Monolayer V2O5/TiO2 and MoO3/TiO2 catalysts prepared by different methods

Machej, T.; Haber, J.; Turek, Andrzej M.; Wachs, Israel E.

doi:10.1016/s0166-9834(00)84158-5

Cited by 152 publications

(86 citation statements)

References 31 publications

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“…The analysis of the EXAFS data of 1V-Nb-H, 1V-Zr-H and 1V-Al-H showed that the small increase in intensity of the FT's between 0.5 < R < 1.5 Å after hydration is not due to a change in coordination geometry but due to a slight decrease in disorder of the first coordination sphere (V-O (1) and V-O (2) ). No observable changes are observed in the coordination geometry of the interface between the VO 4 cluster and the support.…”

Section: Exafs Data-analysismentioning

confidence: 97%

“…It was tried to apply a R-space fit (k 1 , Δk = 2.5 -11 Å -1 , ΔR = 0.7-2.4 Å), which allowed the use of 10.6 fit parameters. [37] A three-shell model was applied using a geometry with the following oxygen coordination: V-O (1) (CN = 1, R = 1.58 Å), ascribed to the V=O bond, a V-O (2) (CN = 3) and V---O (3) (CN = 1), the latter two to explain the large differences around 1.8 Å. This three-shell model requires 12 fit parameters in total.…”

Section: Exafs Data-analysismentioning

confidence: 99%

“…When the V=O distance and coordination are taken as independent input for the EXAFS fit, 10 parameters are required to fit the coordination shells (V=O (1) , V-O (2) and V-O (3) ) for the three shell fit of the 1V-Si-H catalyst. Since 10.6 independent parameters are permitted for this fit, according to the Nyquist theorem, the data are not over fitted.…”

Section: Exafs Data-analysis: the Number Of Independent Parametersmentioning

confidence: 99%

“…[1,2] The extent of hydration, the vanadium oxide loading and the type of support oxide are known to influence the molecular structure of vanadium oxide species under ambient and hydrated conditions. [3][4][5][6][7] Hydrated vanadium oxide species can be of interest for the understanding of their catalytic action.…”

Section: Introductionmentioning

confidence: 99%

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Elucidation of the molecular structure of hydrated vanadium oxide species by X-ray absorption spectroscopy: correlation between the V⋯V coordination number and distance and the point of zero charge of the support oxide

Keller

Koningsberger

Weckhuysen

2006

Phys. Chem. Chem. Phys.

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The effect of the point of zero charge (PZC) of the support oxide (Al 2 O 3 , Nb 2 O 5 , SiO 2 and ZrO 2 ) on the molecular structure of hydrated vanadium oxide species has been investigated with EXAFS spectroscopy for low-loaded vanadium oxide catalysts. It was found that the degree of clustering (i.e., the V---V coordination number) and the V---V distance increase with decreasing PZC of the support oxide;i.e., Al 2 O 3 (8.7) < ZrO 2 (7) < Nb 2 O 5 (3.3) < SiO 2 (2). Upon hydration the silicasupported vanadium oxide exhibited a clear alteration in the position of the oxygen atoms surrounding the central vanadium atom and thenumber of oxygen atoms around vanadium increased to five. In contrast, only minor changes in the molecular structure were detected for the alumina-, niobia-and zirconia-supported vanadium oxide catalysts. Based on a detailed analysis of the EXAFS data a semi-quantitative distribution of vanadium oxide species present on the surface of the different support oxides can be obtained, which is in good agreement with earlier characterization studies making primarily use of Raman spectroscopy.

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Section: Exafs Data-analysismentioning

confidence: 97%

Section: Exafs Data-analysismentioning

confidence: 99%

Section: Exafs Data-analysis: the Number Of Independent Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Elucidation of the molecular structure of hydrated vanadium oxide species by X-ray absorption spectroscopy: correlation between the V⋯V coordination number and distance and the point of zero charge of the support oxide

Keller

Koningsberger

Weckhuysen

2006

Phys. Chem. Chem. Phys.

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“…Although many different synthesis methods have been used in preparing supported vanadium oxide catalysts, all supported vanadium oxide catalysts were found to contain essentially the same vanadium oxide configurations after prolonged calcination treatments [163]. This means that the preparation method does not influence the local coordination environment of supported vanadium oxides.…”

Section: Preparation Methods Of Supported Vanadium Oxide Catalystsmentioning

confidence: 98%

Chemistry, Spectroscopy and the Role of Supported Vanadium Oxides in Heterogeneous Catalysis

Weckhuysen

Keller

2003

ChemInform

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Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular structure of vanadium in water and in the solid state and an overview of the spectroscopic techniques enabling to study the chemistry of supported vanadium oxides. In the second part, it will be shown that advanced spectroscopic tools can be used to obtain detailed information about the coordination environment and oxidation state of vanadium oxides during each stage of the life-span of a heterogeneous catalyst. Three topics will be discussed: (1) the molecular structure of supported vanadium oxide catalysts under hydrated, dehydrated and reduced conditions, including the parameters, which influence the molecular structures formed at the surface of the support oxide; (2) elucidation of the active surface vanadium oxide during the oxidation of methanol to formaldehyde, the reaction mechanism and the vanadium oxide-support effect; and (3) deactivation of fluid catalytic cracking (FCC) catalysts by migration of vanadium oxides and the development of a method preventing the structural breakdown of zeolites by trapping the mobile vanadium oxides in an aluminum oxide coating.

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Spreading and Wetting

Knözinger

Taglauer

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Theoretical Considerations Thermodynamics of Wetting and Spreading Qualitative Discussion of the Dynamics of Interfacial Processes Supported Metal Catalysts Sintering and Redispersion Strong Metal Support Interactions ( SMSI ) Bimetallic Catalysts Supported Oxide Catalysts Molybdenum‐Based Catalysts Vanadium‐Based Catalysts Tungsten‐Based Catalysts Zeolites as Supports Solid‐State Ion Exchange of Zeolites

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Monolayer V2O5/TiO2 and MoO3/TiO2 catalysts prepared by different methods

Cited by 152 publications

References 31 publications

Elucidation of the molecular structure of hydrated vanadium oxide species by X-ray absorption spectroscopy: correlation between the V⋯V coordination number and distance and the point of zero charge of the support oxide

Elucidation of the molecular structure of hydrated vanadium oxide species by X-ray absorption spectroscopy: correlation between the V⋯V coordination number and distance and the point of zero charge of the support oxide

Chemistry, Spectroscopy and the Role of Supported Vanadium Oxides in Heterogeneous Catalysis

Spreading and Wetting

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