التفاصيل البيبلوغرافية
| العنوان: |
Siliceous extra-framework species in dealuminated Y zeolites generated by steaming |
| المؤلفون: |
Lutz, W.1 wolfgang.lutz@tricatgroup.de, Toufar, H.1, Heidemann, D.2, Salman, N.3, Rüscher, C.H.3, Gesing, T.M.3, Buhl, J.-Chr.3, Bertram, R.4 |
| المصدر: |
Microporous & Mesoporous Materials. Aug2007, Vol. 104 Issue 1-3, p171-178. 8p. |
| مصطلحات موضوعية: |
*SILICATE minerals, *SILICA gel, *NUCLEAR magnetic resonance spectroscopy, *LATTICE theory |
| مستخلص: |
Abstract: The dealumination of NH4Y zeolite by steaming at 873K and 1bar water pressure is accompanied by a partial decomposition of the framework. X-ray amorphous aluminosilicate and silica gel are formed as extra-framework siliceous species in addition to the known polymeric aluminium ions. Source of the aluminosilicate and silica gel are Al-rich and Si-rich parts of the non-homogeneously crystallized FAU framework which are unstable during steaming. The Al-rich part consists of a Si/Al gradient as characterized by means of Molybdate experiments. The extra-framework siliceous species are identified by 29Si MAS NMR spectroscopic measurements as extra Si(4Al) and Si(0Al) signals which appear separated from the corresponding signal distribution of the zeolite framework. A certain portion of this silica gel superimposes, however, the Si(0Al) and Si(1Al) signal distribution of the zeolite framework. This “non-visible” part is quantified by the calculation of Si/Al ratio obtained by 29Si MAS NMR spectroscopy with respect to results obtained using the characteristic lattice parameter values. [Copyright &y& Elsevier] |
| قاعدة البيانات: |
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