Preparation and Characterization of Coal Pitch-Based Needle Coke (Part II): The Effects of β Resin in Refined Coal Pitch

Refined coal tar pitch is considered as a promising material for the production of needle coke owing to its excellent physical–chemical properties. It was generally accepted that the basic properties of refined coal pitch played a vital role in affecting the resulting quality of the derived needle coke during the delayed coking process. Our previous research showed that an fa of 0.95–0.98 of refined coal pitch was optimal and produced needle coke of the highest quality. What is more, we found that the contents of β resin in refined pitch were also important to the properties (microstructure, microstrength, and true density) of the derived needle coke. Therefore, the effects of the contents of β resin on the properties of needle coke were investigated thoroughly, and eight types of refined coal pitch (the fa range from 0.9621 to 0.9725) with varied contents of β resin were employed as the precursors of needle coke. The techniques of proton nuclear magnetic resonance and gel permeation chromatography were utilized to determine the fa and molecular weight of each refined coal pitch, respectively. Microstructures (optical microstructure and surface morphology) have been analyzed by polarizing microscopy and scanning electron microscopy, separately. X-ray diffraction, Raman spectra, and curve-fitting enabled the quantitative examination of the microcrystalline structure. What is more, the microstrength and true density of each needle coke have also been examined in this study. It was concluded that a β resin content of 13–16% in the refined coal pitch achieved the best results and was optimal for needle coke production.