A Computational Method To Characterize Framework Aluminum in Aluminosilicates

García-Pérez, Elena; Dubbeldam, David; Liu, Bei; Smit, Berend; Calero, Sofı́a

doi:10.1002/anie.200603136

Cited by 48 publications

(54 citation statements)

References 34 publications

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“…The adsorption isotherms in both structures overlap. The original force field does not perform as well as in the reference 54 , as the calculated adsorption in FAU-type zeolites depends on the specific location of alumina atoms in the zeolite 21 , which is not provided in the reference data. The force field developed in this work provides a lower water adsorption in hydrophylic zeolites than the force field of Fuchs et al, resulting in a worse description of water adsorption in the FAU zeolite, but an excellent agreement with the LTA4A water isotherms.…”

Section: Resultsmentioning

confidence: 99%

“…Although some research groups have used a determined force field to study adsorption in different hydrophilic zeolites 19,20 , it is not clear if these force fields can reproduce the adsorption isotherms for different zeolites at different conditions. It has been shown that the adsorption calculated by molecular simulation in zeolites with non framework cations depends on the specific location of the alumina atoms in the structure 21 , which is usually unknown. In the case of the LTA4A zeolite, which has a Si/Al ratio equal to one, the location of the non-framework cations is well known.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Water adsorption in hydrophilic zeolites: experiment and simulation

Castillo

Silvestre-Albero

Rodriguez-Reinoso

et al. 2013

Phys. Chem. Chem. Phys.

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We have measured experimental adsorption isotherms of water in zeolite LTA4A, and studied the regeneration process by performing subsequent adsorption cycles after degassing at different temperatures. We observed incomplete desorption at low temperatures, and cation rearrangement at successive adsorption cycles. We also developed a new molecular simulation force field able to reproduce experimental adsorption isotherms in the range of temperatures between 273 K and 374 K. Small deviations observed at high pressures are attributed to the change of the water dipole moment at high loadings. The force field correctly describes the preferential adsorption siting of water at different pressures. We tested the influence of the zeolite structure, framework flexibility, and cation mobility when considering adsorption and diffusion of water. Finally, we performed checks on force field transferability between different hydrophilic zeolite types, concluding that classical, non-polarizable water force fields are not transferable. 2

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Water adsorption in hydrophilic zeolites: experiment and simulation

Castillo

Silvestre-Albero

Rodriguez-Reinoso

et al. 2013

Phys. Chem. Chem. Phys.

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“…This suggestion in ref 206 was followed up by Liu and co-workers. 122,123,207 Liu et al showed that, with the united-atom force field of Dubbeldam et al, 94,97 which uses a σ CH 2 O ) 3.58 Å, an excellent agreement with the experimental data could be obtained. Interestingly, this agreement could only be obtained if the model included the effect of the acid sites in FER.…”

Section: Other Zeolitesmentioning

confidence: 89%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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“…The results support the assumption that the difference between the free energy of formation of different hydrocarbons in the same zeolite is almost unaffected by the exact location-and even the presence-of acid sites; that is, freeenergy differences depend almost exclusively on zeolite topology. All computations of free energies of formation are based on free-energy differences between the molecule that is formed and a reference molecule, so simulations aimed at determining free-energy differences can use all-silica structures as excellent approximations of acid zeolites and thus avoid the complex problem 33 of having to account for the exact location-or at least the distribution-of acid sites.…”

Section: Simplification To Successmentioning

confidence: 99%

Towards a molecular understanding of shape selectivity

Smit

Maesen

2008

Nature

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505

437

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Shape selectivity is a simple concept: the transformation of reactants into products depends on how the processed molecules fit the active site of the catalyst. Nature makes abundant use of this concept, in that enzymes usually process only very few molecules, which fit their active sites. Industry has also exploited shape selectivity in zeolite catalysis for almost 50 years, yet our mechanistic understanding remains rather limited. Here we review shape selectivity in zeolite catalysis, and argue that a simple thermodynamic analysis of the molecules adsorbed inside the zeolite pores can explain which products form and guide the identification of zeolite structures that are particularly suitable for desired catalytic applications.Z eolites are microporous mineral materials that have found wide use in industry since the late 1950s, with one of their most important applications being chemical catalysis. They are particularly important as cracking catalysts in oil refining. One of their defining features-apart from being solid catalysts that are easy to recycle-is that the shape, or topology, of the internal pore structure of a zeolite can strongly affect the selectivity with which particular product molecules are formed in chemical transformations catalysed by the zeolite. Here, we will argue that this shape selectivity can be explained by very simple thermodynamic analyses that consider the impact of zeolite topology on the free energy landscape; that is, on the free energies of formation of the various molecules involved in the catalysed reactions.The analyses presented here are simple and straightforward, yet have become feasible only relatively recently as advances in molecular simulation techniques have started to provide access to the thermodynamic data underpinning them. After a short introduction of zeolites and their use as catalysts, we will therefore also briefly outline the developments in simulation capabilities that give access to the thermodynamic information crucial for our understanding of zeolite catalysis. We then show how the free-energy-landscape approach can elucidate the molecular-level mechanism(s), giving rise to shape selectivity in a number of simple yet industrially important processes. We conclude this review by outlining the crucial issues that need to be addressed to take the free-energy-landscape approach to the next stage, where the combined use of simulations and thermodynamic analysis might have profound implications for how we screen and develop zeolite-based catalysts. Zeolites as industrial catalystsZeolites are crystalline aluminosilicates with a three-dimensional framework that consists of nanometre-sized channels and cages and imparts high porosity and a large surface area to the material. The basic structural unit of all zeolite frameworks consists of a silicon or aluminium atom tetrahedrally coordinated to four oxygen atoms. Any zeolite built of silica and oxygen only is neutral, but replacing Si 41 by Al 31 creates a negative charge on the framework. All such framework ch...

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A Computational Method To Characterize Framework Aluminum in Aluminosilicates

Cited by 48 publications

References 34 publications

Water adsorption in hydrophilic zeolites: experiment and simulation

Water adsorption in hydrophilic zeolites: experiment and simulation

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Towards a molecular understanding of shape selectivity

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