Chromic acid dealumination of zeolites

Babić, Viktoria; Koneti, Siddardha; Moldovan, Simona; Debost, Maxime; Gilson, Jean‐Pierre; Valtchev, Valentin

doi:10.1016/j.micromeso.2021.111513

Cited by 9 publications

(19 citation statements)

References 32 publications

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“…103,107 For example, Valtchev and co-workers recently reported the mild dealumination of zeolites with chromic acid. 114 The Si/Al ratio of 9.0 of the parent CHA zeolite was increased to 9.4 and further to 10.5, while the Si/Al ratio of the MFI zeolite was increased to 21 from 19. During the mild dealumination, the framework was well preserved and Brönsted acid sites (BASs) was preserved and their accessibility was increased.…”

Section: "Top-down" Tuning the Si/al Ratios Of Zeolitesmentioning

confidence: 95%

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

Gao

2023

Chem. Sci.

104

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Section: "Top-down" Tuning the Si/al Ratios Of Zeolitesmentioning

confidence: 95%

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

Gao

2023

Chem. Sci.

104

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“…www.advsustainsys.com 29 Si MAS NMR spectra of nanosized CHA samples and the corresponding percentage of different Q n species (n = number of Si atoms surrounding a SiO 4 tetrahedron) are presented in Figure 2, Figures S2 and S4a, and Table S2 (Supporting Information). All samples display five distinct resonances at −89, −94, −99, −104, and −109 ppm corresponding to the five crystallographic SiO 4 sites coordinated by either Al 3+ or hydroxyl groups assigned to Q 0-4 species.…”

Section: Resultsmentioning

confidence: 99%

“…were employed to leach out Al from different zeolite structures. [ 26–30 ] Yet, dealumination with acids leads to significant structural and porosity losses. [ 31 ]…”

Section: Introductionmentioning

confidence: 99%

“…were employed to leach out Al from different zeolite structures. [26][27][28][29][30] Yet, dealumination with acids leads to significant structural and porosity losses. [31] In this work, we report a new hydrothermal postsynthetic treatment consisting of a concurrent silylation and In this work, a new post-synthetic hydrothermal approach leading to simultaneous dealumination and silylation of zeolite nanocrystals is presented.…”

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confidence: 99%

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Altering the Atomic Order in Nanosized CHA Zeolites by Postsynthetic Silylation Treatment

Ghojavand

Dib

Riodent

et al. 2023

Advanced Sustainable Systems

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In this work, a new post‐synthetic hydrothermal approach leading to simultaneous dealumination and silylation of zeolite nanocrystals is presented. Starting from a nanosized chabazite (CHA) type zeolite with a Si/Al ratio equal to 2, a set of samples with Si/Al ratios up to 4 are obtained by altering the acidity and concentration of the added silica modifier during the post‐synthesis treatment leading to concurrent dealumination and silylation. The effect of the acidity during the post‐synthetic silylation treatment at different pH of 1.0–8.5 at a constant silicon concentration is investigated. The nanosized CHA samples are characterized in details by Fourier transform infrared spectroscopy and NMR spectroscopy (1H, 29Si, 27Al), X‐ray diffraction, and thermogravimetric analyses. The post‐synthesis approach reported here can be applied to other zeolite types for fine‐tuning of their structural features including type and location of T‐atoms, silanol sites, and active sites.

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“…On the contrary, the cationic surfactant, CTAB, slowed down the sedimentation of zeolite particles, but the effect was mild. The EDX analysis of the dried powders collected after sedimentation tests shows that charged species, such as the added polyelectrolytes, may also change the ion balance (Si/Al/Na ratios) of the zeolites (Table S2), which indicates the partial dissolution of the zeolites in use. , Low molecular weight PVP addition resulted in the sedimentation of all particles in almost 2 h (Figure S6), while PEG addition could postpone this up to 11 h (Figure a).…”

Section: Resultsmentioning

confidence: 99%

Colloidal Stabilization of Submicron-Sized Zeolite NaA in Ethanol–Water Mixtures for Nanostructuring into Thin Films and Nanofibers

et al. 2022

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Despite the growing use of organic or mixed solvents in zeolite processing, most studies focus only on aqueous suspension systems. We investigated the colloidal characteristics of submicron-sized zeolite NaA in mixed ethanol−water solvents. The effects of the mixing ratio of solvents and various additives on the dispersion of the zeolite powders were studied. The zeolite NaA particles were destabilized in solvent mixtures at a high ethanol-to-water ratio, a reduction in the zeta potential was observed, and the destabilization was rationalized by the Derjaguin, Landau, Verwey, Overbeek (DLVO) theory. An improved stabilization of the zeolite NaA suspensions was achieved in ethanol-rich solvent mixtures using nonionic low molecular weight organic additives, but not with their ionic counterparts such as anionic, cationic surfactants or inorganic acids or bases. Polyethylene glycol (PEG)-400 was found to be a good dispersant for the submicron-sized zeolite NaA particles in the ethanol−water mixtures, which was attributed to its interaction with the zeolite surface, leading to an increased zeta potential. The PEG-stabilized zeolite suspensions led to low suspension viscosities as well as uniform and consistent spin-coated films.

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Chromic acid dealumination of zeolites

Cited by 9 publications

References 32 publications

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

Regulation of the Si/Al ratios and Al distributions of zeolites and their impact on properties

Altering the Atomic Order in Nanosized CHA Zeolites by Postsynthetic Silylation Treatment

Colloidal Stabilization of Submicron-Sized Zeolite NaA in Ethanol–Water Mixtures for Nanostructuring into Thin Films and Nanofibers

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