Variation Regularity Of Chemical Structure And Reaction Performance Of FCC Slurry During Hydrotreating

FCC slurry is an important by-product from catalytic cracking process.FCC slurry is riched in polycyclic aromatics and most likely to condense to coke.Recycling FCC slurry can result in the increasement of carbon-burning load in regenerator and even coking in the disengager,which affect the normal operations.So the refineries are inclined to throw away the FCC slurry.This paper aims to understand FCC slurry's properties and composition deeply,study the hydroprocessing of polycyclic aromatics and investigate the affect of process methods on the reaction performance of FCC slurry.In the first place,two different kinds of FCC slurry were cut into several narrow fractions according to the boiling points by high vacuum distillation apparatus.The properties of narrow fractions were analyzed by common analysis methods combined ESI FT-ICR MS,GC×GC-TOF MS,~1H-NMR and FT-IR.The results show that narrow fraction of Changqing FCC slurry,which is paraffin base,contained amounts of alkanes.The condensed aromatics with 3 to 5 rings made up a large portion of aromatics.When the boiling point is lower than500?,the heavier the narrow fraction is,the more aromatics rings it contains and the higher degree of condensation it has.But when the boiling point is higher than 500?,the number of aromatic rings keeps relatively stable at 5,while the number of naphthenic rings rise and the side chain's length become longer.Besides,as the boiling point range of narrow faction increasing,the molecular weight and viscosity increase while the density,refractive index and aromatic carbon ratio increase firstly and then decrease.But the content of saturates shows the opposite trend.Their inflection point emerges at about 500?.For Qingdao FCC slurry of intermediate base,as the boiling point range of narrow fractions rising,the variation regularity of properties shows a similar trend just as crude oil.The triaromatics and tetraaromatics are the major part of narrow fractions while the pentaaromatics is concentrated in 450~500?.Besides,the heavier the narrow fractions,the higher degree of condensation.The higher aromatic carbon ratio,the more aromatic ring numbers and the shorter average length of side chain.Secondly,the narrow fractions of Qingdao FCC slurry were hydrotreated by using an autoclave.The results show that hydrogenation saturation and hydrocracking occur at the same time.By hydrotreating,the density,refractive index and molecular weight decrease.H/C atom ratio increases 0.05~0.12.The removal ratio of sulfur reaches 48.51%~65.43%.This result is 24.24%~40.00%for nitrogen.Due to the different hydrocarbon group compositions,different narrow fractions show different hydro-conversion behavior.But the ring number of aromatic hydrocarbon reduce in general.Thirdly,the effect of hydroprocessing on the catalytic cracking performance of FCC slurry was researched.The results show that for the IBP~375?narrow fraction of Qingdao FCC slurry,the yield of LPG and gasoline increase while the diesel's yield decreases after hydrotreating;for the 425~450?narrow fraction of Qingdao FCC slurry,the yield of gasoline and diesel increase after hydrotreating.For the Changqing light FCC slurry,after hydrotreating,the yield of LPG,gasoline and diesel increase.Finally,several Changqing light FCC slurry were separated according to different distillation temperature by high vacuum distillation apparatus and the cutting temperature on the reaction performance of light FCC slurry was studied.The results show that the conversion of each sample is low.As the cutting temperature increasing,the yield of LPG and gasoline decrease firstly and then increase,the diesel yield decreases and the coke yield increases obviously.