Study on the inhibitory mechanism of dehydrogenated antioxidants on coal spontaneous combustion

In order to comprehensively and systematically analyze the reasons why antioxidant inhibitors can scavenge free radicals in coal and inhibit coal spontaneous combustion, this paper studies the effects of VC, TBHQ, EGCG and BHT on coal spontaneous combustion by means of coal spontaneous combustion characteristics experiments and quantum chemical simulation methods. The low-temperature oxidation characteristics of coal were studied through temperature-programmed experiments. The results showed that the CO emission of coal samples with antioxidants was significantly lower than that of raw coal. At 170 °C, the maximum decrease was 37.74%. Fourier infrared test showed that compared with the coal samples without antioxidant treatment, the adsorption strength of hydroxyl structure and oxygen-containing functional groups of the treated coal samples was significantly reduced. The area percentages of hydroxyl and methylene changed significantly, decreased by 7.14% and 6.46%, respectively. Subsequently, molecular models of four antioxidants were constructed using quantum chemical theory, and their Mulliken charges, BDE values ​and frontier orbitals were calculated according to density functional theory (DFT), and the active sites and inhibition mechanisms of antioxidants were discussed. The results showed that H9 of VC, H33 of EGCG, H1 of TBHQ and H40 of BHT all had strong ability to scavenge oxygen-containing free radicals, and their order of strength was TBHQ > BHT > EGCG > VC. Antioxidant inhibitors mainly reduce the number of active free radicals by removing the peroxide groups in the initial stage of the coal oxygen reaction, and remove the hydroxyl groups to prevent the further spontaneous combustion of coal and inhibit the low temperature oxidation process of coal.