Abstract: A method for passivating a catalyst used to crack hydrocarbon feedstock to lower molecular weight products in a reaction zone is disclosed where the feedstock contains at least one metal contaminant selected from the class consisting of nickel, vanadium and iron and where the contaminant becomes deposited on the catalyst such that at least a major portion of the total of said metal contaminant deposited on the catalyst comprises only one of the metal contaminants. The method comprises monitoring the composition of said metal contaminant on the catalyst, adding a predetermined amount of at least one of said metal contaminants not present as the major contaminant on the catalyst, and passing the catalyst from the reaction zone through a reduction zone maintained at an elevated temperature for a time sufficient to at least partially passivate said metal contaminant.CROSS-REFERENCE TO RELATED APPLICATIONSThis application is related to U.S. Patent Application, Ser. No. 108,395 filed on even date herewith.

Abstract: A method for passivating a catalyst utilized to crack hydrocarbon feedstock to lower molecular weight products in a reation zone is disclosed, where the feedstock contains at least two metal contaminants selected from the class consisting of nickel, vanadium and iron and where these contaminants become deposited on the catalyst. The method comprises passing the catalyst from the reaction zone through a reduction zone maintained at an elevated temperature for a time sufficient to at least partially passivate the catalyst.