Theoretical studies of Na+ location in ZSM-5: Model selection for accurate coordination structure and energetics

Chu, Zhen-Kun; Fu, Gang; Xu, Xin

doi:10.1016/j.cattod.2010.12.043

Cited by 7 publications

(21 citation statements)

References 79 publications

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“…Previously, we have examined the basis set effects and found that B3LYP − in conjunction with 6-31G* − was able to give a reliable coordination structure and relative stability sequence for different Na-sites for the T1 Al-site . Hence, in our present ONIOM calculations, B3LYP/6-31G* is used as the high-level method.…”

Section: Computational Methods and Modelsmentioning

confidence: 99%

“…A 75T cluster model was found to provide a reliable local geometry and stability sequence for all four probable Na-sites for the T1 Al-site. On the basis of this finding, a general scheme to set up suitable cluster models for metal cation location calculations in zeolites was proposed, where so-called C-5-type models can be constructed by allowing all atoms on the rings around the Al-site to relax during the geometry optimization and then expanding the region by another three shells of Si atoms . Such C-5-type models will serve as guidelines in this study to investigate various Na-sites associated with all 12 distinct Al-sites in ZSM-5.…”

Section: Introductionmentioning

confidence: 99%

“…It has to be emphasized that quantum chemical calculations by using the C-5-type models are computationally very demanding. At the level of B3LYP/6-31G*, a geometry optimization job for the C-5-type models for the T1 Al-site (75T) usually requires more than 20 days on a modern dual-quad-core PC server . The sizes of the C-5-type models for other Al-sites are even larger (e.g., 146T for the T12 Al-site; see the Supporting Information for details).…”

Section: Introductionmentioning

confidence: 99%

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Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Chu

傅刚

et al. 2011

J. Phys. Chem. C

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There exist 12 crystallographically distinct Al-sites in the ZSM-5 zeolite, associated with which there are various Na-sites. Understanding their locations, while being the key to the understanding of the catalytic properties of this material, remains a great challenge in both experiment and theory. We present here a theoretical survey of the Na(+) location along with the Al distribution in ZSM-5 by using hybrid methods, ONIOM (our Own N-layer Integrated molecular Orbital molecular Mechanics) as well as the newly developed extended ONIOM (XO) (Guo, W. P.; Wu, A. A.; Xu, X. Chem. Phys. Lett. 2010, 498, 203-208) method. The reliability and efficiency of different methods/models have been systematically tested. Using the T1 Al-site as an example, our calculations demonstrate that the high-level layers of ONIOM models have to include all rings around the [AlO(4)] tetrahedron to have reliable coordination structures and energetics of different Na-sites, while XO can provide reliable results with 60% savings of computational time as compared to that of ONIOM. Our XO calculations reveal that, in most Al-sites, Na(+) preferentially occupies the six-membered-ring sites, and the most favorable Al-sites along with the Na-sites are T8/M6, T10/Z6, and T4/Z6. Conversely, those Al-sites only surrounded by five-membered rings, such as T6 and T3, are predicted to be energetically unfavorable.National Natural Science Foundation of China[10774126, 20923004]; Ministry of Science and Technology[2007CB815206, 2011CB808504

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Section: Computational Methods and Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Chu

傅刚

et al. 2011

J. Phys. Chem. C

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“…Besides, it is worth mentioning that there are also rapid advancements for the other metal exchanged zeolites. By virtue of ONIOM method, Xu and coworkers pointed out that Na + ions mostly occupy the six‐membered‐ring sites after testing 12 distinct Al sites in ZSM‐5 zeolites with various of Na + locations. Rice et al published a series of papers investigating the location, structure, stability, and coordination of divalent cations (Cu, Ni, Co, Pt, Zn, etc.)…”

Section: Theoretical Investigation Of the Zeolite Structures And Its mentioning

confidence: 99%

Theoretical investigation of NH₃‐SCR processes over zeolites: A review

Mao

Wang

2014

Int J of Quantum Chemistry

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The selective catalytic reduction (SCR) of NO x compounds with NH 3 is a hot topic in recent years. Among various catalysts, zeolites are proved to be efficient and promising for NH 3 -SCR, yet the whole processes and intrinsic mechanism are still not well understood due to the structural complexity of zeolites. With the improvement of theoretical chemistry techniques, quantum-chemical calculations are now capable of modeling the structure, acidity, adsorption, and ultimately reaction pathways over zeolites to some extent. In this review, a brief summary of relevant concepts of NH 3 -SCR is presented. Cluster approaches, embedded techniques, and periodic treatments are described as three main methods. Details of quantum-chemical investigations toward the key issues such as, the structure of active sites, the adsorption of small molecules, and the reaction mechanism of NH 3 -SCR over zeolites are discussed. Finally, a perspective for future theoretical research is given. V C 2014 Wiley Periodicals, Inc.

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“…19) that would appear to have a too large value of DH 0 when compared to Na-FER. This is likely due to the fact that Na + cations located at the intersection of two 10-member ring channels in ZSM-5 148,149 have a low coordination with framework oxygen atoms, which leaves the Na + ion wide open for coordination with the incoming H 2 molecule. Finally, it should be noted that both, the small size of the dihydrogen molecule and the T-shape of its adsorption complexes with alkali and alkaline-earth cations, render such a molecule unable to bridge two extra-framework cations in zeolites.…”

Section: Hydrogen Adsorption On Alkaline Zeolitesmentioning

confidence: 99%

The nature of cationic adsorption sites in alkaline zeolites—single, dual and multiple cation sites

Nachtigall

Delgado

Nachtigallová

et al. 2012

Phys. Chem. Chem. Phys.

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Gas adsorption on zeolites constitutes the base of many technological applications of these versatile porous materials. Quite often, especially when dealing with small molecules, individual extra-framework (exchangeable) cations are considered to be the adsorption site on which molecules coming from a gas phase form the corresponding adsorption complex. Nonetheless, while that can be the case in some instances, recent research work that combines variable temperature infrared spectroscopy with periodic DFT calculations showed that some types of adsorption sites involve two or more cations, which constitute dual and multiple cation sites, respectively. Adsorption complexes formed on these cationic adsorption sites differ in both structure and stability from those formed on a single cation alone. Examples concerning CO, CO(2) and H(2) adsorption on alkali and alkaline-earth metal exchanged zeolites are reviewed, with the double purpose of clarifying concepts and highlighting their relevance to practical use of zeolites in such fields as gas separation and purification, gas storage and heterogeneous catalysis.

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Theoretical studies of Na+ location in ZSM-5: Model selection for accurate coordination structure and energetics

Cited by 7 publications

References 79 publications

Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Theoretical investigation of NH₃‐SCR processes over zeolites: A review

The nature of cationic adsorption sites in alkaline zeolites—single, dual and multiple cation sites

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Theoretical studies of Na+ location in ZSM-5: Model selection for accurate coordination structure and energetics

Cited by 7 publications

References 79 publications

Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Exploring the Sodium Cation Location and Aluminum Distribution in ZSM-5: A Systematic Study by the Extended ONIOM (XO) Method

Theoretical investigation of NH3‐SCR processes over zeolites: A review

The nature of cationic adsorption sites in alkaline zeolites—single, dual and multiple cation sites

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Theoretical investigation of NH₃‐SCR processes over zeolites: A review