Study Of Preparation On Mesophase Pitch By Heavy Components Of FCC Oil

In this research,the heavy components that obtained by removing the solid from FCC oil(FCC-HC)was used to prepare the mesophase pitch(MP)with the method of direct polymerization,co-carbonization and hydrogen-supply modification.MP was analyzed by polarizing microscope,elemental analysis,FT-IR and XRD,and the forming process and mechanism were also discussed in the end.The optimal conditions of direct polymerization were at the temperature of 440℃,reaction time of 10 h and reaction pressure of 2 MPa,in which MP have small domain optical structures.The residual carbon value of MP was 83.1 %,and the softening point was 204 ℃.The reaction of MP follows radical reaction mechanism,and the reaction temperature and time played important roles in the formation process of MP.At the right temperature and pressure,the formation process were as follows: cracking of raw materials →polycondensation of small molecules →polycondensation of planar aromatic macromolecules →formation of mesophase spheres → growth and fusion of mesophase spheres →bulk MP →domain structure MP.Too high temperature and too long reaction time could lead to excessive reaction,and finally carbonization.The optimal conditions of co-carbonization are at the temperature of 440℃,reaction time of 10 h and reaction pressure of 2 MPa with addition of 15 wt% NHD.The solid yield and softening point are 62.14 %and 189.4 ℃ separately,and the optical structure of MP is small domain mainly.Compared with the direct polymerization method,MP obtained by co-carbonization have lower softening point and better optical structures.NHD,composed of naphthenes ad side chain structures,significantly increases the reaction activity and reduces the viscosity of the system,which promotes the formation and growth of MP.FCC-HC is selected to prepare MP though a two-step process with tetrahydronaphthalene(THN)as addition agent.The first step is that FCC-HC is translated into petroleum pitch(PP)at the temperature of440 ℃,reaction pressure of 2 MPa and reaction time of 4 h.The second step is that PP is further modified to prepare MP at the temperature of 440 ℃,reaction pressure of 4 MPa and reaction time of 8 h with addition of 15 wt% THN.The softening point of MP is 163 ℃,and the optical structure is mainly large domain.THN can produce plentiful free radicals in reaction process,which will have strong interaction with FCC-HC and restrain the excessive condensation.In addition,the content of Naphthenic molecules increase significantly which reduces the viscosity of the reaction system and promotes the formation of MP.