Regeneration of cracking catalyst in two successive zones

A process for treating solid particles of partially or completely deactivated cracking catalyst which process comprises:

• (1) passing said solid particles into a first fluidized bed reactor and therein contacting the solid particles at elevated temperatures with a first gas stream consisting essentially of (a) oxygen plus steam, (b) oxygen plus carbon dioxide, or (c) oxygen plus steam plus carbon dioxide and adjusting the ratio of oxygen to steam and/or carbon dioxide so that some carbon is removed form the solid particles without major net evolution of heat in the first reactor, thereby partially regenerating the said cracking catalyst particles to produce synthesis gas containing a mixture of steam, carbon monoxide, carbon dioxide and hydrogen, and thereafter
• (2) passing the thus-treated solid particles from the base of said first fluidized bed reactor downwardly by gravity to the top of a second fluidized bed reactor and therein contacting the solid particles at elevated temperature wih a second gas stream comprising oxygen thereby substantially completely regenerating the said cracking catalyst particles and removing the regenerated catalyst from the base of the second fluidized bed reactor, provided that the first fluidized bed reactor is disposed substantially vertically above the second fluidized bed reactor located within one vessel,
• the contacting and the reactions occurring in both reactors being controlled so that there is no major evolution of heat from either reactor.