Elastic behavior of MFI-type zeolites: 3 - Compressibility of silicalite and mutinaite
- Dipartimento di Scienze della Terra, Universita di Messina, Viale Ferdinando Stagno d'Alcontres 31, 98166 Messina S. Agata (Italy)
- Dipartimento di Scienze Mineralogiche e Petrologiche, Via Valperga Caluso 35, 10125 Torino (Italy)
- Dipartimento di Scienze della Terra, Universita di Modena e Reggio Emilia, Via S. Eufemia 19, 41100 Modena (Italy)
- Institut Charles Gerhardt de Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1, 8 rue Ecole Normale, 34296 Montpellier (France)
- Swiss-Norwegian Beam Line at ESRF, BP220, 38043 Grenoble Cedex (France)
We report the results of an in-situ synchrotron X-ray powder diffraction study - performed using silicone oil as 'non-penetrating' pressure transmitting medium - of the elastic behavior of three zeolites with MFI-type framework: the natural zeolite mutinaite and two silicalites (labeled A and B) synthesized under different conditions. While in mutinaite no symmetry change is observed as a function of pressure, a phase transition from monoclinic (P2{sub 1}/n) to orthorhombic (Pnma) symmetry occurs at about 1.0 GPa in the silicalite samples. This phase transition is irreversible upon decompression. The second order bulk moduli of silicalite A and silicalite B, calculated after the fulfillment of the phase transition, are: K{sub 0}=18.2(2) and K{sub 0}=14.3 (2) GPa, respectively. These values makes silicalite the most compressible zeolite among those up to now studied in silicone oil. The structural deformations induced by HP in silicalite A were investigated by means of complete Rietveld structural refinements, before and after the phase transition, at P{sub amb} and 0.9 GPa, respectively. The elastic behaviors of the three MFI-type zeolites here investigated were compared with those of Na-ZSM-5 and H-ZSM-5, studied in similar experimental conditions: the two silicalites - which are the phases with the highest Si/Al ratios and hence the lowest extraframework contents - show the highest compressibility. On the contrary, the most rigid material is mutinaite, which has a very complex extraframework composition characterized by a high number of cations and water molecules. - Graphical abstract: High-pressure behavior of silicalite compressed in silicone oil: projection of the structure along the [0 1 0] direction at Pamb(a), 0.9 GPa (b). (c) Comparison of the unit-cell volume variations as a function of pressure for mutinaite, H-ZSM5, Na-ZSM5, silicalite A, and silicalite B compressed in silicone oil. Highlights: Black-Right-Pointing-Pointer X-ray powder diffraction study of silicalite and mutinaite compressibility. Black-Right-Pointing-Pointer Silicalite is the most compressible zeolite up to now studied. Black-Right-Pointing-Pointer A phase transition from monoclinic to orthorhombic symmetry occurs in silicalite. Black-Right-Pointing-Pointer Among MFI-type zeolites the most rigid material is mutinaite.
- OSTI ID:
- 22012193
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. . 191; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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