SIMULATION STUDIES OF ADSORPTION IN ROUGH-WALLED CYLINDRICAL PORES

A model is developed for porous materials in which the atomic nature of the solid is explicitly included. The result is a gas-solid interaction law for molecules in rough-walled pores of arbitrary shape. Simulations of adsorption isotherms and energies are reported for methane at 300 K in several model porous solids. The methane-solid interaction was obtained from a summation over solid atoms using parameters for the pairwise energies appropriate for methane in coal. Rough-walled cylindrical pores were considered in this work with radii equal to 6.5, 10.0, and 13.4 angstrom; for reference, adsorption on the flat adsorbent surface was also studied. Calculations of the average gas-solid adsorption energy which show the effects of variable pore radius are shown. The average methane-methane energy on these heterogeneous surfaces is shown to be non-negligible. The isotherm data are subjected to a simple analysis that allows one to fit their dependence on pore radius in a straightforward way.