Molecular Model Construction and Optimization Study of Gas Coal in the Huainan Mining Area

To construct the macromolecular model of gas coal in the Huainan mining area, C-13 nuclear magnetic resonance spectroscopy (C-13-NMR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) tests were used to analyze the microstructure characteristics of coal including the aromatic ring type, the linkage mode, and the chemical bonding composition. The model was simulated and optimized by molecular mechanics (MM) and molecular dynamics (MD). The experimental results showed that the coal macromolecular formula in the Huainan mine was expressed as C181H150O9N3. The aromatic ring was dominated by anthracene and phenanthrene. Aliphatic carbon mainly existed in the form of methylene and methine. The oxygen atoms existed in the form of ether-oxygen bonds. The ratio of pyridine nitrogen to pyrrolic nitrogen was 2:1. The molecular simulation results showed the pi-pi interaction between the aromatic lamellae within the molecule. The van der Waals energy was the major factor of coal molecular structure stability and energy change. The results of the calculated C-13-NMR carbon spectrum and density simulation agreed well with the experimental results. The study provides a scientific and reasonable method for coal macromolecular model prediction and theoretical support for coal spontaneous combustion prevention technology.