Study On Deolefin Of FCC Slurry By Mild Hydrogenation

FCC slurry is rich in aromatic hydrocarbons and is an important potential raw material for preparing high-value products such as rubber filling oil,needle coke and carbon fiber.The premise of using such high value in FCC slurry is to remove the up to 0.2%?1% solids.It is expected that the efficient de-solidification of the FCC slurry can be achieved by distillation,which has the advantages of mature technology,convenient operation and simple equipment.However,FCC slurry begins to condense and form coke when it is heated to about 300°C,which greatly inhibits the improvement of the yield of the FCC de-solidification slurry.Therefore,this paper focuses on determining the molecular basis of poor thermal stability of FCC slurry,and designing a suitable chemical reaction system to stabilize the unstable FCC slurry molecules with mild chemical reaction conditions before distillation,i.e.,olefin hydrogenation for saturation to deolefin,which can increase the degree of stabilization reaction.Thus the target on inhibiting the coke formation in the process of distillation and subsequent treatment of the de-solidified slurry,and improving the distillation yield of the de-solidified slurry,has theoretical and practical significance.In this paper,a FCC slurry was used as raw material,and a straight-run atmospheric residue was used for comparison.The tests on coking tendency of different raw materials at different temperatures,the starting point of asphaltene precipitation,olefin content and the thermal stability of FCC slurry observed by optical microscope were performed.The suitable distillation temperature was determined,and the relationship between the olefin and the thermal stability of the FCC slurry was preliminarily analyzed.Secondly,the bromine number method,the diene value method,the ultraviolet spectroscopy method,the nuclear magnetic resonance spectroscopy method,and GC-MS were used to determine the distribution of the olefinic compounds in the FCC slurry.At the same time,the relationship between the olefin and the thermal stability of FCC slurry was investigated by using the olefin model compound.Then,the simulated FCC slurry and the olefin model compound and oil-soluble catalyst were used to stabilize the catalytic oil slurry by hydrogenation.The conditions were optimized.Finally,the hydrogenation stabilization experiment was carried out under the optimal conditions of the real FCC slurry to evaluate the olefin removal effect,with the thermal stability of the FCC slurry after deolefinization being investigated.In this way,a de-solidified FCC slurry with high yield and excellent properties can be obtained.The results show that the FCC slurry is less thermally stable than the atmospheric residue.The olefin(double bond)and the conjugated olefin(double bond)are present in the FCC slurry,and the contents are about 21% and 6%,respectively.The types of olefins(double bonds)differ among different components and fractions.There are 58 kinds of olefins in the FCC slurry(?500°C),and the content of conjugated aromatic olefins is the most.Olefin,especially the more active and high molecular weight polycyclic conjugated aryl olefins,can promote the FCC slurry to coke and increase its thermal instability.The olefin removal rate and the conjugated olefin removal rate after catalytic hydrogenation are as high as 90.50%and 91.25%,respectively,which drastically inhibits the coke formation phenomenon in the distillation process,and the distilled de-solidified slurry satisfies the solid-content requirement for the preparation of needle coke.