Mild dealumination of template-stabilized zeolites by NH<sub>4</sub>F

Bolshakov, Aleksei; Hidalgo, Douglas E. Romero; Mezari, Brahim; Hoof, Arno J. F. van; Hensen, Emiel J. M.

doi:10.1039/c9cy00593e

Cited by 18 publications

(12 citation statements)

References 41 publications

(57 reference statements)

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“…Such a type of dissolution is most probably due to the diffusion limitation of water-soluble fluoride anions through the pores of SSZ-13. This was also observed in the work of Bolshakov et al while treating ZSM-5 with NH 4 F solution [43].…”

supporting

confidence: 76%

Preparation of hierarchical SSZ-13 by NH4F etching

Babić

Koneti

Moldovan

et al. 2021

Microporous and Mesoporous Materials

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supporting

confidence: 76%

Preparation of hierarchical SSZ-13 by NH4F etching

Babić

Koneti

Moldovan

et al. 2021

Microporous and Mesoporous Materials

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“…Several reports have shown that controlled hydrothermal treatment in ammonium fluoride solution is a versatile strategy to lower both the surface Si/Al ratio and number of framework defects. [158,159] The NH 4 F treatment is particularly efficient for removing Al from the external surface. As a result, the zeolite materials treated with NH 4 F display a significant improvement of the framework stability.…”

Section: Process Intensification and Regeneration Stabilitymentioning

confidence: 99%

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

2020

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strong C-H bonds complicates the selective conversion of methane to higher hydrocarbons and oxygenates. Currently, the main industrial method to use methane as a material feedstock involves the transformation to syngas by steam reforming, followed by processes such as methanol synthesis and Fischer-Tropsch synthesis to obtain liquid fuels and other useful chemicals. A disadvantage of this indirect technology is the high capital cost of reforming plants, making it only economically attractive at a very large scale. An efficient direct process for the conversion of methane to higher hydrocarbons or oxygenates remains one of the "holy grails" of chemistry. [6,7] The approaches to directly convert methane can be categorized into oxidative and non-oxidative methods. Oxidative processes are often met with low product selectivity because of the higher reactivity of targeted products as compared to methane itself, resulting in overoxidation to CO 2. Non-oxidative methods are generally more atom-efficient, because, in addition to valuable hydrocarbon products, pure CO xfree hydrogen gas (H 2) is obtained, which can be used for instance in fuel cells. [8] Among several alternatives, including non-oxidative coupling of methane to ethylene and deep methane dehydrogenation to solid carbon and hydrogen, [9-12] methane dehydroaromatization (MDA) remains one of the most promising non-oxidative reactions for the direct valorization of natural gas. MDA involves the selective conversion of methane to a mixture of easily transportable aromatics, that is, benzene (predominantly), naphthalene, and toluene. As all other non-oxidative methane conversion reactions, MDA is a highly endothermic process: 6CH C H 9H 532 kJ mol Non-oxidative dehydroaromatization is arguably the most promising process for the direct upgrading of cheap and abundant methane to liquid hydrocarbons. This reaction has not been commercialized yet because of the suboptimal activity and swift deactivation of benchmark Mo-zeolite catalysts. This progress report represents an elaboration on the recent developments in understanding of zeolite-based catalytic materials for high-temperature non-oxidative dehydroaromatization of methane. It is specifically focused on recent studies, relevant to the materials chemistry and elucidating i) the structure of active species in working catalysts; ii) the complex molecular pathways underlying the mechanism of selective conversion of methane to benzene; iii) structure, evolution and role of coke species; and iv) process intensification strategies to improve the deactivation resistance and overall performance of the catalysts. Finally, unsolved challenges in this field of research are outlined and an outlook is provided on promising directions toward improving the activity, stability, and selectivity of methane dehydroaromatization catalysts.

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“…In the processing of hydrocarbons, the importance of mesoporosity was recognized, − ,,,, and specifically, high mesoporosity is intrinsic for the processing of large molecules such as polyoleffins, ,,, biomass, and VGO. , It was reported that hierarchical ZSM-5 prepared by using organosilanes as a mesopore-directing agent and desilication treatment with alkali exhibited the higher yield of C2–C5 hydrocarbons and the lower deactivation rate due to their secondary porosity in catalytic cracking of low-density polyethylene (LDPE). LDPE was also rapidly cracked in the presence of hierarchical ZSM-5 in the experiment using a TG apparatus .…”

Section: Results and Discussionmentioning

confidence: 99%

“…On the other hand, recent catalytic cracking is aimed to obtain light olefins of ethylene and propylene, raw materials for petrochemical products, as main products, which makes the process more important. , Zeolites and matrices are usually included in catalysts of catalytic cracking, and their types and ratios significantly have influence on conversion and product selectivity. Many catalysts for catalytic cracking have been developed; however, the improvement of zeolites is often aimed. − Although matrices have not been referred in many cases, − ,− it is known that there have been many positive effects with the use of matrices, for example, weakening zeolite acidity and activity, diffusing not only reactants but also products on the inside of catalysts, increasing the stability of catalysts, maintaining pore structure of zeolites, increasing heat transfer during catalysis and regeneration, etc. We have already reported the preparation and reactivity of many new types of matrices for catalytic cracking.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Catalytic Cracking of Vacuum Gas Oil by a Y Zeolite-Containing Two-Layered Catalyst and a Novel Three-Layered Hierarchical Catalyst Using a Curie Point Pyrolyzer Method

et al. 2020

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A Y zeolite-containing two-layered catalyst and a novel three-layered hierarchical catalyst were prepared using a template and the gel skeletal reinforcement (GSR) method. Initially, two-layered catalysts were prepared by the sol–gel method using malic acid as the template in the presence of HY zeolite (HYZ). The two-layered hierarchical catalyst, 2L(S-HYZ), consisted of 50 wt % the mesoporous part of silica (S) and 50 wt % the microporous part of HYZ. The three-layered hierarchical catalyst, 3L(GSR-S)2L(S-HYZ), was made by GSR silica (GSR-S) production in the presence of 2L(S-HYZ) where silica gel particles including 2L(S-HYZ) inside were reinforced by a reinforcing solution of hexamethyldisiloxane–acetic anhydride before aging and successive calcination and consisted of 50 wt % large-mesoporous GSR-S and 50 wt % the 2L(S-HYZ) hierarchical catalyst. It was confirmed by XRD and N2 adsorption and desorption measurement that this catalyst possessed three characters of microporous zeolite crystals, small mesoporous silica, and large mesoporous silica. Catalytic cracking of vacuum gas oil over these hierarchical catalysts was performed using a Curie point pyrolyzer method. 3L(GSR-S)2L(S-HYZ)(Z25), which included 25 wt % HYZ, exhibited the highest activity. Further, it was proposed that the activity could be related to not only the amount of acid sites but also the size of mesoporous pore volume.

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Mild dealumination of template-stabilized zeolites by NH₄F

Abstract: A novel method to remove aluminium from the framework of as-synthesized zeolite crystals is presented.

Cited by 18 publications

References 41 publications

Preparation of hierarchical SSZ-13 by NH4F etching

Preparation of hierarchical SSZ-13 by NH4F etching

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Estimation of Catalytic Cracking of Vacuum Gas Oil by a Y Zeolite-Containing Two-Layered Catalyst and a Novel Three-Layered Hierarchical Catalyst Using a Curie Point Pyrolyzer Method

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Mild dealumination of template-stabilized zeolites by NH4F

Abstract: A novel method to remove aluminium from the framework of as-synthesized zeolite crystals is presented.

Cited by 18 publications

References 41 publications

Preparation of hierarchical SSZ-13 by NH4F etching

Preparation of hierarchical SSZ-13 by NH4F etching

Reactivity, Selectivity, and Stability of Zeolite‐Based Catalysts for Methane Dehydroaromatization

Estimation of Catalytic Cracking of Vacuum Gas Oil by a Y Zeolite-Containing Two-Layered Catalyst and a Novel Three-Layered Hierarchical Catalyst Using a Curie Point Pyrolyzer Method

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Mild dealumination of template-stabilized zeolites by NH₄F