Study on the microcosmic mechanism of inhibition of coal spontaneous combustion by antioxidant diphenylamine

Abstract

Diphenylamine has been applied to suppress coal spontaneous combustion with good results, but its microscopic reaction mechanism is not clear. In this paper, the free radical reaction process of coal spontaneous combustion is calculated more systematically, and the quantum chemical method is applied to analyze in detail the process of diphenylamine depletion of reactive free radicals in coal from three perspectives: hydrogen atom transfer, direct radical capture, and regeneration cycle chain. By destroying the molecular structure of coal to generate free radicals as the initial condition of coal spontaneous combustion, the oxidation process of the free radical chain reaction was analyzed, the thermodynamic data of all reactions were calculated, the microscopic mechanism of free radical capture by diphenylamine was revealed, and the transition state structure model of the reaction process was given. The active sites of each reactant were determined by quantitative molecular surface analysis, the spontaneity of the reaction was measured by the free energy change, and the interaction relationship between different conformations was graphically represented by applying the IRI (interaction region indicator) method. The results show that most of the free radical reactions during the spontaneous combustion of coal are exothermic, and they provide heat for the spontaneous combustion of coal, which can react directly with oxygen when accumulated to a certain temperature. Diphenylamine can break the N-H bond, allowing hydroxyl radicals and carbon radicals to obtain hydrogen atoms to form stable compounds, and the generated diphenylamine radicals can reduce the content of free radicals in coal by direct capture. In addition, the process of diphenylamine inhibition of coal spontaneous combustion has a circular regeneration chain, which can indeed effectively reduce the content of reactive radicals and inhibit the spontaneous combustion of coal, which is reflected in the macroscopic level of reducing the generation of coal spontaneous combustion indicator gas, which is consistent with the experimental results.