Insights into the structures of coals and chars from a bond and radical perspective using Raman spectroscopy

• Published in: Fuel (Guildford) 2022-03, Vol.312, p.122980, Article 122980
• Main Authors: Guo, Xiaojin, Xu, Xiang, Xue, Xiaoyong, Li, Xiquan
• Format: Article
• Language: English
• Subjects: Char structure; Deconvolution; Electron paramagnetic resonance; Electron spin; Electron spin resonance; Electron spin resonance spectra; NMR; Nuclear magnetic resonance; Nuclear magnetic resonance spectra; Raman spectra; Raman spectroscopy; Spectrum analysis; Spin resonance
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.122980

•9-sub curve deconvoluting method with high reproducibility are presented.•The same function obtained by direct integration and by deconvoluting are compared.•The area ratio of D and G band in Raman spectra linearly correlate to the aromaticity.•New function can be correlated to the concentration of stable radicals is constructed.•Some sub curves’ physical meaning can be evaluated from the comparison of spectra. Deconvoluting method is crucial for Raman spectra of coals or chars because the obtained parameters are used to correlate with various reaction behaviors. In this work, Raman spectra of 15 coals and 45 chars prepared under 300, 600, and 900 °C, were deconvoluted into nine sub-curves. Using cross-polar/magic angle spinning 13C solid-state NMR spectra (CP/MAS 13C NMR) and Electron Spin Resonance (ESR) spectra, the validities of traditional functions AD/AG and A(Gr+Vl+Vr)/AD were evaluated, and new function AD/A(S+A1+A2) correlated with defects was constructed. The physical meaning of some sub-curves was determined by analyzing the comparison between the Raman and other spectra. The deconvoluting method can be adopted to other hydrocarbons and new functions reflect other structural characteristics can be constructed using similar method.