The Infrared Characterization and Mechanism of Oxygen Adsorption in Coal

The remarkable differences between the infrared spectra of oxygen adsorption and nitrogen desorption in coal have been experimentally and theoretically investigated. Density functional theory calculations were performed to better explain the mechanism of oxygen adsorption using six different molecular models of coal. In addition, the remarkable differences of infrared spectra between oxygen adsorption and nitrogen desorption was defined as the index V, which was used to classify the spontaneous combustion tendency of coal. The experimental data indicated that the spectra in the 4000–2000 cm−1 and 1250–1050 cm−1 regions exhibited significant changes. These results suggest that the mechanism of oxygen adsorption is the alteration and transfer of charge density around the activated sites, which leads to the observed changes of the infrared spectra. The V, which is related to the alteration of spectral intensity, is found to decrease with the increase of adiabatic oxidation time and the relative spon...