Selective adsorption of NOx from gas streams

Claim 1

Process for selectively adsorbing gaseous oxides of nitrogen from a gas stream which comprises in addition to said oxides of nitrogen, water vapor, oxygen and nitrogen which comprises passing said gas stream through an adsorbent bed of activated silica gel to adsorb water therefrom and thereafter contacting the gas stream constituents unadsorbed by said silica gel with a zeolite adsorbent comprising zeolite Y ion exchanged with non-metallic ions consisting essentially of NH 4 + or H+ or mixtures thereof having a SiO 2 /Al 2 O 3 molar ratio of from 4.5 to 5.5, containing from 8 to 30 equivalent percent metal cations in association with AlO 4 - tetrahedra of the zeolite framework, at least 8 equivalent percent of said metal cations being sodium cations, said zeolite having been calcined at a temperature of from 400° C. to 800° C. to reduce the unit cell size and to obtain a unit cell size, a o , to a value of from greater than 24.55 to 24.63 Angstrom units, whereby oxides of nitrogen are adsorbed and separated from the nitrogen and oxygen present.