Probing the basicity of lattice oxygen on H-form zeolites using CO2

Ryota Osuga, Toshiyuki Yokoi, Junko N. Kondo

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The basicity of lattice oxygen in H-form zeolite was characterized by the CO2-probe IR method at room temperature and in the low-pressure region. The adsorbed CO2 species on basic oxygens (>2350 cm−1) were distinguished from hydrogen-bonded (2349 cm−1) and physisorbed (2339 cm−1) species. The pairing of a basic oxygen and an acidic OH group was evidenced by quantitative ammonia adsorption, where the amount of basic oxygen was decreased linearly with the amount of acidic OH consumed by ammonia adsorption. This clearly indicates the presence of basicity on H-form acidic zeolites. The number of lattice oxygens of H-form zeolites located around Al in (AlO4) units was affected by the environment of the central Al atoms in the framework of the zeolites. Consequently, the number of base sites was dependent on zeolite topology. Zeolites diverse in the location of T sites represented by MFI showed plural IR absorption bands of adsorbed molecular CO2 (2370–2350 cm−1) due to the presence of various types of base sites, in contrast to zeolites with fewer types of T sites, such as CHA. While CO2 adsorption onto basic metal oxides results in forming carbonate species through chemical reactions, IR observation of molecularly adsorbed CO2 could be an appropriate method to detect weakly basic sites on acid catalysts.

Original languageEnglish
Pages (from-to)291-297
Number of pages7
JournalJournal of Catalysis
Volume371
DOIs
Publication statusPublished - 2019 Mar
Externally publishedYes

Keywords

  • Basicity
  • CO probe
  • IR spectroscopy
  • Lattice oxygen
  • Zeolites

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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