Characterization of the textural properties of dealuminated HY forms

Lynch, John P.; Raatz, F.; Dufresne, P.

doi:10.1016/0144-2449(87)90036-4

Cited by 145 publications

(74 citation statements)

References 15 publications

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“…Similar zeolite morphology was observed earlier by Lynch et al who reported on a secondary pore system without direct connection to the exterior of the crystals in the steamed and, particularly, in acid leached USY samples [8]. The scheme given in Fig.…”

Section: Introductionsupporting

confidence: 69%

Formation of Mesopores in USY Zeolites: A Case Revisited

Lutz¹,

Kurzhals²,

Kryukova³

et al. 2010

Zeitschrift anorg allge chemie

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Steaming of NH4Y zeolite at 723 K and 873 K is accompanied by the formation of extra‐framework amorphous aluminosilicate and silica gel in addition to earlier observed extra‐framework aluminum species. Their occurrence is directly associated with the formation of mesopores. Bulk (intracrystalline) mesopores occur inside the crystallite nuclei and surface (intercrystalline) mesopores are located nearby the crystallite surface. Corrosion of the zeolite framework results in a loss of crystallinity and, consequently, decreased catalytic activity of the USY catalysts synthesized. Analysis of the reasons of mesopore formation may help to reduce these disadvantages.

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Section: Introductionsupporting

confidence: 69%

Formation of Mesopores in USY Zeolites: A Case Revisited

Lutz¹,

Kurzhals²,

Kryukova³

et al. 2010

Zeitschrift anorg allge chemie

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“…At our laboratory a methodology has been developed that is based on the analysis by scanning-transmission electron microscopy (STEM) of thin foils of the solids obtained by ultramicrotomy, in conjunction with the other conventional techniques of characterization. This approach has been applied successfully to different types of finely divided materials in the field of heterogeneous catalysis (Lynch et al, 1987;Szymanski et al, 1987;Toulhoat et al, 1987). In the present paper, the advantage of this approach is illustrated for investigating the synthesis of Al-rich HTs by coprecipitation methods in the Zn-A1 system.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of Al-Rich Zn-Al Hydrotalcite-Like Compounds

Thévenot

Szymanski

Chaumette

1989

Clays and clay miner.

111

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Abstract--Hydrotalcite-like compounds, described by the formula [Zn, xAlx(OH)2] [(CO3)x/2 9 nHzO], were prepared by coprecipitation methods at 80~ and characterized by bulk chemical analysis, X-ray powder diffraction (XRD), nuclear magnetic resonance (NMR), and scanning-transmission electron microscopy (STEM). An x value of 0.33 was previously assumed to be an upper limit, but recently, Al-rich hydrotalcitelike compounds have been prepared with x as large as 0.44 by hydrothermal synthesis. In the Zn-Al system, #p-rich hydrotalcite was synthesized at normal pressure by coprecipitation. Zn-#P hydrotalcitelike compounds were obtained in the range of x = 0.3 to 0.4. An #P-rich hydrotalcite-like compound with x = 0.44 was formed in mixtures containing large amounts of a poorly crystalline Zn-A1 phase. A continuous contraction of the hydrotalcite-like structure occurred as x increased, both the a and c lattice parameters decreasing for x values as large as 0.44. This study illustrates the advantages of using quantitative analytical electron microscopy with high spatial resolution to complement conventional (and bulk) characterization techniques for correlating structural and compositional characteristics of finely divided materials.

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“…Dealumination is known to occur when zeolites are subjected to acid treatments [23,24]. To investigate this effect, silicon magnetic resonance was conducted on a number of the samples.…”

Section: Resultsmentioning

confidence: 99%

Electrochemically controlled ion exchange: proton ion exchange with sodium zeolite X and A

Stephenson

Attfield

Holmes

et al. 2015

J Solid State Electrochem

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Structural characterisation of proton-exchanged zeolites, prepared using ion-transfer at the liquid-liquid interface, is reported. Specifically, electrochemical exchange of protons for sodium with zeolites X and A is described: the structural integrity of the resultant materials was probed by solid-state NMR spectroscopy and temperature-dependent powder X-ray diffraction. It is shown that replacement of ca. 40 % of the Na + can be achieved using this approach for both zeolites; however, the results indicate that exchange is accompanied by significant structural degradation in the case of zeolite A, with proton exchange occurring at the amorphous regions of the sample. In contrast, zeolite X retains its structure, and the level of proton exchange is comparable with the highest levels reported using conventional chemical methods, highlighting the utility of the electrochemical approach.

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Characterization of the textural properties of dealuminated HY forms

Cited by 145 publications

References 15 publications

Formation of Mesopores in USY Zeolites: A Case Revisited

Formation of Mesopores in USY Zeolites: A Case Revisited

Preparation and Characterization of Al-Rich Zn-Al Hydrotalcite-Like Compounds

Electrochemically controlled ion exchange: proton ion exchange with sodium zeolite X and A

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