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

• Sequential oxidation gradually improved the selectivity of NCBPCAs from Or1 to Or6.
• Benzenehexacarboxylic acid was concentrated over 34% by solvent extraction.
• peri-Condensed aromatic structures are predominant in J15A.

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 (Or1–Or6), 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 Or1 to Or6. 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.