Effect of solvent swelling on structure and pyrolysis product distribution of Ordos lignite

Four kinds of organic solvents were used to pretreat Ordos lignite to obtain swelling coal. The effect of swelling on the structure and pyrolysis characteristics of Ordos lignite was investigated by fast pyrolysis of swelling coal in a powder-particle fluidized bed. The swelling coal and pyrolysis products were characterized by FT-IR, TGA, GC-MS, ¹³C NMR, XRD. The results show that non-polar solvent has little effect on coal structure. The polar solvents can reduce the hydrogen bond crosslinking of oxygen-containing functional groups of lignite, increase the fluidity of small molecules and the average pore diameter of coal. After swelling, The yield of coal tar and gas phase yield increases, the pyrolysis water yield decreases. After pretreatment with methanol, acetone, and tetrahydrofuran, the yield of pyrolysis tar increased by 18.88%, 26.72%, 33.58% respectively. Compared with raw coal, and the contents of phenolic, monocyclic and bicyclic aromatic hydrocarbons components in the light components of tar were significantly increased.