甲苯热裂解机理的AM1研究(Ⅱ)动力学分析  

AM1 Kinetics Research of the Pyrolysis Mechanism of Toluene?

作　　者：王惠[1] 杨海峰[1] 冉新权[1] 史启祯[1] 文振翼[2] 

机构地区：[1]西北大学化学系陕西省物理无机化学重点实验室,西安710069 [2]西北大学现代物理研究所,陕西省物理无机化学重点实验室,西安710069

出　　处：《无机化学学报》2001年第4期545-550,共6页Chinese Journal of Inorganic Chemistry

基　　金：博士后基金;陕西省教委专项基金资助项目(No.99JK100)。

摘　　要：在?报热力学的基础上,本文用Gaussian98程序包中AM1法UHF计算,对碳材料用碳前驱体甲苯热裂解机理进行了动力学研究。通过用QST2方法寻找过渡态并经过内禀反应坐标IRC验证,计算得到了甲苯5种热裂解路径的活化能;用过渡态理论,计算得到了这些路径在298～1073K温度范围内的速率常数。动力学计算结果表明:甲苯在热解温度低于963K时的主反应路径为甲苯热裂解生成苄基自由基的反应;该主反应路径又是经由反应物→中间体→产物而完成,速控步为反应物→中间体,速控步的活化能ΔE0≠=E(TS1')-E(R)=277.20kJ·mol-1;当温度高于963K或1073K左右时,主反应路径转为苯环上脱甲基生成苯基和甲基自由基的路径。以上研究结果与实验结果相一致。According to the previous article about thermodynamics research, dynamics research were done by calculating with semi empirical method AM1 of Gaussian 98 program package for the pyrolysis mechanism of the carbon source toluene used for carbon/carbon composite material. The transitional states were found by QST2 method and were proved by IRC calculation. The activation energy of the five reaction paths were obtained, and the rate constant from 298K to 1073K were also got based on transition state theory. The dynamic calculation results show: when the pyrolysis temperature of toluene is lower than 963K,the main reaction path is C H bonds of the methyl on the benzene ring breaking. This main reaction is completed via the process: reactant(R) → transition state(TS1′) →intermediate(IM)→ transition state(TS1″)→ product (P), the rate control step of the process is reaction(R) → transition state (TS1′). The activation energy of the step is ΔE0≠=-E(R)=277.20kJ·mol-1 and its rate constant is k=3.0×10-5s-1 at 843K. When temperature is higher than 963K or 1073K , the main reaction path is the reaction that produces benzene radical and methyl radical, its activation energy is ΔE0≠=345.27kJ·mol-1 and rate constant is k=2.3×10-1s-1 at 1073K. This mechanism is in accord with the experiment.

关 键 词：碳材料前驱体 甲苯 热裂解机理 动力学参数 AM1计算 量子化学 

分 类 号：O625.11[理学—有机化学] O641.121[理学—化学]