Structural Characteristics of the Yunnan Deashed Lignite and Construction of the Macromolecular Structure Model

The structural characteristics and macromolecular model of lignite are important for its effective utilization. In this paper, Yunnan (YN) lignite was taken as the study object, and deashing pretreatment was carried out to remove the influence of minerals in lignite before spectroscopic analysis. Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and ¹³C nuclear magnetic resonance (NMR) spectroscopy of deashed lignite and gas chromatography and mass spectrometry (GC/MS) of methanol lignite extract were subsequently performed. Then, the lignite structural parameters were calculated, and lignite macromolecular models were constructed and optimized. The results showed that the aromatic carbon ratio and molar fraction of aromatics in YN lignite were 0.62 and 0.19, respectively. The numbers of benzene, naphthalene, phenanthrene, pyrrole and pyridine groups were calculated as 4, 4, 1, 1, and 4, respectively. Afterward, 2D and 3D macromolecular structure models of YN lignite were drawn and optimized by ChemDraw software, and the chemical shift regions of the predicted ¹³C NMR spectrum agreed well with the experimental spectrum, suggesting the reliability of the constructed macromolecular structure model of YN lignite.