The study of the high-pressure behaviour of microporous compounds, e.g. zeolites, experienced, in last decades, a raising interest related to the P-mediated intrusion of solvated ions/molecules, from the so-called “penetrating” P-transmitting fluids into the zeolitic structural voids [1]. These phenomena may occur when the molecules have a kinetic diameter that allow their adsorption into the structural cavities and may be potentially exploited in the tailoring of functional materials. In this study, we have investigated the P¬-mediated intrusion of H2O and alcohols molecules, carried by the P¬-transmitting fluids, into the structural cavities of the natural zeolite erionite-K, by means of in situ high-pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell, at the Xpress beamline of the Elettra synchrotron (Trieste, Italy). Erionites are a series of minerals belonging to the zeolite group, with a wide chemical variability expressed as solid solution among three end-members: erionite-Ca, erionite-K and erionite-Na. The samples we analysed are classified as erionite-K, with an average chemical formula: K2.31Na0.02Ca2.15Mg0.69Ba0.04Sr0.02(Al9.00Si27.19)O72·18.66H2O. The erionite-type framework is based on the repetition of six-membered rings with a sequence AABAAC. This stacking leads to a structure characterized by the presence of large cages (23-hedron, called “erionite-cage”), superposed along the c-axis, hosting most of the extra-framework population. To constrain the crystal-fluid interaction, we performed two high-P ramps using different P-transmitting media: 1) with the non-penetrating silicone oil, up to 2.60(5) GPa, and 2) with the potentially penetrating methanol:ethanol:H2O = 16:3:1 (hereafter mew) mixture, up to 4.97(5) GPa. Silicone oil data allowed the refinement of the isothermal bulk modulus of the pristine sample, expressed as KV0 = 44(1) GPa (βV0 = KV0-1 = 0.0227(5) GPa-1, where βV0 is the bulk volume compressibility), after a fit of a II-order Birch-Murnaghan equation of state to the experimental P-V data. The P-V data from the mew ramp unambiguously show a marked decrease in compressibility, which is unequivocally related to the P-induced intrusion of H2O (and possibly alcohols) molecules from the P-transmitting fluid. This phenomenon, which appears to be irreversible in decompression, apparently occurs in three different steps, approximately at 0.2, 1.2 and 2 GPa. In addition, the magnitude of the intrusion appears to be comparable with that observed for synthetic zeolites as SiO2-ferrierite [2] or AlPO4-5 [3] and this is somehow unexpected if we consider that the studied erionite is a natural sample, with structural cavities largely filled by extra-framework cations and H2O molecules. Further experiments, with different classes of potentially penetrating fluids, will allow to fully understand and constrain the P-induced adsorption phenomena in natural erionite. [1] Gatta GD, Lotti P, Tabacchi G Phys. Chem. Miner. 2018 45, 115-138. [2] Lotti P, Arletti R, Gatta GD, Quartieri S, Vezzalini G, Merlini M, Dmitriev V, Hanfland M Micropor. Mesopor. Mater. 2015 218, 42-54. [3] Lotti P, Gatta GD, Comboni D, Merlini M, Pastero L, Hanfland M. Micropor. Mesopor. Mater. 2016 228, 158-167.

P-induced crystal-fluid interactions in erionite-K : a natural nano-sponge / T. Battiston, F. Pagliaro, P. Lotti, G.D. Gatta, B. Joseph. ((Intervento presentato al 49. convegno Meeting of the Italian Crystallographic Association (AIC) tenutosi a Parma nel 2021.

P-induced crystal-fluid interactions in erionite-K : a natural nano-sponge

T. Battiston;F. Pagliaro;P. Lotti;G.D. Gatta;
2021-09-07

Abstract

The study of the high-pressure behaviour of microporous compounds, e.g. zeolites, experienced, in last decades, a raising interest related to the P-mediated intrusion of solvated ions/molecules, from the so-called “penetrating” P-transmitting fluids into the zeolitic structural voids [1]. These phenomena may occur when the molecules have a kinetic diameter that allow their adsorption into the structural cavities and may be potentially exploited in the tailoring of functional materials. In this study, we have investigated the P¬-mediated intrusion of H2O and alcohols molecules, carried by the P¬-transmitting fluids, into the structural cavities of the natural zeolite erionite-K, by means of in situ high-pressure single-crystal synchrotron X-ray diffraction, using a diamond anvil cell, at the Xpress beamline of the Elettra synchrotron (Trieste, Italy). Erionites are a series of minerals belonging to the zeolite group, with a wide chemical variability expressed as solid solution among three end-members: erionite-Ca, erionite-K and erionite-Na. The samples we analysed are classified as erionite-K, with an average chemical formula: K2.31Na0.02Ca2.15Mg0.69Ba0.04Sr0.02(Al9.00Si27.19)O72·18.66H2O. The erionite-type framework is based on the repetition of six-membered rings with a sequence AABAAC. This stacking leads to a structure characterized by the presence of large cages (23-hedron, called “erionite-cage”), superposed along the c-axis, hosting most of the extra-framework population. To constrain the crystal-fluid interaction, we performed two high-P ramps using different P-transmitting media: 1) with the non-penetrating silicone oil, up to 2.60(5) GPa, and 2) with the potentially penetrating methanol:ethanol:H2O = 16:3:1 (hereafter mew) mixture, up to 4.97(5) GPa. Silicone oil data allowed the refinement of the isothermal bulk modulus of the pristine sample, expressed as KV0 = 44(1) GPa (βV0 = KV0-1 = 0.0227(5) GPa-1, where βV0 is the bulk volume compressibility), after a fit of a II-order Birch-Murnaghan equation of state to the experimental P-V data. The P-V data from the mew ramp unambiguously show a marked decrease in compressibility, which is unequivocally related to the P-induced intrusion of H2O (and possibly alcohols) molecules from the P-transmitting fluid. This phenomenon, which appears to be irreversible in decompression, apparently occurs in three different steps, approximately at 0.2, 1.2 and 2 GPa. In addition, the magnitude of the intrusion appears to be comparable with that observed for synthetic zeolites as SiO2-ferrierite [2] or AlPO4-5 [3] and this is somehow unexpected if we consider that the studied erionite is a natural sample, with structural cavities largely filled by extra-framework cations and H2O molecules. Further experiments, with different classes of potentially penetrating fluids, will allow to fully understand and constrain the P-induced adsorption phenomena in natural erionite. [1] Gatta GD, Lotti P, Tabacchi G Phys. Chem. Miner. 2018 45, 115-138. [2] Lotti P, Arletti R, Gatta GD, Quartieri S, Vezzalini G, Merlini M, Dmitriev V, Hanfland M Micropor. Mesopor. Mater. 2015 218, 42-54. [3] Lotti P, Gatta GD, Comboni D, Merlini M, Pastero L, Hanfland M. Micropor. Mesopor. Mater. 2016 228, 158-167.
erionite; pressure; molecules intrusion; zeolite; microporous; synchrotron XRD
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
Settore GEO/06 - Mineralogia
Italian Crystallographic Association (AIC)
P-induced crystal-fluid interactions in erionite-K : a natural nano-sponge / T. Battiston, F. Pagliaro, P. Lotti, G.D. Gatta, B. Joseph. ((Intervento presentato al 49. convegno Meeting of the Italian Crystallographic Association (AIC) tenutosi a Parma nel 2021.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/871723
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