Adding fuel in catalyst regeneration

A method for removing nitrogen-containing coke from coke-containing particulate catalyst which comprises:

• (a) passing a regeneration gas comprising free oxygen upwardly through a vertically extending fluidized bed of substantially coke-free particulate catalyst, and introducing said coke-containing catalyst into said fluidized bed;
• (b) burning said nitrogen-containing coke off coke-containing catalyst present in a lower portion of said fluidized bed and burning substantially all carbon monoxide generated in said lower portion of said bed in the presence of a combustion-promoting metal, sufficient free oxygen being introduced into said bed in said regeneration gas to provide at least 1 volume percent residual-free oxygen in said regeneration gas in said lower portion of said bed, whereby coke is removed from said coke-containing catalyst and nitrogen oxide are formed in said lower portion of said bed;
• (c) generating a reducing atmosphere including at least 0.05 volume percent carbon monoxide and less than 0.5 volume percent free oxygen in said regeneration gas above said lower portion of said fluidized bed by reacting said residual free oxygen with a combustible fuel introduced into said regeneration gas above said lower portion of said bed, thereby decreasing the amount of nitrogen oxides in said regeneration gas by reacting at least a portion of said nitrogen oxides in said reducing atmosphere to form free nitrogen;
• (d) and burning the carbon monoxide present in said regeneration gas above the lower portion of said bed with additional free oxygen while in contact with said bed above said reducing zone.