Mild oxidative cracking of Shanxi bituminous coal to carboxylic acids via sequential oxidation with aqueous hydrogen peroxide-acetic anhydride

Shanxi bituminous coal (SBC) was subjected to mild oxidative cracking with aqueous hydrogen peroxide (AHPO)-acetic anhydride (AAH) in order to promote the clean and efficient utilization of coals, aligning with the objective of carbon neutrality. The total yields of oxidation products produced from sequential oxidation are 33.87 %, with the maximum yield of 16.40 % attaining at 2nd oxidation, and simultaneously more than 90 % of the organic matter in SBC are converted. Noteworthily, benzene carboxylic acids and alkanedioic acids are the main products resulting from the oxidative cracking of SBC accounting for 59.31 % and 26.90 % of the oxidation products, indicating the predominant existence of condensed aromatic and diarylalkane structures in SBC. In addition, 3 carboxylic acids, i.e., alkanoic acids, alkanetricarboxylic acids, and arenecarboxylic acids, were also detected with a low relative abundance of 9.72 %, 0.32 %, and 3.75 %, respectively. Meanwhile, during the sequential oxidative cracking process, the radicals ^.OH and ^.OOH generated from the reaction of AHPO and AAH are highly reactive and capable of degrading the macromolecular networks in SBC into soluble carboxylic acids. The present study provides a clean method for efficient utilization of coals in the production of high value-added oxygen-containing organic chemicals, especially carboxylic acids such as phthalic acid and succinic acid.