Molecular structural information on a Chinese Xishan bituminous coal was obtained using elemental analysis, high resolution transmission electron microscope (HRTEM), laser desorption time-of-flight mass spectrometry (LD-TOF MS), solid state 13 C nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) techniques. The size and distribution of aromatic structures were determined by HRTEM, providing 300 base aromatic skeletons for a coal model. Aliphatic side chains and heteroatoms were introduced into these aromatic skeletons according to 13 C NMR and XPS results, which created 300 individual coal fragments. The individual fragments were cross-linked randomly with aromatic−aromatic, aromatic−aliphatic, aromatic−oxygen, aliphatic−aliphatic, and aliphatic-oxygen linkages to match the molecular weight distribution observed in LD-TOF MS. As a result, the coal model was constructed. The proposed model was comprised of 62 unique individual molecules with a composition of C 7972 H 4882 O 115 N 50 S 30 , which is reasonable consistent with the structural and molecular properties determined by experiments. They were also assembled into three-dimensional (3D) structure, followed by molecular simulation. The refined 3D model was also verified through the matched helium density between calculated and experimental data. This is the first large scale Chinese bituminous coal model incorporation of diverse molecular weight and structure, which may lead to a further understanding of the coal structure−behavior relationship from a molecular level.

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Despite its importance, limited representations of the anthracite models have been developed. The first molecular representation of Chinese Jincheng anthracite with the incorporation of diverse molecular structures was constructed based on the available analytical data. Three hundred individual aromatic sheets were first built based on the aromatic fringe distribution obtained from high-resolution transmission electron microscopy. Alkyl chains and nitrogen, sulfur, and oxygen heteroatoms were added in the aromatic skeletons to form diverse anthracite structural units based on 13 C NMR, X-ray photoelectron spectroscopy, and ultimate analyses. Fifty-five different anthracite molecules were formed by covalent cross-linking considering the constraint imposed by the molecular weight distribution of the Jincheng anthracite obtained from laser desorption time-of-flight mass spectrometry (LD-TOF MS). These molecules were packed into a three-dimensional cell to form a Jincheng anthracite model (C 7730 H 3916 O 133 N 123 S 25 ). We showed that the proposed model can provide a reasonable representation of the Jincheng anthracite by comparing the simulated and experimental magnetic resonance spectroscopy, LD-TOF MS, density, and X-ray diffraction data. Because of the large, molecularly diverse structure, many anthracite behavioral processes can be further explored using this model in the future.

In order to explore the effect of the attachment site of the benzene ring in the backbone of the surfactant on its diffusion characteristics on the surface of anthracite, the molecular dynamics simulation method was used, and the four isomers (m-C16, m = 2,4,6,8; m represents the attachment site of the benzene ring in the backbone) of sodium hexadecyl benzene sulfonate (SHS) were selected. Binary models of surfactant/anthracite, surfactant/graphene modified by oxygen-containing functional groups, and a ternary model of water/surfactant/anthracite were constructed. By analyzing a series of properties such as interaction energy, contact surface area, relative concentration distribution, radial distribution function, hydrophobic tail chain order parameter, etc., it is concluded that the adsorption strength of 4-C16 on the surface of anthracite is the highest; the reason is that 4-C16 has the highest degree of aggregation near the oxygen-containing functional groups on the surface of anthracite. Further investigations find that 4-C16 can be densely covered on the ketone group, and the longer branch chain of 4-C16 has the highest degree of order in the Z-axis direction.