Molecular simulation of adsorption: Gibbs dividing surface and comparison with experiment

Talu, Orhan; Myers, Alan L.

doi:10.1002/aic.690470521

Cited by 219 publications

(172 citation statements)

References 17 publications

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“…Talu and Myers [25] proposed a simulation methodology that mimics the experimental procedure. For consistency with experiment, the helium void fraction j is determined by probing the framework with a helium molecule using the Widom particle insertion method:…”

Section: Surface Area Void Fraction and Pore-size Distributionmentioning

confidence: 99%

“…Excess adsorption is the number of molecules in the nanopores in excess of the amount that would be present in the pore volume at the equilibrium density of the bulk gas. [25,26] RASPA calculates absolute adsorption and, if the pore-volume fraction is given (can be computed separately), it also calculates the excess adsorption for convenience. With this type of modelling, the experimental results are well reproduced.…”

Section: Adsorption In the Npt Gibbs Ensemblementioning

confidence: 99%

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RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

Dubbeldam

Calero

Ellis

et al. 2015

Molecular Simulation

1,560

1,529

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A new software package, RASPA, for simulating adsorption and diffusion of molecules in flexible nanoporous materials is presented. The code implements the latest state-of-the-art algorithms for molecular dynamics and Monte Carlo (MC) in various ensembles including symplectic/measure-preserving integrators, Ewald summation, configurational-bias MC, continuous fractional component MC, reactive MC and Baker's minimisation. We show example applications of RASPA in computing coexistence properties, adsorption isotherms for single and multiple components, self-and collective diffusivities, reaction systems and visualisation. The software is released under the GNU General Public License.

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Section: Surface Area Void Fraction and Pore-size Distributionmentioning

confidence: 99%

Section: Adsorption In the Npt Gibbs Ensemblementioning

confidence: 99%

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

Dubbeldam

Calero

Ellis

et al. 2015

Molecular Simulation

1,560

1,529

View full text Add to dashboard Cite

show abstract

“…We probed the coal structure with an LJ helium atom at millions of random points, Fig. 8 Comparison of the bulk density for CH 4 , C 2 H 6 , and CO 2 at a 308 K; b 370 K computed the energy difference with and without the particle, and estimated the average Boltzmann weight which directly corresponds to the void fraction (Talu and Myers 2001). In our simulation, all micropores are accessible because of the inherent feature of the MC method.…”

Section: Excess Sorptionmentioning

confidence: 99%

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

et al. 2015

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Sorption isotherms of hydrocarbon and carbon dioxide (CO 2 ) provide crucial information for designing processes to sequester CO 2 and recover natural gas from unmineable coal beds. Methane (CH 4 ), ethane (C 2 H 6 ), and CO 2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo (MC) and molecular dynamics (MD) simulations at temperatures of 308 and 370 K (35 and 97°C) and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption (expressed as a mass basis) divided by bulk gas density has negligible temperature effect on CH 4 , C 2 H 6 , and CO 2 sorption on dry coal when pressure is over 6 MPa. CO 2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO 2 molecules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ''a'' constant (proportional to T c 2 /P c ) in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO 2 injection pressures of lower than 8 MPa may be desirable for CH 4 recovery and CO 2 sequestration. This study provides a quantitative understanding of the effects of temperature on coal sorption capacity for CH 4 , C 2 H 6 , and CO 2 from a microscopic perspective.

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“…A cuto radius r cˆ1 3 A Ê corresponding to the length of one side of the unit cell has been used frequently. More conservative calculations use cuto radii of 19 A Ê [21] or 20 A Ê [22]. In one simulation [23], a cuto radius of 8 A Ê was used to speed up the calculation.…”

Section: Adsorption In Silicalitementioning

confidence: 99%

“…We calculated the methane±oxygen radial distribution function shown in ®gure 3 using the potential par-ameters in table 1 and methods described elsewhere [22]. The complicated structure of the radial distribution function is a consequence of the anisotropic structure of silicalite, which consists of intersecting straight and zig-zag channels.…”

Section: Adsorption In Silicalitementioning

confidence: 99%

Long range corrections for computer simulations of adsorption

2002

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Long range corrections are routinely applied to simulations of bulk¯uids by assuming that the radial distribution function is unity beyond a certain cuto radius for pairwise interactions. Similar long range corrections for gas±solid interactions in adsorption frequently are ignored because of the anisotropic structure of the solid. However, the error associated with assuming isotropy beyond the cuto radius is small compared with the magnitude of the long range correction. The long range correction to the Henry constant for a cuto radius of 13 A Ê is 14% for CH 4 and 70% for SF 6 for adsorption in silicalite at 298 K. The large errors incurred by neglecting long range corrections can be concealed by increasing the well depth of the gas± solid interaction, but this approximation reduces the accuracy and portability of the potential parameters. Consistency in the cuto radius is more important than the inclusion or neglect of long range corrections to the energy. IntroductionMolecular simulation of adsorption is based upon a detailed model of the potential energy of the adsorbate molecules as a function of their location and orientation inside the pores of the solid adsorbent. Assuming pairwise additivity, the total potential energy of a con®gura-tion is obtained by summing gas±gas and gas±solid interaction energies. At the limit of zero loading, the gas±gas interactions are negligible and the energy consists entirely of gas±solid interactions. The total potential energy of a gas molecule adsorbed at a particular location includes interactions between the gas molecule and every other atom in the simulation box, as well as images in the surrounding boxes. This summation contains an in®nite number of terms and is impossible to calculate in practice [1].The approximation for dispersion/repulsion forces in bulk¯uids is to use a spherical cuto radius (r c ). Corrections for the missing long range part of the potential are based on the approximation that the radial distribution function g…r † º 1 for r > r c . Long range corrections can be introduced at the end of the simulation in ensembles where the density is constant. In NPT and ·VT ensembles, the long range corrections must be applied to the instantaneous energies and pressures during the course of the simulation, because the corrections change as the density¯uctuates [2].

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Molecular simulation of adsorption: Gibbs dividing surface and comparison with experiment

Cited by 219 publications

References 17 publications

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

Long range corrections for computer simulations of adsorption

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