Fractionation of air by zeolites S.Sircar, M.B.Rao, T.C.Golden

Fractionation of air by selective adsorption of Nz on zeolites has become a common industrial practice. Many different zeolites and air separation processes have been developed for this purpose. 

Pure gas isotherms for adsorption of N2 and O2 on five commercial zeolites (NaX, 5A, Na- Mordenite, CaX and CaLSX) at two different temperatures are reported. The isotherms can be described by the Langmuir model in the range of the data. Mixed gas Langmuir model is used to evaluate the relative N2 adsorption and desorption characteristics for these zeolites in connection with air separation application by the pressure swing adsorption (PSA) concepts. 

Nine different PSA processes for air separation using zeolites are reviewed and their process performances are compared. These processes can be designed to produce low (23-50 mole%) and medium purity (90-95 mole%) 02-enriched air and high purity (98+ mole%) N2-enriched air. Processes can be tailor made to match the adsorptive properties of the zeolite for a given separation need or vice versa. 

Barrer and Robbins first demonstrated in 1953 that N2 can be selectively adsorbed over Ar from a mixture of these gases on natural 

PSA processes for air separation differ by (a) the type of zeolite used, 

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