Influences of regeneration atmospheres on structural transformation and renderability of fluidized catalytic cracking catalyst

Abstract

The regeneration of fluidized catalytic cracking (FCC) catalysts is an essential process in petroleum processing. The current study focused the regeneration reaction characteristics of spent fluidized catalytic cracking catalyst (SFCC) at different atmospheres with influences on pore evolution and activity, for a potential way to reduce emission, produce moderate chemical product (CO), and maintain catalyst activity. The results show that regeneration in air indicates a satisfaction on removing coke on the catalyst surface while giving a poor effect on eliminating the coke inside micropores. This is attributed that the combustion in air led to a higher temperature and further transformed kaolinite phase to silica-aluminum spinel crystals, which tended to collapse and block small pores or expand large pores, with similar results observed in pure O2 atmosphere. Nevertheless, catalysts regenerated in O2/CO2 diminished the combustion damage to the pore structure, of which the micro porosity after regeneration increased by 32.4% and the total acid volume rose to 27.1%. The regeneration in pure CO2 displayed low conversion rate due to the endothermic reaction and low reactivity. The coexistence of gasification and partial oxidation can promote regeneration and maintain the original structure and good reactivity. Finally, a mechanism of the regeneration reaction at different atmospheres was revealed.