Maximizing Yield Of Propylene By Two-stage Riser Catalytic Pyrolysis Technology

Maximizing Yield of Propylene by Two-stage Riser Catalytic Pyrolysis is the new technology on the basis of the TSRFCC technology and basic studies on reaction rules and catalyst of converting heavy oil, C4 mixture gas and FCC light gasoline to propylene. Firstly, a conceptual model is presented for describing reaction dynamics of heavy oil converting to propylene.The rule of producing propylene by FCC gasoline and C4 is studied in laboratory. Using FCC gasoline as raw material, compared experimental results between catalytic cracking and heat cracking, we found that higher yield of ethylene and propylene can be obtained by catalytic cracking, especially the yield of propylene. At the same time, the outgrowth of catalytic cracking process is fewer. In addition, the properties of HZSM-5 catalyst are also studied. Using C4 as raw material, The effect of temperature, m(H2O)/m(Feed) and resident time on reaction effect is observed by fixed bed reactor under normal pressure condition. Effect of Si/Al (catalyst active composition) ratio and granule diameter on propylene yield is also investigated in this paper.According to reaction characteristics of producing gasoline with high olefin by Daqing raw material and converting butylene to propylene, MMC-2 and the catalyst for maximizing yield of propylene developed by Lanzhou petro-chemic academe are used to perform trial study considering reaction conditions. After evaluating MMC-2 and the catalyst for maximizing yield of propylene and test results, some advices are put forward including that we can only consider recycle light gasoline, and contact times of light gasoline and butylene with catalyst should be controlled in 0.3s and 0.4s respectively.Some problems are found by analyzing running data of industrial unit in Daqing refinery, such as severe catalyst damage, bad light gasoline cut and high olefin in steady gasoline. The reasons for these problems are studied for giving the direction of future investigations.Aimed at avoiding severe catalyst damage, CFD simulator is studied at different reactor structures and feed-in styles. Results show that the contact probability of oil and catalyst is little in the reactor. Distribution of catalyst in axis and radial is not even. Catalyst abrasion is serious because of the design of reactor is not good. Some improvements are brought forwarding in this paper according to the simulation results.In addition, two key technologies for light gasoline cutting are developed. Further studies should be done in the future on the two new technologies.