| 摘要 |
A decationized crystalline aluminosilicate zeolitic molecular sieve having a silicon dioxide/aluminum trioxide ratio greater than 3, a pore size of at least 5.6</>rA and in which at least 10% of the aluminium atoms of the zeolite are not associated with cations, is prepared by contacting a zeolitic molecular sieve with hydrogen or ammonium cation-containing material, thereby replacing at least 10% of the zeolitic cations with hydrogen or ammonium and thereafter removing the latter cations by heating the substituted zeolite at 350-600 DEG C. Zeolites referred to are zeolite Y (see Specification 909,266), zeolite L (see Specification 909,264), and faujasite. The cations replaced are generally sodium, calcium or silver. Exchange is preferably effected with ammonium ions in a batch or continuous process at elevated temperatures employing any ammonium salt which forms a soluble salt with the replaced cation. A degree of hydrogen cation exchange may be effected by washing with acid and such a process may precede the ammonium ion substitution. A small amount of hydrogen cation exchange may be effected by simple water leaching. Removal of the ammonium cation is facilitated by heating in an oxygen-containing atmosphere while applying a vacuum. The decationized zeolite may be re-hydrated and re-activated without loss of molecular sieving characteristics. Examples refer to the replacement of about 30% of the sodium cations of a zeolite by treatment with hydrochloric acid and up to 86% substitution by treatment with ammonium chloride. Further examples relate to the treatment of a silver substituted zeolite Y with ammonium cyanide or thiocyanate, the treatment of a calcium substituted zeolite Y with ammonium chloride, and the effect on the decationization of the ammonium substituted zeolite Y in vacuum, dry air, dry nitrogen and dry hydrogen. The decationized sieve may be employed as an absorbent or as a hydrocarbon cracking catalyst. Specifications 777,233, 972,831 and 972,832 also are referred to. |
