Adsorption and Separation of N₂/CH₄/CO₂/SO₂ Gases in Disordered Carbons Obtained Using Hybrid Reverse Monte Carlo Simulations

Adsorption and separation of gases in porous carbon models are studied using molecular simulations. We use three porous carbon models (named as cs400, cs1000, and cs1000a) developed in a previous work obtained from Hybrid Reverse Monte Carlo simulations. The density of carbon atoms as well as the presence of heteroatoms (hydrogen and oxygen) differ between the three carbon models. Gas adsorption in the carbon models were studied using Grand Canonical Monte Carlo simulations. We found that cs1000 sample (with highest carbon density) shows the largest separation ability for N 2 /CH 4, CH 4 /CO 2, and N 2 /CO 2 systems. cs1000a sample (with larger pore width up to 1.2 nm) shows higher selectivity for SO 2 /N 2 and SO 2 /CO 2 systems. We also studied the influence of surface chemistry (presence of carbonyl and carboxyl groups) in the porous carbon models on adsorption and separation of gases. We found that the presence of carbonyl and carboxyl groups has a significant effect on the adsorption and separation of polar gas molecules. Interestingly, the presence of functional groups does not seem to have much impact on SO 2 /CO 2 separation at moderate to high pressures for carbonyl functional groups. For carboxyl functional groups, this is not the case, and the selectivity curves remain flat or decrease slightly at moderate to high pressures. We found increasing selectivity for all binary gas systems except for the N 2 /CH 4 system, which is expected, as both the gases are nonpolar. For all binary gas systems studied, the maximum selectivity was found for SO 2 /N 2 system.