Process for producing a crystalline aluminosilicate

A process for producing a crystalline aluminosilicate having the following characteristics:

• (A) an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio as determined by chemical analysis of from 5 to 11;
• (B) a unit cell dimension of from 24.45 to 24.55 .ANG.;
• (C) a molar ratio of the Al contained in the zeolite framework to the total Al contained in the aluminosilicate of from 0.3 to 0.9, said molar ratio being calculated using the following equations (1) to (3):
• N.sub.Al =(a.sub.0 -2.425)/0.000868 (1)
• where a.sub.0 is the unit cell dimension (nm) and
• N.sub.Al is the number of Al atoms per unit cell,
• (Si/Al)=(192-N.sub.Al)/N.sub.Al ( 2)
• where 192 is the number of Si and Al atoms per unit cell of zeolite Y, and
• (Al in the zeolite framework)/total (Al)={(Si/Al) determined by chemical analysis}/{(Si/Al) determined by using equation (2)} (3)
• (D) an alkali metal content, in terms of oxide, of from 0.02 to 1.5% by weight;
• (E) an X-ray diffraction pattern having peaks characteristic of zeolite Y;
• and
• (F) an ignition loss of from 0.5 to 20% by weight;
• which process comprises calcining stabilized zeolite Y in the temperature range of from 400.degree. to 590.degree. C. for 5 to 300 minutes such that the decrease in the crystallinity of said stabilized zeolite Y is 20% or less, said stabilized zeolite Y initially having an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio of from 5 to 11, a unit cell dimension of from 24.50 to 24.72 .ANG., and an alkali metal content in terms of oxide of from 0.02 to 1.5% by weight.