Construction and optimization of lignite molecular structure model

Abstract

In view of the current situation that there are many but no uniform coal molecular modeling methods, this paper explores the structuve of lignite macromolecules and optimizes them from a microscopic perspective by selecting physical methods that have less impact on molecular structure.A relatively simple coal macromolecule modeling method was put forward.Based on the experimental methods of elemental analysis, 13C-NMR and XPS, molecular dynamics simulation software method was used to analyze and study lignite and build molecular structure models.The results show that the aromatic structure of lignite macromolecules is mostly pentaphenyl.The fat carbon structure is mostly methylene and methine, and the alkane chain is mostly cycloalkanes.Oxygen atoms are mostly ether bond oxygen, followed by carboxyl oxygen and carbonyl oxygen.Nitrogen atom exist in the form of Pyridinic nitrogen N-6.After the optimization, the structure of the coal molecular model is more compact and the energy is obviously reduced.As the main component of the non-bonding potential energy and the main factor to maintain the stability of the coal molecular structure, the van der Waals potential energy has the most obvious change.In order to construct coal molecular cell, periodic boundary conditions were added.According to the energy variation, the cell density was 1.2 g/cm3 and the total energy was 1 140.624 kJ/mol, which was basically consistent with the actual situation and verified the effectiveness of the modeling method.This study provides a method for the direct understanding of the macromolecular structure of coal, and is of great significance for the mechanism research and prevention of coal and gas outburst, coal spontaneous combustion and other disasters.

Keywords

• lignite
• macromolecular modeling
• molecular dynamics
• structure optimization