Sequential extraction and thermal dissolution of Shengli lignite

• BSPs and MSPs from SL mainly consist of hydrocarbons and phenols.
• Most of the phenols in the SPs are alkylphenols and alkoxyphenols.
• Acetone is an excellent solvent to isolate and enrich the NCOCs from SL.
• SE and STD are effective approaches for isolating the organic species in SL.

Shengli lignite (SL) was subjected to sequential extraction (SE) with carbon disulfide, benzene, methanol, acetone, and tetrahydrofuran under ultrasonication to afford extracts 1–5, respectively, and the residue (RSE, i.e., residue from SE). The RSE was subjected to sequential thermal dissolution (STD) in benzene, methanol, and acetone in a batch autoclave from 210 to 330 °C to afford soluble portions (SPs) and the residue (RSTD, i.e., residue from STD). The total yield of extracts 1–5 is only 2.86%, while the yields of SPs from STD in benzene, methanol, and acetone are 5.69%, 10.15%, and 48.41%, respectively. The SPs from STD in benzene and methanol mainly consist of hydrocarbons and phenols, while ketones are the main compounds detected in the SP from STD in acetone and most of nitrogen-containing organic compounds appear in the SP from STD in acetone. During STD in acetone, acetone conversion to phorone, isophorone, and their derivatives was confirmed.

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