Thermal dissolution of Shengli lignite in ethyl acetate

Thermal dissolution (TD) of Shengli lignite (SL) in ethyl acetate (EA) was carried out under different conditions, including temperature, solvent to SL ratio (R_S/SL), and time. The yields of EA-extractable fractions (EAEFs) increased with raising temperature from 240-300°C, but then decreased when the temperature was higher than 300°C, and the effects of R_S/SL and time on EAEF yields was slight when R_S/SL and time exceeded 20/1 and 1 h, respectively. These results suggest the optimal conditions for the TD of SL are 300°C, 20/1 of R_S/SL, and 1 h. Then a couple of scale-up experiments were carried out under the optimal conditions with SL and dehydrated SL. According to analysis with a gas chromatography/mass spectrometry, major species in the EAEF from the TD of SL are oxygen-, sulfur-, and nitrogen-containing organic compounds along with elemental sulfur. The sulfur- and nitrogen-containing organic compounds detected include thioethers, thiophenes, amines, and nitrocyclic compounds. According to the structural characteristics of organic compounds in the EAEF, the mechanism for the TD of SL with EA was presumed.