The oxidation state of vanadium in V-P-O catalysts before and after use has been examined using 31P NMR spin echo mapping. The presence of V4+ and V5+ species could be detected for β-VOPO4, (VO)2P2O7 and industrially-related materials with P/V=0.9, 1.0, and 1.1. Magnetic susceptibility measurements were used to confirm the presence of para-magnetic vanadium in most catalysts which had been exposed to n-butane or 1-butene. Several models of active V-P-O catalysts have been offered previously which can be related to the NMR results.
- catalyst characterization (P NMR)
- oxidation catalysts
- oxidation states
- vanadium-phosphorus oxides.
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