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  • 1
    Electronic Resource
    Electronic Resource
    Gelling Temperatures of Gellan Solutions as Affected by Citrate Buffers (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 64 (1999), S. 0 
    Details
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of citrate buffers at pH 3.5 and 5.0 on gelling temperatures of gellan solutions with 0.4–1.8% gellan and 1.5–60 mM Ca2+were studied. Partial dissociation of the carboxyl groups in gellan polymer in pH 3.5 solutions resulted in weakened gels. The pH 3.5 buffer exhibited weak chelating ability for Ca2+. The gelling temperature of gellan solutions at pH 3.5 was quantitatively related to polymer and cation concentrations using a similar model to that for gellan water solutions. The pH 5.0 buffer exhibited strong chelating ability. Gelling temperatures at pH 5.0 were generally lower than those at pH 3.5, except at low calcium concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2621.1999.tb15103.x
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  • 2
    Electronic Resource
    Electronic Resource
    1H broad-line and MAS NMR: application to the study of acid sites of desilicated zeolite ZSM-5 (1995)
    Springer
    Catalysis letters 34 (1995), S. 139-149 
    Details
    ISSN: 1572-879X
    Keywords: solid state proton NMR ; zeolite ZSM-5 ; desilication ; surface acidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Broad-line1H NMR study of desilicated zeolite ZSM-5 was carried out as a function of the number of adsorbed water molecules in amounts lower than or equal to that of the Brønsted acid sites. The dissociation coefficient of the acid OH groups, currently associated with the acid strength, was shown not to be affected by the selective removal of Si from the zeolite ZSM-5 framework which resulted in more Brønsted acid sites per unit surface area. On the other hand, by using MAS NMR, bridging Brønsted acid sites hydrogen-bonded to the zeolite framework were identified on the “anhydrous” surface of the desilicated ZSM-5. Moreover, MAS NMR spectra of the desilicated zeolite partially rehydrated showed the presence of some Lewis acid sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808330
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  • 3
    Electronic Resource
    Electronic Resource
    Production of porous materials by dealumination of Ca-A zeolite (1995)
    Springer
    Journal of porous materials 1 (1995), S. 175-183 
    Details
    ISSN: 1573-4854
    Keywords: mesoporous materials from Ca-A zeolite by dealumination
    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 Three conventional methods of dealumination were tested on the alumina-rich Ca-A zeolite. The mild acid leaching and the hydrothermal treatment led to mesoporous materials with a sharp distribution of pore size in the 4 nm region. On the other hand, treatment with ammonium hexafluorosilicate resulted in materials with mesopores of 12 nm in size. The latter technique produced the best thermally resistant materials which exhibited also the largest void volume and the highest cation exchange capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486656
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