Dealumination of faujasite, mazzite, and offretite with ammonium hexafluorosilicate

Chauvin, B.; Boulet, Marc; Massiani, Pascale; Fajula, François; Figuéras, F.; Courières, T. Des

doi:10.1016/0021-9517(90)90018-f

Cited by 37 publications

(4 citation statements)

References 12 publications

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“…For both structures, Al is the T 2 site, suggesting a greater stability of this site. This is in agreement with the experiental finding that dealumination is easier in T 1 than in T 2 , a greater population of Al in T 2 than in T 1 was found.…”

Section: Protonated Offretitesupporting

confidence: 93%

Cation Siting and Dynamical Properties of Zeolite Offretite from First-Principles Molecular Dynamics

et al. 1997

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We have used density functional theory, both within the local density (LDA) and generalized gradient (GGA) approximations, to study the structure, energetics, and vibrational properties of zeolite offretite in the presence of different monovalent cations (H+, Na+, K+, and Cu+). We find that the spatial locations of the most favorable cation-binding sites are similar for the different cations, being related to the minima of the electrostatic potential. However, the relative stability of the sites does depend on the nature of the counterion, as well as on the Al/Si ratio and on the mutual interactions between cations. At low Al/Si ratios, the preferred site for H+ is in the channel, where it is accessible for reaction with incoming molecules. For both Na+ and Cu+, the most stable site is within the 6-fold ring of the gmelinite cage, but for Na+, two other sites are present within a few tenths of a kilocalorie/mole from the lowest site (small site selectivity). For K+, two sites, one inside the cancrinite cage and the other near the 8-fold ring of the gmelinite cage, are very close in energy, consistent with the X-ray experiments on natural hydrated and dehydrated offretites. Dynamical simulations have been carried out for H− and Na−offretite. The vibrational spectrum of the framework agrees well with the available experiment. OH stretching frequencies calculated for a number of different H+ locations show that more “open” positions, e.g., in the channel, have higher frequencies, in agreement with experiment.

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Section: Protonated Offretitesupporting

confidence: 93%

Cation Siting and Dynamical Properties of Zeolite Offretite from First-Principles Molecular Dynamics

et al. 1997

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“…Moreover, the condensation of the Si species formed in FSAH treatment could be able to fill up vacancies created in the framework by the extraction of aluminum atoms. , It has been suggested that aluminum is removed in the form as a soluble fluoride complex, whereas the inserted species is monomolecular silicic acid, Si(OH) 4 . If a proper balance could be obtained between the rate of aluminum extraction and the rate of silicon insertion, the structural collapse could be avoided. , Clearly, the FSAH treatment present here contributes to form a Si-rich structure and a perfect framework for the zeolite. As shown in Tables S2 and S3 of the Supporting Information, both the microporosity and Si/Al molar ratio of the zeolite are improved after the FSAH treatment.…”

Section: Resultsmentioning

confidence: 99%

“…The origin of the perfect crystallinity could be, originating from the proper precursors, prepared in the FSAH treatment. FSAH could act as a source for bonding Si atoms to the defect positions while generating some extra-framework Si debris during the dealumination process. ,, …”

Section: Resultsmentioning

confidence: 99%

Hierarchical Zeolite Y with Full Crystallinity: Formation Mechanism and Catalytic Cracking Performance

Zheng

Luo

et al. 2017

Energy Fuels

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Hierarchical zeolite Y with high mesoporosity, integrate crystallinity, and hydrothermal stability is desired urgently for heavy oil conversion. Here, an approach combining steam treatment, acid treatment, and alkaline treatment approachs is reported for fabricating hierarchical zeolite Y with high mesoporosity and extraordinarily high crystallinity. A robust zeolite precursor with good crystallinity was prepared first through an acid pretreatment step using fluorosilicic and hydrochloric acids, in which the zeolite crystal could be healed by the migration of Si into the skeleton. Moreover, it was deduced that the formation of hierarchical zeolite Y with extraordinarily high crystallinity was closely related to the unique desilication mechanism. The obtained hierarchical zeolite Y showed remarkable catalytic activities, high selectivity of liquid products, and low selectivity of bottom oil in the conversion of heavy oil.

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“…However, Corma et al [34] have stated that during steam dealumination, the EF-Al species produced can block the channels such that the accessibility of n-hexane molecules to the acid sites is reduced due to diffusion restriction [19,34]. However, it has been reported that EF-Al may be positively effective [35,36], negatively effective [37,38] or dependent on the level of extracting this EF-Al species [39]. Extraction of the latter can be accomplished by acid leaching.…”

Section: Hydroisomerization Of N-hexanementioning

confidence: 99%

Platinum Loaded Dealuminated H-Mor and H-Bea Zeolites for N-Hexane Hydroconversion

Aboul-Gheit

Abdelhamid

Awadallah

2006

The International Conference on Chemical and Environmental Engi

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n-Hexane was isomerized in a micro-catalytic pulse reactor over a series of platinum loaded dealuminated H-MOR and H-BEA catalysts with various Si/Al ratios. Steaming and HCl processes were applied in the dealumination of the two zeolites. TPD data showed that H-MOR zeolite and its dealuminated samples possess higher acid sites number and strength than the corresponding H-BEA zeolite versions, whereas the dispersion of 0.35wt%Pt was higher on the latter samples. The results showed that the steam treatment inhibits the hydroisomerization activity on both zeolites due to the formation of extra-framework aluminum species in the pores of the zeolites as shown from SEM studies. However, acid leaching promotes the catalytic activity by widing the pore opening. Generally, H-BEA containing catalysts either untreated or dealuminated showed higher hydroisomerization activities than the other H-MOR containing catalysts.

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Dealumination of faujasite, mazzite, and offretite with ammonium hexafluorosilicate

Cited by 37 publications

References 12 publications

Cation Siting and Dynamical Properties of Zeolite Offretite from First-Principles Molecular Dynamics

Cation Siting and Dynamical Properties of Zeolite Offretite from First-Principles Molecular Dynamics

Hierarchical Zeolite Y with Full Crystallinity: Formation Mechanism and Catalytic Cracking Performance

Platinum Loaded Dealuminated H-Mor and H-Bea Zeolites for N-Hexane Hydroconversion

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