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.

Study on co-carbonization characteristics and thermal conversion kinetics of medium- and low-temperature and high-temperature refined pitch
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Preparation of blended refined pitch
        2.3 Synthesis of mesophase pitch
        2.4 Preparation of needle coke
        2.5 Characterization
            2.5.1 Thermogravimetric analysis (TGA)
            2.5.2 Polarized light microscopy (PM) analysis
            2.5.3 X-ray diffraction (XRD) analysis
            2.5.4 Raman spectroscopic analysis
            2.5.5 Scanning electron microscopy (SEM) analysis
            2.5.6 Determination of powder resistivity by four-probe method
            2.5.7 True density analysis
        2.6 Kinetic approach to thermal conversion
            2.6.1 Isoconversional method
            2.6.2 Fit theory
    3 Results and discussion
        3.1 TGDTG curves analysis
        3.2 Effect of different blending ratios on mesophase pitch
            3.2.1 Polarized light microscopy analysis of mesophase pitch
            3.2.2 XRD analysis of mesophase pitch
            3.2.3 Raman spectroscopic analysis of mesophase pitch
        3.3 Analysis of the needle coke
        3.4 Kinetic analysis of thermal conversion in co-carbonation of blended refined pitch
            3.4.1 Calculation of reaction activation energy
            3.4.2 Identification of kinetic reaction models for thermal conversion
    4 Conclusions
    Acknowledgements 
    References

• Shiquan He(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Jiaojiao Liu(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Sijie Wang(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Yanyan Song(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Ting He(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Tao Liu(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Huaan Zheng(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Yonghong Zhu(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China)
• Dong Li(School of Chemical Engineering, The Research Center of Chemical Engineering Applying Technology for Resource of Shaanxi, Northwest University, Xi’an 710069, Shaanxi, China) Corresponding author
• Louwei Cui(Northwest Research Institute of Chemical Industry, Xi’an 710600, Shaanxi, China)