Abstract: Designing a catalyst for DE SO x additives of FCC catalysis is a challenging problem.The catalyst must be incorporated into a particle having physical properties,in particular,attrition characteristics,compatible with FCC catalysts and be able to (1) oxidize SO 2 to SO 3,(2)chemisorb the SO 3 in the FCC regenerator,and then (3) release it as H 2S in FCC reactor.A cerium dioxide containing magnesium aluminate spinel catalyst was proved to display an even better DE SO x function.Spinels were formed in acidic solution that wound be the cheapest method for commercial preparation.A systematic X ray diffraction characterize of the stoichiometric and the magnesia excess spinels were also given.