Catalytic cracking process using ammonia-stable zeolite catalyst

Claim 1

A process for the catalytic cracking of a hydrocarbon feedstock to produce lower boiling hydrocarbons, which comprises contacting said feedstock, under non-hydrogenative cracking conditions, with a cracking catalyst comprising a major proportion of a refractory oxide of a difficulty reducible metal, and intimately admixed therewith a minor proportion of an ammonia-stable Y zeolite composition prepared by the steps of: 1. calcining an ammonium-sodium Y zeolite containing about 0.6 - 5 weight-percent of sodium as Na 2 O, said calcining being carried out at a temperature between about 600° and 1650° F. in contact with at last about 0.2 psi of water vapor for a sufficient time to substantially reduce the unit cell size of said zeolite and bring it to a value between about 24.40 and 24.64 A; 2. subjecting the calcined zeolite to further ammonium ion exchange under conditions adjusted to replace at least about 25 percent of its residual zeolitic sodium ions with ammonium ions and produce a final product containing less than about 1 weight-percent Na 2 O; and 3. calcining the product from step (2) at a temperature between about 600° and 1500° F. for a time sufficient to effect substantial deammoniation, but insufficient to reduce the unit cell size thereof to below about 24.40 A.