Study On HDS Of Heavy Fraction Of FCC Gasoline:Reaction Law,Kinetics And Thermodynamics

Removing the sulfur impurities in FCC gasoline is the key to decrease the sulfur content of motor gasoline.The most efficient method is hydrodesulfurization(HDS).Recently,researches for HDS of gasoline focused on the preparation of new catalysts and exploitation of new processes to achieve better desulfurization and lower loss of RON.As HDS of heavy fraction of FCC gasoline becomes the predominated choice,understanding HDS of heavy fraction of FCC gasoline comprehensively and deeply is significant.However,few studies on reaction laws of that were reported,so it is very important to the preparation of new catalysts and the exploitation of new processes.In this paper,the effect of operating conditions on HDS of heavy fraction of FCC gasoline over the catalyst HR806 was studied.The results revealed that within the temperature range of 240 to 320 oC,the elevation of the temperature would promote the HDS and olefins hydrogenation reactions.However,with the further increase of temperature,the promotion effect on HDS decreased,while the promotion effect on hydrogenation of olefins gradually decreased after 280 oC.Raising pressure from 1 MPa to 3 MPa and reducing LHSV from 1 h-1 to 4 h-1 could also promote these two reactions and the promotion reduced.Raising the ratio of H2 to oil from 100 to 500 had insignificant effect on hydrogenation of olefins.When the ratio of H2 to oil was below 300,increasing the ratio would promote HDS.Compared with hydrogenation of olefins with different carbon numbers,it is found that the effects of temperature and pressure on olefins reduced with the increases of carbon numbers.The kinetic and thermodynamic studies on HDS of heavy fraction of FCC gasoline has also been studied in this work.The n-order model could express the HDS of real gasoline more accurately than the first-order model.The reaction order was 1.74 and the intrinsic reaction active energy was 68.12 k J/mol.The heat emission of hydrogenation of aromatics is the most and that of hydrogenation of olefins was the least.The reaction equilibrium constant of hydrogenation of olefins is the bigest,it is milions at 240 oC.The reaction equilibrium constants of three reactions reducd like curve “L” with raising of temperature,which meaned that they reduced faster at lower temperature.