Elucidation of a preparation method for copper ion-exchanged ZSM-5 samples exhibiting extremely efficient N2-adsorption at room temperature: Effect of counter ions in the exchange solution

Atsushi Itadani, Yasushige Kuroda, Mahiko Nagao

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The adsorption of N2 on a copper ion-exchanged ZSM-5 sample (CuZSM-5) prepared by ion exchange using an aqueous solution of copper propionate, Cu(C2H5COO)2, was examined at room temperature by measuring the FT-IR spectra, adsorption isotherms and heat of adsorption. This sample was found to be extremely efficient in terms of N2 adsorption with regard to both the amount and the energy (i.e., heat) of adsorption, compared with samples prepared by a conventional ion-exchange method using an aqueous solution involving Cu2+ and simple counter ions, Cl- or NO3-. To clarify the specificity of the newly-prepared sample, the ion-exchange of ZSM-5 with Cu2+ was carried out by employing aqueous solutions involving Cu2+ and various types of counter ions [propionate (C2H5COO-), acetate (CH3COO-), formate (HCOO-), chloride (Cl-) and nitrate (NO3-) ions]. When the ion exchange was performed by using a Cu(C2H5COO)2 or Cu(CH3COO)2 solution, the Cu2+ species with propionate or acetate ligand (in the monomer state) were ion-exchanged in ZSM-5, as confirmed by the DR, EPR and FT-IR spectra for CuZSM-5. In contrast, Cu2+ species were present in the form of aquo-complexes in samples prepared with other solutions. This distinct difference can be ascribed to the difference in the pKa values of the counter ions; carboxylate ions, with a high pKa value, are inclined to form a complex with Cu2+. Using this newly applied Cu(C2H5COO)2 solution, the present ion-exchange method has the potential to develop new effective materials that possess the specific adsorption and catalytic properties of CuZSM-5.

Original languageEnglish
Pages (from-to)119-126
Number of pages8
JournalMicroporous and Mesoporous Materials
Volume70
Issue number1-3
DOIs
Publication statusPublished - May 21 2004

Keywords

  • Copper propionate
  • Copper-ion exchange
  • Counter ion
  • N adsorption
  • ZSM-5

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials

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