Coordination structures of vanadium and iron in MCM-41 and the catalytic properties in partial oxidation of methane

Qinghong Zhang, Wei Yang, Xiaoxing Wang, Ye Wang, Tetsuya Shishido, Katsuomi Takehira

Research output: Contribution to journalArticle

52 Scopus citations

Abstract

The coordination structures of vanadium and iron introduced into MCM-41, a typical mesoporous silica, by both direct hydrothermal synthesis (DHT) and template-ion exchange (TIE) methods have been studied by X-ray absorption spectroscopy (XANES and EXAFS). Vanadium is tetrahedrally coordinated with oxygen in V-MCM-41 prepared by both methods but the location of vanadium is probably different; vanadium is mainly incorporated inside the framework of MCM-41 by the DHT method as the content is lower than approximately 1 wt%, while the vanadyl tetrahedra are probably dispersed on the wall surface of MCM-41 over the samples by the TIE method. In the case of Fe-MCM-41, the DHT method results in iron atoms mainly in tetrahedral coordination and isolated from each other in the framework of MCM-41. However, aggregated iron oxides with iron in octahedral coordination are mainly observed in the TIE samples. The V-MCM-41 by the TIE method shows better catalytic performances than that by the DHT method in the partial oxidation of methane to formaldehyde with oxygen. However, the Fe-MCM-41 by the DHT method exhibits remarkably higher methane conversion and formaldehyde selectivity than that by the TIE method.

Original languageEnglish (US)
Pages (from-to)223-234
Number of pages12
JournalMicroporous and Mesoporous Materials
Volume77
Issue number2-3
DOIs
StatePublished - Jan 26 2005

All Science Journal Classification (ASJC) codes

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

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