Study On Influencing Factors On Preparation Of Coal-Based Mesocarbon Microbeads By Thermal Condensation Method

Mesocarbon Microbeads（MCMB）,which are usually obtained from high temperature coal tar pitch by thermal condensation,are a new type of functional coal-based carbon materials with excellent chemical stability,high specific surface area and high order carbon microcrystalline structure.However,the further development of MCMB is limited by its high preparation cost and wide particle size distribution.In this thesis,high temperature coal tar pitch（HCTP）produced by a coking plant in Shanxi was used as raw material to prepare MCMB by thermal condensation method.On the premise of optimizing the thermal condensation process conditions based on single factor method,The factors affecting the preparation of MCMB were systematically discussed from three aspects:the content of primary quinoline insoluble substance（PQI）,the amount of ethylene residue pitch（ETP）and the amount of nano TiO₂.The materials are characterized by industrial analysis,elemental analysis,thermogravimetric analysis,polarized light analysis,particle size analysis,FT-IR,SEM,Raman,XRD and other methods.The specific research contents include:（1）Using HCTP from a coking plant in Shanxi as raw material,the effects of polymerization temperature,constant temperature time and stirring speed on the morphology and structure of MCMB were investigated.The optimum polymerization temperature of MCMB was 430℃,the constant temperature time was 4.5 h,and the stirring speed was 120 rpm.Under these conditions,the yield of MCMB was 29.62%.Particle size uniformity index was 0.93;When the obtained MCMB was carbonized at1100℃,the content of its ideal graphitic carbon microcrystalline structure was75.45%.（2）The influence of different PQI contents in HCTP on the preparation of MCMB was explored.Pitch with different PQI contents were prepared by mixing solvent method and mixing method,and MCMB was prepared from them under the same thermal condensation conditions.When the content of PQI in raw pitch is7%～13%,MCMB with good morphology and structure is more favorable.When the content of PQI is 9%,the sphericity of MCMB is the best,the particle size uniformity index is 1.05,and the yield is as high as 33.09%.After carbonization at 1100℃,the content of ideal graphitized carbon microcrystal is 79.92%.（3）The effect of cocondensation of ETP and HCTP on the preparation of MCMB was investigated.A series of MCMB were prepared by adding different proportions of ETP to HCTP and conducting co-condensation reaction under the same thermal condensation conditions.When the ETP content was 7%,the optimal MCMB yield was 32.7%,the particle size uniformity index was 1.12,and the ideal graphitized carbon microcrystalline structure content was 79.94%after carbonization at 1100℃.（4）The effect of nano TiO₂on the preparation of MCMB was studied.TiO₂was added to the refined HCTP in a certain proportion（the HCTP was purified and QI was removed）,and the MCMB was prepared by co-polycondensation under the conditions of reaction temperature of 420℃,constant temperature time of 3.5 h,and stirring rate of 120 rpm.When TiO₂is added to the system,the generation of small scale MCMB can be promoted.When TiO₂content reached 1.5%,the yield of small scale MCMB was 6.44%,the average particle size was 0.56μm,the sphericity and morphology were good,and the particle size uniformity index was 1.23.After carbonization at 1100℃,the content of ideal graphitized carbon microcrystal is 77.61%..