Evolution of oxidation states in vanadium-based catalysts under conventional XPS conditions

Suchorski, Yuri; Rihko‐Struckmann, Liisa; Klose, F.; Ye, Yinmei; Alandjiyska, M.; Sundmacher, Kai; Weiß, Helmut

doi:10.1016/j.apsusc.2004.11.083

Cited by 72 publications

(37 citation statements)

References 27 publications

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“…In samples no. 2-5, the doublet peaks V2p 1/2 (522-523.9 eV) and V2p 3/2 (515.4-517.2 eV), characteristic for the V-O bond in vanadium oxides of different oxidation states: V 2 O 3 , VO 2 , V 2 O 5 [16,17], which correlates, to a certain extent with the XRD data obtained for these samples in earlier studies were detected [5].…”

Section: −supporting

confidence: 73%

The XPS investigations of the surface composition of nanoscale films formed by thermal oxidation of VxOy/InP heterostructures

Sladkopevtcev¹,

Золотухина²,

Томина³

et al. 2017

Nanosystems: Phys. Chem. Math.

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The dependence of oxide films surface layers' compositions on the method of depositing of V 2 O 5 on InP and regimes of thermal oxidation of the formed heterostructures was established by the XPS method. Lower indium content near the surface for all samples in comparison with the standard indicates a partial blocking of its diffusion into films during the chemostimulated thermal oxidation of the semiconductor. The presence of vanadium oxides in certain oxidation states and their ratio depends on the method of deposition for the chemostimulator, and on the regime of thermal oxidation. In the case of the electric arc synthesis method, at shorter reaction times, vanadium compounds in the +4 and +5 oxidation states were present in the near-surface layer, which gives evidence for the catalytic mechanism.

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Section: −supporting

confidence: 73%

The XPS investigations of the surface composition of nanoscale films formed by thermal oxidation of VxOy/InP heterostructures

Sladkopevtcev¹,

Золотухина²,

Томина³

et al. 2017

Nanosystems: Phys. Chem. Math.

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“…This V(V) percentage cannot be enlarged even after exposure of the catalysts to air at temperatures up to 650 ° C. In contrast, the catalysts with agglomerated vanadia species have an oxidation state ratio of V(V) : V(IV) = 80 : 20. It should be noted that, under time on stream in ODHE, a considerable part of the less reducible agglomerated vanadia phases is converted into a kind of multilayer polyvanadate phase with reducibility comparable to the dispersed monolayer vanadates (Suchorski et al , 2005 ;Klose et al , 2007 ).…”

Section: Mechanistic Aspects: Correlation Between Structure and Activitymentioning

confidence: 99%

Catalysis and Reaction Kinetics of a Model Reaction

et al. 2010

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The development of new and the improvement of existing reactor concepts is diffi cult without understanding the reaction mechanism and -if a catalyst is used -its operation principles. In the ideal case an accurate kinetic model with detailed structure -activity relations would be available. However, in industrial practice in general only simplifi ed strategies are applied in order to minimize experimental effort and to reduce the complexity of the corresponding mathematical expressions. Often simplifi ed kinetic models of the power law type are used to describe reaction rates and catalytic performance for a limited parameter range. Nevertheless, for the understanding and the correct prediction of the performance of alternative reactor concepts, as the membrane reactors treated in this book, a more detailed understanding of the kinetic relations is essential. In membrane reactors the concentration profi les of the reactants and the contact time profi les in the catalyst bed are infl uenced simultaneously. A reliable kinetic model has to describe also the reaction behavior for conditions which are far from those present in conventional packed -bed reactors.In order to deliver reliable data for the comparison between conventional and membrane reactors on the one hand, and between different membrane reactor concepts on the other, it is important to study the same reaction system and to apply the same catalyst. In this and the following chapters, the focus is set on the catalyzed oxidative dehydrogenation of ethane ( ODHE ). Although this reaction is currently far from a wide industrial application, it has several advantages for the purpose of this conceptual study:• The expected reaction network is limited to a rather low number of main products and byproducts, which facilitates mechanistic as well as kinetic studies.• There are no condensable products under reaction conditions, which is benefi cial for monitoring the reactor performance with high accuracy.

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“…We note, however, that the present data result from a ''fast transfer'' XPS i.e., are recorded after minimised exposition of the sample to the ultra high vacuum (UHV) conditions. We have shown before that vanadyl pyrophosphate samples can be remarkably reduced even during the first 10s of minutes of exposure to UHV [14]. Most of the published data were presumably collected under such circumstances.…”

Section: X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 87%

“…A possible vacuum-induced reduction of the VPO samples was minimised by fast sample transfer times of less than 5 min between the start of the evacuation of the load lock and the first XPS spectrum at a pressure better than 5Â10 )9 mbar [14]. The X-ray source (Mg-K a , excitation energy 1253.64 eV, operation power <200 W) was used in a ''stop-and-go'' mode in order to reduce possible damage due to sample irradiation.…”

Section: X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 99%

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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Evolution of oxidation states in vanadium-based catalysts under conventional XPS conditions

Cited by 72 publications

References 27 publications

The XPS investigations of the surface composition of nanoscale films formed by thermal oxidation of VxOy/InP heterostructures

The XPS investigations of the surface composition of nanoscale films formed by thermal oxidation of VxOy/InP heterostructures

Catalysis and Reaction Kinetics of a Model Reaction

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

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