Compressibility behaviour of as-synthesized high-silica Ferrierite.

Ferrierite (FER framework topology) is a well-known aluminosilicate zeolite mineral. An understanding of the structure and properties of FER remains important because of its role as a catalyst in commercial reactions. For example, it is important in the petrochemical industry, where it has been used as a shape selective catalyst for the production of isobutene. The thermal behavior of this phase (in its high silica form) was recently studied by Bull et al [1], while its compressibilty has never been investigated before. The high pressure (HP) behavior of synthetic high silica zeolite ferrierite (FER) was investigated by means of in-situ synchrotron X-ray powder diffraction, with the aim to understand the P-induced deformation mechanism. The microporous material was synthesized starting from pure silica and pyridine and propyl-amine as structure directing agents. Here we report the preliminary results on the compressibility of the as-synthesized phase. The study of the compressibility of the calcinated one will be carried out in the following steps of the project. The crystal structure of ferrierite is built up of rings of fivecorner-shared SiO4 tetrahedra (known as five-membered ringsor 5MRs) building units, which form layers in the ab plane. The layers are connected to form a matrix of 10MR channels running parallel to the c axis, which are intersected by 8MR channels running parallel to the b axis. Six-membered rings connect the 10MRs alongthe c axis direction. The HP diffraction experiments were performed at BM01a beamline (ESRF), at the fixed wavelength of 0.71 Å, using a modified Merril-Basset DAC and a mixture of methanol:ethanol:water (16:3:1) as P-transmitting medium. The powder patterns were collected from Pamb to 6.2 GPa. Some patterns were also measured upon pressure release up to Pamb, to check the reversibility of the compression effects. The unit cell parameters were refined by means of Rietveld method. The main results of this study are: 1) No complete X-ray amorphization is observed up to about 6.6 GPa; 2) No abrupt change of the elastic behavior is observed in the whole pressure range. Between Pamb and 6.2 GPa the reduction of the cell parameter are 4%, 5% and 6% for a, b and c respectively, accounting for a volume reduction of about 14 %. 3) The P-induced effects on the as-synthesized Si-ferrierite cell parameters are completely reversible. 4) The bulk modulus obtained using a second order Birch-Murnaghan equation of state and data weighted by the uncertainties in P and V was K0 = 30.1(3) GPa. This compressibility is one of the highest when compared with the other natural and synthetic zeolites studied with “penetrating” aqueous media [2, 3] and is very similar to that of SAPO-34 [4], another microporous material studied at HP in its as-synthesized form containing the organic template

High-pressure behavior of high silica ferrierite

Ferrierite (FER framework topology) is a well-known aluminosilicate zeolite mineral. An understanding of the structure and properties of FER remains important because of its role as a catalyst in commercial reactions. For example, it is important in the petrochemical industry, where it has been used as a shape selective catalyst for the production of isobutene. The thermal behavior of this phase (in its high silica form) was recently studied by Bull et al [1], while its compressibilty has never been investigated before. The high pressure (HP) behavior of synthetic high silica zeolite ferrierite (FER) was investigated by means of in-situ synchrotron X-ray powder diffraction, with the aim to understand the P-induced deformation mechanism. The microporous material was sinthesized starting from pure silica and pyridine and propyl-amine as structure directing agents. Here we report the preliminary results on the compressibility of the as synthesized phase. The study of the compressibility of the calcined one will be carried out in the following steps of the project.The crystal structure of ferrierite is built up of rings of fivecornershared SiO4 tetrahedra (known as five-membered ringsor 5MRs) building units, which form layers in the ab plane.The layers are connected to form a matrix of 10MR channels running parallel to the c axis, which are intersected by 8MR channels running parallel to the b axis. Six-membered rings connect the 10MRs alongthe c axis direction. The HP diffraction experiments were performed at BM01a beamline (ESRF), at the fixed wavelength of 0.71 Å, using a modified Merril- Basset DAC and a mixture of methanol- ethanol and water (16:3:1) as penetrating P-transmitting medium. The powder patterns were collected from Pamb to 6.2 GPa. Some patterns were also measured upon pressure release up to Pamb, to check the reversibility of the compression effects. The unit cell parameters were refined by means of Rietveld method. The main results of this study are: 1) No complete X-ray amorphization is observed up to about 6.6 GPa; 2) No abrupt change of the elastic behavior is observed in the whole pressure range. Between Pamb and 6.2 GPa the reduction of the cell parameter are 4%, 5% and 6% for a, b and c respectively, accounting for a volume reduction of about 14 %. 3) The bulk modulus obtained using a second order Birch-Murnaghan equation of state and data weighted by the uncertainties in P and V was K0 = 30.1(3) GPa. This compressibility determined in m.e.w. is one of the highest when compared with other natural and synthetic zeolites studied with “penetrating” aqueous media [2], [3]. 4) The P-induced effects on as-syntehsized ferrierite structure are completely reversible

Thermal behaviour of siliceous faujasite: further structural interpretation of negative thermal expansion

The high-temperature behaviour of siliceous faujasite (Si-Y) was investigated by in situ synchrotron Xray powder diffraction from room temperature up to 1123 K. This porous phase is remarkably stable when heated, and no phase transitions or changes in symmetry are observed. A marked negative thermal expansion (NTE), already reported in literature for a heating range from 25 to 573 K, was confirmed up to about 923 K. Above this temperature a positive thermal expansion was observed. Si-Y’s thermal behaviour was interpreted on the basis of the transverse thermal vibrations of the oxygen atoms involved in the T–O–T linkages and a series of other structural features characterizing the faujasite structure, namely the T–T distances between adjacent tetrahedral sites, the thickness of the double 6-membered rings, and the ditrigonal index of the 6-membered rings. Moreover, the thermal behaviour of several other anhydrous porous materials with NTE behaviour is discussed and compared to that of Si-Y

Fluorenone dye-Zeolite L hybrid: a novel optical material

A major challenge facing humanity is developing renewable source of energy. Following the biological blueprint of the natural photosynthesis is possible design synthetic systems for converting light into stored energy: the so called artificial antenna systems. The encapsulation of ordered chromophore molecules into one dimensional zeolite channel systems results in host-guest compounds suitable for the development of novel optical materials such as lenses, infrared light-emitting diodes (used in telecommunications) or dye nanostructured materials for optical data storage [1]. X-ray powder diffraction study of zeolite K-L loaded with 0.5, 1, 1.5, 2 fluorenone-dye (FL) molecules per unit cell (ZL/FL hybrid) [2], was carried out to understand the functionality of these host-guest systems from the structural point of view. These data evidenced a significant change of the unit cell parameters due to the embedding of FL into the ZL 12-membered channels. The Rietveld refinements revealed that the maximum loading is 1.5 FL molecules per unit cell. A strong interaction between FL carbonyl group and two extraframework potassium cations is proved by the short bond distances which make this composite very stable

The Influence of the Framework and Extraframework Content on the High Pressure Behavior of the GIS Type Zeolites: The Case of Amicite.

This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K4 Na4 (Al8 Si8 O32 )\ub710H2 O], the GIS-type phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out up to 8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.) and 8.68(5) GPa in silicone oil (s.o.). The crystal structure refinements of the patterns collected in m.e.w. were performed up to 4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined as a function of pressure. The observed framework deformation mechanism\u2014similar to that reported for the other studied phases with GIS topology\u2014is essentially driven by the distortion of the \u201cdouble crankshaft\u201d chains and the consequent changed shape of the 8-ring channels. The pressure-induced over-hydration observed in the experiment performed in aqueous medium occurs without unit cell volume expansion, and is substantially reversible. A comparison is made with the high pressure behavior of the other GIS-type phases, and the strong influence on compressibility of the chemical composition of both framework and extraframework species is discussed

Compressibility behavior and pressure-induced over-hydration of zeolite K-AlSi-L

This paper reports a study, performed by in-situ synchrotron X-ray powder diffraction, of the high-pressure behavior of zeolite L. The experiments were performed using both penetrating (methanol: ethanol: water mixture, m.e.w.) and non-penetrating (silicon oil, s.o.) pressure transmitting media (PTM) to study the compressibility and the possible pressure-induced hydration (PIH) of this synthetic zeolite, technologically relevant as host-guest system exploited in numerous application fields. The experiments were performed from Pamb to 6.2 and 6.3 GPa in s.o. and m.e.w., respectively. The crystal structure refinements were performed up to 6.3 GPa and 3.1 GPa for the patterns collected in m.e.w. and s.o., respectively, while the unit cell parameters were determined in the whole pressure range for both media. A strong PIH effect is evident when zeolite L is compressed in m.e.w. and the over-hydration is essentially ascribable to the filling of most the H2O sites, to the appearance of a new H2O site and to the partially filling of the K sites. The over-hydration starts at a very low pressure (0.5 GPa) and the maximum H2O content can be estimated in 31.1 H2O molecules, against the original value of 18. The PIH is completely reversible upon P release. The main difference between the compression behavior of zeolite L in the two media is the higher compressibility in the non-penetrating one, evidenced by ΔV=− 6.3% and −9.9% in m.e.w. and s.o, respectively. Our data are consistent with the general behavior of zeolites compressed with penetrating media, when the intrusion of H2O molecules hinders the effects of the applied pressure. The results of this work are compared with those obtained on a K-gallosilicate with LTL topology, where PIH induces the formation of H2O nanotubes inside the zeolite channel

Elastic behavior and high pressure-induced phase transition in chabazite: new data from a sample from Nova Scotia

Recently, the high pressure (HP) behavior of a natural chabazite from Vallerano [1] (VALL), and on the synthetic phases SAPO-34 [1] and ALPO-34 [2], was investigated in the frame of a wider project aimed at understanding the role of the framework/extraframework content on the compressibility of CHA-type porous materials. In this work, further structural information is obtained studying the response to HP of another natural chabazite sample from Nova Scotia (Canada) (NS) (s.g. R-3mR [3]), characterized by a different chemical composition with respect to VALL. The study was performed by means of in situ synchrotron X-ray powder diffraction (XRPD) and silicone oil as non-penetrating P-transmitting medium. XRPD experiments were performed in DAC at the BM01 beamline at ESRF (Grenoble, France) with a fixed =0.7355 Å. Powder patterns were collected from Pambup to 8.6 GPa and upon decompression. All the features of the Pamb pattern and the unit cell parameters are well recovered upon P release. Below 2.1 GPa, a and cell parameters slightly decrease and increase respectively with a resulting volume reduction of 3.6 %. Above 2.1 GPa, a transition to a triclinic P-1 pseudo-rhombohedral phase is observed. The rhombohedral to triclinic phase transition is accompanied by an abrupt decrease in the unit cell parameters and in the unit cell volume ( V=-4.0%). Between 2.5 and 5.9 GPa, the triclinic/pseudo-rhombohedral cell parameters decrease regularly and the unit cell volume variation ( V=-3.0%) indicates a lower compressibility with respect to that observed before the transition. In the highest P regime (5.9-7.2 GPa), a further slope change, with an increase in compressibility, is observed. As a whole, V between Pamb and 7.2 GPa is -12.6%. The elastic parameters, calculated with a second order BM-EoS, are V0 = 826 (1) Å3, K0 = 54(3) GPa and V0 = 784(2) Å3, K0 = 91(5) GPa, for the rhombohedral and triclinic phase, respectively. Preliminary results from Rietveld refinements up to about 1 GPa, suggest that the deformation mechanism acting in the low-P regime is a cooperative tilting of the tetrahedra belonging to the double 6-ring – resulting in a decrease of its thickness – accompanied by a simultaneous di-trigonalization of the two 6-rings. A similar mechanism was previously observed during compression of levyne [4]. The HP-induced cell volume contraction of NS (12.6 %) is higher than that of VALL (10.3%) in the same P range. This is congruent with the lower content in large extraframework potassium cations of NS, which contribute to sustain the porous structure in VALL