The structure and composition of coal determine its fast pyrolysis characteristics, and the study of the relationship between them can play an important role in the efficient and clean utilization of coal. So, in this work, hydrothermal pretreatment was used to artificially change the structure and composition of ShengLi (SL) lignite, which was used to investigate the influence of structural changes on pyrolysis. The physicochemical structure and composition of samples were characterized by X-ray diffraction, specific surface area and porosity analyzer, solid-state 13C nuclear magnetic resonance, Fourier transform infrared spectroscopy, and elemental analyzer. Pyrolysis experiments were carried out in a powder-particle fluidized bed reactor, and the distribution and composition of the pyrolysis products were analyzed. The gasification activity of char was investigated by thermogravimetric analysis with a CO2 atmosphere. The results show that hydrothermal pretreatment (HTP) can destroy the cross-linking structure of SL lignite, and affect its aromaticity, pore structure, functional group, and carbon structure to change the distribution and composition of pyrolysis products of SL lignite, especially the composition of tar. Finally, the structure–activity relationship between the structure, composition, and pyrolysis characteristics of coal was comprehensively studied.
