Changes in the Properties of Native Low-Metamorphozed Coal in Contact with Air

Abstract

Data on the analysis of the chemical composition and physicochemical properties of native low-metamorphosed coal at the initial moment of its contact with the air are presented. Diffuse reflectance IR spectroscopy, EPR spectroscopy, NMR spectroscopy, gas chromatography, chemical analysis of oxygen-containing groups, and the determination of the specific surface area and wettability of the contacting surface were used to identify changes in the organic matter of coal. The dynamics of changes in the numbers of paramagnetic centers and functional groups showed that the most intense transformations in the surface layer occurred in the first day of coal exposure to air. Next, oxidation at room temperature proceeded in a periodic mode of the accumulation and consumption of radicals and functional O groups. After four days, the process of low-temperature oxidation passed from the accessible outer surface into the diffusion region of the porous space of coal and gradually slowed down.