QUANTUM CHEMISTRY CALCULATION STUDY ON REACTION PATHWAYS OF CARBOXYL GROUPS DURING COAL SELF-HEATING

摘要

Carboxyl group plays an important role in coal self-heating.However, their reaction pathways during this process still have not been revealed.This study analyzed their reaction pathways and their enhancement effect on coal self-heating process by the method of quantum chemistry calculation.Based on existing molecular models of coal, active sites existing in coal structure were calculated by quantum calculation.And the interactional modes of active orbits and detailed reaction sequences during coal self-heating were proposed.By the method of quantum chemistry calculation, the structural parameters and thermodynamic data were calculated and the orders of reactions in transformation between functional groups were identified based on the activation energy.The results indicate that there are two reaction steps for the reaction process of carboxyl groups during coal self-heating.The first reaction step is the hydrogen abstraction reaction by oxygen.The second is the generation reaction of carbon dioxide, which plays an important role in the generation of CO2 during coal self-heating.The activation energy for the two reaction steps is 56.42 kJ/mol and 73.30 kJ/mol.These reaction steps are endothermic reactions and the corresponding heat absorption is 17.85 kJ/mol and 54.48 kJ/mol.It indicates that the reaction of carboxyl groups during coal self-heating is not spontaneous and will not occur until reaching a higher temperature.