Preparation of pitch-based carbon fiber from medium coal tar pitch refined by wash oil

• Published in: Fuel (Guildford) 2025-03, Vol.384, Article 133939
• Main Authors: Zuo, Pingping, Fu, Shaobo, He, Xiaoqiang, Niu, Hongxian, Qu, Shijie, Shen, Wenzhong
• Format: Article
• Language: English
• Subjects: Air-blowing; Medium coal tar pitch; Pitch-based carbon fiber; Wash oil
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.133939

Composition and structure of spinnable pitch determines the resultant carbon fiber performance. Compared with spinnable pitch from THF-refined pitch, spinnable pitch from wash oil-refined pitch(WO-SP) displayed a slower descent of viscosity with temperature raising, and resultant pitch-based carbon fiber had a better tensile strength of 790 ± 37 MPa and modulus of 40.8 ± 3.2 GPa, because WO-SP had more large molecules (600–1200 Da) and quinoline solubles, more components of structure bigger than benzo[g,h,i]perylene-like and little perylene-like component. Therefore, coal tar pitch refined by wash oil could be a promising precursor of spinnable pitch to prepare pitch-based carbon fiber. [Display omitted] •Refining of coal tar pitch was foundation to obtain an ideal spinnable pitch.•WO-Pitch had more aliphatic chains and large molecules(>600 Da) than THF-Pitch.•Main components in pitches/spinnable pitches were identified by EEM-PARAFAC.•More six fused rings and less perylene-like structure at Fmax were found in WO-SP.•Carbon fiber from WO-SP had a tensile strength of 790 MPa and modulus of 40.8 GPa. The composition and structure of spinnable pitch was always the key issue of pitch-based carbon fiber preparation, with the foundation step of coal tar pitch purifying. In this work, wash oil was chosen as refining solvent due to its aromatic properties, compared with tetrahydrofuran (THF). Two isotropic spinnable pitches (WO-SP and THF-SP) were prepared by air-blowing of refined pitches, with similar elementary compositions, soften points (250 ℃) and aromaticity, but WO-SP displayed a slower descent of viscosity with temperature rising, which was related to the molecular weight distribution and aromatic structure. The main aromatic components of pitches/spinnable pitches were determined by using fluorescence excitation-emission spectroscopy with parallel factor analysis (EEM-PARAFAC), combined with a stepwise extraction and mass spectrometry analysis. Difference between WO-SP and THF-SP mainly lied in 9.16 wt% more proportion of components with molecular weight > 600 Da in the THF-soluble fraction of WO-SP, forming less pyrene-like structure (four fused rings) and more structure bigger than benzo[g,h,i]perylene (six fused rings). Meanwhile, WO-SP had 9.6 wt% more content of large quinoline-soluble components than THF-SP, with little aromatic structures smaller than five fused rings. These characteristics made carbon fiber from WO-SP with a better tensile streng