Molecular Simulation of Adsorption: Gibbs Dividing Surface and Comparison With Experiment

At low temperature near the normal boiling point, computer simulations of adsorption of gases can be compared directly with experiment . However, for adsorptive gas separations in which the gas is adsorbed near or above its critical temperature, absolute simulation variables must be converted to excess variables for comparison with experiment . The conversion of absolute to excess variables requires the helium pore volume of the adsorbent. Lennard-Jones potential parameters for helium gas molecules interacting with the oxygen atoms of silicalite are ε/k = 28.0 K and σ = 2.952 Å. The helium pore volume of silicalite is 0.175 cm ³ /g. Lennard-Jones potential parameters derived for Ar-O interactions in silicalite are ε/k = 93.0 K and σ = 3.335 Å. Density profiles for adsorption of argon in silicalite at 300 K show that the local density is highest in the middle of the channels where the gas-solid potentials overlap.