Oxygen and Nitrogen generators on an industrial scale is done via pressure swing adsorption (PSA).  To generate oxygen, a 13X or Li-X molecular sieve is employed.   Nitrogen and CO2 are adsorbed while Oxygen is separated.   Li-X allows for better selectivity between Oxygen and Nitrogen.   Carbon molecular sieves work much in the same way (PSA) but  instead generates nitrogen gas.  SEPCOR provides both types of adsorbent for the generation of oxygen or nitrogen.