Non-equilibrium molecular dynamics simulation on permeation and separation of H₂/CO in nanoporous carbon membranes

Permeation and separation of H₂/CO binary mixtures in nanoporous carbon membranes are investigated by non-equilibrium molecular dynamics simulations. The carbon membrane pores are modeled as slit-like pores with entrance and exit. The buffer regions between the control volumes and membrane pores are employed to take into account the effects of the entrance and exit of the membrane pores. The effects of pore width, separation temperature, feed gas pressure, the molar fraction of hydrogen, and membrane thickness on flux and dynamic separation factor are discussed. The simulation results indicate that the pore width strongly affects the flux and dynamic separation factor. In addition, molecular sieving dominates the separation of H₂/CO mixtures, when the pore width is smaller by about 0.64 nm, and, in this case, the dynamic separation factor reaches 52.88 at 0.5 MPa and 300 K. The dynamic separation factor increases with the separation temperature and the decrease of feed gas pressure, while changes slightly with the molar fraction of H₂ in the feed gas. Moreover, the dynamic separation factor increases with membrane thickness at the pore width of 0.64 nm, while decreases at the pore width of 1.01 nm due to different separation mechanisms.