Molecular Structure Model Building And Supermolecule Characteristic Of Wumuchang NO.11Coal

According to the temperature and pressure relationship, the metamorphism of coal can be classified into three types:low temperature and high pressure, high temperature and high pressure, high temperature and low pressure. There is difference in the coal structure formed in different temperature and pressure conditions. Knowing the difference and the reasons of it are the basis in predicting the quality of coal and using coal in high efficiency. Classical lignite to bituminous coal transition zones formed in high temperature and low pressure metamorphism are distributed in Wumuchang, Inner Mongolia. Theoretical research on the structure of coal in that district is performed based on the molecular study. According to the proximate analysis, elementary analysis,13C-NMR, FTIR and XPS analysis, the structure information of raw coal, residual coal and asphaltine molecules including carbon skeleton structure, aliphatic structure, oxygen containing functional groups types and ratio, nitrogen atoms existence forms and ratio are achieved. Molecular structure models of the three kinds of molecules are constructed according to experimental analysis and revised by the13C-NMR predicting software ACD/CNMR predictor. As a result, structure models of raw coal, residual coal and asphaltine molecules which coincide with experimental NMR spectra are achieved. The aromatic structure units of raw coal are benzene, naphthalin, anthracene and phenanthrene, with quantities of1,2,2and1. Oxygen atoms exist in forms of phenolic hydroxyl, carbonyl and carboxyl groups. Nitrogen atoms exist in forms of pyridine and pyrrole. The aromatic structure units of residual coal are nthracene and phenanthrene. Oxygen atoms exist in forms of phenolic hydroxyl and carboxyl groups. Nitrogen atoms only exist in forms of pyrrole. The aromatic structure units of asphatine are benzene, naphthalin, anthracene and phenanthrene, and the quantity of anthracene is the most. The ratio of carboxyl and carbonyl groups is8:5. Using the Focite module of the software Material Studio, stable configurations and energy characteristics of the molecules are calculated. Densities of molecules are calculated by using the Amorphors module adding periodic boundary conditions, and the results are in consistence with that of experiments. The VAMP module is used to calculate bond lengths, bond angles and atomic charges of molecules, as to compare the stable difference in different kinds of bonds. The extract content shows that the supermolecule structure is consisted of one asphaltine molecule and three residual coal molecules. Molecular mechanics and molecular dynamics simulations are performed to study the characteristics of supermolecules. Stable configurations, energy relationships and identification patterns are achieved based on calculations of supermolecules with different combinations. According to the extract content of asphatine and residual coal molecules, molecular models are built to calculate the relationship between the density and energy of supermolecules. The density of the most stable supermolecule is1.32g/cm3, which coincides with the experimental result1.41g/cm3.