Preparation and structure evolution of coal-based needle coke by co-carbonization of coal direct liquefaction pitch and waste engine oil

Needle coke, a high-performance artificial carbon material, requires precise composition control of its raw materials as this critically determines the structural characteristics and performance of the final product. In this study, needle coke samples were prepared from coal direct liquefaction pitch (CDLP) and waste engine oil (WEO) through component optimization and a co-carbonization process. The microstructure and properties were investigated using the following characterization techniques: Fourier Transform Infrared Spectroscopy (FT-IR), Polarized Light Microscopy (PLM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Raman Spectroscopy, Thermogravimetric Analysis (TGA), Micro-Strength (MS) and Powder Resistivity (PR). The co-carbonization mechanism of CDLP and WEO was systematically investigated. The results indicated that the incorporation of WEO significantly reduced the viscosity of the co-carbonization system, and its abundant aliphatic structures provided alkyl radicals and active sites. The synergistic interaction of aromatic components between the CDLP and WEO effectively promoted the growth and order accumulation of aromatic carbon layers. When 50% WEO was introduced, the prepared needle coke exhibited an excellent microstructure and properties. The fibrous and leaflet structure content reached 76.2%, the ideal graphite lattice content reached 89.7%. These results demonstrated remarkable oxidation resistance and electrical conductivity, with a powder resistivity of 605.1 mΩ·mm. This work establishes a process with cost advantages for the production of needle coke.