In situ-electron spin resonance: a useful tool for the investigation of vanadium phosphate catalysts (VPO) under working conditions

Brückner, Angelika; Kubias, B.; Lücke, Bernhard

doi:10.1016/s0920-5861(96)00077-6

Cited by 51 publications

(42 citation statements)

References 14 publications

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“…Indeed, recently Coulston et al (12) have shown that the presence of V 5+ appears to be essential for the initial activation of n-butane, an observation that is essentially in agreement with earlier TAP pulse reactor experiments (13). To some extent, the debate concerning the involvement of specific VPO phases is complicated by the observation that many vanadium phosphate catalysts contain significant amounts of disordered material (5,6,(9)(10)(11)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). Some studies suggest the amorphous material is an active component (5,6,15,18,19,(26)(27)(28)(29), whereas others consider this not to be the case (8)(9)(10)(11)22).…”

Section: Introductionsupporting

confidence: 58%

“…We consider that the presence of an amorphous overlayer on (VO) 2 P 2 O 7 , as noted in many studies (9)(10)(11)15,18,19,23,24), may result from a combination of one or more of the following processes: (i) exposure of the crystalline surfaces to the reactor feed producing amorphous material in situ; (ii) electron beam damage of the (VO) 2 P 2 O 7 crystallites (which are known to completely amorphise after 20-30 s under typical electron beam irradiation conditions in the microscope) and/or (iii) preferential electron beam sensitivity of a crystalline surface layer (e.g. VOPO 4 which is known to completely amorphise in a few seconds in the electron beam of the microscopy) (33).…”

Section: Discussionmentioning

confidence: 99%

“…Many studies have suggested that an amorphous overlayer on the crystalline VPO subsurface may be the active surface for this reaction (5,6,15,18,19,(26)(27)(28)(29). This has also been observed on related vanadium carbide catalysts for butane oxidation (21).…”

Section: Discussionmentioning

confidence: 99%

“…To some extent, the debate concerning the involvement of specific VPO phases is complicated by the observation that many vanadium phosphate catalysts contain significant amounts of disordered material (5,6,(9)(10)(11)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). Some studies suggest the amorphous material is an active component (5,6,15,18,19,(26)(27)(28)(29), whereas others consider this not to be the case (8)(9)(10)(11)22). Amorphous VPO compounds have been used as one way to secure in situ regeneration in industrial reactors (30) by using a high temperature treatment with pure n-butane.…”

Section: Introductionmentioning

confidence: 99%

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Amorphous Vanadium Phosphate Catalysts Prepared Using Precipitation with Supercritical CO2 as an Antisolvent

Hutchings

López-Sánchez²,

Bartley³

et al. 2002

Journal of Catalysis

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A new preparative route for vanadium phosphate catalysts is described using supercritical CO2 as an antisolvent. The amorphous microspheroidal VPO produced is shown to be more active than comparable crystalline VPO catalysts for the selective oxidation of n-butane to maleic anhydride and, furthermore, does not require an extensive pre-treatment or activation period to establish full catalytic activity. VPO catalysts prepared using supercritical CO2 as an antisolvent maintain their amorphous nature throughout the catalyst test period. In contrast, amorphous VPO catalysts can also be prepared using liquid CO2 as antisolvent, or by solvent evaporation in vacuo, however, these materials are found to partially crystallise during the oxidation of n-butane. The wholly amorphous catalysts are characterised using transmission electron microscopy, X-ray absorption spectroscopy, 31 P spin echo mapping NMR spectroscopy and X-ray photoelectron spectroscopy. The role of amorphous material in vanadium phosphate catalysis is discussed in detail.

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Section: Introductionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Amorphous Vanadium Phosphate Catalysts Prepared Using Precipitation with Supercritical CO2 as an Antisolvent

Hutchings

López-Sánchez²,

Bartley³

et al. 2002

Journal of Catalysis

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“…In situ ESR measurements were performed with the cw spectrometer ERS 300 in X-band (ZWG, Berlin) equipped for these investigations with a flow reactor and a gas as well as liquids (with subsequent vaporization) supplying system [20,21]. 0.4 g of the solids (0.5-1 mm fraction) each were applied as catalyst.…”

Section: Methodsmentioning

confidence: 99%

Ammoxidation of toluene on vanadyl polyphosphates-VO(PO3)2, 1. synthesis and characterization of the parent samples

Hannour

Martin

Brückner

et al. 1998

React Kinet Catal Lett

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Vanadyl polyphosphates with a P/V ratio = 2 (crystalline (~-VO(PO3)2 and 13-VO(PO3)2 as well as amorphous VO(PO3)2) were synthesized, starting from Usually prepared precursor VO(H2PO4)2 but pursuing new methods using V2Os/H3PO4 as well as VOHPO4 9 1/2 H20/H3PO4, too. The products were characterized by chemical analysis and X-ray diffractometry. In situ ESR spectroscopy was used as a tool to predict their catalytic activity in the ammoxidation reaction.

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In-situ-IR-, -NMR-, -EPR- und -UV/Vis-Spektroskopie: Wege zu neuen Erkenntnissen in der heterogenen Katalyse

Hunger

Weitkamp

2001

Angew. Chem.

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Die Entwicklung neuer Festkörperkatalysatoren für den Einsatz in der industriellen Chemie beruht bisher noch zu einem sehr großen Teil auf dem empirischen Erproben einer Vielzahl unterschiedlicher Materialien. Nur in wenigen Ausnahmefällen ist es gelungen, durch die Aufklärung der einzelnen Teilaspekte einer heterogen katalysierten Reaktion den gesamten, meist sehr komplexen Mechanismus der chemischen Umsetzung zu verstehen. Mit modernen Konzepten der kombinatorischen Katalyseforschung ist es möglich geworden, innerhalb kurzer Zeiträume eine große Zahl unterschiedlicher Materialien zu präparieren und zu testen und damit schneller als vorher geeignete Katalysatoren zu finden oder ihre chemische Zusammensetzung zu optimieren. Unser Verständnis der Mechanismen der von diesen Materialien katalysierten Reaktionen muss jedoch durch spektroskopische Untersuchungen an arbeitenden Katalysatoren unter möglichst praxisnahen Bedingungen (Temperatur, Partialdruck der Reaktanten, Katalysatorbelastung) entwickelt werden. Dies erfordert die Entwicklung und den Einsatz neuer Techniken der In‐situ‐Spektroskopie. Der vorliegende Aufsatz soll zeigen, auf welchen Wegen dieses Ziel erreicht wird. Der Begriff in situ (lat.: an Ort und Stelle) beinhaltet im eigentlichen Sinne die Untersuchung der direkt im Spektrometer ablaufenden chemischen Reaktionen und die mit ihnen verbundenen Veränderungen des Katalysators.

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In situ-electron spin resonance: a useful tool for the investigation of vanadium phosphate catalysts (VPO) under working conditions

Cited by 51 publications

References 14 publications

Amorphous Vanadium Phosphate Catalysts Prepared Using Precipitation with Supercritical CO2 as an Antisolvent

Amorphous Vanadium Phosphate Catalysts Prepared Using Precipitation with Supercritical CO2 as an Antisolvent

Ammoxidation of toluene on vanadyl polyphosphates-VO(PO3)2, 1. synthesis and characterization of the parent samples

In-situ-IR-, -NMR-, -EPR- und -UV/Vis-Spektroskopie: Wege zu neuen Erkenntnissen in der heterogenen Katalyse

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