Quantum Chemistry Study On The Mechanism For The Pyrolysis Of Coal-related Oxygen-containing Model Compounds

The quantum chemistry calculation method has been gradually used to study the correlation between coal structure and reactivity in coal chemistry. The method has gradually formed a new study field. The calculation method is not restricted to experimental conditions, so it can investigate the researches which are difficult to experiment or in which bigger error occurs. Meanwhile, the quantum chemistry calculation method based on the first element can calculate the selected model compounds credibly, thereby carry out theoretic analysis and research. At present, quantum chemistry calculation method has provided a feasible scheme for dealing with coal structure.In this dissertation, pyrolysis mechanisms of Coal-related oxygen-containing compounds anisole, benzoic acid and benzaldehyde have been explored using DFT calculation module Dmol³ with the DND basis set. According to the molecular microstructure parameters, thermodynamic and kinetic function changes, four conclusions have been gained: (1) The selected method and basis set in this paper to calculate the three oxygen-containing models are credible, and the results are good with experiment results. (2) Pyrolysis mechanism of anisole representing model compounds with ether-oxygen bond functional group in coal is studied in higher temperature, the intermediates o-, p-methyl-cyclohexadienone are formed following by the production of o-, p-cresoles, the major products of the reaction. Tow parallel bunch ones of the three pathways which are suggested based on the conjugate configuration of phenoxyl radical may be exist by analyzing the thermodynamic and dynamic data. (3) Escaping of CO₂, CO is corresponding to decarboxylation and decarbonylation in coal, activation energy of decarbonylation is higher than decarboxylation, it indicates that CO₂ is easy to escape than CO. (4) H-migration mechanism is easier than radical mechanism in decarboxylation of benzoic acid, it can be concluded that low temperature cross-linking in coal is not corresponding to decarboxylation directly.