Fractional Extraction and Biodepolymerization of Shengli Lignite

Abstract

Shengli lignite (SL) was sequentially extracted with aqueous NaOH solution, n-hexane, dichloromethane, an azeotropic mixture of benzene and ethanol, and acetone to obtain extracts 1–5 (E1–E5). Each extract was analyzed using a gas chromatograph/mass spectrometer (GC/MS) and then depolymerized by an isolated fungus. Most of E1 cannot be detected by GC/MS perhaps because of strong polarity, and E1 is recognized as humic acids. E2–E5 consist of normal alkanes, arenes, alkanols, phenols, ketones, carboxylic acids, esters, and organonitrogens according to GC/MS analysis. The biodepolymerization (BDP) of E1 is much easier than that of other extracts. According to GC/MS analysis, both 2,4-xylenzo[h]quinoline and methyl 3-(acetoxymethyl)biphenylene-2-carboxylate disappeared, while 3-(1-ethoxyethoxy)butanal, propane-1,2-diyl diformate, 3-phenylbutan-2-ol, and 2-methyl-7-phenyl-1H-indole were produced from the BDP of E1. In comparison to E1 before BDP, the phenoxy moiety in E1 after BDP was significantly reduced according to analysis with a Fourier transform infrared spectrometer, implying that the BDP facilitated the degradation of lignin in SL. This study will provide an important scientific basis for lucubrating bioconversion of lignite.