Simulation Of Characteristics Of Coal And Oxygen Adsorption With Quantum Chemistry Methods

Coal is one of China's important energies, but the coal was easy to spontaneous combustion, during the process of mining and piled up for storage. Coal spontaneous combustion, its essence is that coal combines with oxygen and release reactive heat. Therefore, study the adsorptive characteristics of O₂ on coal surface, which is helpful to study the micro reaction mechanism and essence of combination of coal and oxygen, thus, it can provide theoretical basis for the prediction of coal combustion and development of prevention technologies.Firstly, FTIR experiments were carried out on 13 coal samples collected from Lingxin Coal Mine and other coal mines. According to the characteristic peaks of infrared curve, the active groups in coal samples were analyzed, combined with Coal Chemistry knowledge and the research results of the active groups, the baldheaded groups, such as methyl, carboxyl, hydroxyl, were chosen as research objects, molecular simple models of coal surface were built, the physical adsorption process of early stage of coal oxygen combination were studied, from the microscopic view. Then, Gauss 03W quantum chemical analysis software was applied for simulate the adsorption process of O₂ on active groups of coal surface molecules, the changes of bond lengths and energies during the adsorption process were analyzed and discussed, main active groups and key links were identified, in which density functional theory methods were used, B3LYP DFT - 6-311G yankees groups were selected. Through the simulation research, activity order of the active groups to oxygen molecule was summerized, namely, methoxy group>aldehyde group>methylene with hydroxyl group>methyl group>carboxyl group. Finally, the influence of two polar molecules, CO and H₂O, three nonpolar molecules, N₂ CH₄, CO₂, were analyzed and discussed, the conclusions were that: the adsorption of CO and H₂O had influence on oxygen adsorption process on active groups, through occupying the combination positions of oxygen and coal surface or absorbing energies from environment, to block the adsorption of O₂ on active groups. The three nonpolar molecules, CH4,CO₂ and N₂, could not be absorbed on active groups, thus they affected little on O₂ adsorption on active groups.