Phase separation in hydrated LTA zeolite

Ishikawa, Atsushi; Sakurazawa, Yosuke; Shindo, Junpei; Shimada, Momoe; Ishimaru, Taisuke; Ishikawa, Shigeru; Sasane, Akinobu

doi:10.1016/j.micromeso.2004.10.006

Cited by 3 publications

(6 citation statements)

References 29 publications

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“…There is, moreover, ample evidence for phase separations within a miscibility gap. For example, the phase separation of FAU type zeolite single crystals into large and small frameworks can be observed indi- (Ishikawa, et al, 2005). This occurs when ions with large ionic radius are exchanged for e.g., Na þ to induce cracks within the crystals (Olson & Sherry, 1968).…”

Section: Discussionmentioning

confidence: 99%

“…100 Å ) layer repeat of domain lath sections normal to a flat crystal face of MCM-22 that would lead to the thin sections containing the c-axis. Phase-separated FAU and KFI frameworks (Ishikawa, et al, 2005, Olson & Sherry, 1968, Albert & Cheetham, 2000 tend to contain large domains of a given framework size and are not layered. Aluminum enrichment in ZSM-5 occurs at the crystal rims (Ballmoos & Meier, 1981), not as bands through the crystal and normal to any unit cell axis.…”

Section: Discussionmentioning

confidence: 99%

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Electron crystallography of MWW zeolites – filling the missing cone

Dorset¹,

Roth²

2011

Zeitschrift Für Kristallographie

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Given that many zeolites crystallize in habits that lead to preferred orientation, and that there is a AE60 tilt limitation in many electron microscope goniometer stages, collection of a three 3-D electron diffraction data set from these materials is severely restricted. To overcome this, preparative measures must be taken to produce other sample orientations. Using a number of MWW framework zeolites (MCM-22, MCM-22P, MCM-49, ITQ-1) as examples, thin-sectioned views onto the edge stacking of lamellar layers can be prepared by a number of methods. While ultamicrotomy is a traditional approach to this problem, sections are often very thick and sparsely distributed. Other extreme mechanical processing techniques, such as extrusion and jet milling produce numerous thin crystals with the desired orientation. Dealumination, initiated by steaming, calcination or low pH, also yields a similar result. Additional intensity data from the 'missing cone' in addition to those obtained by tilting hexagonal plate crystals provides a more complete data set and hence a more easily interpreted structure analysis. Crystallographic phase determination by maximum entropy and likelihood, followed by Fourier refinement, yields a structural model very close to that of the known MWW framework.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Electron crystallography of MWW zeolites – filling the missing cone

Dorset¹,

Roth²

2011

Zeitschrift Für Kristallographie

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“…Recently, a new type of spinodal phase separation induced by ion-exchange was reported [24] reported in the reference [24]. )…”

Section: Introductionmentioning

confidence: 99%

“…The biphasic zeolite has a unique property [24,25]. When the biphasic zeolite was formed by Li ion exchange, 7 Li isotopes 5 moved to the aqueous phase as tetrahydrate [Li(OH 2 ) 4 ] + , whereas 6 Li isotopes were left in the six-membered oxygen rings of the biphasic zeolite with two hydrated water molecules of the [Li 0.08 (NH 4 ) 0.92 ]A and [Li 0.33 (NH 4 ) 0.67 ]A hydrates.…”

Section: Introductionmentioning

confidence: 99%

Chromatographic formation of a triadic band of lithium in hydrated LTA zeolite: An investigation on lithium isotope separation effects by ion exchange

Ishikawa

Sasaki

Narita

et al. 2017

Microporous and Mesoporous Materials

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Lithium concentrations [Li] and isotopic ratios [ 7 Li]/[ 6 Li] were measured for effluent fractions from a biphasic zeolite column. The biphasic state was ascribed to a mixture of hydrated Linde Type A (LTA) zeolites, [Li 0.08 (NH 4) 0.92 ]A and [Li 0.33 (NH 4) 0.67 ]A, which were formed by Li ion exchange from hydrated ammonium in the form (NH 4) 12 [Al 12 Si 12 O 48 ]•nH 2 O (NH 4 A). The biphasic Li band of the column was displaced by ion exchange with a solution of NH 4 NO 3. A constant [Li] with a much lower level than the concentration of NH 4 + in the displacer (NH 4 NO 3) was observed for the effluent from a short column. This constant lower level of [Li] was attributable to the biphasic state. On this [Li] plateau of the effluent, the level of [ 7 Li] shifted higher than the original isotopic composition of the Li feed, whereas 6 Li was concentrated on the biphasic zeolite solid. The accumulation of 6 Li in the zeolite proceeded by a mechanism of differential 3 elution of 7 Li from the biphasic zeolite. For the long column experiment, a significant enrichment of 6 Li in the zeolite was observed, whereby a triadic band of Li was probably formed in the column. Two monophasic and a biphasic state were assigned. The biphasic band was deemed to push the monophasic bands forward, thereby enriching the monophasic bands with 7 Li, while 6 Li accumulated at the end of the biphasic band. The trio structure of the Li band and isotopic discrimination in the band were analyzed.

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“…This waste is composed predominantly of kaolinite, and its use as a source of silicon and aluminum in the synthesis of zeolites, including zeolite A, has become technologically feasible [4][5][6] . Zeolite A is a hydrated aluminum silicate composed of alkali metals and alkaline earths that has porous characteristics favorable to the production of ultramarine pigments [7][8][9][10][11][12][13][14][15] . The crystal structure of this zeolite allows for a cleaner production process because its sulfur gas emissions are almost zero.…”

Section: Introductionmentioning

confidence: 99%

Color and shade parameters of ultramarine zeolitic pigments synthesized from kaolin waste

et al. 2014

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Ultramarine pigments were successful synthesized from zeolite A obtained from kaolin waste. This waste has been used as an excellent source of silicon and aluminum for zeolite synthesis because of its high kaolinite concentrations and low contents of other accessory minerals. The cost is naturally less than the industrialized product. Color additives (Sulfur and Sodium Carbonate) were mixed with different proportions of zeolite A and further calcined for 5 h at 500 °C. They were characterized by XRD and XRF in addition to visual classification by color and shade. These products show colors from blue to green at different shades, both influenced by the amount of additives and cooling rate after calcination. Thus, a different quantity of the same additives in the same zeolitic matrix provides an increase in the color intensity. Cooling rate after calcination induces the color change which is substantially important in the pigments production.

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Phase separation in hydrated LTA zeolite

Cited by 3 publications

References 29 publications

Electron crystallography of MWW zeolites – filling the missing cone

Electron crystallography of MWW zeolites – filling the missing cone

Chromatographic formation of a triadic band of lithium in hydrated LTA zeolite: An investigation on lithium isotope separation effects by ion exchange

Color and shade parameters of ultramarine zeolitic pigments synthesized from kaolin waste

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