Temperature Study of Structure and Dynamics of Methane in Carbon Nanotubes

Bartuś, Katarzyna; Bródka, A.

doi:10.1021/jp501959r

Cited by 13 publications

(25 citation statements)

References 33 publications

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“…20 Also, the activation energies of translational diffusion for the five-site model of methane were slightly lower than those for the one-site model. 72 Furthermore, modifying CNTs with functional groups and the incorporation of CNTs in a polymer matrix are attractive for applications in the gas separation processes. 16,73,74 For example, H 2 was found to be more selective for CNT/polymer nanocomposites in comparison to N 2 and CO 2 .…”

Section: Theoretical Detailsmentioning

confidence: 99%

Adsorption and Diffusion of Carbon Dioxide, Methane, and Their Mixture in Carbon Nanotubes in the Presence of Water

2020

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Molecular simulations were performed to investigate the adsorption and diffusion properties of methane and carbon dioxide in carbon nanotubes (CNTs) with preadsorbed water at 300 K and pressures up to 40 bar. Our results show that, at low pressures, a high uptake of methane and carbon dioxide is obtained in relatively small pores, and the presence of water enhances the adsorption of carbon dioxide in CNTs with large diameters. The effect of preadsorbed water is more pronounced on the mobility of methane than that of carbon dioxide. Importantly, at high water contents, we see that the mobility of methane is a nonmonotonic function of the nanotube diameter. This is probably due to the splitting of the water clusters in the small pores, which may lead to a faster diffusion process. Simulations were also performed for the methane/carbon dioxide mixture in CNTs with preadsorbed water. Here, the overall adsorption and diffusion properties are similar to those observed for the methane/water and carbon dioxide/water mixtures in CNTs. The adsorption selectivity of carbon dioxide over methane increases with water content, which may be because of the relatively stronger water–carbon dioxide interactions. A significant result is that the mobility of methane in CNTs decreases with decreasing bulk mole fraction of methane. In general, this decrease is more pronounced at higher loadings of methane and lower water contents. However, the presence of methane has less effect on the diffusion properties of carbon dioxide in CNTs. These results may be explained by the preferential adsorption of carbon dioxide over methane in the CNTs. Furthermore, these simulated adsorption isotherms and diffusivity results are in reasonable agreement with the theoretical predictions based on the ideal adsorbed solution theory and the Krishna and Paschek approach, respectively.

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Section: Theoretical Detailsmentioning

confidence: 99%

Adsorption and Diffusion of Carbon Dioxide, Methane, and Their Mixture in Carbon Nanotubes in the Presence of Water

2020

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“…28 Finally, only for small molecules, investigations have been performed using theoretical molecular dynamics simulations to describe, for example, the translational and rotational diffusion of methane molecules in carbon nanotubes. 35,36 ■ METHODS…”

Section: ■ Introductionmentioning

confidence: 99%

“…Nevertheless, solid-state NMR spectroscopy has been successfully used for studies of the molecular dynamics of ferrocene on the paramagnetic surface of AC , as mentioned above . Finally, only for small molecules, investigations have been performed using theoretical molecular dynamics simulations to describe, for example, the translational and rotational diffusion of methane molecules in carbon nanotubes. , …”

Section: Introductionmentioning

confidence: 99%

Benzene Adsorbed on Activated Carbon: A Comprehensive Solid-State Nuclear Magnetic Resonance Study of Interactions with the Pore Surface and Molecular Motions

2020

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Benzene-d 6 and cyclohexane-d 12 have been adsorbed on the surface within the pores of high-surface-area activated carbon (AC). Their molecular motions have been characterized by variable-temperature 2H and 13C solid-state NMR spectroscopy. Three different states of benzene molecules on the AC surface have been found: isotropically moving molecules, bound molecules, and intermediates between these states. In contrast to cyclohexane, benzene assumes stationary states that are stabilized by π–p interactions with the AC surface. Hereby, fast in-plane C6 rotations take place. The adsorption enthalpy −ΔH 0 for benzene on the surface of AC within the pores was determined as 4.6 ± 0.3 kcal/mol. The strongly adsorbed molecules undergo slow exchange with isotropically moving, liquid-like molecules. In contrast to this, exchange between the molecules in a liquid-like state with benzene in semibound states (T-complexes) is very fast, requiring only low activation energies E act and ΔH ‡ of 3.1 and 2.7 kcal/mol, respectively.

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“…This comes from a combination of temperature effects on both the molecular diffusivity and the driving force, since the friction force between the benzene and the graphene is expected to change with the velocity and to linearly increase at increasing temperature. At low pressure, the diffusion coefficient of gas molecules roughly increases with T 3/2 , [35,36] which can be approximated as a linear dependence for the here-used temperature range. The sub-linearly increase of v is coupled with the fact that the anharmonicity of the vdW potential is enhanced at high temperature.…”

Section: Resultsmentioning

confidence: 99%

Chirality-Selective Transport of Benzene Molecules on Carbon Nanotubes

Wang

2020

J. Phys. Chem. C

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Using molecular dynamics simulations, we predict an effect of chirality on the conduction of benzene molecules along the surface of carbon nanotubes (CNTs) subjected to a thermal gradient. The group drift velocity of the molecules is found to be maximal in the case of an armchair CNT, and to decrease with decreasing chiral angle. This chirality effect on thermodiffusion is induced by a variation in the optimized paths of molecules that change with different electronic overlap at the interface. The mechanism for the thermophoretic transport is identified to be coupled with a gradient of adsorbate-substrate interaction energy, which originates from the anharmonic nature of the van der Waals potential.

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Temperature Study of Structure and Dynamics of Methane in Carbon Nanotubes

Cited by 13 publications

References 33 publications

Adsorption and Diffusion of Carbon Dioxide, Methane, and Their Mixture in Carbon Nanotubes in the Presence of Water

Adsorption and Diffusion of Carbon Dioxide, Methane, and Their Mixture in Carbon Nanotubes in the Presence of Water

Benzene Adsorbed on Activated Carbon: A Comprehensive Solid-State Nuclear Magnetic Resonance Study of Interactions with the Pore Surface and Molecular Motions

Chirality-Selective Transport of Benzene Molecules on Carbon Nanotubes

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