碳/碳复合材料碳源化合物乙苯热裂解机理的热力学研究

Thermodynamic Research on Pyrolysis Mechanism of Carbon Matrix Precursor Ethylbenzene Used for Carbon/Carbon Material

主要采用Gaussian 0 3程序中的密度泛函理论 (DFT) ,在UB3LYP/6 3 1G 水平上对碳材料用碳源化合物乙苯的初期热裂解反应机理进行了研究 .对反应物和产物的结构进行了能量梯度法全优化 ,计算了不同温度下 ( 2 98～ 15 73K)的热力学参数 .结果表明 :在 2 98～ 15 73K下 ,热力学首先支持生成甲苯自由基和甲基自由基的反应为主反应路径 .低温下 ,生成苯乙基自由基 (α位脱氢 )的反应比例大于生成苯基自由基的反应 ,而高温下 ( 82 3K) ,生成苯基自由基的反应比例大于苯乙基自由基 (α位脱氢 )的反应 .

In this paper, the pyrolysis mechanism of the carbon matrix precursor ethylbenzene used for carbon/carbon material was investigated by density functional theory at the UB3LYP/6-31G* level of Gaussian 03 package. The equilibrium geometries of the reactants and products were optimized and the standard thermodynamic parameters in different temperature ranges (298 similar to 1573 K) were calculated. The calculations show that, in 298 similar to 1573 K, the reaction path producing cresyl and methyl is the major reaction path. At low temperature, the ratio of forming phenylethyl (dehydrogenation at alpha-position) is larger than that of forming phenyl in pyrolysis reaction. At high temperature (about 823 K), the ratio of forming phenyl is larger than that of forming phenylethyl.