Abstract: Based on analyzing the reaction chemistry of deep catalytic cracking, a basic idea for producing more propylene while reducing dry gas yield was proposed. The effect of monomolecular reactions and bimolecular reactions on the yields of propylene and dry gas was investigated in a fixed-bed micro-activity test unit using n-hexadecane and Daqing VGO as feedstocks respectively, under various reaction conditions and catalyst types. The results showed that enhancing monomolecular reactions could be favorable for increasing the propylene content in LPG, but the dry gas yield increased significantly. Promoting bimolecular reactions, mainly hydride transfer reactions, to some extent, would be helpful to inhibit the formation of dry gas; however, the high ratio of bimolecular reactions could cause the decrease of propylene yield. Hence, proper adjusting the ratio and/or the sequence of monomolecular reactions and bimolecular reactions might be an effective way for maximizing propylene yield and reducing dry gas yield simultaneously in deep catalytic cracking process.

Key words: deep catalytic cracking, propylene, reaction chemistry