Systems and methods for regenerating a spent catalyst

Systems and methods for regenerating a spent catalyst are provided. The method can include mixing a spent catalyst with a carrier fluid to provide a mixture. The spent catalyst can include carbon deposited on at least a portion thereof. The carrier fluid can include an oxygen containing gas. The mixture can be introduced to or above an upper surface of a dense phase catalyst zone disposed within a regenerator. A gas can be introduced to a lower zone of the dense phase catalyst zone. At least a portion of the carbon deposited on the catalyst can be combusted to provide a flue gas, heat, and a regenerated catalyst.