Thermal dissolution of lignite and liquefaction behaviors of its thermal dissolution soluble fractions

Thermal dissolutions (TDs) of a Chinese Shengli lignite (SL) in various solvents at different temperatures were carried out, and the characterization and hydro-liquefaction behavior of thermal dissolution soluble fractions (TDSFs) were probed in this study. The results suggest that thermal dissolution soluble yield (TDSY) in 1-methylnaphthalene (1-MN) dramatically increased at 380 °C due to the obvious depolymerization of SL. Addition of polar solvent methanol or ethanol into 1-MN and crud methylnaphthalene oil (CMNO) can greatly increase the TDSY because of the methanolysis or ethanolysis reactions. Characterization of TDSFs suggests that the TDSF obtained from 1-MN at higher TD temperature contained more amounts of aromatic components. Addition of polar solvent into 1-MN, the TDSF obtained contained more amounts of oxygen groups and heavy components compared to that obtained from 1-MN. Liquefaction of TDSF suggests that TDSF can be almost completely converted by NiMoS/Al2O3 catalytic hydro-liquefaction with much higher yield of oil compared to SL raw coal. The liquefaction of the TDSF obtained from 1-MN with addition of polar solvent gave lower yield of oil and higher yield of gas than that of the TDSF obtained from 1-MN.