Zeolite Molecular Sieve 4A: Anomalous Compressibility and Volume Discontinuities at High Pressure

Abstract

Unit cell parameters of synthetic zeolite 4A were measured at several pressures to 40 kilobars with both water and an alcohol mixture as hydrostatic pressure media. Compression in water was normal, with no observed phase transitions. Compression in alcohols was twice as great as in water, and three volume discontinuities were observed. These volume changes in alcohol were rapid with increasing pressure but sluggish in reverse. High-pressure "phases," all of which are dimensionally cubic, are progressively more compressible at high pressure. These unusual high-pressure phenomena, which indicate significant interactions between zeolite 4A and the hydrostatic media, are consistent with differences in zeolite adsorption of water alcohols.

Zeolites at high pressure: A review

“…zeolite Na-A, Hazen, 1983;Hazen and Finger, 1984). The first structure-refinements that showed, unambiguously, the P-induced ''overhydration effect'' in natrolite and ''natrolite-like'' materials (i.e.…”

“…Its framework shows strong structural homologies with that of sodalite. The elastic behaviour of this zeolite was first studied by Hazen (1983) and Hazen and Finger (1984) by in situ single-crystal diffraction up to 4 GPa using both penetrating and non-penetrating P-media. The authors observed a significantly different compressional behaviour of this zeolite in response to the molecular size of the P-transmitting medium: the compressibility was higher when non-penetrating P-media were used.…”

Pressure induced phase transformations in NaZr2(PO4)3 studied by X-ray diffraction and Raman spectroscopy

“…This occurs due to distortion of polyhedral network without bond breaking but only altering their bond angles with greater change in large cation cavity [14]. Compounds with such polyhedral links including silica polymorphs [15][16][17][18], LiCsSO 4 [19], NaTiPO 5 and related compounds [20,21], perovskites [22][23][24], feldspars [25], zeolites [26][27][28] have been extensively studied experimentally to understand their structural behavior at high pressures. For example, the principal compression mechanism in the structure of KTiPO 5 with corner linked TiO 6 octahedra and PO 4 tetrahedra under pressure are changes in polyhedral angles and coordination environment of K atom [29].…”

Pressure-induced hydration and cation migration in a Cs+ exchanged gallosilicate zeolite LTL: Synchrotron X-ray powder diffraction study at ambient and high pressures

“…The chemistry of these confined species, coupled with the confinement geometry, play an important role in determining catalytic, ion exchange and molecular sieving properties [1]. To alter the chemistry and geometry of a given framework, cation substitution and temperature effect have been applied extensively [2][3][4][5], while pressure effect has been limited to measuring compressibilities and investigating structural amorphizations [6,7]. Recently, however, interests in exploring the high pressure chemistry of zeolites have expanded in both experimental and theoretical studies and demonstrated how a zeolitic framework responds to applied hydrostatic pressure and how this can regulate the zeolitic water content, cation distribution, and selectivity toward foreign species [8][9][10][11].…”