometry (Si-O and Al-O bond lengths and Si-O-H as well as Si-O-Al angles) of zeolites on the vibrational frequencies of their OH groups were modeled by H3SiOHAlH3; whereas to study the influence of chemical composition models with formula H3SiOSi(OH)3 and H2 AlOSi(OH)3 have been studied. It is observed that structural characteristic influences the vibrational frequency more in comparison to chemical composition. A case study with H-Y zeolite has been performed with the models having formula (HO)3SiOHAl(OH)3 and [(HO)3SiOAl(OH)3]-. It is observed that between O1 and O4 type oxygens present in H-Y zeolite, the O1-H group lies at a higher frequency than the O4-H group. All the results were compared with experimental IR frequencies.

Original languageEnglish
Pages (from-to)555-560
Number of pages6
JournalApplied Surface Science
Volume130-132
DOIs
Publication statusPublished - 1998 Jan 1
EventProceedings of the 1997 4th International Symposium on Atomically Controlled Surfaces and Intefaces, ACSI-4 - Tokyo, Jpn
Duration: 1997 Oct 271997 Oct 30

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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