The need for more active and hydrothermally stable fluid catalytic cracking(FCC)catalysts to combat the effect of metal contaminants has led to an increase in demand for rare earth oxides.Rare earth oxides enhance catalyst activity and prevent the loss of acid sites during the FCC unit operation,especially when heavy residue with high metal content is used as feed.In this paper,a review was carried out to show the effects of rare earth elements on the structure,activity,and stability of FCC catalysts.Also,the use of rare earth elements as vanadium traps was analyzed in conjunction with the mechanism of catalyst deactivation by vanadium.The objective was to elucidate the interaction of vanadium species with the zeolite component of the FCC catalysts and the role of rare earth elements in countering the deleterious effects of vanadium on the FCC catalysts. The need for more active and hydrothermally stable fluid catalytic cracking (FCC) catalysts to combat the effect of metal contaminants has led to an increase in demand for rare earth oxides. Rare earth oxides enhance catalyst activity and prevent the loss of acid sites during the FCC unit operation, especially when heavy residue with high metal content is used as feed.In this paper, a review was carried out to show the effects of rare earth elements on the structure, activity, and stability of FCC catalysts. Also, the use of rare earth elements as vanadium traps was analyzed in conjunction with the mechanism of catalyst deactivation by vanadium. The objective was to elucidate the interaction of vanadium species with the zeolite component of the FCC catalysts and the role of rare earth elements in countering the deleterious effects of vanadium on the FCC catalysts.