Hydrothermal crystallization of zeolite Y from Na2O-Fe2O3-Al2O3-SiO2-H2O system

Gao, Zi; Tian, Dake; Zhou, Ruiming

doi:10.1016/s0144-2449(88)80220-3

Cited by 20 publications

(5 citation statements)

References 2 publications

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“…9), que apenas a relação de Si/Al igual a 2 não formou zeólita Y como fase dominante. Foi mostrada a existência de uma relação específica entre o Fe, Al e Si capaz de modificar a cristalinidade desta zeólita [34]. Dessa maneira, observase na Fig.…”

Section: Caulimunclassified

Síntese de zeólita do tipo faujasita: comparação entre caulim beneficiado e caulim flint

2015

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<p>O trabalho tem como objetivo a síntese de zeólita faujasita a partir de três tipos de caulim da região amazônica: dois caulins provenientes do processo de beneficiamento de caulim para cobertura de papel e caulim duro, um caulim não processado originado da lavra do caulim. Produtos da zeolitização dos caulins mostraram a formação de zeólita do tipo faujasita. O caulim duro mostrou baixo potencial de zeolitização na relação de Si/Al igual a 2 em comparação com os caulins beneficiados, possivelmente relacionado a presença de compostos de ferro no caulim não processado. Após a remoção do ferro, novos resultados mostraram uma completa mudança quanto a formação de zeólita faujasita, passando esta para a fase mineralógica dominante.</p>

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Section: Caulimunclassified

Síntese de zeólita do tipo faujasita: comparação entre caulim beneficiado e caulim flint

2015

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“…The higher-order perturbation terms For signal assignment, the hyperfine-selective (HS) ENDOR cause deviations of the splitting of the doublets from 2n I sequence (29) (see Eq. [1]) and shift the center of the doublets (19).…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the characteristics of the orientation-selective spectra in orientationally disordered samples have not been addressed. It is expected that the ZFS interaction will introduce a significant MW p-T-p/2-t-p-t-echo RF 1 p…”

Section: Introductionmentioning

confidence: 99%

X-Band Pulsed ENDOR Study of57Fe-Substituted Sodalite— The Effect of the Zero-Field Splitting

Vardi

Bernardo

Thomann

et al. 1997

Journal of Magnetic Resonance

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“…One of the most extensively studied transition metals in the context of framework substitution has been iron. In many natural and synthetic zeolites it is found as an impurity, − and there have been numerous reports on its successful incorporation into the frameworks of zeolites and aluminophosphate molecular sieves. − In these materials the iron usually does not occupy exclusively tetrahedral (T) framework sites. It can also exist as extra-framework cations and/or as an interstitial phase of small particles located either within the zeolite pores or on its external surface. − ,, The techniques commonly used to characterize iron sites in molecular sieves and oxide catalysts include Mössbauer, UV−vis, IR, and EPR spectroscopies , and extended X-ray absorption fine structure (EXAFS). − Unambiguous assignment of the iron sites usually requires a combination of several methods.…”

Section: Introductionmentioning

confidence: 99%

Studies of Framework Iron in Zeolites by Pulsed ENDOR at 95 GHz

et al. 1996

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High frequency (95 GHz, W-band) pulsed ENDOR measurements were carried out on the 57Fe-containing zeolites: Fe-sodalite (FeSOD), Fe-L (FeLTL), Fe-mazzite (FeMAZ), and Fe-ZSM5 (FeMFI), where 57Fe(III) was introduced during synthesis. The echo-detected EPR spectra of all zeolites investigated, recorded at 1.8 K, show mainly the |−5/2〉 to |−3/2〉 EPR transition. Accordingly, the ENDOR spectra exhibit only two 57Fe ENDOR transitions at 67.8−68.8 and 39.0−39.6 MHz, corresponding to M S = −5/2 and −3/2, respectively. From these frequencies isotropic hyperfine couplings of −29.0, −29.3, −29.5, and −29.6 MHz were derived for 57FeSOD, 57FeL, 57FeMAZ, and 57FeMFI, respectively. On the basis of an earlier assignment of the g = 2 signal in FeSOD to Fe(III) in tetrahedral framework sites it is concluded that hyperfine couplings in the range −29.0 to −29.6 MHz are characteristic of 57Fe(III) in zeolite frameworks. In contrast to the X-band 57Fe ENDOR signals, the W-band signals are free from second- and third-order contributions of the hyperfine and zero-field splitting (ZFS) interactions and are thus significantly simpler to assign and interpret. The ZFS contributions caused excessive inhomogeneous broadening of the X-band ENDOR spectra of 57FeL, 57FeMAz, and 57FeMFI and the detection of the ENDOR spectra was practically impossible: All zeolites studied exhibited ENDOR signals from 27Al and 57FeSOD showed also clear 23Na ENDOR signals. The hyperfine interaction of the 23Na was significantly larger than that of the 27Al, confirming the assignment of the Fe(III) to framework sites, substituting for Al. Moreover, the value obtained for the 23Na anisotropic hyperfine component, 0.53 MHz, corresponding to a distance of 3.4 Å, is in good a agreement with the known structure of sodalite where the distance between a framework atom and the Na+ cations in the center of the six rings is 3.35 Å. This work demonstrates the power and potential of high-field ENDOR in terms of resolution, signal assignment, and spectral analysis.

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Hydrothermal crystallization of zeolite Y from Na2O-Fe2O3-Al2O3-SiO2-H2O system

Cited by 20 publications

References 2 publications

Síntese de zeólita do tipo faujasita: comparação entre caulim beneficiado e caulim flint

Síntese de zeólita do tipo faujasita: comparação entre caulim beneficiado e caulim flint

X-Band Pulsed ENDOR Study of57Fe-Substituted Sodalite— The Effect of the Zero-Field Splitting

Studies of Framework Iron in Zeolites by Pulsed ENDOR at 95 GHz

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