Study On The Differential Formation And Mechanism Of Primary Mesophase Pitch

In this paper,the aromatic heavy oil HHHTO was used as the raw oil,and the molecular weight and aromatic distribution of HHHTO-60 and HHHTO-80 were obtained by distillation treatment.The aromatic components of HHHTO-80-FEO were obtained by solvent extraction of HHHTO-80.Primary mesophase pitch was prepared by direct thermal condensation with the above raw materials,and HHHTO-60 was prepared by direct thermal condensation and hydrogen supply condensation,respectively.Experiments were designed to investigate the effects of different raw materials and different reaction conditions on primary mesophase pitch,optimize the production process,and explore the differentiation formation mechanism of primary mesophase pitch.Primary mesophase pitch was prepared by direct thermal condensation polymerization.After 6 hours of reaction at 420℃ and 6MPa,the reaction time was 4h at low pressure.Under these conditions,primary mesophase pitch with a yield of 72.18%,a mesophase content of17.8%,a softening point of 72℃ and a large number of mesophase spheres were obtained.After enrichment treatment,the yield is 31.65% and the softening point is 343℃.The reaction process follows the free radical reaction mechanism.The higher the reaction temperature and the longer the reaction time,the more the side chain breaks,the closer the accumulation of aromatic lamellae and the higher the orientation degree.The presence of reaction pressure can make more small molecule free radicals participate in the reaction,reduce the viscosity of the system,increase the fluidity of the system,and improve the orientation of the crystal.Primary mesophase pitch was prepared by hydrogen supply condensation polymerization method.The reaction temperature was 430℃,the amount of THN was 10wt%,and the time point was 1h.Under these conditions,the yield of the product was 67.61%,the content of mesophase was 21.35%,and the softening point was 68℃.After solvent extracton and enrichment of primary mesophase pitch,the yield of the product is 17.51% and the softening point is 284℃.The reaction mechanism of hydrogen supply polycondensation is free radical,and the temperature plays a controlling role.The addition of THN increased the content of naphthenes in the raw material,and a large number of hydrogen free radicals were generated during the reaction process.The hydrogen free radicals preferentially combined with the free radicals with higher degree of condensation of the aromatic hydrocarbons,thus alleviating the degree of condensation of the aromatic hydrocarbons,which was conducive to the formation of primary mesophase pitch with lower softening point and more concentrated distribution of components.Comparing the properties of primary mesophase asphalt prepared from different raw materials,it can be seen that the presence of high boiling point components increases the molecular weight,ash content and asphaltene of raw materials,and the viscosity of the system is greatly improved compared with the presence of recombinant components.The primary mesophase pitch prepared from raw materials containing higher boiling point components has higher softening point,uneven mesophase development and excessive carbonization.The existence of low boiling point components reduces the viscosity of the system,and increases the alkane and alkyl content of the system.Hydrogen free radicals generated during the reaction process can relieve the condensation degree of the viscous cyclic aromatic hydrocarbons to a certain extent,thus reducing the softening point of the primary mesophase asphalt,and improving the polarization structure of the mesophase.Furfural extraction can make the components of the raw material evenly distributed,relatively uniform component properties,high viscosity in the molecule,short alkyl side chain,the reaction of mesophase asphalt products more uniform,moderate softening point.