Multiscale Structural Elucidation of Vitrinite and Inertinite in Tar-High Coal: A Combined Characterization via FTIR,...

The structural differences in the macerals of coal significantly affect the transformation and utilization characteristics. Thoroughly analyzing the molecular structures of each maceral and constructing accurate models can provide a theoretical basis for clean coal technology and carbon resource optimization. This study comprehensively utilized industrial analysis, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ¹³C solid-state nuclear magnetic resonance (¹³C NMR) analysis techniques to systematically characterize the chemical structural characteristics of tar-high coal and its macerals. Molecular simulation methods were used to construct a maceral macromolecular model based on experimental data, and the rationality of the model was verified through classical molecular dynamics and density functional theory approaches. The inertinite was more aromatic (77.29%), with the lowest proportion of aliphatic chains and oxygen-containing functional groups. The vitrinite contained more aliphatic chains (15.68%), oxygen-containing functional groups, and small aromatic ring structures with the lowest aromaticity (63.58%). The structural characteristics of the original sample were between the two. The constructed molecular model was in good agreement with experimental data and can effectively reveal the structural differences of various macerals. The molecular formulas of structure models for the tar-high coal and its macerals were C₁₉₀H₁₄₄N₂O₃₃ (ZC-coal), C₁₈₃H₁₆₁N₃O₃₆ (ZC-V), and C₂₀₅H₁₃₄N₂O₂₃ (ZC-I). This study achieved a precise reconstruction of the molecular structure of coal and its macerals through multiscale characterization and molecular simulation. The model can provide a reliable basis for simulating the mechanisms of coal pyrolysis, gasification, and polycyclic aromatic hydrocarbon generation.