Macromolecular structural model of the pyridine extracted residue of vitrain from No.3 coalbed, Liulin and molecular simulation

The pyridine extraction residue from LL 3^#vitrain (LLR) was studied by ¹³C CP/MAS NMR and XPS analysis. ¹³C NMR tests show the structure characteristics of carbon atom and 12 structure parameters. Aromatic structure units are dominated by anthracene; aliphatic C atoms exist in the side-chain; O atoms exist in the form of -O-, C=O and -OH; N atoms exist in pyridine and pyrrole. Macromolecular structure model of LLR is constructed based on the results of proximate and ultimate analysis. ¹³C chemical shift of LLR macromolecular structure is calculated by ACD/CNMR predictor, then the structure is corrected according to the calculation results. And finally the macromolecular structure which is consistent with the experimental results is obtained. Molecular mechanics (MM) and molecular dynamics (MD) were adopted to simulate the energy-minimum conformation of LLR model. The results show that the order of main energy for LLR model is van der waals>torsion>angle>bond. The simulation results indicate that the parallel aromatic layer structure occupies a small proportion. Finally, LLR density is 1.22 g/cm³ by enclosing coal model into the periodical boundary condition. Semi-empirical quantum chemistry methods (PM3) simulation indicates that the C-C bonds adjacent to aliphatic side chain C atoms exhibit higher activity. The terminal C atoms are more negatively charged, and therefore prone to undergo oxidation reactions. The aromatic C atoms are characterized by fewer charges and very high stability.