| abstract |
Coke is removed from particulate catalyst by passing coke-containing catalyst downwardly through a regenerator without backmixing, in a countercurrent flow with respect to a regeneration gas having a limited free-oxygen content, so that nitrogen oxides are reacted to form free nitrogen in a substantially oxygen-free atmosphere in an intermediate level of the regenerator, and carbon monoxide formed in the intermediate level is burned in contact with coke-free catalyst with additional oxygen introduced into an upper level of the regenerator. |