Fractionation of air by zeolites

Fractionation of air by selective adsorption of N-2 on zeolites has become a common industrial practice. Many different zeolites and air separation pr ocesses have been developed for this purpose. Pure gas isotherms for adsorption of N-2 and O-2 on five commercial zeolite s (NaX, 5A, Na- Mordenite, CaX and CaLSX) at two different temperatures are reported. The isotherms can be described by the Langmuir model in the rang e of the data. Mixed gas Langmuir model is used to evaluate the relative N- 2 adsorption and desorption characteristics for these zeolites in connectio n with air separation application by the pressure swing adsorption (PSA) co ncepts. Nine different PSA processes for air separation using zeolites are reviewed and their process performances are compared. These processes can be design ed to produce low (23-50 mole%) and medium purity (90-95 mole%) O-2-enriche d air and high purity (98+ mole%) N-2-enriched air. Processes can be tailor made to match the adsorptive properties of the zeolite for a given separat ion need or vice versa.