Abstract: The density gradient centrifugation method (DGC) was used to purify three parent coals with obvious deoxidation degrees into two main organic macerals, inertinite and vitrinite accordingly. These coal macerals were studied by molecular mechanics and molecular dynamics. The structure of weakly deoxidized coal was found to be in the structure of sheet layers with many open holes while the strongly deoxidized coal has a stacked structure with many closed holes. The physical aromatic sheet structure of macerals has a strong influence on coal extract yields. The combination of modeling, 13C-NMR and XRD analyses reveals that to obtain higher extraction yields of coal the non-bond chemical force energy should be low. Fewer aromatic sheet layers and lower non-bond chemical force energy within structures would result in higher extraction yields of coal macerals.

Key words: Coal, Molecular mechanics, Molecular dynamics, Solvent extraction, NMR, XRD