Adsorption equilibrium and separation of methane and carbon dioxide mixtures on 13X molecular sieve

Pure gas and binary gas mixture adsorption isotherms of methane and carbon dioxide on 13X molecular sieve were measured by using the high-precision intelligent gravimetric analyzer at temperature of 298, 310 and 326 K, respectively. Double-Langmuir model was used to study the pure gas adsorption; the DL model and the ideal adsorbed solution theory (IAST) were combined to predict the binary gas mixture adsorption isotherms and using the model, the adsorption amount of the single component of gas mixture and the selectivity of CO₂ were calculated. It shows that the combined method (DL-IAST) can be applied to describe the adsorption of CH₄ and CO₂ binary mixtures on 13X molecular sieve perfectly. The selectivity of CO₂ increases with increasing pressure and finally reaches 80 at 298 K; when the temperature is constant, the selectivity of CO₂ decreases with increasing the CO₂ concentration.