Research on Catalytic Cracking Performance Improvement of Waste FCC Catalyst by Magnesium Modification

In this study, the deactivation mechanism caused by high accessibility of strong acid sites for the waste FCC catalyst was proposed and verified for the first time. Based on the proposed deactivation mechanism, magnesium modification through magnesium chloride impregnation was employed for the regeneration of waste FCC catalyst. The regenerated waste FCC catalyst was characterized, with its heavy oil catalytic cracking performance tested. The characterization results indicated that, in comparison with the unmodified waste FCC catalyst, the acid sites strength of the regenerated waste FCC catalyst was weakened, with no prominent alterations of the total acid sites quantity and textural properties. The heavy oil catalytic cracking results suggested that the catalytic cracking performance of the regenerated waste FCC catalyst was greatly improved due to the suitable surface acidity of the sample. In contrast with the unmodified waste FCC catalyst, the gasoline yield over the regenerated waste FCC catalyst significantly increased by 3.04 percentage points, meanwhile the yield of dry gas, LPG, coke and bottoms obviously decreased by 0.36, 0.81, 1.28 and 0.87 percentage points, respectively, making the regenerated waste FCC catalyst serve as a partial substitute for the fresh FCC catalyst. Finally, the acid property change mechanism was discussed.