Investigation on structural features of Shengli lignite through oxidation under mild conditions

Structural features of Shengli lignite (SL) were investigated through ruthenium ion-catalyzed oxidation and oxidations in aqueous hydrogen peroxide (AHPO) and sodium hypochlorite (ASHC) under mild conditions. The results suggest that SL is rich in condensed aromatic species and hydroxyl-, methoxy-, and/or methyl-substituted benzene rings, and –CH2CH2– is a dominant bridged linkage connecting aromatic rings in SL. Aliphatic linkages connecting three aromatic rings also exist in SL. Most of the organic matter in SL was converted into soluble fractions in either AHPO or ASHC. The products from SL oxidation in AHPO are rich in hydroxyl- and/or methoxyl-substituted benzoic acids, alkanoic acids (AAs), and long-chain alkanedioic acids (ADAs), whereas those from SL oxidation in ASHC are mainly composed of benzene carboxylic acids, chloro-substituted short-chain AAs and ADAs. The nitrogen- or sulfur-containing species produced from SL oxidation provide important information on structural features of organic nitrogen and sulfur species in SL.