Exchanged zeolites X, in particular exchanged with lithium, their process of preparation and their use as adsorbents of nitrogen in the separation of the gases of the air

Process for the preparation of zeolite X having a Si/Al atomic ratio of less than 1.5, the exchangeable cations of which comprise, referred to as equivalents,

• from approximately 50 to approximately 95% of lithium ions,
• from approximately 4 to approximately 50% of trivalent ions selected from aluminum, scandium, gallium, iron (III), chromium (III), indium, yttrium, lanthanides or rare earth metals, alone or as a mixture, and/or of divalent ions selected from calcium, strontium, zinc, copper, chromium (II), iron (II), manganese, nickel or cobalt, alone or as a mixture, and
• 0 to approximately 15% of residual ions selected from sodium, potassium, ammonium or hydronium, alone or as a mixture, comprising:
• a) suspension of the zeolite in water, then;
• b) exchange of the exchangeable cations of the suspended zeolite with at least one di- and/or trivalent ion by simultaneous and/or successive contacts(s) in a static mixer of the said suspension with at least one solution comprising compounds of the at least one di- and/or trivalent ion;
• and
• c) exchange of the exchangeable cations of the zeolite resulting from stage b) with lithium.