Process for regenerating fluidizable particulate cracking catalysts

Claim 1

A process for regenerating spent fluidizable catalyst particles contaminated with carbonaceous deposits comprising the steps of: introducing spent catalyst particles and hot regenerated catalyst particles directly from a secondary regeneration dense phase zone into a stream of oxygen-containing gas and entraining the catalyst particles in the gas stream to produce a dilute phase catalyst particle stream; the amount of oxygen in said dilute phase stream being sufficient to oxidize substantially all of the carbonaceous deposits on said spent catalyst particles to gaseous combustion products; the temperature of the hot regenerated catalyst particles being greater than the minimum temperature required to initiate rapid oxidation of the carbonaceous deposits on the spent catalyst particles, and the proportion of hot regenerated catalyst introduced into said gas stream being sufficient to raise the temperature of the dilute phase stream to at least the minimum temperature required to induce rapid oxidation of said carbonaceous deposit; passing said dilute phase particle stream through an upwardly directed primary regeneration zone while maintaining regeneration conditions suitable for rapid oxidation of said carbonaceous deposit in said primary zone and oxidizing substantially all of the carbonaceous deposits on said spent catalyst particles to gaseous combustion products in said dilute phase stream in the primary zone to regenerate the catalyst particles; passing said dilute phase stream containing regenerated catalyst particles and gaseous combustion products from the top of said primary zone to the bottom of a dense phase bed of regenerated catalyst particles in a secondary regeneration zone disposed above the primary zone; introducing a secondary oxygen-containing gas into the lower portion of the dense phase bed in the secondary regeneration zone to assist in maintaining the dense phase bed in a fluidized state and to assure substantially complete combustion of carbon monoxide in the dense phase bed to carbon dioxide; exhausting the gaseous combustion products from said secondary regeneration zone; said exhausted gaseous products containing between about 1 percent and about 5 percent oxygen and less than 1,500 ppm by volume carbon monoxide; and withdrawing hot regenerated catalyst particles from said secondary regeneration zone; said regenerated catalyst particles containing less than 0.1 weight percent carbon.