Construction and optimization of Liuzhuang coal molecular model for wettability mechanism analysis

This study investigates the molecular structure and wettability of Liuzhuang coal using integrated experimental and computational approaches. FTIR, solid-state ¹³C NMR, and XPS analyses were conducted to identify functional groups and carbon skeleton structures. A 2D coal molecular model with the formula C₁₁₇H₈₀O₁₇N₂S was constructed, and its reliability was validated by strong agreement with experimental ¹³C NMR spectra. Further 3D geometry optimization using the Forcite and DMol³ modules significantly reduced the total energy and enhanced structural stability. Electrostatic potential analysis revealed a surface potential range of –0.08382 to +0.106 a.u., with sparse hydrophilic regions, indicating poor intrinsic wettability. Molecular dynamics simulations demonstrated that the addition of surfactant AEO9 led to the formation of a compact interfacial layer, enhancing both wettability and interfacial stability. Mean square displacement analysis showed that the diffusion coefficient of water molecules decreased from 0.4925 Ų/ps (without AEO9) to 0.1802 Ų/ps (with AEO9), indicating that AEO9 formed a hydrogen-bonding network that restricted water mobility and improved wetting layer compactness. Simulated contact angle results aligned well with experimental data, confirming the model's reliability in capturing wetting behavior. This study establishes a structurally accurate coal molecular model and elucidates the mechanism by which AEO9 improves interfacial wetting, offering theoretical support for the design of effective dust suppressants.