Influence of Hydroxyl Groups on the Oxidative Reaction Characteristics of Active Groups in Lignite at Room Temperature

Abstract

In this paper, through the Fourier infrared spectrum analysis of the Inner Mongolia Hulunbeier Yannan coal mine lignite sample, phenyl and active groups, methoxy (−OCH 3 ) and methylene (−CH 2 −), were taken as the research objects, and a simple small molecule model of hydroxyl (−OH) at the ortho, meta, and para positions of active groups was constructed. The structural optimization and simulation calculation of simple small molecules were carried out by Gaussview 6.0.16 and Gaussian 16 software at room temperature and pressure. The DFT-B3LYP method and 6-311G(d,p) basis set were used to study the effect of the −OH position on the oxidation reaction characteristics from various aspects of electrostatic potential, frontier orbital, activation energy, enthalpy change, and Gibbs free energy change. The results show that the coexistence of the active groups −OCH 3 and −CH 2 − with −OH makes the small molecule model add an active site, that is, the oxygen atom in −OH, which makes the active groups generate hydrogen radicals (H • ). Comparing different positions of −OH, the analysis shows that −OH at the ortho position has a vital impact on the oxidation reaction, and the oxidation reaction releases the largest amount of heat and has the fastest occurrence rate, making it easier to overcome energy barriers and making the reaction easier to proceed. The purpose of this study is to reveal the interaction and complex reaction path of lignite through an in-depth study of its properties, structural composition, and reaction behavior and to accurately grasp its chemical composition, thermal properties, and microstructure, so as to lay a foundation for further efficient conversion and comprehensive utilization.