| The research on the composition and structure of coal has been one of the most important issues in coal science, which has been the foundation for improving the existing coal exploration and utilization technologies and developing the new technologies. A lot of work has been done in this field in the past decades, but the achievements are not satisfactory because of the complexity of coal itself. The structure of inertinite and the characteristics of oxygen functional groups in coal are very important issues in coal structure science, which have been little approached. With the development of the coal processing and conversion technologies, it is necessary to understand the structure of inertinite and the characteristics of oxygen functional groups in coal. So, the molecular structure of inertinite and the characteristics of oxygen functional groups are studied emphatically in this paper by different means. The relevant data and the theoretic analysis are put forward so as to get an overall comprehension on the coal molecular structure. At the same time, the research offers the theoretic support to the development of the coal processing and conversion technologies.Five typical coals of low-to-medium rank (Huolinhe brown coal, Majiata non-caking coal, Datong weakly caking coal, Huozhou gas coal, Lingshi fat coal) and their macerals (vitrinite and inertinite) are prepared. The molecular structure and the oxygen functional groups of the selected coals and their macerals (vitrinite and inertinite) are studied by means of the conventional coal properties analysis, chemical analysis and the advanced instrumental methods such as FTIR,XRIK 13C-NMR.N XPS. The molecular structure characteristics, regularities and the results are discussed. Additionally, the total oxygen content and distribution characteristics of different oxygen functional groups in the raw coals and their macerals are studied. The proximate and ultimate analysis shows that there are differences in the structure and properties between inertinite and vitrinite: the carbon content of inertinite is higher than that of vitrinite, and the volatile matter hydrogen contentand oxygen content are respectively lower than that of the latter. The differences between inertinite and vitrinite will become smaller and smaller with the increasing coal rank. So, it is important to research the differences in structure and properties between inertinite and vitrinite in the low-to-medium rank coal.The infra-red spectrum (FTIR) analysis indicates that there exists more substituted arene and less aliphatic hydrocarbon in inertinite than that in raw coal and vitrinite. So, the order of the aromaticity is: inertinite > raw coal > vitrinite, and the aromaticity of the raw coal and the macerals increases gradually with the increasing coal rank.The high-resolution solid 13C NMR spectrum shows that there are less aliphatic hydrocarbon and more aromatic hydrocarbon in inertinite, and the side chain hydrocarbon is shorter than that in the vitrinite. The aromaticity of inertinite is 0.769-0.834, which is higher than that of vitrinite (0.669-0.774). With the increase of coal rank, the aromaticity of both inertinite and vitrinite increases, but the aromaticity of the former increases more slowly than the latter. The mean size parameter of arene cluster (Xb) of inertinite is 0.522-0.602, which is similar to that of vitrinite (0.559-0.616), and it changes little with the increase of the coal rank.The result from X-ray diffraction (XRD) analysis indicates that there is higher degree of aromatization in inertinite, and the inertinite is of higher regularity and orientation in the spatial arrangement of the arene layers than vitrinite. With the increase of the coal rank, the ratio of aromatic hydrocarbon increases, the condensation polymerization of the arene cluster occurs in both the crosswise direction and the lengthwise direction, and the structure of coal is gradually close to the graphitic structure.The research on the characteristics of oxygen functional groups by th... |
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