Prediction of carbon dioxide permeability in carbon slit pores

A one-site spherical CO2 model and five three-site linear CO2 models are compared for adsorption in carbon slit pores, using grand canonical Monte Carlo (GCMC) simulation. A three-site CO2 model validated with bulk density experimental data is used to predict adsorption isotherms and diffusivities in the slit pore with the width from 0.65 nm to 0.75 nm. In the range of temperature from 298 K to 318 K and pressure from 0.01 bar to 20 bar permeability is calculated from the GCMC adsorption isotherms and the collective diffusivity obtained from equilibrium molecular dynamics (EMD). The permeability within the pore widths exceeds by three orders of magnitude that of reported macroscopic measurements. The simulation permeability obtained in this study is comparable to that derived from modified Knudsen diffusion with an energy barrier of 3.5–5 kJ/mol. The simulation results give an upper bound of the permeability for an ideal carbon membrane without pore mouth resistance and complex pore network.