Preparation And Application Of Coal Tar Pitch-based High Quality Pitch

High softening point mesophase pitch has the characteristics of high carbon residue rate and easy processing.It is recognized as a precursor of many high performance materials and is widely used in lithium anode materials and high performance carbon fiber.In this paper,the high softening point mesophase pitch was prepared by using bromine free radical induction method with Xinjiang coal pitch as raw materials.The main conclusions of this paper are as follows:(1)Compared with coal tar pitch Ri,refined coal tar pitches R2 and R3 are more suitable as raw materials for preparing mesophase pitch in this experiment.Comparing the polarized photographs and XRD results of different brominated samples of R2 and R3,it is known that the optimum amounts of bromine introduced by R2 and R3 are 15%and 10%,respectively,and are recorded as R2-15%and R3-10%.And debromination samples at different temperatures(250-350 ?)and time(6-12 h)were subjected to thermogravimetric TG,softening point,elemental analysis,group composition,1H-NMR,viscosity-temperature properties,etc.The analysis results show that R2-15%can be completely removed by heat treatment at 350 ? for 6 h,and the debrominated pitch with softening point of 246 ? and carbon residue rate of 55.2%is obtained and is recored as R2-15%-350-6h.R3-10%can be completely removed by heat treatment at 350 ? for 6 h,and the debrominated pitch with softening point of 257 ? and carbon residue rate of 63.6%is obtained and is recored as R3-10%-350-6h.Comparing the physical properties of debrominated pitches with thermal polymerization pitches,it indicates that the introduction of bromine significantly increases the softening point and carbon residue rate of coal tar pitch.The viscosity-temperature curve indicates that the debrominated pitches R2-15%-350-6h and R3-10%-350-6h have good spinnability.(2)The debrominated coal tar pitches are pre-oxidized and carbonized to prepare a debrominated pitch-based lithium ion electric anode materials.Through the structural characterization of the negative electrode material,it is found that the negative electrode material has the characteristics of a typical hard carbon negative electrode material such as small specific surface area,low degree of graphitization and high degree of disorder.The electrochemical properties of the material show that the initial discharge capacity of the material increases with the increase of the pre-oxidation temperature.However,the introduction of excess oxygen leads to a decrease in the first coulombic efficiency of the material.Among them,the first charge capacity of DR2-290OD-1000 reached 500.9 mAh g-1,the first coulon efficiency was 64.7%;the first charge capacity of DR3-2700D-1000 reached 420.5 mAh g-1,and the first coulombic efficiency was 63.8%.