Macromolecular pore model construction and theoretical study of Inner Mongolia Long-flame coal

Abstract

Studying the sorption and wettability behavior of coal by molecular simulation requires an understanding of its molecular structural characteristics. Herein, a plane molecular model of coal in the Ordos region of Inner Mongolia was established through elemental analysis, nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared reflection (FTIR) and X-ray photoelectron spectroscopy (XPS) experiments. The results show that the coal belongs to long-flame coal. Its aromatic hydrocarbon content was 56.14 %, mainly dominated by benzene and naphthalene rings. The oxygen-containing functional groups (OGs) existed mainly in the CO form. The aliphatic carbons were mainly composed of methylene groups. The N and S elements were present as pyrrole nitrogen and thiophene nitrogen, respectively. The molecular formula of the long-flame coal model was C₁₄₅H₈₇O₂₁NS. A microporous network of long-flame coal structures was constructed by molecular simulation. It was found that with the increase of the probe radius, the shape of the inaccessible holes changed to pear-shaped, tongue-shaped, and inverted bottle-shaped with a small mouth and large cavity, and aggregation and connection phenomena appeared between the holes. The appropriate aperture detection range should be determined to be between 0.1 and 0.44 nm. The main distribution regions of LUMO and HOMO orbitals of long-flame coal were determined by quantum chemical calculation. The IGMH (independent gradient model based on Hirshfeld partition) isosurfaces between long-flame coal and water were calculated, and the adsorption regions and interaction types of water on the surface of long-flame coal were clarified. The results provide the basis for enhanced coal wettability and improved dust suppression efficiency.