Study on the influence of raw material composition on the structure of needle coke

The refined raw material was first prepared from the low-medium temperature coal tar through hydrogenation for 1.5 h under 330–390 °C and 8 MPa, with a catalyst/oil mass ratio of 1∶40, which was then used to produce needle coke through thermal polymerization and calcination. The composition of refined raw materials was analyzed by elemental analysis, Fourier-transform IR spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) and the structure of needle coke was characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD) and polarizing microscope; the effect of raw material composition (related to the hydrogenation temperature) on the structure of needle coke was then investigated. The results indicate that a proper increase in the hydrofining temperature is beneficial to the removal of heteroatoms (especially sulfur). By hydrogenation at 390 °C, the aromatics in the feedstock are polarized due to the cracking and polycondensation. In addition, a higher content of tricyclic and tetracyclic aromatics in the refined raw materials may also lead to a higher graphitization degree for the needle coke product.