| Fluidized catalytic cracking?FCC?slurry is an important and yield-rich by-product of FCC process.It contains high content of aromatic components,which are mainly polycyclic aromatic hydrocarbons with short-chain of 3 to 5 rings that can be used as high-quality raw material of high-value carbon materials,such as carbon blacks,needle coke and carbon fiber.However,FCC slurry contains a large amount of solid impurities such as catalyst powder,which seriously affect its high value-added utilization.This paper focuses on how to remove solid particles effectively from the FCC slurry,studies the charring behavior and coke structure of different coking processes,and is thus of important significance in needle coke preparation from the viewpoints of both theory and practice.Distillation can be used to separate FCC slurry according to the boiling point,and then adjust the distillation range to obtain fractions of moderate molecular weight and remove the solid particles at the same time.But distillation has a very limited target distillate yield.In order to increase this yield,it is necessary to increase the temperature of distillation.It is easy for olefins,conjugated olefins?especially olefins conjugated with benzene rings?and macromolecular fused aromatic hydrocarbons in FCC slurry to generate radicals at 260-306?,and then coke is formed through condensation reaction.Through hydrogenation pretreatment before distillation,the olefins?especially conjugated olefins?in FCC slurry can be removed,and the number of condensed aromatic rings of macromolecular aromatic hydrocarbons can be reduced,which can improve their hydrogen supply capacity.And then the coking in the distillation process is inhibited and the distillate yield is improved while achieving efficient removal of impurities.When using a molybdenum-containing organometallic compound as the catalyst,and its amount?measured based on molybdenum?was 100?g·g-1,and the stability of FCC slurry improved significantly after the hydrotreating at 380?with 6.0 MPa reaction pressure for120 minutes.Hydrotreated FCC slurry did not generate coke after distillation process with a harsh condition,and the solid particles content of distillate oil reduced to 100?g·g-1.Due to the hydrosaturation reaction of some aromatic rings of the highly condensed polycyclic aromatic hydrocarbons,so that the yield of distillate oil below 500?increased significantly to 68.39%compared to the untreated FCC slurry.Using a distillation-electrostatic-solvent extraction combined process,the solid particles content of the deep-purified FCC slurry is reduced to 20?g·g-1,and its aromatic component can be increased from 35.23%of untreated FCC slurry to 60.43%,which is 1.72 times that of the raw material.FCC slurries with different degrees of purification were selected to perform stagewise carbonization experiments,and the heating rates were controlled by adding heating stages.Then carbonization was carried out at 500?for 240 minutes.The light and shade structures of coke in polarized optical microscopic images are ordered,and its fiber structures are much wider,which represent that the wide streamline structure has a larger proportion.The rich aromatic component of FCC slurry by combined process can generate much supreme coke through stagewise carbonization,which can be used as raw material of high quality needle coke. |
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