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Phosphorus(P) and metal(M) components were incorporated into promoters for enhancing FCC propylene yield,and the reactive behavior of promoters,before and after modification,were investigated.The results showed that both LPG and propylene yields were increased,and propylene selectivity was improved after the incorporation of P or M into the matrix,resulting in an increased C_3 to C_4 ratio in LPG during FCC process.But the sole incorporation of M into the matrix also led to an increase in coke and H_2 yields on the other hand.Simultaneous modification of the matrix by P and M components resulted in more enhancement in propylene yield and selectivity along with little influence on FCC product distribution.Physico-chemical characterizations and model compound reactions were used to assist in analyzing the mechanism for improving propylene selectivity.Two types of active centers could strengthen the oligomerization of C_4~= olefins in LPG and these oligomers could be further cracked into C_3~= olefins on ZSM-5 zeolite,therefore maximizing the ratio of C_3 to C_4 in liquefied petroleum gas obtained during FCC process.
Phosphorus (P) and metal (M) components were incorporated into promoters for FCC FCC yield, and the reactive behavior of promoters, before and after modification, were investigated. The results showed that both LPG and propylene yield were increased, and propylene selectivity was improved after the incorporation of P or M into the matrix, resulting in an increased C_3 to C_4 ratio in LPG during FCC process. The sole incorporation of M into the matrix also led to an increase in coke and H_2 yields on the other hand . Simultaneous modification of the matrix by P and M components derived in more enhancement in propylene yield and selectivity along with little influence on FCC product distribution. Physico-chemical characterizations and model compound reactions were used to assist in analyzing the mechanism for improving propylene selectivity. Two types of active centers could enhance the oligomerization of C_4 ~ = olefins in LPG and these oligomers could be further cracked into C_3 ~ = olefins on ZSM-5 zeolite, maximizing the ratio of C_3 to C_4 in liquefied petroleum gas during FCC process.