Process for preparing a nanometric zeolite Y

A process for preparing a nanometric zeolite Y of FAU structural type with a crystal size of less than 100 nm and an A/B ratio of greater than 2, said process comprising:

• i) mixing, in an aqueous medium, at least one source AO2 of at least one tetravalent element A chosen from silicon, germanium and titanium, alone or as a mixture, at least one source BOb of at least one trivalent element B chosen from aluminum, boron, iron, indium and gallium, alone or as a mixture, at least one source C2/mO of an alkali metal or alkaline-earth metal C chosen from lithium, sodium, potassium, calcium and magnesium, alone or as a mixture, said source C2/mO of alkali metal or alkaline-earth metal C also including at least one source of hydroxide ions, to obtain a gel, the reaction mixture having the following molar composition:
• vAO2:wBOb:xC2/mO:yH2O
• v being 1 to 40,
• w being 0.1 to 5,
• x being 1 to 40,
• y being 30 to 1000,
• b being 1 to 3, b being an integer or rational number, and
• m being equal to 1 or 2,
• ii) maturing the gel obtained from step (i) at a temperature of −15° C. to 60° C., with or without stirring, for a time of 10 hours to 60 days,
• iii) after at least 10 hours and less than 48 hours of maturation, single or repeated addition of at least one source AO2 of at least one tetravalent element A chosen from silicon, germanium and titanium, alone or as a mixture, to said gel, the molar composition of the gel on conclusion of the addition being as follows:
• vAO2:wBOb:xC2/mO:yH2O
• v being 5 to 50,
• w being 0.1 to 5,
• x being 1 to 40,
• y being 200 to 1000,
• b being 1 to 3, b being an integer or rational number, and
• m being equal to 1 or 2,
• iv) hydrothermal treatment of the gel obtained from step (iii) at a temperature of 20° C. to 200° C., at an autogenous reaction pressure, for a time of 1 hour to 14 days, to obtain crystallization of said nanometric zeolite Y of FAU structural type.