Time-resolved in situ X-ray diffraction in the crystallization of VOHPO4 · 0.5H2O

L. O'Mahony, J. Henry, D. Sutton, T. Curtin, B. K. Hodnett

Research output: Contribution to journalArticlepeer-review

Abstract

Time-resolved in situ X-ray diffraction was used to study the formation of the vanadium phosphorous oxide (VPO) catalytic precursor phase VOHPO4 · 0.5H2O in organic media. In situ energy-dispersive X-ray diffraction has identified a new phase at early reaction times (less than 300 s) at d-spacings of 7.5 and 3.1 Å. At short reaction times, thin symmetrical platelets of 10 by 10 μm dimensions were observed. Scanning Electron Microscopy combined with energy-dispersive X-ray analysis (EDXA) indicated that these platelets contained vanadium and phosphorus. The features at 7.5 Å, which shift to 6.7 Å during the first 20 min of synthesis, are associated with VOPO4 · 2H2O and VOPO4 · H2O and disappear as VOHPO4 · 0.5H2O forms. The platelets appeared to delaminate, possibly associated with the strain generated when a d-spacing shifts from 7.5 Å to 6.7 Å, from which epitaxial growth of the VOHPO4 · 0.5H2O into the familiar rosette morphology occurs.

Original languageEnglish
Pages (from-to)171-175
Number of pages5
JournalCatalysis Letters
Volume90
Issue number3-4
DOIs
Publication statusPublished - Sep 2003

Keywords

  • Crystallization
  • In situ energy-dispersive X-ray diffraction
  • Nucleation
  • Vanadyl hydrogen phosphate hemihydrate

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