Polyoxometalates catalyst materials: X-ray thermal stability study of phosphorus-containing heteropolyacids H3 +xPM12 –xVxO40·13–14H2O (M = Mo,W; x= 0–1)
- 1 January 1992
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry
- Vol. 2 (9) , 971-978
- https://doi.org/10.1039/jm9920200971
Abstract
The phase evolution, under thermal treatment, of the 12-molybdo(tungsto)phosphoric acids and their related 1-vanado-substituted compounds has been studied by in situ X-ray diffraction methods. The anhydrous acid temperature range is clearly observed for the 12-molybdo(tungsto)phosphoric acid parents via formation of a tetragonal phase. However, the vanadium monosubstituted acids seem to transform into the 12-metallo parents. In the case of the 1-vanado-11-tungstophosphoric acid a curious evolution, via a very stable cubic lattice, suggests thermal stabilization of the 12-tungstophosphate anion through the formation of an anhydrous VO2 + salt.Keywords
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