The evolution difference of macromolecular structures and its dynamic mechanism of coal macerals：Research status and prospect

The physical and chemical properties of macerals are important factors affecting the clean and efficient utilization of coal and the physical properties of coal reservoirs. It has been recognized that the essential cause of determining the properties of macerals lies in their macromolecular structure. In order to reveal the evolution characteristics of macromolecular structure of macerals and its controlling factors, the research progresses at home and abroad were summarized and the shortcomings were analyzed from several aspects, such as the chemical and physical structure of macromolecules, the tectonic stress effect on the macromolecular evolution, and the evolution characteristics of macromolecules in the whole stage of coal metamorphism. The extensive distribution and important industrial use of vitrinite-rich coal make it the main research object of coal macromolecular structure, while reach on inertinite is relatively less, which hinders the comprehensive understanding of coal characteristics. Putting forward an research idea that the thermal-stress condition of coal metamorphism determines the microstructure evolution of macerals, and the macromolecular structure evolution of inertinite and vitrinite is different. Then, the high temperature and pressure simulation, artificial thermal simulation experiments of vitrinite/inertinite were carried out and compared with the natural evolution sequence of metamorphic-deformed coal, to study the microstructure evolution characteristics and their controlling factors of macerals. The objectives of the study are to characterize quantitatively the relationship between macromolecular structure of macerals and temperature/pressure conditions, to reveal the tectonic stress control on the chemical structure and nanopore structure of macerals, to identify the evolution path of macromolecular structure of inertinite in the whole process of coal metamorphism, and to establish the dynamic model of macromolecular dynamics of inertinite. The above results will enrich the overall understanding of microstructure evolution and its controlling factors, and provide the scientific basis for clean and efficient utilization of coal and evaluation of physical properties of coal reservoir.