Study of copper - and iron - containing ZSM-5 zeolite catalysts: ESR spectra and initial transformation of NO

J. Varga, J. Halász, D. Horváth, D. Méhn, J. B. Nagy, Gy Schöbel, I. Kiricsi

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7 Citations (Scopus)

Abstract

For a better understanding of the first steps of the reaction of NO over Cu-ZSM-5 and Fe-ZSM-5 zeolites the following measurements were performed: (i) the products of the gas phase interactions were followed by MS, (ii) the valence state and coordination of transition metal ions in zeolites by ESR spectroscopy. Catalysts were prepared both by conventional and solid-state ion-exchange methods and pretreated in vacuum, in oxidative and in reductive atmosphere. The conventional ion-exchanged samples are more active in NO decomposition than the solid-state exchanged ones. Over the reduced catalysts the first step consists in N2O formation and the oxidation of Cu+ → Cu2+ (Fe2+ → Fe3+) followed by N2O reduction to N2 (in these conditions O2 release was not detected). These results are consistent with a simple redox mechanism in which NO adsorption and decomposition on active (reduced) sites leads to the formation of gaseous nitrogen and adsorbed oxygen. Over oxidized samples NO transformation is slower than over reduced ones, and the first step is to be the reduction of metal ions (Cu2+, Fe3+) with NO as reducing agent.

Original languageEnglish
Pages (from-to)367-376
Number of pages10
JournalStudies in Surface Science and Catalysis
Volume116
Publication statusPublished - Jan 1 1998

ASJC Scopus subject areas

  • Catalysis
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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