Molecular simulation on adsorption of methane in single wall carbon nanotubes

By using grand canonical ensemble Monte Carlo method, mechanism for the ads orption of methane in single wall carbon nanotubes (SWNTs) at 74.05 K has b een investigated. It is found that the adsorption of methane in smaller SWN Ts, whose diameters are 1.22 nm and 1.632 nm, exhibits "pore filling" behav ior. In contrast, for the SWNTs of diameter larger than 2.04 nm, capillary condensation takes place. Simulation shows that the required condition for the capillary condensation is that two layers of molecules can be accommoda ted in SWNTs. In addition, a relationship between the quantity of methane a dsorbed and the diameter of SWNT for the capillary condensation is develope d. A comparison of the isotherms for the SWNT diameters of 2.04 nm and 4.07 7 nm at ambient temperature, T = 300 K, indicates that proper adsorption pr essure range is 5.0 similar to 6.0 MPa. In this case, the weight fraction o f adsorbate is about 16% similar to 19%.