Zeolite Chemistry II. The Role of Aluminum in the Hydrothermal Treatment of Ammonium-Exchanged Zeolite Y, Stabilization

Breck, D. W.; Skeels, G.W.

doi:10.1021/bk-1977-0040.ch023

Cited by 141 publications

(191 citation statements)

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“…Examples include the AMO 3 perovskites, viewed as a framework of cornersharing MO 6 octahedra with interstitial A ions, and the dense framework silicates such as quartz, with their framework of corner-sharing SiO 4 tetrahedra. The zeolites [1] -a broad group of framework minerals whose cornersharing tetrahedral aluminosilicate frameworks contain cages, pores and channels large enough to contain not only ions but also H 2 O and other small molecules-are of particular interest in chemical industries [2,3] as molecular sieves, shape-selective catalysts and ion-exchange materials.…”

Section: Copyright C Epla 2011mentioning

confidence: 99%

Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Wells¹,

Sartbaeva²,

Gatta³

2011

EPL

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The analcime-like feldspathoids are a group of microporous minerals with the ANA framework topology. Analcime proper has predominantly Na as its channel cation content, while leucite contains predominantly K, pollucite contains Cs and wairakite contains Ca. Under compression, all these minerals display structural displacive phase transitions to low-symmetry forms at relatively low pressures (0.5-3.2 GPa). We show, using geometric simulation, that these phase transitions are controlled by the "flexibility window" of the ANA framework, defined as the range of framework densities over which the tetrahedral units of the framework can in principle be made geometrically ideal. We discuss experimental compression data for these minerals and its relationship to the theoretical flexibility of the ANA framework, the influence of cation content, and framework ordering.

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Section: Copyright C Epla 2011mentioning

confidence: 99%

Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Wells¹,

Sartbaeva²,

Gatta³

2011

EPL

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“…These applications make use of the unique physicochemical properties of zeolites, including selective ionic exchange, catalysis, and related molecular sieve properties. 3 For this reason, a number of experimental and theoretical studies have been carried out in recent years to investigate the structural and thermal properties of zeolites. [4][5][6][7][8] These studies reveal that the unusual framework topology of zeolites allows for "negative" thermal and mechanical behaviors.…”

Section: Introductionmentioning

confidence: 99%

Brillouin scattering study on the single-crystal elastic properties of natrolite and analcime zeolites

Sanchez-Valle

Sinogeikin

Lethbridge

et al. 2005

Journal of Applied Physics

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The Brillouin light-scattering technique was used to investigate the single-crystal elastic properties of two aluminosilicate zeolites, natrolite ͑NAT͒ and analcime ͑ANA͒, at ambient conditions. An inversion of the acoustic velocity data results in the full set of elastic stiffness moduli ͑C ij 's͒ for both materials. From the single-crystal moduli the aggregate adiabatic bulk moduli ͑K s ͒, shear moduli ͑G͒, and Poisson's ratios ͑ ͒ were found to be K s = 48.5͑1.0͒ GPa, G = 31.6͑1.0͒ GPa, and = 0.232͑5͒ for NAT, and K s = 59.8͑1.2͒ GPa, G = 32.1͑1.0͒ GPa, and = 0.272͑5͒ for ANA ͑Voigt-Reuss-Hill averages͒. The bulk and shear moduli of both zeolites are relatively low compared with those of densely packed aluminosilicates, reflecting an open framework structure of ͑Al, SiO 4 ͒ tetrahedra which is easily deformed by bending the Si-O-Al angles. As expected for a less dense crystal, NAT is softer and more compressible than ANA. An evaluation of the directional Young's moduli shows that the compressibility of NAT is nearly uniform along the ͓100͔ and ͓010͔ axes, while ͓001͔ is stiffer, in agreement with previous compression studies. We do not find experimental evidence of negative Poisson's ratios for NAT zeolites as predicted by recent theoretical calculations.

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“…The following equation was used to calculate the upper bound line according to Robeson's work: 3 where n ) d j -d i where d j is the kinetic diameter of the lower permeability gas and d i is the kinetic diameter of the higher permeability gas. The kinetic diameters as reported by Breck 28 are listed in Table 5. The exact position of the upper bound line was chosen from the best data of Park et al 2 For the O 2 /N 2 gas pair, poly-(tetrabromofluorene tetrabutyl isophthalate) gives the Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Enhancement in the Gas Permeabilities of Novel Polysulfones with Pendant 4-Trimethylsilyl-α-hydroxylbenzyl Substituents

et al. 2003

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A series of modified polymers with 4-trimethylsilyl-R-hydroxylbenzyl (HBTMS) substituents were made as new materials for membrane gas separation. HBTMS was introduced onto polysulfone (PSf), tetramethylpolysulfone (TMPSf), and hexafluoropolysulfone (6FPSf) by forming lithiated polymer intermediates followed by treatment with an electrophile, p-trimethylsilylbenzaldehyde. The resulting side substituent contains the bulky trimethylsilyl (TMS) groups separated from the polymer chain by an aromatic ring. The polymer structures were characterized by NMR spectroscopy, and thermal properties were investigated by differential scanning calorimetry and thermogravimetry. The permeability coefficients of the resulting polymers PSf-HBTMS, TMPSf-HBTMS, and 6FPSf-HBTMS showed considerable increases over the unmodified polymers. TMPSf-HBTMS showed the greatest improvements in gas transport properties with large increases in both CO 2 and O2 permeabilities of ∼3-fold (72 and 18 Barrers, respectively) compared with TMPSf. In the case of the CO2/N2 gas pair, there was an absence of the typical accompanying tradeoff shown by decreases in permselectivity with increasing permeability. Comparisons of this series of polymers containing the new HBTMS substituent were made with those having other TMS pendant groups.

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Zeolite Chemistry II. The Role of Aluminum in the Hydrothermal Treatment of Ammonium-Exchanged Zeolite Y, Stabilization

Cited by 141 publications

References 0 publications

Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Flexibility windows and phase transitions of ordered and disordered ANA framework zeolites

Brillouin scattering study on the single-crystal elastic properties of natrolite and analcime zeolites

Enhancement in the Gas Permeabilities of Novel Polysulfones with Pendant 4-Trimethylsilyl-α-hydroxylbenzyl Substituents

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