五氟乙烷灭火剂高温热解机理研究

Study on thermal decomposition mechanism of pentafluoroethane fire extinguishing agent

根据均裂的化学键类型提出了五氟乙烷(C2HF5)的9条初级裂解反应路径,采用DFT/B2LYP/6-31G*、DFT/B2LYP/6-311G**、MP2/6-31G*和MP2/6-311G**方法计算了C2F5H各裂解反应的焓变、中间态分子模型以及反应中生成的卡宾的能态。结果表明C2HF5裂解最易发生H转移反应生成C2F4;伴随H转移生成CF3CF:卡宾,F转移生成CHF:,C—C键断裂生成CF2H.和CF3.,自由基或卡宾之间相互结合生成微量的C2F6、C4F8和C4F10等气体产物。热解实验证实,C2HF5在750～850℃时主要发生脱HF反应生成C2F4,随着反应温度的增加,C2HF5分解程度提高。理论计算的C2HF5裂解产物与实验检测结果一致。

Nine primary pyrolysis pathways of pentafluoroethane （C2HF5 ） are proposed based on the chemical bond types of the homolytic cleavage. The enthalpy of decomposition reaction for C2F5H, transition-state molecules, and en- ergies of carbenes have been studied theoretically using DFT/B2LYP/6-31G~ , DFT/B2LYP/6-311G＊＊ , MP2/6- 31 G ＊ , and MP2/6-31 l G ＊＊ methods. Of a total of 9 primary reaction pathways, the decomposition of C2 HF5 to form C2 F4 is the most important initiation mechanism. With the H-transfer reaction to CF3 CF： carbene, F-transfer reaction to CHF：, and C-C bond fission reaction to CF2H - and CF3 · , a trace of products such as C2F0 , C4F8 and C4F10 are pro- duced due to the reactions between radical and carbene. It is proved by thermal decomposition that hydrogen fluoride e- liminated to form C2F4 is the main reaction between 750 ℃ and 850 ℃. As the reaction temperature increases, the ther- mal decomposition degree of C2FsH become higher. Theoretically calculated results are consistent with the experimental observation.