Medium- and low-temperature coal tar pitch can be prepared as coal-based mesophase pitch for its high value-added utilization. However, its lower aromaticity and higher content of heteroatoms (especially O atoms) led to a higher content of the resulting mesophase pitch mosaic structure. In this study, mesophase pitch was prepared by co-carbonization of high aromaticity, low oxygen content high-temperature refined pitch (RHCTP) with medium- and low-temperature coal tar refined pitch (RCTP). The impact of various blending ratios on the optical and microcrystalline structures of mesophase pitch was analyzed using polarized light microscopy, X-ray diffraction, and Raman spectroscopy. The addition of RHCTP to modify RCTP significantly enhanced the optical and microcrystalline structures of the co-carbonized products. The optimal blending ratio (R-25%) was obtained. Needle coke prepared from mesophase pitch obtained from R-25% had superior fine fiber structure, lowest average resistivity (157.37 μΩ·m) and high true density (2.125 g/cm3). The thermal conversion behavior of the blended refined pitch during co-carbonation was analyzed using thermogravimetric data of the R-25% sample through four isoconversion methods. The thermal conversion of the R-25% sample occurs in three stages: the first stage follows the Parabola law model, while the second and third stages adhere to the random nucleation and nuclei growth model. This analysis of thermal conversion kinetics offers theoretical insights for optimizing mesophase pitch preparation process conditions and reactor design.

Modified pitch A (MPA) and modified pitch B (MPB) were prepared by oxidative polymerization and thermal polycondensation reaction with refined pitch as the raw material, respectively. The toluene soluble components (TS-1 and TS-2) were obtained by solvent extraction from MPA and MPB, separately. The Flynn-Wall-Ozawa method and Kissinger-Akahira- Sunose method were used to calculate the pyrolysis activation energy of TS. The Satava- Sestak method was used to investigate the pyrolysis kinetic parameters of TS. Moreover, the optical microstructure of the thermal conversion products (TS-1-P and TS-2-P) by calcination shows that TS-1-P has more contents of mosaic structure and lower contents of fine fiber structure than TS-2-P. The research result obtained by a combination of X-ray diffraction and the curve-fitting method revealed that the ratios of ordered carbon crystallite (Ig) in TS-1-P and TS-2-P were 0.3793 and 0.4417, respectively. The distributions of carbon crystallite on TS-1-P and TS-2-P were calculated by Raman spectrum and curve-fitting analysis. They show that the thermal conversion product of TS-2 has a better graphite crystallite structure than TS-1.