Molecular dynamics computer simulation of gas permeation in thin silicalite membranes

Pohl, Phillip Isabio; Heffelfinger, Grant S.; Smith, Douglas M.

doi:10.1080/00268979609482570

Cited by 74 publications

(37 citation statements)

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“…The absence of internal density gradients has also been observed by Pohl and Heffelfinger [56], and more recently by iYitta et al [57] The presence of surface barriers could be viewed as an anomaly associated with the extremely thin membrane sample which we have used. In fact, it could explain why our permeability predictions lie far below the experimental range.…”

Section: Permeation Studiesmentioning

confidence: 65%

Beyond the Classical Transport Laws of Electrochemistry: New Microscopic Approach to Ionic Conductance and Viscosity

Chandra

Bagchi

2000

J. Phys. Chem. B

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We present the results of molecular dynamics simulations of n-butane and isobutane in silicalite. We begin with a comparison of the bulk adsorption and diffusion properties for two different parameterizations of the interaction potential between the hydrocarbon species, both of which have been shown to reproduce experimental gas-liquid coexistence curves. We examine diffusion as a function of the loading of the zeolite, as well as the temperature dependence of the diffusion constant at loading and for infinite dilution. We continue with simulations in which interfaces are formed between single component gases and the zeolite. After reaching equilibrium, we examine the dynamics of exchange between the bulk gas and the zeolite. Finally, we calculate the permeability of the zeolite for n-butane and isobutane as a function of pressure. Our simulations are performed for a number of different gas temperatures and pressures, covering a wide range of state points.1

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Section: Permeation Studiesmentioning

confidence: 65%

Beyond the Classical Transport Laws of Electrochemistry: New Microscopic Approach to Ionic Conductance and Viscosity

Chandra

Bagchi

2000

J. Phys. Chem. B

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“…(12J were used to calculate the DQ via Eq. (22). The resultant profiles for 0 1 2 and 0 2 1 are shown in Fig.…”

Section: Binary Diffusionmentioning

confidence: 99%

Direct molecular simulation of gradient-driven diffusion of large molecules using constant pressure

Thompson

Heffelfinger

1999

The Journal of Chemical Physics

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Dual control volume grand canonical molecular dynamics (DCV-GCMD) is a boundary-driven non-equilibrium molecuIar dynamics technique for simulating gradientdriven diffusion in multicomponent systems. Two control volumes are established at opposite ends of the simulation box. Constant temperature and chemical potential of diffusing species are imposed in the control volumes (Le. constant-pl -..pn-lpnyy). This results in stable chemical potential gradients and steadystate diffusion fluxes in the region between the control volumes. We present results and detailed analysis for a new constant-pressure variant of the DCV-GCMD method in which one of the diffusing species for which a steady-state difhsion flux exists does not have to be inserted or deleted. Constant temperature, pressure and chemical potential of all diffusing species except one are imposed in the control volumes (Le. constant-p1 .+,,-I NJ'T). The constant-pressure method can be applied to situations in which insertion and deletion of large molecules would be prohibitively difficult. As an example, we used the method to shulate diffusion in a binary mixture of spherical particles with a 2:l size ratio. Steady-state difhion fluxes of both diffusing species were established. The constant-pressure diffusion coefficients agreed closely w i t h the results of the standard constant-volume calculations.In addition, we show how the concentration, chemical potential and flux profiles can be used to calculate local binary and Maxwell-Stefan diffusion coefficients. In the case of the 2:l size ratio mixture, we found that the binary diffusion coefficients were asymmetric and composition dependent, whereas the Maxwell-Stefan diffusion coefficients changed very little with composition and were symmetric. This last result verified that the Gibbs-Duhem relation was satisfied locally, thus validating the assumption of local equilibrium.

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“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] In many of these studies, only linear, branched and aromatic hydrocarbons were considered. Only four studies, two by Snurr et al 24,25 and two by Fox et al, 26,27 include cycloalkanes (naphthenes).…”

Section: Introductionmentioning

confidence: 99%

Molecular simulations of the adsorption of cycloalkanes in MFI-type silica

Schenk

Smit

Maesen

et al. 2005

Phys. Chem. Chem. Phys.

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A new force field for the simulation of the adsorption of cycloalkanes in nanoporous silica affords a significant improvement over any previously employed force field. The simulated isotherms reproduce the most salient features in the experimental isotherms extremely well. The study of cyclo-pentane, -hexane, and -heptane adsorption in MFI-type silica indicates an inflection for cyclopentane but not for cyclohexane at intermediate pressure. If corroborated by experiments, such an inflection point would afford an excellent calibration point for further force field developments. At low pressures, mixture isotherms of cyclohexane and n-hexane show a temperature dependence on the selectivity in accordance with recent results by J. P. Fox and S. P. Bates, J. Phys. Chem., 2004, 108, 17136. This dependence is caused by a difference in temperature dependence of the Henry coefficient for both molecules. At high pressures entropy effects due to packing always favor the sorption of n-hexane. Furthermore, the influence of the flexibility of the zeolite framework on the adsorption of these rather bulky molecules is investigated. It is found that this influence of the flexibility on the adsorption of cyclohexane is as small as with n-alkanes.

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Molecular dynamics computer simulation of gas permeation in thin silicalite membranes

Cited by 74 publications

References 0 publications

Beyond the Classical Transport Laws of Electrochemistry: New Microscopic Approach to Ionic Conductance and Viscosity

Beyond the Classical Transport Laws of Electrochemistry: New Microscopic Approach to Ionic Conductance and Viscosity

Direct molecular simulation of gradient-driven diffusion of large molecules using constant pressure

Molecular simulations of the adsorption of cycloalkanes in MFI-type silica

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