FisMat2017 - Submission - View

Abstract's title: Unravelling the energetic performances of all silica zeolites: High-Pressure X-Ray Powder Diffraction experiments on Si-CHA
Submitting author: Rossella Arletti
Affiliation: Dipartimento Di Scienze della Terra
Affiliation Address: via Valperga Caluso 35 10125 TORINO
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: Alberto Bettelli (Dipartmento di Scienze della Terra - Università degli Studi di Torino) Michelangelo Polisi (Dipartimento di Scienze Chimiche e Geologiche - Università degli Studi di Modena e Reggio Emilia) Simona Quartieri (Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra - Università di Messina) Giovanna Vezzalini (Dipartimento di Scienze Chimiche e Geologiche - Università degli Studi di Modena e Reggio Emilia) Jean Daou (Université de Strasbourg (UDS), Université de Haute Alsace (UHA), Equipe Matériaux a Porosité Contrôlée (MPC), Institut de Science des Matériaux de Mulhouse) Joel Patarin (Université de Strasbourg (UDS), Université de Haute Alsace (UHA), Equipe Matériaux a Porosité Contrôlée (MPC), Institut de Science des Matériaux de Mulhouse)
Abstract

The behavior of pure Si-chabazite1 (CHA framework type, s.g. R-3m, a=13.5454 c=14.7635) compressed in the penetrating fluid m.e.w. - a mixture of methanol:ethanol:water (16:3:1) - was investigated by in situ synchrotron X-ray powder diffraction (XRPD) in the  pressure range Pamb - 4.82 GPa.

The HP experiments were carried out at XPRESS beamline at Elettra synchrotron (Trieste). The sample was loaded in a Merrill-Bassett Diamond anvil cell (DAC) and the diffraction patterns were collected on an image plate MAR345 at increasing pressure.

The characterization of the Si-chabazite at ambient pressure, performed with XRPD and thermo-gravimetric analysis, indicates a water content of 2.5 molecules per unit cell, confirming the hydrophobic nature of this material. No phase transitions were induced by compression.  A cell volume decrease of about 3.7% was observed up to  4.8 GPa.

The structural refinements indicate the penetration of both alcohol and water molecules in the zeolite porosities, even at the lowest investigated pressure (0.1 GPa).  Interestingly, a segregation between methanol and ethanol was observed.  In fact, on the basis of the interatomic distances and of the steric hindrances, the two alcohol types cannot occupy simultaneously the same CHA cage (Fig.1).

The process is completely reversible, both concerning  the recovering of the original cell volume and the removal of the guest alcohol and water molecules. The reversibility of the intrusion process - already detected by porosimetric experiments performed by using pure water2 - suggests that this materials can be used as a “spring device”, able to store and restore the mechanical energy. Preliminary results will be shown also on the effects of the changes of the solution composition on the  penetration pressure.

The study is part of the ZAPPING project (www.zapping-prin.it), financed by Italian MIUR.

 

References:

1Diaz-Cabañas, M.J.; Barret, P.A.; Camblor, M.A. Chem. Commun. 1998, 1881-1882.

2Trzpit, M.; Soulard, M.; Patarin, J., Chem. Letters Vol.36, 2007, 8, 980-981.