Process for producing Y-type zeolite

Claim 1

A process for producing a Y-type zeolite which consists essentially of the steps of: incorporating an aqueous alkali silicate solution with an aqueous alkali aluminate solution in the presence of an alkali in such an amount that the ratio of M 2 O (M: an alkali metal) to Al 2 O 3 , present in the resulting incorporated solution, is in the range of from about 7 to about 30 by mole and the ratio of SiO 2 to Al 2 O 3 , present in the resulting incorporated solution, is in the range of from 2 to 10 by mole, forming a gel having a SiO 2 /Al 2 O 3 molar ratio of from about 2.7 to about 3.0 in the incorporated solution, by maintaining the incorporated solution at a temperature of of from 40° C. to 70° C. for a period of at least 20 minutes, separating the gel from the mother liquor by filtration; and then, incorporating the separated gel in an aqueous solution of an alkali silicate or a mixture of an alkali silicate and an alkali to obtain a slurry having the following oxide molar ratios: M 2 O/SiO 2 : 0.25 to 0.50 SiO 2 /Al 2 O 3 : 6 to 20 H 2 O/M 2 O: 20 to 80 wherein M is an alkali metal, followed by forming Y-type zeolite crystals in the slurry.