Quantitative solid-state NMR investigation of V5+ species in VPO catalysts upon sequential selective oxidation of n-butane

Frey, Jörg; Lieder, Christian; Schölkopf, Thomas; Schleid, Thomas; Nieken, Ulrich; Klemm, Elias; Hunger, Michael

doi:10.1016/j.jcat.2010.03.004

Cited by 20 publications

(13 citation statements)

References 31 publications

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“…Moreover, a band at ca. 300 nm has been reported to be due to polymeric V 5+ in tetrahedral coordination [49][50][51][52][53][54]. Accordingly, absorption within the region 200-300 nm is clearly present in the VP2 and VP3 catalysts spectra as well, both samples consisting of a V 5+ -containing bulk phase (VOPO4.2H2O).…”

Section: General Characterizationmentioning

confidence: 92%

“…Accordingly, absorption within the region 200-300 nm is clearly present in the VP2 and VP3 catalysts spectra as well, both samples consisting of a V 5+ -containing bulk phase (VOPO4.2H2O). With respect to the latter phase, the structure of which mainly consists of hexacoordinated V 5+ species, an absorption band at 400-450 nm has been reported to be related to those V 5+ species [49][50][51][52][53][54]. This is also observed in VP2 and VP3 spectra, although with a strong difference in the relative intensity between both samples.…”

Section: General Characterizationmentioning

confidence: 99%

“…Despite the complexity of the spectra obtained, as they consist of several broad and overlapping bands, complementary information can be extracted from them. Thus, a strong band at 200-250 nm (associated with a charge transfer transition from O 2+ to V 4+ ) and a weak band at 600-650 nm, both found in VP1, VP1H, VP4 and VP4H samples, indicate the presence of V 4+ species [49][50][51][52][53][54] which is in agreement with the expected vanadium oxidation state of (VO)2P2O7 (in VP1 and VP1H catalysts) and VO(PO3)2 (in VP4 and VP4H catalysts). However, while the band at 600-650 nm is more specific to V 4+ , and therefore barely observed in the samples with a major V 5+ -containing VPO structure (VP2 and VP3 catalysts), absorption at 200-250 nm has also been related to isolated V 5+ species in tetrahedral coordination.…”

Section: General Characterizationmentioning

confidence: 99%

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Relationship between bulk phase, near surface and outermost atomic layer of VPO catalysts and their catalytic performance in the oxidative dehydrogenation of ethane

Ivars‐Barceló

Hutchings

Bartley

et al. 2017

Journal of Catalysis

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A set of vanadium phosphorous oxide (VPO) catalysts, mainly consisting of (VO)₂P₂O₇, VO(PO₃)₂ or VOPO₄∙2H₂O bulk crystalline phases, has been investigated for the oxidative dehydrogenation (ODH) of ethane to ethylene, a key potential reaction for a sustainable industrial and socioeconomic development. The catalytic performance on these VPO catalysts has been explained on the basis of the main crystalline phases and the corresponding suface features found by XPS and LEISS at 400 ˚C, i.e. within the temperature range used for ODH reaction. The catalysts based on (VO)₂P₂O₇ phase presented the highest catalytic activity and productivity to ethylene. Nevertheless, the catalysts consisting of VO(PO₃)₂ structure showed higher selectivity to ethylene, reaching 90% selectivity at ca. 10% ethane conversion. To the best of our knowledge, this is the highest selectivity reported on a vanadium phosphorous oxide at similar conversions for the ethane ODH. In general, catalysts consisting of crystalline phases with vanadium present as V⁴⁺, i.e. (VO)₂P₂O₇ and VO(PO₃)₂, were found to be significantly more selective to ethylene than those containing V⁵⁺ phases. The surface analysis by XPS showed an inverse correlation between the mean oxidation state of vanadium near surface and the selectivity to ethylene. The lower averaged oxidation states of vanadium appear to be favoured by the presence of V³⁺ species near the surface, which was only found in the catalysts containing V⁴⁺ phases. Among those catalysts the one based on VO(PO₃)₂ phase shows the highest selectivity, which could be related to the most isolated scenario of V species (the lowest V content relative to P) found at the outermost surface by low energy ion scattering spectroscopy (LEISS), a "true" surface technique only sensitive to the outermost atomic layer

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Section: General Characterizationmentioning

confidence: 92%

Section: General Characterizationmentioning

confidence: 99%

Section: General Characterizationmentioning

confidence: 99%

See 1 more Smart Citation

Relationship between bulk phase, near surface and outermost atomic layer of VPO catalysts and their catalytic performance in the oxidative dehydrogenation of ethane

Ivars‐Barceló

Hutchings

Bartley

et al. 2017

Journal of Catalysis

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“…Moreover,t he 31 PMAS NMR spectra of activated PV 2 Mo 10 -SBA-15 resembled those of aV PO-SBA-15 sample treatedu nder oxidative and reductive conditions. [34] Ab road resonance observed for the VPO-SBA-15 sample between À12 and À38 ppm was attributed to various vanadyl orthophosphates phases (À8.4 to 21.2 ppm) and P bound to the SBA-15 support (%À38 ppm). Comparable structural motifs may be assumed for activated PV 2 Mo 10 -SBA-15.…”

mentioning

confidence: 91%

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

2015

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Vanadium‐containing Keggin‐type heteropolyoxo molybdate ([PV2Mo10O40]5−) was supported on silica SBA‐15 (denoted as PV2Mo10‐SBA‐15). The structural evolution and catalytic activity of PV2Mo10‐SBA‐15 and a suitable reference V2Mo10Ox‐SBA‐15 were investigated under selective propene oxidation conditions by using in situ X‐ray absorption spectroscopy. 31P MAS NMR measurements of supported PV2Mo10‐SBA‐15 and reference H3PO4‐SBA‐15 were performed after the catalytic reaction. PV2Mo10‐SBA‐15 formed a mixture of mainly tetrahedral [MoOx] and [VOx] units during thermal treatment under propene oxidation conditions. Changes in the average local structure around V centers coincided with the changes in the average local structure around Mo centers and the onset of catalytic activity. In addition, mainly tetrahedral [MoOx] and [VOx] units seemed to be in close proximity and interacted under catalytic conditions. Conversely, in the reference material V2Mo10Ox‐SBA‐15 synthesized with individual V and Mo source precursors, Mo and V centers appeared to be more separated from each other. The structural environment of P in PV2Mo10‐SBA‐15 under catalytic conditions corresponded to a mixture of various species. P was connected to both the support material SBA‐15 via POSi bonds and [MoOx] or [VOx] units. Apparently, the proximity of V and Mo in Keggin precursors was a prerequisite for obtaining (Mo,V) oxide species on the support material.

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“…Vanadium(V) environments are ubiquitous in nature and in manmade systems 1–3. Applications of vanadium(V) molecules range from catalysis by enzymes1, 4–8 and inorganic solids (e.g., vanadate,1, 9–12 vanadium‐substituted polyoxoanionic solids,13–16 and bioinorganic complexes17–25) to their applications in pharmaceutical chemistry,1, 23, 26, 27 and biology. Recently, vanadium has found use in clean energy production, and the vanadium flow battery is emerging as a new storage system 28…”

Section: Introductionmentioning

confidence: 99%

NMR Crystallography of an Oxovanadium(V) Complex by an Approach Combining Multinuclear Magic Angle Spinning NMR, DFT, and Spin Dynamics Simulations

Pourpoint

Yehl

et al. 2015

ChemPhysChem

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Bioinorganic vanadium(V) solids are often challenging for structural analysis. Here, we explore an NMR crystallography approach involving multinuclear (13) C/(51) V solid-state NMR spectroscopy, density functional theory (DFT), and spin dynamics numerical simulations, for the spectral assignment and the 3D structural analysis of an isotopically unmodified oxovanadium(V) complex, containing 17 crystallographically inequivalent (13) C sites. In particular, we report the first NMR determination of C-V distances. So far, the NMR observation of (13) C-(51) V proximities has been precluded by the specification of commercial NMR probes, which cannot be tuned simultaneously to the close Larmor frequencies of these isotopes (100.6 and 105.2 MHz for (13) C and (51) V, respectively, at 9.4 T). By combining DFT calculations and (13) C-(51) V NMR experiments, we propose a complete assignment of the (13) C spectrum of this oxovanadium(V) complex. Furthermore, we show how (13) C-(51) V distances can be quantitatively estimated.

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Quantitative solid-state NMR investigation of V5+ species in VPO catalysts upon sequential selective oxidation of n-butane

Cited by 20 publications

References 31 publications

Relationship between bulk phase, near surface and outermost atomic layer of VPO catalysts and their catalytic performance in the oxidative dehydrogenation of ethane

Relationship between bulk phase, near surface and outermost atomic layer of VPO catalysts and their catalytic performance in the oxidative dehydrogenation of ethane

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

NMR Crystallography of an Oxovanadium(V) Complex by an Approach Combining Multinuclear Magic Angle Spinning NMR, DFT, and Spin Dynamics Simulations

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