Flexibility of ideal zeolite frameworks

Kapko, Vitaliy; Dawson, Colby; Treacy, M.M.J.; Thorpe, M. F.

doi:10.1039/c003977b

Cited by 88 publications

(130 citation statements)

References 26 publications

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“…We stress that it is not obvious a priori that this idealisation should be possible at all. Indeed, we found, and subsequent research has confirmed [8,9], that this flexibility window phenomenon is almost universal in all known zeolites, with only a single known exception (framework GOO, goosecreekite), but is very uncommon in hypothetical structures. This immediately suggests that the existence of a flexibility window in a hypothetical structure is one of the missing criteria for the selection of good candidates for synthesis.…”

Section: Flexibility Windowmentioning

confidence: 89%

Framework flexibility and rational design of new zeolites for catalysis

Sartbaeva

Wells

2012

Appl Petrochem Res

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Zeolite materials have proved very useful as chemical catalysts and the search for new zeolite structures with novel channel and pore shapes is ongoing. We discuss a geometric feature of zeolite frameworks, the flexibility window, which may provide a criterion to identify hypothetical structures which can be synthesised as zeolites. In recent research using data on zeolite frameworks under compression, we show strong links between this geometric feature and the physics of zeolite frameworks.

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Section: Flexibility Windowmentioning

confidence: 89%

Framework flexibility and rational design of new zeolites for catalysis

Sartbaeva

Wells

2012

Appl Petrochem Res

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“…[12,42,43] It emerges that, first, actually existing real (natural or synthetic) zeolites can indeed attain ideal geometry when modelled as silica in geometric simulations. Second, this can be done over a range of densities; limits arise on expansion from extension of SiZO bonds, and in compression from steric collisions of oxygen atoms on adjacent tetrahedra ('codimeric' oxygens).…”

Section: The Flexibility Window In Zeolitesmentioning

confidence: 99%

GASP: software for geometric simulations of flexibility in polyhedral and molecular framework structures

Wells

Sartbaeva

2015

Molecular Simulation

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Template-based geometric simulation is a specialised method for modelling flexible framework structures made up of rigid units using a simplified, localised physical model. The strengths of the method are its ability to handle large all-atom structural models rapidly and at minimal computational expense, and to provide insights into the links between local bonding and steric geometry and global flexibility. We review the implementation of geometric simulation in the 'GASP' software, and its application to the study of materials including zeolites, perovskites and metal -organic frameworks. The latest version (5) of GASP has significant improvements and extensions, in particular an improved algorithm for relaxation of atomic positions, and the capacity to handle both polyhedral and molecular structural units. GASP is freely available to researchers.

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“…Every zeolite topology exhibits a flexibility window as theoretically demonstrated by Kapko and co-workers. [21] It was observed that gas molecules with a Lennard-Jones diameter larger than the time-averaged narrow sodalite windows can diffuse through the sodalite zeolite due to framework flexibility. [22,23] Also the 5 flexibility of any bulky reaction intermediate implies a significant increase in conformational degrees of freedom that should be appropriately accounted for.…”

mentioning

confidence: 99%

Complex Reaction Environments and Competing Reaction Mechanisms in Zeolite Catalysis: Insights from Advanced Molecular Dynamics

Wispelaere

Ensing

Ghysels

et al. 2015

Chemistry A European J

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The methanol to olefins process is a show case example of complex zeolite-catalyzed chemistry. At real operating conditions, many factors such as framework flexibility, adsorption of various guest molecules and competitive reaction pathways, affect reactivity. In this paper we show the strength of first principle molecular dynamics techniques to capture this complexity by means of two case studies. Firstly, the adsorption behavior of methanol and water in H-SAPO-34 at 350 °C is investigated. Hereby we observed an important degree of framework flexibility and proton mobility. Secondly, we studied the methylation of benzene by methanol via a competitive direct and stepwise pathway in the AFI topology. Both case studies clearly show that a first principle molecular dynamics approach enables to obtain unprecedented insights into zeolite-catalyzed reactions at the nanometer scale.Keywords: ab initio calculations, molecular dynamics, proton mobility, methylation, zeolites 3 IntroductionChemical conversions in zeolites play an essential role in today's industrial catalysis. [1][2][3] Within the field of heterogeneous catalysis, the conversion of methanol to hydrocarbons (MTH) or olefins (MTO) over acidic zeolites received a lot of attention during the last decades, due to its relevance in the search for alternative processes to produce hydrocarbon products. [4][5][6][7] The MTO process has experimentally been developed in the past 3-4 decades and is currently being industrialized. [5] Methanol can be obtained from coal, natural gas or biomass and is in turn converted into ethene, propene or other hydrocarbons. The process proved extremely difficult to unravel at the nanoscale level due to various factors such as pressure, temperature and the occurrence of competing reaction mechanisms, which highly influence the catalytic performance of the system. Due to its complexity, it is a very challenging case study for theoretical modeling studies. [8] Currently, there is a consensus that a hydrocarbon pool (HP) mechanism operates during the methanol conversion process. Herein, an organic center is trapped in the zeolite pores and acts as co-catalyst. [9][10][11] The HP may be of aromatic or aliphatic nature and the two corresponding types of catalytic cycles are in close connection with each other, a concept that is called the dual cycle. [12] Depending on the catalyst topology and operating conditions either one or both cycles may be responsible for olefin formation during the methanol conversion process. [12][13][14] Theoretical contributions have proven to be indispensable within MTO research.Methodological developments and a steady increase in computer power, contributed to the fact that many properties, in particular rate coefficients of well-defined elementary reactions, are now routinely calculated with high accuracy. [8,[15][16][17] However, theoretical chemists are still confronted with paramount challenges to thoroughly explain experimental observations. The true challenge lies in linking the model system wit...

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Flexibility of ideal zeolite frameworks

Cited by 88 publications

References 26 publications

Framework flexibility and rational design of new zeolites for catalysis

Framework flexibility and rational design of new zeolites for catalysis

GASP: software for geometric simulations of flexibility in polyhedral and molecular framework structures

Complex Reaction Environments and Competing Reaction Mechanisms in Zeolite Catalysis: Insights from Advanced Molecular Dynamics

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