Study On Polymer Modified Coal Tar Pitch And Its Carbonized Materials

As a high performance precursor of functional carbon materials,coal tar pitch has the specialties of high carbon residue,low cost and easy graphitization,and its carbonized materials are widely used in the new energy industry.How to adjust the carbonization process through coal pitch modification,optimize structure arrangement of carbon materials,make it easier to graphitization,and improve the application performance of carbonized materials is the key technical problem in the research of coal chemical industry.And when the polymer is directly added into the coal pitch,the compatibility between the two is poor and the homodisperse cannot be achieved.How to achieve the fine dispersion of the polymer single chain segment in the coal pitch,so as to regulate the carbonization process and microstructure of the coal pitch through the structures of polymer is a key scientific problem in the research of coal chemical industry.Based on the principle of in situ free radical polymerization,polymer modified coal pitch was prepared in this paper.The effects of imidazoline and free radical modifier on the conversion of coal pitch were investigated,and the effects of optimal dosage,pretreatment temperature,ratio of coal pitch to monomer,polymerization reaction temperature and other factors on the conversion of coal pitch were studied.The highest conversion of polystyrene modified coal pitch（CTP-M1）and polystyrene polyacrylonitrile copolymer modified coal pitch（CTP-M2）were 45.86%and 25.54%respectively in the mixed imidazoline regulating system.In the free radical regulator regulation system,the highest conversion rate of polystyrene modified coal pitch（CTP-T1）and polystyrene polyacrylonitrile copolymer modified coal pitch（CTP-T2）is 34.86%and 22.75%respectively.The structure of polymer modified coal pitch is further analyzed by MALDI mass spectrometry.The carbonization of polymer modified coal pitch（CTP-M）,（CTP-T）and raw coal pitch（CTP）were also studied in this paper.The results of TGA show that the thermal stability of coal pitch can be improved by adding polymer into it.FTIR results show that the aromaticity of the modified coal pitch is higher than that of the raw coal pitch.In the carbonization process,the small molecules gradually disappear,and the alkyl chain structure of the modified coal pitch fat gradually breaks and disappears.The results of SEM,XRD and N₂ adsorption and desorption tests show that the microstructure of the modified coal pitch carbonized material has a layered streamlined structure,and the carbon molecular structure has a high degree of order,and the content of microcrystals in the material increases.After AC impedance（EIS）test and analysis,when the modified coal tar pitch carbonization material is used as the electrode material,the electron transfer barrier is reduced and the conductivity is improved.At the same time,the application of polymer modified coal pitch carbonization materials was studied in this paper.The results show that the thermal expansion coefficient of the prebaked anode carbon rod samples prepared by the modified coal pitch decreases,and the thermal expansion coefficient of the prebaked anode graphite rod prepared by the modified coal pitch is the smallest,which can reach 0.8×10-6℃-1.The CTP-T2 modified coal asphalt-based carbon material coated graphite anode material,the discharge specific capacity is 362m A/g（current density 372m A/g）,the first coulomb efficiency is 97.49%.After three cycles of charge and discharge,the specific discharge capacity and Coulomb efficiency of the anode material basically remain at 353m Ah/g and 99.5%,indicating that the electrode material has stable electrochemical performance.