关键词: 碳, 复合材料, 甲苯, 裂解, 过渡态理论, 反应动力学

Based on the thermodynamic data, the pyrolysis mechanism of the carbon matrix toluene used for carbon material was studied by dynamic computation using the UB3LYP/3-21G^* method in the Gaussian 98 program package. The transition states were found by the QST2 method and were proved by IRC calculations. The activation energies of the five reaction paths were calculated, and the rate constants from 298－ 1 223 K were obtained by the transition states theory. The dynamic calculation results show, when the pyrolysis temperature of toluene is lower than 963 K, the main reaction path is the breaking of the C －H bonds of the methyl on the benzene ring. The reaction is completed via the process: reactant→intermediate→product, with reactant→ intermediate as rate-control step and activation energy △E~0^θ^≠ =402.27 kJ/mol. When temperature is higher than 963 K, but below 1 223 K, the main reaction paths is the one that produces benzene radical and methyl radical. The corresponding activation energy is △E~0^θ^ ≠=456.91 kJ/mol. This mechanism is in accord with the experimental result.

Key words: CARBON, COMPOSITE WOOD, METHYLBENZENE, PYROLYSIS, TRANSITION STATE THEORY, REACTION KINETICS