Two-step depolymerization of Zhaotong lignite in ethanol

摘要

Zhaotong lignite (ZL) was subjected to ethanolysis at 305 degrees C to afford soluble portion 1 (SP1) and residue 1 (R-1). R-1 was ethanolyzed with NaOH at 305 degrees C to obtain soluble portion 2 (5P(2)) and residue 2 (R-2). SP2 was separated to extracts 1-3 (E-1-E-3) by sequential extraction with petroleum ether, carbon disulfide, and dichloromethane. SP1 and E-l-E-3 were analyzed with a gas chromatograph/mass spectrometer, while ZL, R-1, and R-2 were characterized with a Curie-point pyrolyzer-gas chromatograph/mass spectrometer. The total yield of SP1 and E-l-E-3 is 88.8%, indicating that most of organic matter in ZL was converted to soluble species by the two-step depolymerization. Ethyl alkanoates are the most abundant species detected in SP1. The distribution of group components in SP1 is quite different from that in the pyrolysis products from ZL, e.g., the relative content of alkoxyphenols is much lower than that of phenol and alkylphenols in SP1, but much higher in the pyrolysis products from ZL, indicating that the mechanism for ZL ethanolysis is quite different from that for ZL pyrolysis. Carbazole is the predominant nitrogen containing compound in the products from R-1 pyrolysis. Sulfur-containing organic compounds were only released from R-2 pyrolysis. The mechanisms for the formation of typical group components from the ethanolysis of ZL, NaOH-involved ethanolysis of R-1, and pyrolysis of ZL, R-1, and R-2 were discussed. (C) 2017 Elsevier Ltd. All rights reserved.