DFT study of Li+ and Na+ positions in mordenites and hydration stability

Vilhena, Felipe S.; Serra, Ramiro Marcelo; Boix, Alicia Viviana; Ferreira, Gláucio B.; Carneiro, José Walkimar de M.

doi:10.1016/j.comptc.2016.07.017

Cited by 17 publications

(6 citation statements)

References 28 publications

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“…Water has two roles in zeolites: (a) completing the coordination of available cations inside the zeolite channels which increases their mobility and (b) minimizing the electrostatic repulsion of the bridging oxygen in the zeolite framework. , Moreover, the Al content in the zeolite framework controls the amount of adsorbed water because by decreasing the Si/Al ratio, the hydrophilicity of zeolite increases . Understanding the influence of water on the behavior of zeolites or, in other words, the hydrophilicity of zeolites, can be enhanced by comparing the differences between dehydrated and hydrated states of a zeolite system.…”

Section: Discussionmentioning

confidence: 99%

Molecular Modeling of Univalent Cation Exchange in Zeolite N

Murthy

Khosravi

2018

J. Phys. Chem. C

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Molecular dynamics simulations are used to investigate the hydration energy and ion-exchange properties of a synthetic zeolite, zeolite N with composition |K10(H2O)8Cl2|[Al12Si12O40]. The exchange of K+ ions with univalent ions such as NH4 +, Na+, Rb+, and Cs+ is investigated under a range of simulation conditions using a three-dimensional membrane in an electrolyte box containing explicit water molecules. Hydration energy calculations indicate that zeolite N prefers eight water molecules per cage, which is consistent with X-ray and neutron diffraction determination of the structure. Ion density profiles and calculated self-diffusion coefficients show that univalent ion exchange by zeolite N is selective toward NH4 + in preference to other ions. The methodology used here to simulate the uptake of ions from an electrolyte within the zeolite N membrane produces results that are consistent with experimental data and implements a low computational overhead.

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Section: Discussionmentioning

confidence: 99%

Molecular Modeling of Univalent Cation Exchange in Zeolite N

Murthy

Khosravi

2018

J. Phys. Chem. C

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“…Results show that the bimetallic catalysts (AgFeMOR, FeAgMOR, and mAgFeMOR), prepared at both T a and T 60 reach a maximum of NO conversion (about 70-90%) in the temperature range of 300-475 • C (Figure 5b,d), meanwhile, AgMOR and FeMOR monometallic catalysts (both T a and T 60 ) presented much less activity, about 25% at 500 • C and 50% at 300 • C, respectively (Figure 5a,c). Additionally, the initial non-exchanged NaMOR itself showed catalytic activity with maximum (12.4%) at 300 • C which is probably due to Na + cation that acts as a Lewis acid site, while the oxygen framework with partial negative charge acts as a Lewis base [64].…”

Section: Catalytic Conversion Of No With C 3 Hmentioning

confidence: 99%

Bimetallic AgFe Systems on Mordenite: Effect of Cation Deposition Order in the NO Reduction with C3H6/CO

et al. 2019

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Mono- and bimetallic systems of Ag, Fe, and Ag–Fe exchanged in sodium mordenite zeolite were studied in the reaction of NO reduction. The transition metal cations Ag and Fe were introduced by ion exchange method both at room temperature and 60 °C; modifying the order of component deposition in bimetallic systems. These materials were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), ultraviolet-visible spectroscopy (UV-Vis), X-Ray photoelectron Spectroscopy (XPS) and High-resolution transmission electron microscopy (HR-TEM). The XPS and UV–Vis spectra of bimetallic samples revealed that under certain preparation conditions Ag+ is reduced with the participation of the Fe2+/Fe3+ ions transition and is present in the form of a Ag reduced state in different proportions of Agm clusters and Ag0 NPs, influenced by the cation deposition order. The catalytic results in the NO reduction reaction using C3H6/CO under an oxidizing atmosphere show also that the order of exchange of Ag and Fe cations in mordenite has a strong effect on catalytic active sites for the reduction of NO.

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“…The striking feature of the resulting 23 Na spectra is a broader resonance in the amorphous precursor nanoparticles compared to room temperature while the 23 Theoretical and experimental studies on the stabilizing role of inorganic cations for SBU were reported earlier. [22][23] The treatment of the amorphous precursor particles with Na + highlights that, in addition to its role as a charge compensator for Si-(OAl)4units, it is an inorganic template stabilizing the secondary building units (SOD cages) during the crystallization of the amorphous particles.…”

Section: Resultsmentioning

confidence: 99%

Transformation of Discrete Amorphous Aluminosilicate Nanoparticles into Nanosized Zeolites

Guo

Zhao

Martineau‐Corcos

et al. 2020

Adv Materials Inter

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The effect of amorphous aluminosilicate precursor nanoparticles on the formation of nanosized zeolites with faujasite (FAU) and sodalite (SOD) type frameworks is illustrated using a new synthetic strategy to prepare nanosized zeolites with tailored particle size distribution, morphology, and structure. This two‐step synthesis procedure includes the formation of colloidal suspensions followed by separation of the amorphous precursor nanoparticles, and their subsequent transformation into nanosized crystals by treatment with alkali suspensions (NaOH) solutions only. The selective transformation of the amorphous nanoparticles into FAU and SOD nanosized crystals is studied at atomistic and microscopic levels using 29Si and 23Na nuclear magnetic resonanse (NMR) spectroscopy, X‐ray powder diffraction, and N2 physisorption, respectively. The presence of sodalite cages occluding highly mobile sodium in the amorphous nanoparticles is confirmed by 23Na‐1H D‐HMQC NMR spectroscopy. The subsequent treatment of these amorphous precursor particles with aqueous sodium hydroxide illustrates that the cations are not only charge compensators but also inorganic templates stabilizing sodalite cages during the long‐range ordering in the amorphous particles.

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DFT study of Li+ and Na+ positions in mordenites and hydration stability

Cited by 17 publications

References 28 publications

Molecular Modeling of Univalent Cation Exchange in Zeolite N

Molecular Modeling of Univalent Cation Exchange in Zeolite N

Bimetallic AgFe Systems on Mordenite: Effect of Cation Deposition Order in the NO Reduction with C3H6/CO

Transformation of Discrete Amorphous Aluminosilicate Nanoparticles into Nanosized Zeolites

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