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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of Cinchonidine Doped Montmorillonite Supported Noble Metal Catalysts by Thermoanalytical Methods (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 337-343 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; DTG ; immobilized cinchonidine ; Pt/K-10 montmorillonite ; TG ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characterization of new cinchonidine doped K-10 montmorillonite supported noble metal catalysts is described. Our aim was the mapping of thermal stability of these new catalytic materials by thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermoanalysis (DTA) methods accompanied by X-ray diffraction (XRD) measurements. The catalysts were prepared by various methods including conventional, microwave and ultrasonic treatments. They were characterized first by X-ray diffraction to verify the stability of montmorillonite crystal structure during preparation. Then, TG and DTG methods were applied to determine their stability under the experimental conditions usually applied. The main changes observed were the loss of water and the decomposition of the organic modifiers in the higher temperature region. The catalyst showed the best performance were prepared and characterized using microwaves and ultrasonic irradiation in order to get more insight to the effect of preparation methods on their stability. As a consequence, the catalysts were found to be stable and regenerable under 450-500 K, however, higher temperatures resulted in the complete destruction of the catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010198500844
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal Stability of Heteropoly Acids and Characterization of the Water Content in the Keggin Structure (1998)
    Springer
    Journal of thermal analysis and calorimetry 53 (1998), S. 207-215 
    Details
    ISSN: 1572-8943
    Keywords: differential scanning calorimetry ; heteropoly acids ; microwave irradiation ; thermal stability ; water content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal stability of heteropoly acids of the Keggin type (H4[SiMo12O40], H3[PMo12O40], H4[SiW12O40] and H3[PW12O40]), being important new catalytic materials, was studied by DSC. Two groups of signals were observed: the low temperature endothermic peak group belongs to the water content, while the high temperature one is exothermic and indicates the thermal decomposition of the acids. The effect of microwave irradiation on the target compounds was also studied. The emphasis, however, was placed on the characterization of the water content of the acids. Several types of water can be classified and DSC curves provide additional information to explain the differences in the catalytic behavior. The study of the effect of heat treatment and the subsequent water absorption of the acids provided additional unique information concerning the pseudoliquid phase in the secondary structure of heteropoly acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010192309961
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Monitoring of optical isomers of chiral alcohols and derivatives by chiral gas chromatography. Effect of derivatization on the enantio-differentiation (1998)
    Springer
    Chromatographia 48 (1998), S. 81-85 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral separation ; Alcohols ; Diols ; Trimethylsilylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic chiral separation of several chiral 2-and 3-alkanols and diols was studied both in their free hydroxyl and in their trimethylsilyl ether forms. First, the derivatization procedure was verified through the identification of the trimethylsilyl ethers formed on the basis of their mass spectra and optimized to obtain quantitative reaction. The optimized procedure was applied to the trimethylsilylation of racemic mixtures of various hydroxyl compounds. The silylation was found to be highly effective in the improvement of the separation of the individual enantiomers. The major advantages of the derivatization process can be summarized as: (i) excellent baseline separation of the enantiomers of the silyl ethers was achieved in contrast to the parent OH-containing compounds, (ii) the sensitivity of detection highly increased, (iii) the separations do not show any significant concentration dependence and finally (iv) the analysis time needed decreased significantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467521
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    Paper (German National Licenses)
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