Catalytic cracking of hydrocarbons

Claim 1

In a catalytic cracking process wherein said process is carried out in a unit comprising a cracking zone operating in the absence of added hydrogen, a catalytic regeneration zone, and a circulating inventory of solid acidic cracking catalyst and a carbon monoxide oxidation catalyst comprising a metal of the platinum group which cracking catalyst acquires while in the cracking zone a deposit of coke that contains chemically bound nitrogen, said coked catalyst while in the regeneration zone being converted to regenerated catalyst in the presence of the carbon monoxide oxidation catalyst with the formation of a flue gas comprising carbon dioxide and noxious nitrogen oxides, the improvement which comprises: reducing noxious nitrogen oxides in said flue gas by incorporating into said circulating catalyst inventory an amount of additive particles comprising a crystalline zeolite having a silica to alumina ratio of 20 to 100 and a pore size of at least 5 Angstroms, said zeolite containing copper metal or ions equivalent to at least one half mole of CuO for each mole of Al 2 O 3 in said zeolite, with said amount of additive particles constituting 0.1 to 30 weight percent of said circulating inventory including additive.