29Si and 27Al n.m.r. study of steamed faujasites — evidence for non-framework tetrahedrally bound aluminium

Ray, G. Joseph; Meyers, B.L.; Marshall, Christopher L.

doi:10.1016/0144-2449(87)90032-7

Cited by 79 publications

(31 citation statements)

References 15 publications

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“…In the 3‐day sample, the 27 Al shows a broad distribution of signal intensity centered around 61 ppm. The signal at 61 ppm can be attributed to 4‐coordinate 27 Al sites, which are 27 Al species that are incorporated into tetrahedral bonding networks . As time elapsed, a narrowing of the signal peak width is observed, indicating a narrower distribution of 27 Al sites, consistent with the long‐range order observed by XRD, and a small shift in the position by approximately 2 ppm to higher frequency is observed.…”

Section: Resultssupporting

confidence: 59%

Relationship between aqueous chemistry and composition, structure, and solubility of sodium aluminosilicate hydrates

et al. 2019

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Inorganic polymer binders (IPBs) are synthesized by the activation of aluminosilicate precursors with an alkaline solution such as sodium hydroxide. This paper studies the relationship between the composition, structure, and solubility of sodium aluminosilicate hydrates (N–A–S–(H)), the primary binding phase in IPBs. It was found that changing the aqueous Si/Al ratio had little effect on N–A–S–(H) Si/Al ratio, but small changes in the aqueous Si/Na ratio led to substantial changes in N–A–S–(H) Si/Al ratio. Early N–A–S–(H) products were found to be X‐ray amorphous, but a rapid transition to the crystalline phase faujasite occurred after several weeks of aging. The transition of the solid amorphous phase to faujasite was accompanied by a rapid drop in aqueous Si(IV) and Al(III) concentrations. Solubility products were determined, temporally, for the N–A–S–(H) before and after the transition to faujasite and represent new contributions to the literature, particularly for the amorphous state. The results presented here provide fundamental insights that are needed for the development of kinetic and thermodynamic models that can establish phase balances and evolutions of IPBs across a range of precursor compositions and synthesis conditions.

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Section: Resultssupporting

confidence: 59%

Relationship between aqueous chemistry and composition, structure, and solubility of sodium aluminosilicate hydrates

et al. 2019

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“…However, this analysis rules out this hypothesis and confirms that the peak shifts are real. These peak shifts to higher 2 θ values are well-described in the literature and indicate a shift towards a smaller d-spacing and reduced unit cell parameters of the zeolite, as a result of partial zeolite dealumination 14. As a consequence of this dealumination process, the zeolite experiences a loss in Brønsted acidity, which is one of the main causes of catalyst deactivation 15.…”

supporting

confidence: 70%

Correlating Metal Poisoning with Zeolite Deactivation in an Individual Catalyst Particle by Chemical and Phase‐Sensitive X‐ray Microscopy

et al. 2013

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Fluid catalytic cracking (FCC) is the main conversion process used in oil refineries. An X‐ray microscopy method is used to show that metal poisoning and related structural changes in the zeolite active material lead to a non‐uniform core–shell deactivation of FCC catalyst particles. The study links the detrimental effect of V and Ni poisoning with zeolite destruction and dealumination in a spatial manner within a single FCC catalyst particle.

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“…Dealumination itself cannot be responsible for this effect because silicate ions migrate quickly into the newly created Al vacancies inside the USY framework [21,22]. Some observations in the present work and in previous studies by means of 29 Si MAS NMR, XRD and IR spectroscopy [10] as well as energy-dispersive X-ray diffraction (EDXRD) measurements [23] give evidence to a partial amorphization of the zeolite Y crystals under action of steam.…”

Section: Formation Of Mesoporessupporting

confidence: 59%

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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29Si and 27Al n.m.r. study of steamed faujasites — evidence for non-framework tetrahedrally bound aluminium

Cited by 79 publications

References 15 publications

Relationship between aqueous chemistry and composition, structure, and solubility of sodium aluminosilicate hydrates

Relationship between aqueous chemistry and composition, structure, and solubility of sodium aluminosilicate hydrates

Correlating Metal Poisoning with Zeolite Deactivation in an Individual Catalyst Particle by Chemical and Phase‐Sensitive X‐ray Microscopy

Formation of Mesopores in USY Zeolites: A Case Revisited

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