The adsorption method based on solid adsorbents is one of feasible ways to capture and store CO2. Using the ion exchange method, different zeolites NaKA varying in K+ content were produced. The adsorption isotherms and kinetic uptakes were measured. The experimental results show that the optimal NaKA could adsorb significant quantities of CO2 and little N2. On the zeolite NaKA with 14.7 at.% K+, the adsorption capacity for pure CO2 is over 3.10 mmol g−1 and the CO2–N2 selectivity is about 149 at ambient pressure and temperature. The kinetic CO2–N2 selectivity could also achieved 200 within 3 min according to the uptake data. To demonstrate the separation effectiveness, breakthrough curves of pure components and binary mixtures were investigated experimentally and theoretically in a fixed bed. It is found that the breakthrough points of CO2 and N2 are almost at the same time under the atmospheric pressure at 348 K with the raw gas composition CO2/N2 (20:80, v/v). If the pressure has been increased higher than 0.1 MPa, CO2 would break through the bed much slower than N2. Therefore, the pressure may become the limiting factor for the separation performance of zeolites NaKA.The zeolite NaKA with 14.7 at.% K+ exchange for NaA has displayed high CO2–N2 selectivity, which demonstrates potential for the separation of CO2–N2 mixtures.

Adsorption equilibria for binary gas mixtures (methane–carbon dioxide, methane–ethane, and carbon dioxide–ethane) on the graphitized carbon black STH-2 were measured by the open flow method at 293.2 K. The experimental pressure range was (0 to 1.6) MPa. The extended Langmuir (EL) model and the ideal adsorption solution theory (IAST) have been adopted to predict the equilibria of binary gas mixtures. The results indicate that gas mixtures adsorbed on the homogeneous surface of STH-2 exhibit the nonideal behavior, which is mainly induced by adsorbate–adsorbate interactions. The real adsorption solution theory (RAST) has been used to analyze the property of the adsorbed mixtures. The activity coefficients have been correlated with the Wilson equation. The investigation demonstrates that the nonideality of adsorbed phase is completely dissimilar with the bulk liquid phase. The adsorption of the heavier component would benefit the adsorption of the lighter component.

Adsorption equilibrium data for pure carbon dioxide and ethane on STH-2 graphitized carbon black were measured by a volumetric method. The experiments were carried out over the temperature range (253.2 to 303.2) K and the pressure range (0 to 4) MPa. The relative pressure p/p0 and adsorption amount n have been adopted to express adsorption isotherms, and the experimental data present a generalized adsorption isotherm over the research range. On the basis of this generalized isotherm, a method of predicting gas adsorption equilibria was explored. The prediction accuracy is satisfactory. In addition, analysis of the BET equation provides proof that the generalized adsorption isotherm p/p0 ∼ n is reasonable.