Method of initiating essentially complete oxidation of co to co.sub.2 in

Abstract

A method for initiating essentially complete oxidation of carbon monoxide, resulting from the oxidative removal of coke from spent FCC catalyst, to carbon monoxide in a dense-phase bed of catalyst maintained in a regeneration zone. Coke is oxidized at first oxidizing conditions including a temperature of from about 750.degree. F. to about 1250.degree. F. to produce partially spent regeneration gas and regenerated catalyst having a first carbon content. The essentially complete oxidation of carbon monoxide is initiated by: (a) increasing the coke on regenerated catalyst from the first carbon content to a second carbon content and then (b) passing to the dense bed fresh regeneration gas at a flow rate at least stoichiometrically sufficient to produce regenerated catalyst having a third carbon content, less than the first carbon content, and sufficient to produce spent regeneration gas. The heat released in the dense bed by the oxidation of the additional coke (analyzed and reported as weight percent carbon) increases the dense bed temperature and permits a faster rate of CO oxidation so that essentially complete conversion of CO to CO.sub.2 can take place within the dense bed. The availability of sufficient fresh regeneration gas then spontaneously initiates the essentially complete conversion of CO to CO.sub.2. Once initiated, the exothermicity of the oxidation of CO further increases the dense phase temperature to maintain a fast rate of reaction. Thereafter, coke and CO are oxidized at second oxidizing conditions to produce spent regeneration gas and regenerated catalyst having the third carbon content.