Construction and optimization of macromolecular structure model of Tiebei lignite

by Jinzhang Jia, Lingyi Xiao, Dongming Wang, Dan Zhao, Yinghuan Xing, Yumo Wu

Mastering the molecular structure of coal is important for the effective utilization of coal. For a detailed study of the microstructural characteristics of Tiebei lignite, its molecular structure was characterized by elemental analysis, solid ¹³C nuclear magnetic resonance (¹³C NMR), Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results showed that the aromatic carbon content of Tiebei lignite was 51.98%, the aromatic carbon structure was mainly composed of benzene and naphthalene, and the ratio of aromatic bridgehead carbon to surrounding carbon X_bp was 0.14. Oxygen existed in phenol, ether, carbonyl, and carboxyl; nitrogen-containing structures mainly existed in the form of pyrrole and pyridine; sulfur mainly existed in thiophene sulfur; and aromatic substitution was mainly in the form of trisubstitution. The molecular formula of the macromolecular structure model of Tiebei lignite was C₁₉₀H₁₆₁O₅₇N₂, and the ¹³C NMR spectrum of the model was in good agreement with the experimental results, which fully verified the accuracy of the macromolecular structure model of Tiebei lignite. The construction of a macromolecular structure model of Tiebei lignite is essential to intuitively understand the molecular structure characteristics of Tiebei lignite and to provide theoretical support and guidance for the micromechanism research and prevention of lignite spontaneous combustion and other disasters.