Where Does the Zeolite ZSM-5 Nucleation and Growth Start? The Effect of Aluminum

Li, Teng; Krumeich, Frank; Bokhoven, Jeroen A. van

doi:10.1021/acs.cgd.9b00304

Cited by 25 publications

(29 citation statements)

References 30 publications

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“…97,98 The formation of aluminosilicate zeolites at the rim of the NPs has been attributed to the higher alumina concentration in contact with the solution. 35 To our knowledge, the possibility of heterogeneous nucleation of the zeolite by the amorphous− solution interface has not been considered, although heterogeneous nucleation at fluid interfaces has been reported for other crystals. 99−102 To assess the possibility that the amorphous−solution interface promotes the nucleation of the zeolite, we investigate the nucleation of the zeolite from compositionally homogeneous amorphous mixtures of T and S with water at temperatures above the glass transition.…”

Section: Methodsmentioning

confidence: 98%

“…Experimental studies indicate that zeolites preferably form at the rim of the amorphous NPs in solution. 35,97,98 It has been interpreted that the preference for nucleation at the particle surface could arise from higher mobility of the silica and SDA at the solution interface, which would favor the structural reorganization of the silica network needed to nucleate the zeolite from the glassy mixture. 97,98 The formation of aluminosilicate zeolites at the rim of the NPs has been attributed to the higher alumina concentration in contact with the solution.…”

Section: Methodsmentioning

confidence: 99%

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Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

2021

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Zeolites are the most used solid catalysts in the chemical industry. The hydrothermal synthesis of these porous aluminosilicate crystals is a multistep process that involves the polymerization of silica from solution to form amorphous aggregates, their crystallization, growth by oriented attachment, and eventually dehydration by heating. The molecular pathways by which zeolites are formed from the precursor solution are not yet fully understood. Molecular simulations can play an important role in elucidating these microscopic processes but are limited by the lack of models able to represent both the polymerization of silica and its crystallization with feasible computational costs. Here, we present a simple, computationally efficient coarse-grained model for the hydrothermal synthesis of zeolites from aqueous solutions. Our TS + W model has three components: silica, a structure-directing agent, and water, each represented by a single particle with short-range interactions. The model quantitatively reproduces the experimental evolution of silica species during the polymerization from solution, yielding amorphous nanoparticles with shape, composition, and silica speciation in agreement with the amorphous precursors of zeolites in experiments. Importantly, the TS + W model spontaneously nucleates and grows zeolites from the amorphous precursor phase and reproduces the temperature required for their dehydration. Our simulations indicate that the preferential formation of zeolites at the amorphous–water interface does not arise from an ability of that surface to heterogeneously nucleate the zeolite. The simplicity and computational efficiency of the TS + W model make it ideal to investigate the interplay between polymerization and crystallization in zeolite synthesis.

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Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

2021

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“…Valtchev et al indicated that in the synthesis of zeolite A the nucleation was associated with the gel composition, which happens at the borderline among the solution and the solid gel [20]. Li et al showed that the crystallization of nanoscale crystals of ZSM-5 may be controlled by homogeneous nucleation and the primary growth of whole particles [21]. The initial gel composition such as Si/Al molar ratio, structure, and concentration of organic template agent, alkali metal concentration, pH, and water content may be changed by the nucleation and crystal growth rates which modify the final zeolite morphologies [22].…”

Section: Introductionmentioning

confidence: 99%

Structural Effects of HZSM‐5 Zeolite on Methanol‐to‐Propylene Reaction

et al. 2020

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ZSM‐5 zeolite was synthesized using n‐butylamine as a template under hydrothermal conditions. The morphology of the prepared zeolites was changed with the initial gel composition. The influences of OH−/template and H2O/template ratios on the morphology, mesoporosity, acid properties, and crystal size of the synthesized zeolites were evaluated, also the structural effects of the prepared zeolites on the catalytic performances of the methanol‐to‐propylene process. Increasing the external surface area and mesopore volume of the catalysts improved the propylene selectivity. A direct relationship between the deactivation of catalysts and their acidic properties was found. The results were derived from laboratory data and need to be re‐examined on a larger scale to ensure their accuracy on an industrial scale.

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“…The Mobil-type five (MFI) zeolites, ZSM-5, with elaborate micropores have found uses in a broad range of application as catalysts and adsorbents in the chemical industry owing to their high shape-elective performance and outstanding catalytic activity. − However, the microporous structure intrinsically limits the path of diffusion of sizeable molecular reactants and products in the zeolite phase. , It has long been established that the scaling down of the size of zeolite particles to the nanoscale is considered to be an effective approach to optimize the performance of zeolites in catalytic and sorption applications, owing to the shorter diffusion path lengths, which provides more exposed acidic sites and increases the external surface area . In general, ZSM-5 nanocrystals are produced with autogenous pressure via a hydrothermal method, this methodology requires strict synthesis conditions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of ZSM-5 Microspheres Made of Nanocrystals from Iron Ore Tailings by the Solid-Phase Conversion Method

Zhang

Guo

et al. 2020

Langmuir

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ZSM-5 microspheres made of nanocrystals are successfully synthesized from iron ore tailings (IOTs) using a novel and environmentally friendly method, which have a well-defined microporous and mesoporous structure with a large surface area and high acidic strength. In the absence of the liquid water phase during the solidphase conversion, the phase separation between the surfactant and the solid silica phase is able to be bypassed. Compared to conventional methods, such as hydrothermal and steam-assisted conversion methods, this approach enhances the utilization of autoclaves, considerably reduces pollutants, and simplifies the synthetic process, which saves both energy and time. Furthermore, the crystallization of ZSM-5 microspheres via the solid-phase conversion was examined at 413, 433, and 453 K. The results of the kinetic study suggest that the experimental values obtained conform to those of the nonlinear regression model of Kolmogorov−Johnson−Mehl−Avrami for crystallization and nucleation. For the induction, transition, and crystallization stages, the activation energies are 70.96, 39.76, and 36.23 kJ•mol −1 , respectively. The new method is economical and offers a valuable industrially applicable route for the reuse of IOTs to synthesize ZSM-5 microspheres. This synthetic concept could also be expanded to obtain other types of mesoporous zeolites.

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Where Does the Zeolite ZSM-5 Nucleation and Growth Start? The Effect of Aluminum

Cited by 25 publications

References 30 publications

Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

Structural Effects of HZSM‐5 Zeolite on Methanol‐to‐Propylene Reaction

Synthesis of ZSM-5 Microspheres Made of Nanocrystals from Iron Ore Tailings by the Solid-Phase Conversion Method

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