New insights into VOPO[sub 4] phases through their hydration
- Laboratoire de Physicochimie des Interfaces, Ecually (France)
- Institute de Recherches sur la Catalyse Villeubanne (France)
Some VOPO[sub 4] phases can be involved when the V-P-O catalysts used to oxidize n-butane to maleic anhydride are activated. Evidence is given that correct characterization can only be achieved if the catalysts are protected from hydration. Hydration of VOPO[sub 4] phases ([alpha][sub I], [alpha][sub II], [beta], [gamma], [delta]-) was monitored by Raman spectroscopy. It is shown that, with the exception of [beta]-VOPO[sub 4], all VOPO[sub 4] phases can be hydrated, with hydration leading to the same VOPO[sub 4][center dot]2H[sub 2]O. NH[sub 3] was also intercalated within [alpha][sub 1]-VOPO[sub 4]. These experiments give clues to a unified description of all (with the exception of [beta]-VOPO[sub 4]) VOPO[sub 4] phases as layered arrangements of VO[sub 6] distorted octahedra linked by PO[sub 4] tetrahedra. Proposals are given for the structure of [gamma]- and [delta]-VOPO[sub 4]. The proposed structure of [delta]-VOPO[sub 4] allows epitaxy of this peculiar phase onto (VO)[sub 2]P[sub 2]O[sub 7] as well as growth of [alpha][sub II]-VOPO[sub 4] onto [delta]-VOPO[sub 4]. 26 refs., 8 figs.
- OSTI ID:
- 6859636
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 148:1; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
CATALYTIC EFFECTS
HYDRATION
LASER SPECTROSCOPY
OXYGEN COMPOUNDS
PHASE STUDIES
PHOSPHATES
PHOSPHORUS COMPOUNDS
RAMAN SPECTROSCOPY
SOLVATION
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM PHOSPHATES