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  • 1
    Electronic Resource
    Electronic Resource
    In situ high temperature and high pressure exafs studie of Pt/Al2O3 catalysts. Part I: Reduction and deactivation (1991)
    Springer
    Catalysis letters 8 (1991), S. 283-295 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; Pt/Al2O3 catalysts ; chlorine ; temperature ; pressure ; reduction ; deactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract EXAFS has been used to follow in situ the structural evolution of a chlorinated and non-chlorinated Pt/Al2O3 catalyst during reduction in the temperature range of 300–500 °C. Smaller metal clusters are formed from the hydrogen reduction of the chlorinated catalyst, in contrast to the larger cluster formed from the non-chlorinated one. At 460 °C, the total hydrogen pressure was raised to 5 atm. and n-heptane was injected over the samples. EXAFS measurements at the Pt edge were carried out while hydrocarbon conversion was monitored with a gas Chromatograph. We observe the rapid formation of a carbon-platinum bond. This is unmodified while turnover rates and selectivities indicate evidence for deactivation. From this structural information supplied by EXAFS, correlated with the data obtained from gas chromatography, we find that our results are consistent with a model proposed by others where deactivation is due to the build-up of a multilayer of carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764190
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    In situ EXAFS studies of modifications to supported metallic catalysts under reactive atmospheres (1993)
    Springer
    Catalysis letters 20 (1993), S. 1-13 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; Pt ; Pt-Re ; Pt-Sn ; in situ ; deactivation ; coking ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to study the structural evolution of monometallic (Pt/Al2O3) and bimetallic (Pt-Re/Al2O3) catalysts with metal loadings representative of those used industrially under conditions close to those seen during preparation (calcination and reduction), during catalysis (under a hydrogen-hydrocarbon mixture), and during regeneration (simulated by cycles of reduction and oxidation). During the catalytic reforming ofn-heptane, the formation of bonds to carbon species is observed directly by EXAFS. Despite the fact that only platinum-carbon bonds are observed, bimetallic systems show significant differences compared with monometallic systems with, in the case of Pt-Re, a reduction in the temperature range over which carbon bonding is observed, and structural modifications of the metallic particles. Under the same conditions, no carbon bonding is observed for the Pt-Sn system. In the case of Pt-Sn/Al2O3, the EXAFS results, confirmed by transmission electron microscopy, demonstrate the high resistance to sintering of this bimetallic system compared to the monometallic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00772592
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    Paper (German National Licenses)
    Fulltext
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