Roles of Li+ and Zr4+ cations in the catalytic performances of Co(1-x)M(x)Cr(2)O(4) (M = Li, Zr; x = 0-0.2) for methane combustion

Environ Sci Technol. 2011 Oct 1;45(19):8491-7. doi: 10.1021/es201659h. Epub 2011 Aug 30.

Abstract

Co(1-x)M(x)Cr(2)O(4) (M = Li, Zr; x = 0-0.2) catalysts were prepared via the citric acid method and investigated for catalytic combustion of methane. Substitution at tetrahedral (A) sites with monovalent (Li) or tetravalent (Zr) metal ions led to a decrease or increase of the catalytic activity, respectively. The Co(0.95)Zr(0.05)Cr(2)O(4) catalyst proved to be the most active and its catalytic activity reached 90% of methane conversion at 448 °C, which dropped by 66 °C compared with that of the undoped CoCr(2)O(4) catalyst. XRD and Raman results indicated that lithium or zirconium substitution could modify the spinel structure and electronic properties. For lithium-doped catalysts, oxygen deficiency and a strong surface enrichment in lithium and chromium were detected. Zirconium substitution enhanced the reducibility of zirconium-doped catalysts and decreased the strength constant of both the Co-O band and the Cr-O band, which may contribute to the catalytic activity toward methane combustion. In addition, the prevalent catalytic combustion activity of the zirconium-substituted catalysts could be explained by their higher concentration of suprafacial, weakly chemisorbed oxygen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Catalysis
  • Cations
  • Lithium / chemistry*
  • Methane / analysis*
  • Oxidation-Reduction
  • Oxides / chemistry*
  • Oxygen / chemistry
  • Photoelectron Spectroscopy
  • Spectrometry, X-Ray Emission
  • Spectrum Analysis, Raman
  • Surface Properties
  • Temperature
  • X-Ray Diffraction
  • Zirconium / chemistry*

Substances

  • Cations
  • Oxides
  • Lithium
  • Zirconium
  • Methane
  • Oxygen