Synthetic Pitch from Solvent Extraction of Coal as a Source for High-Quality Graphite

Abstract

This work evaluates the potential for obtaining graphitizable precursors from domestically available coal as a possible solution to the declining availability of high-quality precursors and projected rapid growth driven by demand for synthetic graphite in the US. The graphitizability of a coal-derived synthetic pitch (Synpitch) obtained by a novel solvent extraction process is compared with a commercially available petroleum pitch. The process outlined in this paper offers the advantages of lower temperature, pressure, and hydrogen addition requirement. An upgraded (higher H/C) aromatic pitch with low quinoline insoluble (QI) and ash content is obtained. The distinctions between the pitches have been characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis/differential scanning calorimetry. The pitches have been graphitized at 2500 °C and characterized by X-ray diffraction and transmission electron microscopy for graphitic quality assessment. The Synpitch showed larger crystallites (by over 50%) and markedly better nanostructure compared to the commercial pitch used in this study. The structural differences between the pitches are highlighted here to explain the significantly better graphitic quality of the Synpitch.

Structural Characteristics and Graphitizability of Tars from Thermal versus Microwave Plasma Pyrolysis of Coals

“…Figure shows an overlay of FTIR spectra of tars obtained from inert thermal pyrolysis versus MW plasma pyrolysis in an Ar–H 2 environment with the inset (2800–3100 cm –1 ) showing a magnified view of the aromaticity difference between them. The FTIR peak identification for tars and pitches has been well-studied before. − Hp-PRB shows a distinctly different FTIR profile compared to that of thermal-PRB. The results demonstrate substantially higher aromaticity for hp-PRB (aromaticity index = 0.1) compared to thermal-PRB (aromaticity index = 0.023), providing strong evidence for MW plasma-induced aromatization.…”

“…Furthermore, thermal-PRB shows a remarkably higher CO vibration peak around ∼1650 cm –1 and C–O peak ∼1000–1400 cm –1 compared to hp-PRB suggesting that thermally obtained coal tars have significantly higher amounts of oxygen content compared to MW plasma-obtained tars. All these features of hp-PRB have been shown to be favorable for developing better graphitic quality after heat treatment. , …”

“…All these features of hp-PRB have been shown to be favorable for developing better graphitic quality after heat treatment. 40,41 Figure 3 shows an overlay of FTIR spectra of MW plasmareacted samples, with the inset showing a magnified region (2800−3100 cm −1 ) illustrating differences in the aromaticity of the samples. The hp-PRB has the lowest aromaticity index of 0.1 versus 0.21 and 0.226 for cdp-MK and hp-MK respectively.…”

Graphitization Control Using Additives in Pitch Composites─Part I: Effect of Graphene on Temperature-Dependent Crystallite Size Evolution, Carbonization Reactions, and Mesophase Formation

“…Figures and show the TGA-DSC comparisons between pure ARP and ADP pitches versus their Gr composites, respectively. TGA-DSC has proven to be an effective tool for acquiring valuable insights into the relationship between pitch structure, its carbonization reactions, and subsequent graphitization behavior . In aromatic ARP, the addition of Gr marginally increases the carbon yield in excess of the contribution from the nonvolatile nature of Gr as seen in Figure a.…”

“…TGA-DSC has proven to be an effective tool for acquiring valuable insights into the relationship between pitch structure, its carbonization reactions, and subsequent graphi-tization behavior. 51 In aromatic ARP, the addition of Gr marginally increases the carbon yield in excess of the contribution from the nonvolatile nature of Gr as seen in Figure 17a. The measurement was repeated and consistent observations were made with small variance (less than 1 wt % in TGA-derived carbon yield).…”