Abstract: Adsorption of methane in graphite slit-pores and effect of slit-pores width and temperature on methane adsorption were studied with molecular dynamics simulation. It indicates that methane molecules have layering phenomenon in graphite slit-pores. Structure of methane in adsorption layers shows similar characteristics of liquid while to those of gas in free layers. And in a methane molecule there always exist two hydrogen atoms in a plane that parallels to slit-pore wall and other two hydrogen atoms in another plane that also parallels to slit-pore wall in the first layer. Potential of mean force between carbon atoms shows that binding capacity of methane is stronger in adsorption layers than in free layers. Adsorption state is one of the main occurrence state of methane in graphite slit-pores. London force and electric field force generated by net charge in adsorption layers are dominating reasons of methane adsorption and layering. Adsorption capacity of methane in graphite slit-pores decreases with increasing pore width or temperature. Methane is persisted only in adsorption state in slit-pore with width of 16.46 Å. Diffusivity of methane is the weakest in the first layer and the strongest in a free layer. Diffusion coefficients of methane increase with increasing pore width or temperature.

Key words: methane, graphite slit-pore, adsorption, molecular dynamics simulation