On the possibility of AgZSM-5 zeolite being a partial oxidation catalyst for methane

Yasushige Kuroda, Toshinori Mori, Hiroyuki Sugiyama, Yoshinori Uozumi, Katsuhiro Ikeda, Atsushi Itadani, Mahiko Nagao

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

A silver-ion-exchanged HZSM-5 zeolite sample (Ag(H)ZSM-5) evacuated at 573 K exhibited prominent catalytic behavior in the partial oxidation of CH4 at temperatures above 573 K, exceeding the performance of Ag/SiO2ṡAl2O3 and Ag/SiO2 catalysts. From the infrared (IR) and X-ray absorption fine structure (XAFS) spectra, as well as the dioxygen adsorption measurement, it was concluded that the simultaneous existence of Ag+ ions and small clusters of Ag particles leads to the partial oxidation of methane. Taking the magnitude of the formation enthalpy (per oxygen atom) of Ag2O (Δ H = 26 kJ / mol) into consideration, we propose the interpretation that the dioxygen activated on small Ag metal clusters formed in ZSM-5 elaborates a surface oxide layer on small Ag clusters and the thus-formed species is simultaneously and easily decomposed at 573 K or above, and the oxygen activated in this way on the Ag metal spills over and can react with methane that has been activated by the Ag+ ions exchanged in ZSM-5, resulting in the high catalytic activity of the Ag(H)ZSM-5 sample in the partial oxidation of methane. This interpretation is also well evidenced by XAFS and IR data. It is anticipated that this material has the potential to be a promising catalyst in the conversion of natural gas into higher value-added chemicals and fuels.

Original languageEnglish
Pages (from-to)294-299
Number of pages6
JournalJournal of Colloid And Interface Science
Volume333
Issue number1
DOIs
Publication statusPublished - May 1 2009

Keywords

  • Fourier transform infrared spectroscopy
  • Partial oxidation catalyst for methane
  • Silver ion
  • Silver-ion-exchanged ZSM-5-type zeolite
  • Small silver metal clusters
  • X-ray absorption fine structure

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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