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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of surface species on V/SiO2 and V,Na/SiO2 and their role in the partial oxidation of methane to formaldehyde (1996)
    Springer
    Catalysis letters 40 (1996), S. 9-16 
    Details
    ISSN: 1572-879X
    Keywords: vanadium surface species ; silica-supported catalysts ; methane partial oxidation ; sodium poison ; V=O sites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Silica-supported vanadium (1–8 wt%) and vanadium (5 wt%)-sodium (0.4 wt%) catalysts have been characterized by laser Raman spectroscopy, temperature-programmed reduction, X-ray photoelectron spectroscopy, NO + NH3 rectangular pulses and oxygen chemisorption. The presence of different vanadium species was correlated with activity and selectivity during the methane partial oxidation reaction. The pre-impregnation of the silica support with sodium favors vanadium dispersion, but strongly diminishes V=O concentration due to the formation of orthovanadate-like compounds. As a result of these modifications, methane conversion is strongly inhibited while formaldehyde decomposition is favored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807449
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  • 2
    Electronic Resource
    Electronic Resource
    The nature of active sites for the oxidation of methane on La-based perovskites (1996)
    Springer
    Catalysis letters 42 (1996), S. 57-63 
    Details
    ISSN: 1572-879X
    Keywords: perovskites ; methane ; catalytic combustion ; La-carbonate species ; surface carbonates ; explosion method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Highly crystalline, monophasic LaFeO3 and LaCoO3 perovskites, prepared by the explosion method, are shown to be heterogeneous at surface level. The outmost atomic layers of these perovskites contain high concentrations of carbonate-type species. Their specific activities for methane combustion are in fact identical to La2O2CO3 and air-exposed La2O3. These results compared with pertinent data from the literature hint that surface heterogeneity may be often present in mixed oxides catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00814467
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of NO and solids on the oxidation of methane to formaldehyde (1994)
    Springer
    Catalysis letters 29 (1994), S. 339-348 
    Details
    ISSN: 1572-879X
    Keywords: formaldehyde ; gas-phase reactions ; methane partial oxidation ; oxide catalysts ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The selective oxidation of methane has been studied both in the presence and absence of solids (inert or catalysts) with and without NO added, at 1 bar of total pressure. NO enhances the yield to formaldehyde, while the solids favor its decomposition. These results, together with abundant literature data, show a maximum for formaldehyde yield of about 4.0%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807113
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  • 4
    Electronic Resource
    Electronic Resource
    Structural and morphological evolution from a freeze-dried precursor to the La1.85Sr0.15 CuO4 superconductor during thermal processing (1995)
    Springer
    Journal of materials science 30 (1995), S. 1733-1741 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The crystalline phases and morphology of solids with a composition of La1.85Sr0.15CuO4 were studied in terms of thermal processing conditions of freeze-dried acetates. Samples were characterized by X-ray diffraction, scanning electron microscopy and iodometric titration techniques. Results indicate that a full development of the superconducting phase only occurs after pressing sintering and annealing under oxygen of the powders treated at T f=1253 K for 8 h. The structural evolution observed in this case involves a solid-state reaction between La1.67Sr0.33Cu2O5−δ, La(OH)3 and CuO. The existence of transient liquid phase at temperatures around 600 K generates local composition fluctations (lanthanum deficiency) where the non-superconducting ternary compound La1.67Sr0.33Cu2O5−δ develops. The selection of high heating rates (50 K min−1) below 773 K minimizes the deleterious effect of transient melting and, at the same time, ensures a high reproducibility in the morphology of the final material obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351603
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  • 5
    Electronic Resource
    Electronic Resource
    Study of lanthanum-deficient compositions in the systems La-Cu-O and La-Sr-Cu-O (1995)
    Springer
    Journal of materials science 30 (1995), S. 2227-2234 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The effect of varying lanthanum composition upon the formation of the nonsuperconducting La1.67Sr0.33Cu2O5−δ and the stoichiometry variation tolerance of the ternary system La2−xSrxCuO4 (with x=0 and 0.15) were investigated using a variety of techniques. Results indicate that total conversion to La2CuO4 from freeze-dried precursors with an La∶Cu = 2.00∶1 ratio is achieved after sintering (1253 K, 12 h) and annealing in oxygen (773 K, 6 h). Small variations in the stoichiometry of solids La2−xSrxCuO4 with x=0 and 0.15 were detected. Lanthanum-deficient composition in the ternary system induces the formation of the non-superconducting phase whose stoichiometry is better represented by La1.60Sr0.40Cu2O5−δ. The temperature-programmed reduction profiles of the cuprates can be associated with the formation of more or less stable intermediates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01184565
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  • 6
    Electronic Resource
    Electronic Resource
    Computerized catalytic kinetics: A useful extension of the method of Wei and Prater (1971)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 1229-1233 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extension of the method of Wei and Prater has been devised for determining the relative rate constants for an isothermal, first-order, reversible, three-component system, namely, the catalyzed isothermal isomerization of n-butenes. The new method reduces the required work to one experiment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690170532
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  • 7
    Electronic Resource
    Electronic Resource
    Fast, reproducible explosion method to produce crystalline perovskite-type oxides (1995)
    Springer
    Journal of materials science 14 (1995), S. 428-430 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274562
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