Synthesis of type Y zeolite

A process for preparing type Y zeolite comprising:

• (a) preparing a slurry of zeolitic nucleation centers having an average particle size below about 0.1 micron, said slurry having the following mol ratio composition:
• 12 to 19 Na.sub.2 O;
• 0.7 to 9 Al.sub.2 O.sub.3 ;
• 12 to 19 SiO.sub.2 ;
• 220 to 900 H.sub.2 O;
• (b) preparing an intermediate reaction mixture by combining the nucleation center composition of step (a) with additional sources of Na.sub.2 O, Al.sub.2 O.sub.3, SiO.sub.2 and H.sub.2 O to obtain a mixture having the following mol ratio composition:
• 2 to 6 Na.sub.2 O;
• 4.5 to 11 SiO.sub.2 ;
• Al.sub.2 O.sub.3 ;
• 30 to 200 H.sub.2 O;
• (c) agitating and heating said intermediate reaction mixture of step (b) at a temperature of from about 30.degree. to 80.degree. C.;
• (d) mixing an acid compound selected from the group comprising mineral acids, aluminum salts of mineral acids and mixtures thereof to the reaction mixture of step (c) to obtain a final reaction mixture having the following mol ratio composition:
• 0.5 to 2.5 Na.sub.n (A);
• 1.2 to 3 Na.sub.2 O;
• 4 to 7.5 SiO.sub.2 ;
• Al.sub.2 O.sub.3 ;
• 40 to 200 H.sub.2 O;
• wherein A is a mineral acid anion and n is the valence of A;
• and
• (e) heating the final reaction mixture of step (d) to a temperature of from about 80.degree. to 150.degree. C. for from about 2 to 40 hours to obtain type Y zeolite.