Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Hemelsoet, Karen; Nollet, A.J.H.; Speybroeck, Véronique Van; Waroquier, Michel

doi:10.1002/chem.201100920

Cited by 40 publications

(36 citation statements)

References 94 publications

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“…164 These values overestimate the experimentally reported values of À270 and À316 cm À1 , 165 but the relative trend is in good agreement. For example, calculated frequency shifts of the isostructural H-SAPO-34 and H-SSZ-13 were shown to indicate the enhanced acidity of the alumino silicate material.…”

Section: Infrared Spectroscopymentioning

confidence: 70%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

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Zeolites are versatile and fascinating materials which are vital for a wide range of industries, due to their unique structural and chemical properties, which are the basis of applications in gas separation, ion exchange and catalysis. Given their economic impact, there is a powerful incentive for smart design of new materials with enhanced functionalities to obtain the best material for a given application. Over the last decades, theoretical modeling has matured to a level that model guided design has become within reach. Major hurdles have been overcome to reach this point and almost all contemporary methods in computational materials chemistry are actively used in the field of modeling zeolite chemistry and applications. Integration of complementary modeling approaches is necessary to obtain reliable predictions and rationalizations from theory. A close synergy between experimentalists and theoreticians has led to a deep understanding of the complexity of the system at hand, but also allowed the identification of shortcomings in current theoretical approaches. Inspired by the importance of zeolite characterization which can now be performed at the single atom and single molecule level from experiment, computational spectroscopy has grown in importance in the last decade. In this review most of the currently available modeling tools are introduced and illustrated on the most challenging problems in zeolite science. Directions for future model developments will be given.

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Section: Infrared Spectroscopymentioning

confidence: 70%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

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“…For completeness, we calculated dispersion corrections according to both the D2-scheme, 44 as used in our previous work, 11,12,91 and the more recent D3-version. 37 Overall, only minor differences were found between the two approaches.…”

Section: Zeolite Models and Computational Methodsmentioning

confidence: 99%

Efficient Approach for the Computational Study of Alcohol and Nitrile Adsorption in H-ZSM-5

et al. 2012

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Since many industrially important processes start with the adsorption of guest molecules inside the pores of an acidic zeolite catalyst, a proper estimate of the adsorption enthalpy is of paramount importance. In this contribution, we report ab initio calculations on the adsorption of water, alcohols, and nitriles at the bridging Brønsted sites of H-ZSM-5, using both cluster and periodic models to account for the zeolite environment. Stabilization of the adsorption complexes results from hydrogen bonding between the guest molecule and the framework, as well as from embedding, i.e., van der Waals interactions with the pore walls. Large-cluster calculations with different DFT methods, in particular B3LYP(-D), PBE(-D), M062X(-D), and ωB97X-D, are tested for their ability to reproduce the experimental heats of adsorption available in the literature (J. Phys. Chem. B 1997, 101, 3811−3817). A proper account of dispersion interactions is found to be crucial to describe the experimental trend across a series of adsorbates of increasing size, i.e., an increase in adsorption enthalpy by 10−15 kJ/mol for each additional carbon atom. The extended-cluster model is shown to offer an attractive alternative to periodic simulations on the entire H-ZSM-5 unit cell, resulting in virtually identical final adsorption enthalpies. Comparing calculated stretch frequencies of the zeolite acid sites and the adsorbate functional groups with experimental IR data additionally confirms that the cluster approach provides an appropriate representation of the adsorption complexes.

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“…57 In earlier work adsorption energies for methanol adsorption in H-SAPO-34 using static theoretical methods have been reported, which are in the same order of magnitude as our dynamically obtained results. 79 To the best of our knowledge, no experimentally measured adsorption enthalpies for methanol in H-SAPO-34 have been reported. Figure 1a.…”

Section: Competition Between Water and Methanolmentioning

confidence: 97%

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

et al. 2016

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The role of water in the methanol-to-olefins (MTO) process over H- has been elucidated by a combined theoretical and experimental approach, encompassing advanced molecular dynamics simulations and in-situ micro-spectroscopy. First principle calculations at the molecular level point out that water competes with methanol and propene for direct access to the Brønsted acid sites. This results in less efficient activation of these molecules, which are crucial for the formation of the hydrocarbon pool. Furthermore, lower intrinsic methanol reactivity towards methoxide formation has been observed. These observations are in line with a longer induction period observed from in-situ UV-Vis micro-spectroscopy experiments. These experiments revealed a slower and more homogeneous discoloration of H-SAPO-34, while insitu confocal fluorescence microscopy confirmed the more homogeneous distribution and larger amount of MTO intermediates when co-feeding water. As such it is show that water induces a more efficient use of the H-SAPO-34 catalyst crystals at the microscopic level. The combined experimental theoretical approach gives a profound insight into the role of water on the catalytic process at the molecular and single particle level.

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Theoretical Simulations Elucidate the Role of Naphthalenic Species during Methanol Conversion within H‐SAPO‐34

Cited by 40 publications

References 94 publications

Advances in theory and their application within the field of zeolite chemistry

Advances in theory and their application within the field of zeolite chemistry

Efficient Approach for the Computational Study of Alcohol and Nitrile Adsorption in H-ZSM-5

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

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