Research And Development Of Additives Reducing Olefins In FCC Gasoline

Vehiche fuel quality standards become more and more stringent worldwidely for enviroment protection. One of the most obvious problems of fuel quality is from redundant olefin fraction of gasoline in China, which is attributed to the high proportion of FCC gasoline with ample olefin in gasoline pool.At the present time, it is difficult to largely change the gasoline pool compsition, because of the lack of the units for catalytic reforming, alkylation, isomerization and production of oxygenous compounds. Therefore, it is an important method to decrease the olefin content of FCC gasoline to solve the problem of high olefin content in commercial gasoline in China.To reduce the olefin content of FCC gasoline, new process and many catalysts for gasoline olefin reduction have been researched and applied all over the world.Such as GOR of RIPP, RFG of Grace Davison company, TOM COBRA of Akzo Nobel company.Based on the investigation of literatures, according to the principle that gasoline olefin easily take place secondary reaction, additives(LAP)are developed.The modified shape-selective zeolite, are primary active component in the additives. Gasoline olefin are changed into aromatic hydrocarbon and alkane by aromatization reaction and hydrogen transfer reaction, at the same time, the gasoline octane number has been enhanced.In this paper, aromatization activity of metal modified HZSM-5 zeolite have been studied in catalytic cracking of n-heptane. The experiments are carried out in a micro reactor chromatogram system. The results show that gallium and znic etc metal modifiers can evidently improve the aromatization activity and aromatic hydrocarbon selectivity of ZSM-5zeolite. In the certain range of the metal content, increase of metal content leads to the increase of aromatic hydrocarbon content. Aromatic hydrocarbon content hardly increase when the metal content exceed this range.So,a proper metal content is selected when HZSM-5 zeolite are modified by metal. ZnZSM-5 zeolite modified by non-metal phosper may enhance their hydrothermal stability. The results show that hydrothermal treatment can reduce the number of strong Bronsted acid sites , the stability of ZSM-5 zeolite is improved with the aromatization activity lowered slightly.In this paper, experiments, to evaluate the difference between complex zeolites and single ZSM-5 zeolite, are carried out in a micro fixed bed reactor with FCC gasoline. The results show that the former has better ability for FCC gasoline olefin reduction than the latter. At the same time, the acidity characterization show that the former has more acid sites and stronger acid strength than the latter. The increase of Bronsted acid enhances hydrogen transfer reaction.Carriers' ability for gasoline olefin reduction has been studied in the same way. The experiments show that carriers' micro activity and ability for gasoline olefin reduction increase after modification .The results are the same while using complex carriers.Based on the research, the additives for gasoline olefin reduction are prepared. Evaluations have been done in the pilot-plant units with heavy oil feedstoks.The results show that the olefin content obviously decrease over this additives.At the same time, the additives perform nicer adjustability to different feedstocks and nicer hydrothermal stability.The results of industrial application of LAP confirm the research in the lab. The olefin content decearses effectively while the octane numberincreases, at the same time, propylene in the liquid petroleum gasincrease. Refineries will benefit by using the additives.