Impact of H2O on CO2 separation from natural gas: comparison of carbon nanotubes and disordered carbon

The adsorption of pure H2O, CO2/CH4, and H2O/CO2/CH4 mixtures in carbon nanotubes (CNTs) ranging from (6,6) to (15,15), and in a reconstructed model of a silicon carbide derived carbon (SiC-DC), was studied using Monte Carlo simulations, at 300 K. We also investigated the effect of preadsorbed water and the choice of water model including SPC, SPC/E, TIP3P, TIP4P, and TIP5P, on the adsorption of CO2/CH4 and H2O/CO2/CH4 mixtures in the CNTs and SiC-DC. Using the SPC model, our simulations reveal that, below saturation pressure, the adsorption of water is negligible in CNTs with diameters ranging from 0.81 to 2.03 nm, and in the SiC-DC. Water fills the CNTs and the SiC-DC model suddenly when the pressure reaches a critical value that is above the saturation pressure, and exhibits nonmonotonic variation with CNT diameter. It was also found that the small amount of water adsorbed from the saturated H2O/CO2/CH4 mixture has little impact on the adsorption of the components CO2 and CH4. When water is preadsorbed...