Modeling Desorption of Fluids from Disordered Mesoporous Materials

Woo, Hyung‐June; Porcheron, Fabien; Monson, P. A.

doi:10.1021/la035999t

Cited by 55 publications

(56 citation statements)

References 19 publications

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“…The theory gives an approximation to the time evolution of the density distribution averaged over an ensemble of many kinetic Monte Carlo simulations of the lattice gas model. The particular focus here is on Kawasaki dynamics, which we have used extensively to make kinetic Monte Carlo simulations of adsorption/desorption dynamics for fluids in porous materials [47,48,50,51]. We begin by writing the ensemble average density for site i at time t, ρ i (t), as…”

Section: Dynamic Mean Field Theorymentioning

confidence: 99%

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Edison

Monson

2009

J Low Temp Phys

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We review a recently developed dynamic mean field theory for fluids confined in porous materials and apply it to a case where the solid-fluid interactions lead to partial wetting on a planar surface. The theory describes the evolution of the density distribution for a fluid in a pore that has contact with the bulk during a quench in the bulk chemical potential. In this way the dynamics of adsorption and desorption can be studied. By focusing on partial wetting situation we can investigate influence of a weaker surface field on the mechanisms of capillary condensation and desorption. We have studied the dynamics of pore filling in a quench of the chemical potential between two states either side of the pore filling step, tracking the density distributions during the process. The pore filling process features an asymmetric density distribution where a liquid droplet appears on one of the walls. The droplet spreads and grows in size and this is followed by the appearance of a liquid bridge between the pore walls (for longer pores two liquid bridges are seen). The density distributions obtained in the dynamics resemble those obtained from static mean field theory in the canonical ensemble for an infinite pore without contact with the bulk.

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Section: Dynamic Mean Field Theorymentioning

confidence: 99%

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Edison

Monson

2009

J Low Temp Phys

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“…For example, capillary critical temperatures in confined geometries are reported experimentally for SF 6 in porous glass and several gases in MCM-41 by Thommes et al 13 and Morishige Findenegg, 14 respectively; the shift in the critical temperature is found to have linear dependence on the inverse pore width. Numerous theoretical studies and molecular simulations including density function theory [15][16][17][18] and Monte Carlo ͑MC͒ simulations [19][20][21][22][23][24][25] were performed to understand capillary condensation. Vishnyakov et al 26 were the first to perform MC simulations systematically on carbon slit pores and studied the shift of the vapor-liquid critical point under confinement.…”

Section: Introductionmentioning

confidence: 99%

Vapor-liquid critical and interfacial properties of square-well fluids in slit pores

Jana

Singh

Kwak

2009

The Journal of Chemical Physics

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Computer simulation studies of a square-well fluid in a slit pore. Spreading pressure and vapor-liquid phase equilibria using the virtual-parameter-variation method J. Chem. Phys. 112, 5168 (2000) Vapor-liquid phase equilibria of square-well ͑SW͒ fluids of variable interaction range: = 1.25, 1.75, 2.0, and 3.0 in hard slit pores are studied by means of grand-canonical transition-matrix Monte Carlo ͑GC-TMMC͒ simulation. Critical density under confinement shows an oscillatory behavior as slit width, H, reduced from 12 to 1 . Two linear regimes are found for the shift in the critical temperature with the inverse in the slit width. The first regime is seen for H Ͼ 2.0 with linear increase in the slope of shift in the critical temperature against inverse slit width with increasing interaction range. Subsequent decrease in H has little consequence on the critical temperature and it remains almost constant. Vapor-liquid surface tensions of SW fluids of variable well extent in a planar slit pore of variable slit width are also reported. GC-TMMC results are compared with that from slab based canonical Monte Carlo and molecular dynamics techniques and found to be in good agreement. Although, vapor-liquid surface tension under confinement is found to be lower than the bulk surface tension, the behavior of surface tension as a function of temperature is invariant with the variable pore size. Interfacial width, , calculated using a hyperbolic function increases with decreasing slit width at a given temperature, which is contrary to what is being observed recently for cylindrical pores. Inverse scaled interfacial width ͑ / H͒, however, linearly increases with increase in the scaled temperature ͑T c,bulk − T͒ / T c,bulk .

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“…For a nearest neighbor lattice gas in an external field the Hamiltonian can be written (DeOliveira and Griffiths 1978;Ebner 1981;Kierlik et al 2001;Woo and Monson 2003;Monson 2008)…”

Section: Lattice Model and Static Mean Field Approximationmentioning

confidence: 99%

“…The theory gives an approximation to the time evolution of the density distribution averaged over an ensemble of kinetic Monte Carlo simulations of the lattice gas model. The particular focus here is on Kawasaki dynamics, which have been used extensively to make kinetic Monte Carlo simulations of adsorption desorption dynamics for fluids in porous materials (Valiullin et al 2006;Woo and Monson 2003;Woo et al 2004). The transport is restricted to hopping between nearest neighbor sites as in Kawasaki dynamics and the evolution equation for the local density can then be written in mean field theory as…”

Section: Dynamic Mean Field Theorymentioning

confidence: 99%

“…We call this theory, which is based on lattice gas models of confined fluids, mean field kinetic theory or dynamic mean field theory (DMFT). The essence of the theory is an approximation to kinetic Monte Carlo simulations that use Kawasaki dynamics (Woo and Monson 2003;Valiullin et al 2006). It is based on previous work by Gouyet et al (2003) and Matuszak et al (2004), which in turn are based on work on the dynamics of Ising models by Penrose (1991) and of binary alloys by Martin (1990).…”

Section: Introductionmentioning

confidence: 99%

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Modelling relaxation processes for fluids in porous materials using dynamic mean field theory: application to pore networks

et al. 2011

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We present an application of a recently developed dynamic mean field theory to the study of relaxation dynamics in adsorption and desorption from pore networks. The theory predicts the evolution of density distribution in the system, based on an underlying free energy functional from static mean field theory and the system evolves to equilibrium or metastable equilibrium states consistent with the static theory. The theory makes it possible to follow the evolution of the density distribution with time in response to a change in the bulk pressure or chemical potential. We compare uptake dynamics for a 2D slit pore network with that in a single slit pore. We see more rapid uptake dynamics in the pore network in some cases, due to the greater access of the pore space to the bulk. We also observe that the formation of liquid bridges can slow down the mass transfer in the pore network in certain situations.

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Modeling Desorption of Fluids from Disordered Mesoporous Materials

Cited by 55 publications

References 19 publications

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Vapor-liquid critical and interfacial properties of square-well fluids in slit pores

Modelling relaxation processes for fluids in porous materials using dynamic mean field theory: application to pore networks

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