Simulation of Pore Width and Pore Charge Effects on Selectivities of CO2 vs. H2 from a Syngas-like Mixture in Carbon Mesopores

Classical molecular dynamics simulations were performed to study the effect of pore width and surface charge in carbon mesoporous materials on adsorption and diffusion selectivities of CO2/H2 in a syngas-like mixture (mole fraction of CO2 = 0.30). The pore width of the graphite slit varied from 2.5 to 5.0 nm, while the temperature varied from 300K to 400 K. Both selectivities were relatively insensitive to the pore width. Metal contamination, mimicked with localized charges within an electroneutral pore surface, was found to increase the adsorption selectivity ratio for CO2 vs H2 and decrease the diffusion selectivity for CO2 vs H2. Such surface charges interact with CO2 molecules only and can enhance the separation of H2 from the syngas mixture, retaining CO2. Rising temperature will enhance diffusion selectivity, however reduce the adsorption selectivity of CO2. The results imply that surface charges can be used to favor the enrichment process of CO2.