Cracking catalyst poisons passivated with tin compounds plus both sulfur and phosphorus

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 in the absence of added hydrogen or antimony to obtain a cracked product; (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 regenerated catalyst contains contaminants selected from the group consisting of nickel, vanadium and iron deposited on said cracking catalyst in such a way that said cracking catalyst cannot be fully regenerated in the regeneration zone, the improvement comprising contacting the cracking catalyst with a treating agent containing tin, phosphorus and sulfur in an amount sufficient to impart to said cracking catalyst a tin concentration of from about 0.0001 to about 4 percent by weight of contacted cracking catalyst wherein the cracking catalyst is contacted with from about one-half to about 8 parts by weight of sulfur and/or from about one quarter to about one part by weight of phosphorus for each part by weight of tin with which it has been contacted.