found that specific activity of the metal is enhanced in the sense that activity of the mixture for oxidation of carbon monoxide is higher than that of catalyst in which an equal amount of metal is evenly distributed among all the particles application_number US 6621579 A description the invention provides a technique for imparting co oxidation activity to cracking catalysts generally thus it may be applied for promotion of acid treated clay and amorphous silica alumina catalysts as well as the modern catalysts embodying synthetic crystalline aluminosilicate zeolites for example those described in u s pat no 3 140 249 the invention contemplates addition to the circulating catalyst inventory in a moving catalyst system for catalytic cracking either thermofor catalytic cracking tcc or fluid catalytic cracking fcc as previously pointed out fresh catalyst is added to such systems during operation in order to maintain volume of the catalyst inventory in the system and or to maintain cracking activity of the catalyst at a desired level in applying the present invention the mixed catalyst here described may be added for the sole purpose of imparting carbon monoxide oxidation activity upon withdrawal of a suitable portion of the circulating catalyst inventory such catalyst addition for the sole purpose of imparting oxidation activity will be unusual for example if the co boiler is unexpectedly taken off stream in a unit having catalyst of little or no co oxidation activity this unusual step avoids need to discontinue charge to the cracking unit in order to comply with restrictions on discharge of co to the atmosphere the catalyst blend of the invention is provided by mixing a major portion of unpromoted catalyst with a minor portion of catalyst or an.