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  • 1
    Electronic Resource
    Electronic Resource
    Study of the surface composition of vanadyl pyrophosphate catalysts by XPS and ISS – Influence of Cs+ and water vapor on the surface P/V ratio of (VO)2P2O7 catalysts (1999)
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 150-153 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  The investigation of the surface composition of vanadyl pyrophosphate catalysts and the influence of Cs ions and of water vapor on the surface P/V ratio were described and discussed. The characterization was carried out by XPS (X-ray Photoelectron Spectroscopy) and ISS (Ion Scattering Spectroscopy). It was concluded that the P/V ratio on the surface of equilibrated and non equilibrated (VO)2P2O7 catalysts prepared in aqueous solution was between 1.3 and 1.4 (XPS) based on calibrations with different VPO glasses as standard materials having uniform composition of surface and bulk. In the outermost layer of the catalyst the P/V ratio was much higher and laid between 2 and 3 as verified by ISS. Different influences, i.e. addition of alkali metall ions (Cs+) or a treatment with water vapor of the catalyst, caused a further increase in the concentration of phosphorus on the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051462
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  • 2
    Electronic Resource
    Electronic Resource
    Tribomechanical pretreatment of vanadium phosphates: structural and catalytic effects (2000)
    Springer
    Catalysis letters 68 (2000), S. 13-18 
    Details
    ISSN: 1572-879X
    Keywords: vanadium phosphates ; real structure ; tribomechanical pretreatment ; maleic anhydride ; butane oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of the tribomechanical pretreatment of the precursor vanadyl hydrogenphosphate hemihydrate, VOHPO4·0.5H2O, prepared in aqueous medium and of the catalyst vanadyl pyrophosphate, (VO)2P2O7, on the structural and catalytic properties of (VO)2P2O7 in the oxidation of n-butane to maleic anhydride was investigated. Due to the pretreatment the activity and selectivity of the catalyst were markedly increased. The increase in catalytic performance is explained as an effect of the particle size in connection with lattice imperfections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019042311089
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation, structural properties and catalytic selectivity of sulfate-doped (VO)2P2O7 catalysts in the oxidation of n-butane (1997)
    Springer
    Catalysis letters 46 (1997), S. 113-118 
    Details
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sulfate-doped VOHPO4·0.5H2O precursors with molar ratios of 0 〉 S : V 〉 0.1 were prepared by three different methods and calcined to the respective sulfate-doped (VO)2P2O7 catalysts in which the distances of the crystal planes parallel to (200) are enlarged. Sulfate doping influences both the crystal structure and the selectivity to maleic anhydride in the oxidation of n-butane. The best catalytic selectivity was achieved for slightly disordered catalysts and moderate lattice distances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019008821779
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  • 4
    Electronic Resource
    Electronic Resource
    Application of a thermochemical selectivity criterion to the catalytic oxidation of butadiene to furan and maleic anhydride (1999)
    Springer
    Reaction kinetics and catalysis letters 66 (1999), S. 211-216 
    Details
    ISSN: 1588-2837
    Keywords: Butadiene ; furan ; catalytic selective oxidation ; quantum-chemical calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is shown that the selectivity of furan formation from butadiene is not limited by the C−H bond strengths of the molecules involved and that ring fission energies are not suitable data for the criterion applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475792
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  • 5
    Electronic Resource
    Electronic Resource
    Investigation of the surface of vanadyl pyrophosphate catalysts (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 736-741 
    Details
    ISSN: 0142-2421
    Keywords: vanadyl pyrophosphate catalysts ; XPS ; ISS ; surface P/V ratio ; Cs+-doped (VO)2P2O7 catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The surface composition of (VO)2P2O7 catalysts was investigated by x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). The P/V ratio on the surface of (VO)2P2O7 catalysts from aqueously prepared precursors lies between 1.3 and 1.4, based on XPS calibrations with different VPO glasses as standard materials. With ISS we obtained a higher P/V ratio of (VO)2P2O7 catalysts in the outermost layer of ∽2-3.The addition of caesium (Cs+) caused a further increase in the P/V ratio of the surface of (VO)2P2O7 with increasing Cs+ concentration. Ion scattering spectroscopy indicated that Cs+ was mainly confined to the uppermost layers, and at high doping concentrations a total surface coverage with Cs+ was achieved.The influence of water vapour on the surface composition of the catalysts was also investigated. A migration and a loss of phosphorus was found after and during water vapour treatment using XPS, ISS and thermogravimetric measurements. The surface of (VO)2P2O7 is assumed to be a dynamic system influenced by the partial pressure of water vapour in the gas phase. The rate of bulk oxidation of (VO)2P2O7 was dependent on the water vapour content in the gas phase. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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