Molecular Structure Model Construction And Molecular Simulation Of No.2Coal In Duerping Mine

The research of coal structure has been a core part of the science of coal fields. From the physical point of view, coal is an amorphous substance, short-range order, and long-range disorder; from the chemical point of view, the various chemical bonds and secondary bonds distribution is complex in coal. Given the complexity of coal structure, the characters and understanding of coal structure is one of the most challenging issues. However, deeply understanding of the molecular structure of coal is one of the key to realize the clean utilization of coal. Hence, the research of coal structure is the core and leading-edge topic in coal science. Clean Coal Technology, based on macromolecular structure and composition of coal, is a technology which realizes cascade processing and low-carbon utilizing for coal to achieve highly efficient and selective conversion of coal in terms of fine chemicals and clean fuels. This technology extends the cycle of coal utilization and achieves clean, efficiency and sustainable development of coal resources. In this paper, a combination of computer simulation and experiments wasused to build macromolecular model of Duerping NO.2coal and simulate its related properties, in order to understand the molecular structure of coal, achieve highly efficient and clean using of coal and explore a new research idea and method.In this paper, a variety of testing methods, such as infrared spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy etc., were used to obtain the relevant parameters of coal structure, and used computer-aided molecular design (CAMD) methods to build macromolecular structure of Duerping NO.2coal. On this basis, Materials Studio software was used to analyze the characteristic of molecular mechanics, molecular dynamics and quantum chemistry for macromolecular structure model of Duerping NO.2coal, simulate the infrared spectroscopy, Raman spectroscopy of coal. The main conclusions were as follows:1. X-ray photoelectron spectroscopy analysis of Duerping NO.2coal showed that the heteroatoms in coal structure mainly are oxygen atom, nitrogen atom, sulfur atom. The oxygen atom mainly existed in ether-oxygen bond and the phenolic hydroxyl group, nitrogen atom mainly in pyridine type nitrogen and pyrrole type of nitrogen, and sulfur atom mainly in thiophene sulfur.2. The results of high-resolution transmission electron microscopy show that condensation degree of aromatic ring in Duerping NO.2coal was low and the number of condensed aromatic ring was3×3or less. Based on the above analysis, the aromatic skeleton of the model was mainly benzene, naphthalene, anthracene and phenanthrene, and1-2seleted from4×4or5×5aromatic groups.3. The energy analysis on optimized structure of Duerping NO.2coal shows that potential energy of the model mainly was non-covalent bonding energy in which the van der Waals energy predominates. There was no hydrogen bonding energy in non-bonded energy. It indicated hydrogen bonding energy of a single molecule model is not the main non-covalent bonding energy. The torsion of chemical bond in three-dimensional model of Duerping NO.2coal, especially bridge and fatty chain, make different aromatic lamellae arranged approximately parallel, and interactions between π-π of different aromatic rings were enhanced.4. Molecular mechanics and molecular dynamics were used to optimize the multiple molecular aggregation structure of Duerping NO.2coal and simulate X-ray diffraction patterns of it. The results showed that the100peak was same between experimental spectra and calculated spectra, while the002peak of calculated spectra has a higher left peak line significantly and larger intensity of y band compared to the experimental spectrum, which related to the number of coal macromolecules on aggregation state.5. Semi-empirical quantum mechanics was used to simulate Raman spectroscopy of Duerping NO.2coal. The results showed that the first order Raman spectrum of coal has two peaks:D band and G band. D band is from the combined effect of aromatic series and aliphatic series in coal, and G band is mainly from the contribution of π electrons in aromatic series.