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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 321-325 
    ISSN: 1573-4846
    Keywords: magnesia-silica mixed oxides ; sol-gel magnesia-silica ; magnesia-silica acidity ; sulfated magnesiasilica ; isopropanol decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mg−Si binary oxides were prepared by the sol-gel method, using magnesium diethoxide and tetraethoxysilane as starting materials. Mg−Si mixed oxides were prepared at pH3 and 9 at nominal concentrations of 1.3, 4.0, and 6.7 mole% MgO. Density and strength of the acid sites were determined by pyridine thermal programmed desorption. Comparable Lewis acidity was found in pH3 and 9 preparations. However, when the samples were sulfated with sulfuric acid, strong Bronsted acidity was developed, reaching a maximum at 6.7 mole% MgO. The strong acidity of sulfated samples was corroborated using the isopropanol decomposition reaction as catalytic test. Similar conversions are obtained at 100°C on sulfated samples, whereas 260°C are required for non-sulfated ones.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4854
    Keywords: sol-gel ; sulfated SnO2-SiO2 ; superacid catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A series of sulfated SnO2-SiO2 binary oxides were prepared by the Sol-Gel method with different SnO2 molar content. Tin chloride and tetraethylorthosilicate were used as precursors. The resulting solids were characterized by Fourier Transform Infrared spectroscopy (FTIR), ammonia thermodesorption, surface area measurements and also titrated using Hammett indicators. To correlate the acidic properties with catalytic activity, solids were tested in the 2-propanol decomposition reaction. SnO2 addition to SiO2 produce a twofold synergetic effect: an increase in the surface area in most of the resulting mixed oxides and high catalytic activities for the dehydration reaction. The titrated materials, using Hammett indicators, are of superacid nature (Ho ≤ −13.7).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Reaction kinetics and catalysis letters 63 (1998), S. 165-170 
    ISSN: 1588-2837
    Keywords: ZSM-5 ; t-plot ; cracking ; isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polycrystalline ZSM-5 zeolites were studied in the cracking ofn-pentane and the isomerization ofm-xylene. It was found that slow deactivation rates and lowp-selectivity are related to large external surface areas determined by the t-plot method.
    Type of Medium: Electronic Resource
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