On the role of Fe and Co dopants during the activation of the VO(HPO{sub 4}), 0.5 H{sub 2}O precursor of the vanadium phosphorus catalyst as studied by in situ laser Raman spectroscopy
- Institut de Recherches sur la Catalyse, Villeurbanne (France)
- Univ. of Liverpool (United Kingdom)
- Universite Abdelmalek Essaadi, Tetouan (Morocco)
Two vanadium phosphorus oxide precursors doped by Co and Fe have been prepared by a new route consisting of a reduction of VOPO{sub 4}, 2H{sub 2}O by isobutanol which is known to give a particular morphology of VoHPO{sub 4}, 0.5H{sub 2}O, developing crystallites in the [110] direction. Their activation under n-butane/air catalytic atmosphere (1.5%) has been compared to the corresponding undoped precursor prepared under the same conditions and used as a reference. The modification of the structure of the VPO materials has been followed on-line by in situ laser Raman spectroscopy. In a first period of the activation, the nucleation of {alpha}{sub I}-VOPO{sub 4} is favoured for the undoped VPO precursor, while (VO){sub 2}P{sub 2}O{sub 7} appears in a second period. For the Co-doped VPO precursor, {alpha}{sub I}- and {alpha}{sub II}-VOPO{sub 4} first appear, and then (VO){sub 2}P{sub 2}O{sub 7} appears. At variance, the Fe-doped VPO precursor promotes the only nucleation of {alpha}{sub I}-VOPO{sub 4}. When comparing with the classical organic route, catalytic performances are markedly improved when the VOHPO{sub 4}, 0.5H{sub 2}O precursor is prepared via this new route both for the undoped and the Co-doped VPO catalysts. At variance, the Fe-doped catalyst gives poorer performances which have been explained by a high oxidation state for this catalyst (almost (V{sup 5+}) as {alpha}{sub I}-VOPO{sub 4}). This is confirmed by an analysis of the bulk and surface composition of the final catalysts by XRD and XPS spectroscopy. The role of the two dopants on this new morphology of VOHPO{sub 4}, 0.5H{sub 2}O is then quite different at variance with what was observed on the same precursor prepared by the classical route of reduction of V{sub 2}O{sub 5} by isobutanol. 14 refs., 11 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 501845
- Journal Information:
- Journal of Catalysis, Vol. 163, Issue 2; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Characterisation of variations in vanadium phosphate catalyst microstructure with preparation route
On the role of the VO(H{sub 2}PO{sub 4}){sub 2} precursor for n-butane oxidation into maleic anhydride