Microstructural diversity and digestion yields of select bituminous and subbituminous coals as raw material candidates for carbon fiber precursor production

Ercan Cakmak, James C. Hower, Jonathan P. Mathews, Matthew C. Weisenberger, Rachel Kaplan, Justin Lacy, Yuxuan Zhang, Edgar Lara-Curzio

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


This work investigates the use of coals as raw materials for carbon fiber precursor production as a new alternative to coal utilization. Coal being a highly complex and heterogeneous material with different macerals and minerals complicates this task. Extensive microstructural characterization as well as preliminary digestion studies are performed on three bituminous coals (Herrin and Springfield from the Illinois Basin and the Blue Gem from the Central Appalachians) and one subbituminous coal from the Powder River Basin (Monarch), as raw material candidates. The subbituminous coal was richer in oxygen, lower in sulfur, and had a higher volatile matter yield. Microstructural investigations were performed using X-ray diffraction, X-ray/neutron computed tomography, scanning electron microscopy with energy dispersive spectroscopy, and petrology. Mild solvent extraction studies were conducted using creosote and decant oil as solvents in microreactors. The extraction yield was sensitive to temperature and time (350 to 450 °C between 30 and 120 mins.) for both creosote and decant oil digestions. While the Blue Gem coal had more desirable microstructural properties with less mineral content and cleaner macerals, it had the lowest coal conversion to quinoline soluble ‘liquid’ (of the bituminous coals). The lower coal conversion yield was hypothesized to be connected to the lack of FeS2 which could act as a catalyst when Fe is liberated from the structure under solvent extraction conditions. The Herrin and Springfield coals revealed similar microstructures and coal conversion efficiencies (higher than Blue Gem). These coals were the most promising candidates for further examination from this first approximations study. The subbituminous Monarch coal, however, was deemed less suitable due to poor coal conversion and less desirable microstructures. Additionally, the presented results with combined microstructural data from multiple length scales established a framework necessary for a first approximations study in this new coal utilization approach.

Original languageEnglish
Article number128545
StatePublished - Sep 15 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier Ltd


  • Coal
  • Coal digestion
  • Coal Petrology
  • Energy dispersive spectroscopy
  • Microstructure
  • X-ray computed tomography

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry


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