Molecular Simulation Study of the Competitive Adsorption of H₂O and CO₂ in Zeolite 13X

The presence of H₂O in postcombustion gas streams is an important technical issue for deploying CO₂-selective adsorbents. Because of its permanent dipole, H₂O can interact strongly with materials where the selectivity for CO₂ is a consequence of its quadrupole interacting with charges in the material. We performed molecular simulations to model the adsorption of pure H₂O and CO₂ as well as H₂O/CO₂ mixtures in 13X, a popular zeolite for CO₂ capture processes that is commercially available. The simulations show that H₂O reduces the capacity of these materials for adsorbing CO₂ by an order of magnitude and that at the partial pressures of H₂O relevant for postcombustion capture, 13X will be essentially saturated with H₂O