Method of increasing the thermal stability of crystalline zeolites
AssigneeW. R. Grace & Co.
InventorCurtis H. Elliott, Jr.
Life of this patent
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Abstract
Methods of increasing the thermal stability of crystalline zeolites are disclosed. The methods are characterized by the steps of either (i), treating the crystalline zeolite first in at least one step with a dilute solution of a fluorine compound whereby a very small amount of fluoride is incorporated in the zeolite with a subsequent exchange with an ammonium ion, rare earth ion, or other metal ion solution, (ii), first exchanging the zeolite with an ammonium ion, rare earth ion or other metal ion solution followed by a treating with a dilute fluoride solution, or (iii), concurrently treating the zeolite with the fluoride ion and exchanging the zeolite in a simultaneous operation.
Claims15
A method of producing highly stable fluorided crystalline aluminosilicate zeolites comprising:
- a. contacting at least once a crystalline aluminosilicate zeolite in the alkali metal form with a sufficient quantity of a solution of a soluble fluorine compound which in solution yields available fluoride ions to provide from about 2 to 22 grams of available fluoride per 10,000 grams (dry basis) of zeolite, and a slurry pH of about 3 to 11 for a sufficient length of time to allow said solution to thoroughly contact and diffuse into said zeolite;
- b. separating and washing the fluoride treated crystalline aluminosilicate zeolite;
- c. exchanging the alkali ions in said fluoride treated crystalline aluminosilicate zeolite with an aqueous solution selected from the group consisting of ammonium salt solutions, rare earth salt solutions, alkaline earth salt solutions and transition metal salt solutions and mixtures thereof, to a final alkali content of less than about 6 percent by weight calculated as the alkali oxide;
- and
- d. recovering said highly stable crystalline aluminosilicate zeolite.
A method of producing highly stable fluorided crystalline aluminosilicate zeolites comprising:
- a. forming an admixture of a soluble fluorine compound in an amount which in solution is capable of yielding from about 2 to 22 grams of available fluoride per 10,000 gm. of zeolite and a compatible salt of a cation selected from the group consisting of ammonium, rare earth metals, transition metals and mixtures thereof;
- b. contacting a crystalline aluminosilicate zeolite in the alkali metal form at least once with said admixture to form a slurry having a pH of about 3 to 11 whereby said zeolite is concurrently fluorided and exchanged;
- and
- c. washing and drying said zeolite.
Dependencies are inferred from the claim text.