| 摘要 |
PURPOSE: Zeolites X that are exchanged with lithium and with trivalent and/or divalent ions have selective adsorption characteristics for nitrogen as well as have an improved thermal stability together with an improved crystallinity. CONSTITUTION: In a process for the preparation of zeolites X of exchangeable cations in which the Si/Al atomic ratio thereof is less than 1.5 and it comprises, referred to as equivalents, from approximately 50 to approximately 95% of lithium ions, from approximately 4 to approximately 50% of trivalent ions chosen from aluminium, scandium, gallium, iron(III), chromium(III), indium, yttrium, lanthanides or rare earth metals, alone or as a mixture, and/or of divalent ions chosen from calcium, strontium, zinc, copper, chromium(II), iron(II), manganese, nickel or cobalt, alone or as a mixture, 0 to approximately 15% of residual ions chosen from sodium, potassium, ammonium or hydronium, alone or as a mixture, the process is characterized in that it comprises the following stages: a) suspension of the zeolite in water, then b) exchange of the exchangeable cations of the suspended zeolite with one or more di- and/or trivalent ions by simultaneous and/or successive contact(s) in a rapid mixer of the suspension with one or more solutions comprising compounds of the di- and/or trivalent ions, c) exchange of the exchangeable cations of the zeolite resulting from stage b) with lithium.
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