Preparation and characterization of high softening point and homogeneous isotropic pitches produced from distilled ethylene tar by a novel bromination method

• Published in: New carbon materials 2018-02, Vol.33 (1), p.71-81
• Main Authors: Ge, Chuan-zhang, Sun, Zhen-long, Yang, Hai-xiao, Long, Dong-hui, Qiao, Wen-ming, Ling, Li-cheng
• Format: Article
• Language: English
• Subjects: Bromination; Dehydrobromination; Distillation; Ethylene tar; Properties
• ISSN: 1872-5805; 1872-5805
• DOI: 10.1016/S1872-5805(18)60327-0

Homogeneous isotropic pitches with high softening points were prepared from vacuum-distilled heavy residue ethylene tar (ET-HR) by a two-step method of bromination and subsequent dehydrobromination/polycondensation. The ET-HR was first brominated at 30 or 200 oC, and then heat-treated at 350 oC to enable the dehydrobromination/polycondensation reactions. GC/MS and LDI TOF/MS spectra indicated that the ET-HR was mainly composed of compounds containing 3- to 6-ring aromatic species with a considerable aliphatic chain content. Compared with thermal condensation alone, such a two-step method increased the softening point of the pitches from 152 to 264 oC with a yield in the range of 62 wt. %−67 wt.% and a coking value in the range of 57 wt. %−77 wt.%, depending on the bromination temperature and the bromine content. Structural characterization of the as-prepared pitches by elemental analysis, 1H NMR, FT-IR and LDI-TOF/MS showed increased aromatization and polymerization of the precursor during the dehydrobromination/polycondensation. All the homogeneous isotropic pitches showed an ability to transform into an anisotropic texture after coking at 800 °C.