Fluoride etching of AlZSM-5 and GaZSM-5 zeolites

Todorova, Totka; Shestakova, Pavletta; Petrova, Tanya; Popova, Margarita; Lazarova, Hristina; Kalvachev, Yuri

doi:10.1007/s10853-020-05030-6

Cited by 8 publications

(6 citation statements)

References 59 publications

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“…The solution was prepared from 18 mL 0.25 mol/L HF acid, 18 g NH 4 F, and 18 g H 2 O, to which 0.3 g of well-dispersed mordenite crystals were added. The so-obtained mixture was stirred for 20 min at 25 °C and then followed by filtration, washing, and drying at 80 °C [ 52 ]. Platinum, palladium, and copper were impregnated on both ZSM-5 materials (initial and acid treated analogues) by incipient wetness technique.…”

Section: Methodsmentioning

confidence: 99%

“…By impregnation of Zr over hierarchical mordenite crystals, we obtained catalysts with higher catalytic activity in glycerol esterification with acetic acid and selectivity to valuable triacylglycerol [ 51 ]. The structural and morphological changes of Al and Ga analogues of ZSM-5 as a result of HF 2 − treatment were also monitored in reaction of m-xylene transformation [ 52 ].…”

Section: Introductionmentioning

confidence: 99%

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Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

2021

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In order to obtain highly active catalytic materials for oxidation of carbon monoxide and volatile organic compounds (VOCs), monometallic platinum, copper, and palladium catalysts were prepared by using of two types of ZSM-5 zeolite as supports—parent ZSM-5 and the same one treated by HF and NH4F buffer solution. The catalyst samples, obtained by loading of platinum, palladium, and copper on ZSM-5 zeolite treated using HF and NH4F buffer solution, were more active in the reaction of CO and benzene oxidation compared with catalyst samples containing untreated zeolite. The presence of secondary mesoporosity played a positive role in increasing the catalytic activity due to improved reactant diffusion. The only exception was the copper catalysts in the reaction of CO oxidation, in which case the catalyst, based on untreated ZSM-5 zeolite, was more active. In this specific case, the key role is played by the oxidative state of copper species loaded on the ZSM-5 zeolites.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

2021

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“…Similarly, hierarchical structures of ZSM-5 zeolite can be produced by chemically etching with HF and NH 4 F mixed solution. [43][44][45] After treatment, the hierarchical zeolite's relative crystallinity decreases, while its external surface area and mesoporous volume increase. The micropore surface area, volume, and acidity remain relatively unchanged.…”

Section: Simultaneous Extraction Of Silicon and Aluminum By Nh 4 Fmentioning

confidence: 99%

“…This treatment extracts similar amounts of silicon and aluminum elements from the zeolite structure, providing secondary accessibility to active sites. Similarly, hierarchical structures of ZSM‐5 zeolite can be produced by chemically etching with HF and NH 4 F mixed solution [43–45] . After treatment, the hierarchical zeolite‘s relative crystallinity decreases, while its external surface area and mesoporous volume increase.…”

Section: Simultaneous Extraction Of Silicon and Aluminum By Nh4fmentioning

confidence: 99%

Methods for Preparing Hierarchical Zeolites by Chemical Etching and Their Catalytic Applications: A Review

et al. 2023

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Zeolites are widely used in petrochemical processes and refineries due to their well‐ordered microporous network and large surface area. However, the diffusion of reactants and products is hampered by the narrow microporous channels, causing limitations. To overcome this challenge, modifying the pore structure is crucial, and the chemical etching technique is a powerful tool that introduces mesopores and macropores, consequently enhancing mass transfer and accessibility. Diverse chemical etching methods have been invented, including exposure to both acids (organic/inorganic acids), alkali (organic/inorganic alkali), and neutral etchants (e. g., ammonium fluoride). This review summarizes and assesses the chemical etching methods and their relevance to catalytic cracking reactions, methanol to hydrocarbons (MTH), and biomass conversion. The potential of zeolites with modified pore structures has motivated researchers to develop novel methods to tackle the practical challenges associated with their applications.

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“…Among the methods of developing mesoporous or hierarchical zeolites, post-synthesis by dealumination attracted the majority of attention and has been established as a simple and effective approach. It is generally achieved through continuous hydrolysis of the Al–O–Si linkages by steam treatment at elevated temperatures, leaching with acids , (e.g., HCl, HNO 3 and oxalic acid), or fluoride reagents , (e.g., NH 4 F, (NH 4 ) 2 SiF 6 and HF). The removal of a certain number of hydroxylated Al or Si species from the framework leaves vacancy in the crystals and also results in a drop in both acidity and crystallinity.…”

Section: Introductionmentioning

confidence: 99%

Post-Synthesis of HZSM-5 by Aluminum Fluoride in an Acidic Fluoride Solution for Enhanced Reforming of Lignite Pyrolytic Volatiles into Light Aromatics

Liu,

Ning,

et al. 2023

Energy Fuels

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Dealumination by chemical etching with acids has been one of the most common post-treatment methods for secondary porosity engineering of zeolite but inevitably suffers from adverse impacts on its skeleton structure and acidic properties. Herein, we present a novel method to treat HZSM-5 zeolite in a buffer solution of HF/NH 4 F and employ AlF 3 as an external Al source for one-step dealumination and alumination. The as-prepared hierarchical zeolites remain with high crystallinity and acidity, while secondary mesopores are formed. A suitable loading of AlF 3 (1.0 wt %) together with a diluted buffer solution (0.1 M) is the most optimal condition, under which the mesoporous volume of HZSM-5 increases from 23 to 41% from the total volume. Under the synergetic effects of H + and F − , AlF 3 undergoes complexation, hydrolysis, and dehydration reactions and is introduced into the frameworks. The catalytic performances for reforming lignite pyrolytic volatiles into light aromatics at 600 °C showed that the AlF 3 -modified zeolites exhibited higher activity than the parent toward suppressing the coke deposition and yielding the desired products.

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Fluoride etching of AlZSM-5 and GaZSM-5 zeolites

Cited by 8 publications

References 59 publications

Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

Catalytic Oxidation of CO and Benzene over Metal Nanoparticles Loaded on Hierarchical MFI Zeolite

Methods for Preparing Hierarchical Zeolites by Chemical Etching and Their Catalytic Applications: A Review

Post-Synthesis of HZSM-5 by Aluminum Fluoride in an Acidic Fluoride Solution for Enhanced Reforming of Lignite Pyrolytic Volatiles into Light Aromatics

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