Sequential oxidation of Jincheng No. 15 anthracite with aqueous sodium hypochlorite

Jincheng No. 15 anthracite (J15A) was pretreated with aqueous hydrogen peroxide and then subjected to sequential oxidation for 6 times, i.e., oxidation runs 1-6 (O_r1-O_r6), with aqueous sodium hypochlorite. Significantly more organic matter in J15A was oxidized into water-soluble portion (WSP) by sequential oxidation than by one-run oxidation for the same period of time. The relative content of non-chlorine benzenepolycarboxylic acids (BPCAs) in the WSP increased from O_r1 to O_r6. Among BPCAs, benzenehexacarboxylic acid can be concentrated over 34% by subsequent solvent extraction. J15A particles were oxidized from external portion (EP) to internal portion (IP). According to the product types, cata-condensed aromatics and polyaryls in the EP are significantly more than those in the IP, while peri-condensed aromatics in the IP are remarkably abundant than those in the EP. This investigation provides a promising approach for obtaining BPCAs from high-rank coals and for understanding aromatic structural features of high-rank coals.