Study On Preparation Of Coal-Based Mesophase Pitch And Its Homogeneous Structure Properties

In recent years,with the continuous development and progress of science and technology,the requirements for materials in many fields are increasingly high,and the high-end carbon materials is a very important part.As is known to all,mesophase pitch is a macromolecular mixture composed of planar polycyclic aromatic hydrocarbons.It has the advantages of easy orientation,easy graphitization,and high carbon yield,and is a high-quality precursor for the preparation of a variety of high-end carbon materials.Therefore,the research and preparation of high-quality mesophase pitch that can be industrialized has important scientific,practical and strategic significance.In this paper,refined coal tar pitch is used as raw material,and reduced graphene oxide(rGO)and tetrahydronaphthalene(THN)are used as additives to study their effects on the formation and development of mesophase pitch.An optimal preparation route of high-quality mesophase pitch was discovered through systematic research.At the same time,carbon fibers were prepared from the obtained mesophase pitch to verify the quality of the products and the feasibility of the process.Firstly,the optimal basic reaction process was found by exploring the effect of experimental temperature,holding time and reaction system pressure on the thermal polymerization of refined coal tar pitch.During the experiment,in order to reduce the difficulty of preparing mesophase pitch,this study introduced 0.01 wt%rGO as a nucleating agent to promote the formation of mesophase pitch in each set of experiments.The results show that when the thermal polymerization temperature is 400?,the holding time is 10 h,and the reaction system pressure is 2.0 MPa,the pyrolysis products have a high mesophase content,a wide-area polarized texture,a moderate softening point and insoluble content.Then,based on the optimal basic reaction process,the effects of different rGO addition amounts on the thermal polymerization process of refined coal tar pitch were studied.The results show that the addition of rGO can promote the aromatization and polycondensation reaction of pitch small molecules,thereby shortening the formation time of mesophase.But at the same time it can also hinder the coalescence of mesophase spheres to a certain extent However,when 0.01 wt%rGO is added,it can not only accelerate the generation of mesophase,but also not hinder the formation of wide-area streamlined mesophase pitch,which has a good addition effect.Finally,on the basis of all the above experiments,THN was added to solve the problem of phase separation of pyrolysis products,so as to improve the yield of mesophase pitch.In this experiment,because THN has the functions of hydrogen supply,reducing the viscosity of the reaction system and stabilizing free radicals,and combined with the previous research experience of the research group,it was decided to increase the thermal polymerization temperature from 400? to 420? to obtain a better reaction effect.The results show that the addition of THN can change the molecular structure of the product,reduce the viscosity of reaction system and molecular flatness.When the added amount is 5 wt%,it can not only reduce the viscosity of the reaction system,but also ensure the flatness of the generated molecules,which is conducive to the uniform mixing of mesophase molecules and non-mesophase molecules,and thus obtain a homogeneous mesophase pitch.Moreover,the mesophase pitch-based carbon fibers prepared from sample MP-T-5 has high tensile strength and thermal conductivity.In summary,under the conditions of polymerization temperature of 420?,holding time of 10 h,and reaction system pressure of 2.0 MPa,the homogeneous mesophase pitch with good spinnability can be obtained by adding 0.01 wt%rGO and 5 wt%THN.During the polymerization process,the?-? interaction between rGO and planar aromatic molecules can significantly accelerate the formation of the mesophase.And the addition of THN can effectively reduce the viscosity of the reaction system,change the molecular structure,and accelerate the molecular movement,which is conducive to the uniform dispersion of the non-mesophase in the mesophase.