Under different metamorphic environments, coal will form different types of tectonically deformed coal (TDC) by tectonic stress and even the macromolecular structure can be changed. The structure and composition evolution of TDC have been investigated in details using Fourier transform infrared spectroscopy and Raman spectroscopy. The ductile deformation can generate strain energy via increase of dislocation in molecular structure of TDC, and it can exert an obvious influence on degradation and polycondensation. The brittle deformation can generate frictional heat energy and promote the metamorphism and degradation, but less effect on polycondensation. Furthermore, degradation affects the structural evolution of coal in lower metamorphic stage primarily, whereas polycondensation is the most important controlling factor in higher metamorphic stage. Tectonic deformation can produce secondary structural defects in macromolecular structure of TDC. Under the control of metamorphism and deformation, the small molecules which break and fall off from the macromolecular structure of TDC are replenished and embedded into the secondary structural defects preferentially and form aromatic rings by polycondensation. These processes improved the stability of macromolecular structure greatly. It is easier for ductile deformation to induce secondary structural defects than in brittle deformation. 1. Introduction The study of macromolecular structure and complicated composition of coal is the most difficult and important topic in coal chemistry [1–4]. Effective analytical methods for coal structure and chemical composition research, such as Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy are, becoming more and more important for coal chemical researchers [5–15]. Previous studies discussed that with the upgrade of metamorphism, the aromatic structure of primary structure coal increased and expanded, whereas the side chain of aliphatic compound and functional group decreased. The hydrogen and oxygen deplete in coals; as a result, the condensation degree gradually improved. Aromatic structure is mainly composed of anthracite, and the condensation degree is further improved [2, 3, 5, 16, 17]. The coal basins in China experienced multiple tectonic movements and developed widely distribution of tectonically deformed coal (TDC) under the strong tectonic deformation environments [18]. Compared with primary structure coal, the evolution characteristics and ways of macromolecular structure of TDC are more complicated [8, 17–21]. The formation of lignite due
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