Large Scale Molecular Model Construction of Xishan Bituminous Coal

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 C-13 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 C-13 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 C7972H4882O115N50S30, 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.