Carbon nanofiber generation from the precursor containing unprecedently high percentage of inexpensive coal-derived carbon material

Anthropogenic activities, especially fossil fuel utilization, have resulted in large emissions of various pollutants, especially carbon dioxide. This research was designed to develop a new alternative technology for utilization of coal in producing a high-value solid material that can not only fix carbon but also serve as a future energy material. Specifically, for the first time, carbon nanofibers were successfully synthesized with the hexane insoluble-toluene soluble component of coal tar produced with renewable, easy-recycled and benign ethanol and supercritical carbon dioxide along with different percentages of polyacrylonitrile by electrospinning, stabilization and carbonization. The tar used for synthesis of the carbon nanofibers contained 25.53 wt% hexane insoluble-toluene soluble component. This component has a high carbon content of 91.99% and a low oxygen concentration of 0.36%. The existence of aromatic structures in this component was proved by Fourier-transform infrared, H-1 and C-13 nuclear magnetic resonance analyses. The asphaltene concentration of hexane insoluble-toluene soluble component was as high as 60 wt% according to thermogravimetric analysis. The synthesized carbon nanofibers were characterized by different methods, and it was found that the structure of the carbon nanofiber improves with the quantity of hexane insoluble-toluene soluble component used for carbon nanofiber synthesis. Specifically, the surface areas of carbon nanofibers increased from 491.56 m(2)/g to 618.93 m(2)/g with the concentrations of hexane insoluble-toluene soluble component in the carbon nanofibers increased from 50 wt% to 70 wt%. Results from transmission electron microscopy and Raman spectra reveal that the fiber with the highest percentage of hexane insoluble-toluene soluble component has the best carbon ordering structure among the synthesized carbon nanofibers. (C) 2019 Elsevier Ltd. All rights reserved.