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On the crystallization mechanism of ETS-10 titanosilicate synthesized in gels containing TAABr |
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| Authors: | CC Pavel P De Luca J BNagy |
| Institution: | a Al. I. Cuza University of Iasi, Faculty of Chemistry, Department of Chemical Technology and Materials Chemistry, 11 Carol I Bd., 700506 Iasi, Romania b University of Calabria, Dipartimento di Pianificazione Territoriale, 87036 Arcavacata di Rende (Cs), Italy c Laboratoire de R. M. N., Faculté Universitaires N.D. de la Paix, Rue de Bruxelles 61, B-5000 Namur, Belgium |
| Abstract: | Thermal analysis of the products resulted during crystallization of ETS-10 by using starting co gels with molar composition 5.0 Na2O-3.0 KF-TiO2-6.4 HCl-TAABr-7.45 SiO2-197.5 H2O, where tetralkylammonium (TAA) are tetramethyl (TMA), tetraethyl (TEA), tetrapropyl (TPA) and tetrabutylammonium (TBA), was performed. The effect of TAA+ cations (ionic radius in hydrated forms, shapes and hydrophilic/hydrophobic character) on the crystallization of ETS-10 is evident from the induction time, ti (TMA+ ? TEA+ < TPA+ < TBA+), the rate of crystallization, R (TMA+ < TEA+ < TPA+ < TBA+), morphology and size of crystallites. Organic cations play a “pore filling” role rather than as a “structure-directing” agent. The relatively flexible molecules of the symmetric tetraalkylammonium cations mixed with alkali cations (Na+, K+) participate directly at prenucleation and nucleation steps by their interaction with the silicate and titanate in aqueous colloidal dispersion. |
| Keywords: | Crystallization mechanism Thermal analysis TAA cations ETS-10 |
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