A method of operating a continuous or semi-continuous system for a catalyst regeneration process. The system comprises a regenerator, the regenerator comprising a combustion zone and a halogenation zone. The catalyst is fed into the regenerator. A circulating regeneration gas is introduced into a regenerator circuit including oxygen, the circulating regeneration gas having a nitrogen concentration that is less than air. Oxygen from the circulating regeneration gas reacts with the coke to provide water and carbon dioxide. Water and the carbon dioxide formed in this first reaction then further react with the coke to form carbon monoxide and hydrogen.