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  • 11
    Electronic Resource
    Electronic Resource
    Electronic state and location of Pt metal clusters in KL zeolite: FTIR study of CO chemisorption (1995)
    Springer
    Catalysis letters 32 (1995), S. 147-158 
    Details
    ISSN: 1572-879X
    Keywords: Pt/KL zeolite ; CO chemisorption on Pt ; IR spectroscopy ; electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electronic state and location of Pt metal clusters supported on KL zeolite are studied by FTIR spectroscopy of adsorbed CO. Investigation of the CO adsorption was performed within the wide CO pressure range (from 4×10−3 to 102 Pa) and supplemented by the study of the CO desorption at elevated temperature. Comparison of the data on CO adsorption and desorption at increased temperature reveals the existence of two groups of Pt particles in the sample. The first group of the particles is localized on the outer surface of the zeolite microcrystals and in the near surface region; they exhibit CO bands at 2060-2050 cm−1 close to those of Pt supported on conventional supports. The particles of the second group are encaged inside zeolite channels and their electronic structure is presumably strongly perturbed by the zeolite framework. CO adsorbed on the Pt particles of this group exhibits coverage dependent bands at frequencies in the range 1960-1920 cm−1. The marked downward shift of thevCO band is attributed to the increase of electron density on these particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806110
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  • 12
    Electronic Resource
    Electronic Resource
    In situ FTIR and UV/VIS spectroscopic study of the generation of anionic Pt-carbonyl complexes within a faujasite matrix (1994)
    Springer
    Catalysis letters 30 (1994), S. 65-75 
    Details
    ISSN: 1572-879X
    Keywords: anionic Pt-carbonyl complexes ; CO chemisorption on Pt ; IR spectroscopy ; UV/VIS diffuse reflectance spectroscopy ; faujasites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The temporal generation of anionic platinum-carbonyl complexes in platinum ionexchanged zeolites X and Y by reductive carbonylation at 105 Pa and 363 K is monitored by in situ UV/VIS and FTIR spectroscopy. A monomer [Pt3(CO)6]2−, exhibiting bands at 318 and 456 nm in the UV/VIS spectra and at 1790 and 2025 cm−1 in the FTIR spectra, is the only platinum/species formed in NaX. The monomer as well as oligomers are generated in NaY, where the formation of the latter species is due to the stronger acidity in the NaY as compared to NaX. The decomposition of the complexes results in the generation of Pt clusters of the size ≤1 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813673
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  • 13
    Electronic Resource
    Electronic Resource
    In situ FTIR spectroscopy on rhodium-exchanged NaX zeolite with different metal dispersion during syngas reaction (1994)
    Springer
    Catalysis letters 27 (1994), S. 119-130 
    Details
    ISSN: 1572-879X
    Keywords: faujasite-hosted rhodium ; in situ FTIR spectroscopy ; CO hydrogenation ; rhodium dispersion ; methanol selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In situ FTIR spectroscopy has been applied to study the reason of the different selectivity behaviour of rhodium in the CO hydrogenation reaction in dependence on the different particle size. Several forms of molecularly adsorbed CO are observed, such as linearly- and bridgedbonded CO on metallic rhodium as well as dicarbonyl species with Rh(I) centres formed by oxidation of Rh(0) with protons in presence of CO. Furthermore, non-reactive formate, acetate, and carbonate species are produced as side products of the reaction. The higher selectivity to oxygenates, particularly to methanol, is explained by the existence of multiple-bonded CO present only on small rhodium crystallites. The multiple-bonded CO formed at low temperatures is converted at higher temperatures to the highly reactive formyl species, which is hydrogenated to methanol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806985
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  • 14
    Electronic Resource
    Electronic Resource
    Zur Dynamik idealer Speicher. Ein einfaches mathematisches Modell (1982)
    Springer
    Theoretical chemistry accounts 61 (1982), S. 437-460 
    Details
    ISSN: 1432-2234
    Keywords: Chemical oscillations ; Heterogeneous catalysis ; Discrete mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oscillatory and bistable behavior of the heterogeneous catalytic methanol oxidation on a Pd supported catalyst is explained in terms of the changing properties of the active metal phase due to its loading with carbon monoxidde and hydrogen. The metal phase acting as a storage for chemical species is simulated by a discrete mathematical model, which assumes a constant rate of loading and a variable rate of outflow, which at time n depends on the state of the storage at time n − 1. A global analysis regarding the stability of the system is carried out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00549036
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  • 15
    Electronic Resource
    Electronic Resource
    Temperature Oscillations Characterized by An Overall Activation Energy (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 995-1003 
    Details
    ISSN: 1572-8943
    Keywords: overall activation energy ; oxidations ; thermokinetic oscillations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temperature oscillations obtained during the heterogeneous catalytic oxidation of ethanol on Pd-Al2 O3 in a dynamic calorimeter were characterized by an overall activation energy. This parameter was determined by a non-isothermal kinetic method using the minimum and maximum values of the oscillations temperature. Using the bifurcation diagram with the oxygen as a bifurcation parameter an E value between 27.6 and 28.2 kJ mol-1 was obtained. With ethanol as bifurcation parameter the E values lies between 28.1 and 31.1 kJ mol-1 for 3.5 to 4.0 vol% ethanol and between 25.8 and 27.6 kJ mol-1 for 4.0 to 4.7 vol% ethanol. These results have been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010131616337
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  • 16
    Electronic Resource
    Electronic Resource
    Bifurcation diagrams of the heterogeneous catalytic oxidation of methanol (1994)
    Springer
    Reaction kinetics and catalysis letters 53 (1994), S. 391-396 
    Details
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The experimental bifurcation diagrams of the heterogeneous catalytic oxidation of methanol on Pd have been determined by changing the concentration of methanol or oxygen in the feed. Hopf bifurcations have been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02073047
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