Study on microcrystalline structure of medium and low rank coals in Xinjiang

Based on X ray diffraction and Fourier transform infrared spectroscopy, the microcrystalline structure characteristics and evolution patterns of a total of 6 coal samples from the eastern Junggar, southern Junggar, Tuha, and Kubai coalfields in Xinjiang were investigated. The peak shape of 002 and 100 peaks in low-rank coal is gentle, the peak 002 becomes sharper and the “symmetry” becomes better with the increase of coal rank, and the peak height of the peak 100 gradually increases but the peak width gradually shrinks. The height of the peak 100 gradually increases but the width gradually narrows; with the increase of coal sample metamorphism, the stacking height, elongation and quantity of aromatic laminates increase gradually, the spacing of aromatic laminates decreases on the whole, and the condensation degree of aromatic structures in coal increases gradually; the peak shape of aromatic compounds and oxygen-containing functional groups is sharp, and the peak shape of aliphatic hydrocarbons and hydroxyl functional groups is gentle, which gradually widens and slows down with the rise of coal rank; with the increase of coal rank, the aromaticity, fat chain length, branched chain degree and maturity gradually decrease, while the polycondensation degree and hydrocarbon (oil) generation ability gradually increase. The evolution process of coal is characterized by the shedding of oxygen-containing functional groups, the enrichment of aliphatic hydrocarbons, and the condensation of some aromatics.