Molecular structural characteristics of late Jurassic Shengli lignite submacerals

Different lignite submacerals have complex physical and chemical properties, and exploring their molecular structures are of great significance for enrichment the evolution mechanism of coal microstructure and efficient utilization. In this paper, raw lignite with rich-(eu-ulminite) (FJ) and rich-leviglinite (FW), respectively, were selected on the basis of petrographic identification. The proximate analysis and ultimate analysis, FTIR, XPS, 13C NMR, HRTEM and molecular simulation technique were used to construct the molecular structure of FJ and FW. The experimental data and molecular structural models show that FW has a higher aromaticity, larger size of the aromatic layer, and more pronounced directional arrangement. In a single stable molecular configuration, aromatic rings and the aliphatic ring are arranged in a wrapped arrangement. Furthermore, the type of hydrogen bond mainly depends on the type of oxygen-containing functional group of the molecular structure. In addition, the length and angle of the hydrogen bond tend to be polarized. There is a little difference on the value of experimental and simulated density.