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  • 1
    Electronic Resource
    Electronic Resource
    Influence of template on crystallization of ZSM-5 zeolites (1990)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 9 (1990), S. 91-99 
    Details
    ISSN: 1573-1111
    Keywords: Zeolite ; ZSM-5 ; synthesis ; crystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pentasil zeolites of ZSM-5 type are synthesised hydrothermally using triethyl-n-proplyammonium bromide (TEPA-Br) and triethyl-n-butylammonium bromide (TEBA-Br). The crystallization kinetics, followed by XRD, SEM and thermal analysis, clearly demonstrate the influence of size and molecular weight of the templating quaternary ammonium cation (QAC) species on the rates of nucleation and crystallization. The values of the apparent activation energies for nucleation and crystal growth indicate that both nucleation and crystal growth are faster when TEPA-Br rather than TEBA-Br is used as a template. The quantitative identification of intergrown phases characterizes both the phases to be ZSM-5 zeolite. Thermoanalytical curves for both these zeolites in as-synthesised forms exhibit two-step oxidative decomposition of the occluded organic species. This suggests that the quaternary ammonium cation may be located at two energetically different sites within the zeolite channels. The equilibrium sorption capacity, however, is found to increase in the order of size and molecular weight of the templating species in both the zeolites. The nature of acid site distribution, obtained from the temperature programmed desorption of ammonia is found to be independent of the templating species used during the synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01041253
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallisation of zeolite mordenite and ZSM-5 without the aid of a template (1992)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 13 (1992), S. 171-179 
    Details
    ISSN: 1573-1111
    Keywords: Zeolite synthesis ; small port mordenite ; ZSM-5 ; IR ; XRD ; sorption properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites ZSM-5 and mordenite were synthesized without the aid of a template, in the gel composition ofXSiO2 : Al2O3 :YNa2O: 1500 H2O, whereX = 20–40 andY = 3.5–10.0 at 463 K. After 48 h of crystallisation the aluminosilicate gel system yielded either ZSM-5 or mordenite and their mixtures as zeolitic phases in addition to α- quartz depending on the variation in oxide mole composition. Transformation of crystalline ZSM-5 to mordenite was accompanied by a lower yield of solid product as a result of an increase in SiO2/Al2O3 and Na2O/SiO2 ratios in the aluminosilicate gel. At constant Na2O/SiO2 ratio, the decrease in SiO2/Al2O3 in the gel mixture was operative in lowering the product SiO2/Al2O3 ratio. Similarly, at constant SiO2/Al2O3 the increase in Na2O/SiO2 in the gel decreased the product SiO2/Al2O3 ratio. The mordenite obtained was found to be of the small port variety. Crystalline phases obtained were further characterised by XRD, IR, SEM and sorption studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053641
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