Model construction of the macromolecular structure of Yanzhou Coal and its molecular simulation

Based on proximate and ultimate analysis, 13C CP/MAS NMR data of Yanzhou coal, a macromolecular structural model was constructed. In this model, benzene is the main aromatic compound and aliphatic structure exists mainly in the forms of aliphatic side chains, cycloalkanes and hydrogenated aromatic rings. The methyl proportion is similar to the total proportion of methylene and methine groups. Seventeen O atoms are present as carboxyl, carbonyl and hydroxyl groups and three N atoms exist in the forms of pyridine and pyrrole, while five S atoms in the form of thiophenic S. Molecular mechanics (MM) and molecular dynamics (MD) techniques were used to carry out energy minimization simulations on this model. The simulation results indicate that stabilization of the macromolecular structure is due to the energies of van der Waals, torsion, angle, bond and inversion in descending order of importance, and intramolecular π–π interactions between aromatic layers enables their quasi-parallel arrangement. Semi-empirical quantum chemistry (AM1) simulation indicates that the C–C bonds adjacent to carbonyl C atoms exhibit higher activity, and C atoms adjacent to S atoms and terminal C atoms are more negatively charged, which therefore prone to undergo oxidation reactions, while aromatic C atoms are characterized by fewer charges and very high stability.