Passivation of FCC catalysts

Claim 1

In a process comprising: (a) contacting a hydrocarbon feedstock with a fluidized zeolite-containing cracking catalyst in a cracking zone under cracking conditions; (b) recovering the cracked product; (c) passing the cracking catalyst from the cracking zone to a regeneration zone; (d) regenerating the cracking catalyst in the regeneration zone by contact with oxygen-containing gas under regeneration conditions to produce a regenerated catalyst; and (e) introducing the regenerated catalyst to the cracking zone for contact with the hydrocarbon feedstock; wherein the catalyst during the cracking process is eventually contaminated with from about 500 to 10,000 parts per million parts of catalyst with vanadium contained in the feedstock, which vanadium would at regeneration temperatures and conditions affect the catalyst in a manner which would detrimentally affect its efficiency upon being reintroduced to said cracking zone for reuse; the improvement comprising treating the vanadium contaminated cracking catalyst prior to its reaching equilibrium and prior to the subjection thereof to regeneration temperatures with a material consisting essentially of tin or a source thereof, the amount of tin utilized being from 1 to 1999 ppm of catalyst.