Adsorption and diffusion of a Lennard-Jones vapor in microporous silica

Abstract

The properties of a dilute Lennard-Jones vapor in contact with an adsorbing microporous medium are investigated using grand canonical ensemble Monte Carlo and molecular dynamics techniques. The bulk structure of the microporous system is modeled as an assembly of randomly distributed interconnected solid spheres, and vapor/surface interactions are treated in two ways: (i) using a smooth continuous interaction potential and (ii) using a molecular model for the surface structure of the solid. The microporous solid representation employed in these simulations is chosen to conform in realistic manner with the bulk and surface properties of silica gel. The results obtained from the simulations include equilibrium partition coefficients, diffusivities, and related microscopic properties. By comparing these results with available experimental data it is shown that the properties of simple nonpolar gases in microporous silica may be predicted with reasonable accuracy. This is particularly true when the molecular structure of the silica surface is taken into consideration.

Grand Canonical Monte Carlo Simulation of Nitrogen Adsorption in a Silica Aerogel Model

“…Nitrogen adsorption has been a useful method in characterizing the nanoporous materials for pore size distribution [12,13] and SSA estimation [14] and there is plenty of experimental data for comparison. MacElroy [15] studied properties of methane, such as the Henry constant, in microporous silica with a random micro-sphere system and vitreous state sphere structure, and found results in satisfactory agreement with experimental data, and concluded that with a proper microsphere structure the numerical method could give a reasonable prediction on properties of simple nonpolar gases in silica aerogels. Ulker [16] simulated a nitrogen adsorption isotherm in silica aerogel MOF composite with conventional GCMC and it agrees with the experimental data.…”

Computer Simulations of the Dynamic Properties of Methane in a Model Silica Gel

“…It has already been shown that this model is a reasonable first approximation to the structure of silica gel [12].…”

Molecular Description of Electrolyte Solution in a Carbon Aerogel Electrode

“…MacElroy and Raghavan [27] studied dilute Lennard-Jones (LJ) vapor confined in microporous silica modelled in two ways as a network of randomly interconnected, and randomly distributed silica microparticles. Kaminsky and Monson [28,29] developed a model for adsorption of LJ fluid in microporous silica gel comprising a configuration of microspheres, each considered as a continuum of atomic interaction centers.…”

“…The aerogel is modelled as a network of partially overlapping compact carbon nanospheres. To illustrate the effect of the aerogel nanostructure, it is represented by two models which are reminiscent of those used by MacElroy and Raghavan [27]: nanospheres that are almost randomly distributed, and nanospheres associating into a network of branched chains. As shown below, the long-range correlations of aerogel nanoparticles strongly affect the structure and thermochemistry of the EDL formed by the sorbed electrolyte solution at the surface of carbon aerogel nanopores.…”