NH4-exchanged zeolites: Unexpected catalysts for cyclohexane selective oxidation

I. Graça*, D. Chadwick

*Corresponding author for this work

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

NH4-, H-, Na-, Cs-exchanged ZSM-5 zeolites have been investigated as catalysts for the selective oxidation of cyclohexane under mild conditions using molecular oxygen as oxidant. For comparison, Mn- and Fe-exchanged ZSM-5 zeolites were also studied, as Mn and Fe are well-known oxidation metals. It has been shown that the type of compensating cation in the zeolite framework is of extreme importance for the activity of these catalysts in this reaction. Surprisingly, superior selective oxidation performance was achieved with a commercial NH4-ZSM-5 zeolite. The ion-exchanged transition metals (Mn and Fe) were shown to have higher selective oxidation ability compared to the alkali metals, as expected owing to their better redox properties. The rate of cyclohexyl-hydroperoxides transformation into cyclohexanol and cyclohexanone also appears to depend on the ion-exchanged cation, being also much faster over the ammonium and transition metal-exchanged zeolites. Overall, this work has shown for the first time the potential of zeolites ion-exchanged with ammonium to catalyse the selective oxidation of cyclohexane, which in principle offers the possibility of avoiding or reducing the need for more expensive and less environmentally friendly transition metals.

Original languageEnglish
Article number109873
JournalMicroporous and Mesoporous Materials
Volume294
Early online date6 Nov 2019
DOIs
Publication statusPublished - 1 Mar 2020

Keywords

  • Cyclohexane
  • Ion-exchanged zeolites
  • KA oil
  • Selective oxidation
  • OXYGEN
  • FE-MFI ZEOLITES
  • METHANE
  • ALKALI
  • PROMOTION
  • IRON
  • BETA

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