In SituStudy of Redox and of p-Type Semiconducting Properties of Vanadyl Pyrophosphate and of V–P–O Catalysts during the Partial Oxidation ofn-Butane to Maleic Anhydride

Herrmann, Jean-Marie; Vernoux, P.; Bere, Kossi E.; Abon, M.

doi:10.1006/jcat.1997.1537

Cited by 79 publications

(75 citation statements)

References 39 publications

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“…Further increase of the oxygen pressure leads to a less pronounced increase in conductivity, the highest value being 2.1Â 10 )5 W )1 cm )1 at 21 kPa. This behaviour is in qualitative agreement with a study by Herrman et al who reported the dependence of the VPO conductivity on the exposing atmosphere, where the exposure to butane, with its reducing influence, decreased the conductivity remarkably compared to the one in air [16].…”

Section: Influence Of the Oxygen Partial Pressuresupporting

confidence: 92%

Bulk and Surface Properties of a VPO Catalyst Used in an Electrochemical Membrane Reactor: Conductivity-, XRD-, TPO- and XPS-study

Rihko‐Struckmann

Chalakov

et al. 2006

Catal Lett

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In the first part of this work, the electrical conductivity of vanadium phosphorous oxide (VPO) catalyst was investigated by means of the 2-probe EIS method. The VPO showed an extremely low conductivity at low oxygen partial pressure, which is the prevailing condition in the anodic compartment in an electrochemical membrane reactor (EMR). In the second part of this study, fresh as well as VPO catalyst already used in an EMR were characterised with XRD, XPS and temperature programmed oxidation (TPO). The XRD measurements revealed an unchanged bulk phase structure after operation in the EMR. Significant differences in the average oxidation states of vanadium in the catalyst layer in the EMR were determined via XPS, where the catalyst surface facing the electrolyte membrane was more oxidised than the surface facing the anodic gas compartment. The lowered uptake and release of oxygen was observed in TPO experiments for the catalyst used in the EMR.

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Section: Influence Of the Oxygen Partial Pressuresupporting

confidence: 92%

Bulk and Surface Properties of a VPO Catalyst Used in an Electrochemical Membrane Reactor: Conductivity-, XRD-, TPO- and XPS-study

Rihko‐Struckmann

Chalakov

et al. 2006

Catal Lett

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“…The XRD pattern of the precursor, VPDpre (figure 1) was identical and in good agreement with those reported for VOHPO 4 AE 0.5H 2 O, with peaks at 2h=15.5°, 19.6°, 24.14°, 27.0°and 30.4° [14,15]. The peaks at 2h=15.5°a nd 30.4°were corresponds to (001) and (130) reflections, respectively, and the (130) reflection was the dominant feature in the precursor.…”

Section: X-ray Diffractionsupporting

confidence: 75%

Activation of VOHPO4 · 0.5H2O in Propane/Air Mixture: Effect on Structural, Morphological, Oxidant’s Behaviour and Catalytic Property of (VO)2P2O7 Catalysts for Propane Oxidation

2005

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VOHPO 4 AE 0.5H 2 O synthesized by VOPO 4 AE 2H 2 O and isobutanol was activated in a flow of propane/air mixture (1% propane in air) at 673 K for 36, 75 and 132 h. Three vanadyl pyrophosphate catalysts obtained were denoted as VPD36P, VPD75P and VPD132P. The crystallinity of all propane/air pretreated catalysts as shown in XRD increased with the duration of calcination. SEM micrographs showed the formation of more isolated platelets and more prominent rosebud-shape agglomerate as the pretreatment was longer. Four reduction peaks maxima at 752, 920, 1026 and 1140 were observed in the rate of hydrogen consumption for VPD36P. As the calcination duration increased to 75 h, the H 2 reduction peaks were shifted to lower temperatures at 750, 882, 1004 and 1140 K. When the calcination duration was further increased to 132 h, only three reduction peaks were observed at 752, 952 and 1142 K. Despite the progressively shifted of the major reduction peak maximum as the duration of calcination increased from 36 to 132 h, the lattice oxygen from VPD36P was found to be the most reactive. The catalytic performance for propane oxidation to acrylic acid (AA) showed that VPD36P gave the highest activity (9.6%) with 83.0% of selectivity to AA.

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“…phase. Electrical conductivity has been used by Herrmann et al [14] shows that O -and O 2-species are associated with V 4? and V 5?…”

Section: Temperature Programmed Reduction (Tpr) In H 2 /Armentioning

confidence: 99%

Dependence of n-Butane Activation on Active Site of Vanadium Phosphate Catalysts

et al. 2009

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The nature and the role of oxygen species and vanadium oxidation states on the activation of n-butane for selective oxidation to maleic anhydride were investigated. Bi-Fe doped and undoped vanadium phosphate catalysts were used a model catalyst. XRD revealed that Bi-Fe mixture dopants led to formation of a II -VOPO 4 phase together with (VO) 2 P 2 O 7 as a dominant phase when the materials were heated in n-butane/air to form the final catalysts. TPR analysis showed that the reduction behaviour of Bi-Fe doped catalysts was dominated by the reduction peak assigned to the reduction of V 5? species as compared to the undoped catalyst, which gave the reduction of V 4? as the major feature. An excess of the oxygen species (O 2-) associated with V 5? in Bi-Fe doped catalysts improved the maleic anhydride selectivity but significantly lowering the rate of n-butane conversion. The reactive pairing of V 4? -O -was shown to be the centre for n-butane activation. It is proposed that the availability and appearance of active oxygen species (O -) on the surface of vanadium phosphate catalyst is the rate determining step of the overall reaction.

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In SituStudy of Redox and of p-Type Semiconducting Properties of Vanadyl Pyrophosphate and of V–P–O Catalysts during the Partial Oxidation ofn-Butane to Maleic Anhydride

Cited by 79 publications

References 39 publications

Bulk and Surface Properties of a VPO Catalyst Used in an Electrochemical Membrane Reactor: Conductivity-, XRD-, TPO- and XPS-study

Bulk and Surface Properties of a VPO Catalyst Used in an Electrochemical Membrane Reactor: Conductivity-, XRD-, TPO- and XPS-study

Activation of VOHPO4 · 0.5H2O in Propane/Air Mixture: Effect on Structural, Morphological, Oxidant’s Behaviour and Catalytic Property of (VO)2P2O7 Catalysts for Propane Oxidation

Dependence of n-Butane Activation on Active Site of Vanadium Phosphate Catalysts

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