Study On The Nanostructure Of Coal

Coal is a very important type of energy. the coal chemistry research around coal resource has a history of more than 150 years. In the 21 st century, coalbed methane becomes the substitute resource to the petroleum and natural gas which face a crisis of exhausted. The coal architectural feature also turns into a research hotspot, for it and its evolvement laws are the core and basis of coal chemistry and coalbed methane research. Sufficient understanding of the coal architectural feature and its evolution mechanism can not only improve the basis theory of the coal chemistry, but also be helpful to explore and exploit the coalbed methane.In this thesis a large number of relevant data has been summarized. Here coal samples from different coal ranks have been selected to study the form and distribution characteristics of the nanoscale pores, the stacking structure characteristics of the macromolecules and their laws varied with the coal rank, by means of scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), small angle x-ray scattering (SAXS), x-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). The major achievements are as follows:(1) The form of the coal pores is very complicated, circular to oval mainly, triangular, rectangular and irregular secondly. In immaturity stage, pores are mainly protogenetic, with a micron-scale pore size. In general, the nanoscale pore develops with the increasing of thermal evolution degree.(2)The macropores (large than 50 nanometers) are the main nanopores in coal, which volume fraction accounts for about 60% of all nanoscale pores, followed by large mesoporous, medium mesoporous and micro mesoporous. As the increasing of coal rank, the volume percentages of medium mesoporous and micro mesoporous become larger, with logarithmic and linear tendency. The changes of the pore size with the largest volume percentage are obvious. They are slightly down in low coalification bituminous stage, significant down in medium coalification bituminous stage and quickly down in anthracite stage.(3)The parameters of the coal crystal nucleus (doo2,La and Lc) change corresponding to the increasing of coal rank. Results show that while the coal metamorphic grade increases, the condensation of the aromatic ring enhanced; the bridge bonds, side chains and oxygen-containing functional groups decreased; La, Lc enlarged and doo2 reduced; the arrangement of the aromatic layer changed from disorderly to parallel, and lastly concentric (occurring with onion structure).After the research of the three aspects, the evolution model of nanostructure of coal is explored and build.